Perspektiven der Strahlentherapie gutartiger Erkrankungen

PURPOSE: The numbers of patients with nonmalignant diseases referred for radiation therapy had to be evaluated for the last 4 years. PATIENTS AND METHODS: In the years 2002, 2004, and 2005 radiation therapy was performed in 61, 40, and 26 patients, respectively. Regularly, more women than men were treated, median age annually was 57, 54, and 55 years, respectively (Table 1). The radiotherapy scheme was not modified within the evaluated period. RESULTS: The proportion of nonmalignant diseases among all patients treated decreased from 4.7% in 2002 to 3.3% in 2004 and 2.2% in 2005, respectively. A shift was noticed toward the treatment of four main diseases (endocrine orbitopathy, prevention of heterotopic ossification, meningeoma, tendinitis, Table 2). The number of referring physicians decreased from 19 to six. CONCLUSION: Due to administrative restrictions for treatment in hospitals, budget restrictions in private practices and lasting, insufficient revenues for radiotherapy in nonmalignant diseases, radiation therapy for the entire group of benign diseases is endangered.     

Comparison of the risks of cancer incidence and mortality following radiation therapy for benign and malignant disease with the cancer risks observed in the Japanese A-bomb survivors

PURPOSES: To compare the radiation-associated relative risks of cancer incidence and mortality in groups exposed to ionizing radiation in the course of treatment for a variety of malignant and non-malignant conditions with those in the Japanese A-bomb survivor cancer incidence and mortality data. MATERIALS AND METHODS: Comparison of the excess relative risk coefficients derived from published information for each study with the excess relative risk coefficient in comparable (age at exposure, time since exposure, sex) matched subsets of the Japanese A-bomb survivor cancer incidence and mortality data. RESULTS: Sixty-five studies of persons who have received appreciable doses of ionizing radiation in the course of treatment and for whom there is adequate ascertainment of cancer incidence or mortality are identified, from which 116 cancer-site-specific estimates of excess relative risk are derived. Relative risks tend to be lower in the medical series than in the Japanese A-bomb survivors. The most marked discrepancies between the relative risks in the medical series and in the A-bomb survivors are for leukaemia, where 12 of the 17 medical studies have significantly lower relative risks than those observed in the Japanese data. However, the ratio between the relative risks in the medical studies and in the Japanese data tends to diminish with increasing average or maximal therapy dose. This is observed for all cancer sites and is particularly marked for leukaemia. After taking account of cell sterilization and dose fractionation the apparent differences between the relative risks for leukaemia in the Japanese A-bomb survivors and in the medical series largely disappear. This suggests that cell sterilization largely accounts for the discrepancy between the relative risks in the Japanese data and the medical studies. Other factors, such as the differences in underlying cancer risks between the Japanese A-bomb survivors and the medical series, and dose-fractionation effects, may also contribute. CONCLUSIONS: The relative risks of cancer in studies of persons exposed to appreciable doses of ionizing radiation in the course of treatment for a variety of malignant and non-malignant conditions are generally less than those in comparable subsets of the Japanese A-bomb survivor cancer incidence and mortality data. Cell sterilization effects can largely explain the discrepancy between the Japanese and the medical series.     

Quantitative comparisons of cancer induction in humans by internally deposited radionuclides and external radiation

PURPOSE: To compare quantitative estimates of lifetime cancer risk in humans for exposures to internally deposited radionuclides and external radiation. To assess the possibility that risks from radionuclide exposures may be underestimated. MATERIALS AND METHODS: Risk estimates following internal exposures can be made for a small number of alpha-particle-emitting nuclides. (1) Lung cancer in underground miners exposed by inhalation to radon-222 gas and its short-lived progeny. Studies of residential (222)Rn exposure are generally consistent with predictions from the miner studies. (2) Liver cancer and leukaemia in patients given intravascular injections of Thorotrast, a thorium-232 oxide preparation that concentrates in liver, spleen and bone marrow. (3) Bone cancer in patients given injections of radium-224, and in workers exposed occupationally to (226)Ra and (228)Ra, mainly by ingestion. (4) Lung cancer in Mayak workers exposed to plutonium-239, mainly by inhalation. Liver and bone cancers were also seen, but the dosimetry is not yet sufficiently good enough to provide quantitative estimates of risks. Comparisons can be made between risk estimates for radiation-induced cancer derived for radionuclide exposure and those derived for the A-bomb survivors, exposed mainly to low-LET (linear energy transfer) external radiation. Data from animal studies, using dogs and rodents, allow comparisons of cancer induction by a range of alpha- and beta-/gamma-emitting radionuclides. They provide information on relative biological effectiveness (RBE), dose-response relationships, dose-rate effects and the location of target cells for different malignancies. RESULTS: For lung and liver cancer, the estimated values of risk per Sv for internal exposure, assuming an RBE for alpha-particles of 20, are reasonably consistent with estimates for external exposure to low-LET radiation. This also applies to bone cancer when risk is calculated on the basis of average bone dose, but consideration of dose to target cells on bone surfaces suggests a low RBE for alpha-particles. Similarly, for leukaemia, the comparison of risks from alpha-irradiation ((232)Th and progeny) and external radiation suggest a low alpha RBE; this conclusion is supported by animal data. Risk estimates for internal exposure are dependent on the assumptions made in calculating dose. Account is taken of the distribution of radionuclides within tissues and the distribution of target cells for cancer induction. For the lungs and liver, the available human and animal data provide support for current assumptions. However, for bone cancer and leukaemia, it may be that changes are required. Bone cancer risk may be best assessed by calculating dose to a 50 micro m layer of marrow adjacent to endosteal (inner) bone surfaces rather than to a single 10 micro m cell layer as currently assumed. Target cells for leukaemia may be concentrated towards the centre of marrow cavities so that the risk of leukaemia from bone-seeking radionuclides, particularly alpha emitters, may be overestimated by the current assumption of uniform distribution of target cells throughout red bone marrow. CONCLUSIONS: The lifetime risk estimates considered here for exposure to internally deposited radionuclides and to external radiation are subject to uncertainties, arising from the dosimetric assumptions made, from the quality of cancer incidence and mortality data and from aspects of risk modelling; including variations in baseline rates between populations for some cancer types. Bearing in mind such uncertainties, comparisons of risk estimates for internal emitters and external radiation show good agreement for lung and liver cancers. For leukaemia, the available data suggest that the assumption of an alpha-particle RBE of 20 can result in overestimates of risk. For bone cancer, it also appears that current assumptions will overestimate risks from alpha-particle-emitting nuclides, particularly at low doses.     

Radiotherapy CT-based contouring atlas for non-malignant skeletal and soft tissue disorders: a practical proposal from Spanish experience

Objective:Interest in low-dose radiotherapy (LD-RT) for the symptomatic treatment of nonmalignant conditions, including inflammatory and degenerative disorders of the joints and para-articular soft tissues, has increased substantially in recent years. In the present document, we provide a CT-based contouring atlas to help identify and delineate the most common osteoarticular regions susceptible to LD-RT.Methods:The clinical efficacy of LD-RT is supported by a large body of evidence. However, there is no consensus on the parameters for contouring the planning target volume (PTV). Moreover, 3D simulation and planning should be the standard of care even for nonmalignant disorders. For this reason, the present guidelines were prepared to help guide PTV contouring based on CT images, with the same quality criteria for patient immobilization, treatment simulation, planning and delivery as those routinely applied for cancer radiotherapy.Results:PTV for radiotherapy requires precise identification of the target areas based on CT and other imaging techniques. Using a series of cases treated at our institution, we have defined the PTVs for each location on the simulation CT to establish the relationship between the image and the anatomical structures to be treated. We also specify the immobilization systems used to ensure treatment accuracy and reproducibility.Conclusions:This comprehensive atlas based on CT images may be of value to radiation oncologists who wish to use LD-RT for the symptomatic treatment of degenerative or inflammatory osteoarticular diseases.Advances in knowledge:The recommendations and contouring atlas described in this article provide an eminently practical tool for LD-RT in non-malignant conditions, based on the same quality criteria recommended for all modern radiotherapy treatments in Spain.     

Therapeutic external irradiation in women of reproductive age: risk estimation of hereditary effects

Exposure of women of childbearing age to ionizing radiation may result in induction of genetic disorders in future generations. This study aims to estimate the risk of hereditary effects attributable to therapeutic external irradiation in women. An anthropomorphic phantom was used to simulate radiotherapy in female patients and ovarian dose was measured for irradiation of brain, breast and lung cancer, and for treatment of Hodgkin's disease. These malignancies are among the most common tumours presenting in women of reproductive age. Dose measurements were undertaken using thermoluminescent dosemeters and all exposures were made with 6 MV X-ray beams. The dose to ovaries was found to be 2-3 cGy, 8-11 cGy and 11-15 cGy depending on the distance from the primary irradiation field during radiotherapy of brain, breast and lung cancer, respectively. The corresponding ovarian dose resulting from treatment of supradiaphragmatic and infradiaphragmatic Hodgkin's disease was 18-25 cGy and 128-356 cGy, respectively. A small excess risk of genetic diseases of (1-15) x 10(-4) was estimated for radiotherapy above the diaphragm. Pelvic irradiation resulted in an increased risk of hereditary effects of (77-214) x 10(-4).     

The value of and indications for radiotherapy in endometrial carcinoma

Today the endometrial carcinoma is the most frequent malignant tumor found in female genital tract. Endometrial carcinoma ought to be operated in all cases, if possible. Traditionally some form of adjuvant radiotherapy has been given. Despite the large number of patients treated by combined therapy over the last 30 years, surprisingly there is a lack of hard data on which to establish a theory for an improved outcome. It is generally accepted that the risk of local relapses in the vagina is lowered when postoperative vaginal irradiation is applied. The question of the value of additional external irradiation in stage I endometrial cancer still is unsettled. Only two prospective studies led to the conclusion that only patients with poorly differentiated tumors and with deep infiltration of the myometrium might benefit from additional external radiotherapy. Therefore a simple score for these risk factors is proposed enabling assignment into patient groups of similar risk on the base of a point system due to individual prognostic factors. With a score of one to two points prognosis is very good and adjuvant irradiation seems not to be necessary. With three to four points local vaginal irradiation is recommended, with five and more points additionally external beam irradiation to the pelvis should be given. This is necessary in more than the half of the operated cases of endometrial carcinoma. The indication for such a treatment has become more individual and "high risk" cases are treated more intensively, but "low risk" cases have to be excepted from unnecessary adjuvant therapy. In order to judge an individual case of endometrial cancer histopathologic prognosticators have to be considered. Typical adenocarcinomas have a five-year survival of more than 80%, but unfavourable subtypes (adenosquamous, clear-cell, serous-papillary carcinomas) of only 40%, respectively. Tumor grading and depth of myometrial invasion are of high importance for individual prognosis. The new histopathologic staging system of FIGO (1988) takes these items into account. Only patients with severe internal diseases should be treated with radiation therapy alone. Although radiation therapy alone can cure endometrial cancer (five-year-survival approximately 60%), the survival figures are poorer than for the operation (five-year survival 80%, respectively). It should be outlined that in inoperable cases radiotherapy is the best form of treatment.     

Genetic counselling following paternal therapeutic irradiation

We discuss a patient who received adjuvant radiotherapy for stage I seminoma. He was advised to avoid conception for 6 months following treatment. However, his partner became pregnant only shortly after he completed his radiotherapy (i.e. with sperm that had been irradiated). We estimated the dose received by the remaining testis as 30 cGy. Here, we review the information available to advise patients on the risks to the fetus from paternal preconception irradiation. For the population, a doubling dose for hereditary effects of 1 Gy has recently been reaffirmed (United Nations Scientific Committee on the Effects of Atomic Radiation 2001). However, a range of animal studies suggest conception with postmeiotic sperm carries a greater risk of genetic damage than conception with sperm derived from irradiated stem cells. We have attempted to quantify the risks in this particular case. Lead shielding of the testes may reduce radiation received from the primary beam, but internal scatter still produces a risk. In male patients who are potentially fertile, the best advice remains to delay conception after radiotherapy for as long as 6 months. Our case illustrates the need to reinforce such advice.     

Risk of Second Malignancies after Prostate Irradiation?

PURPOSE: Several recent SEER- (Surveillance, Epidemiology and End Results-) analyses gave rise to a highly controversial discussion in how far radiotherapy for prostate cancer is associated with an increased risk of secondary neoplasms. MATERIAL AND METHODS: In order to enable a rational discussion, the available literature was reviewed covering all publications from the mid 80s to January 2007. RESULTS: The reported numbers of secondary cancer (bladder, rectum, lung cancer and sarcoma) after irradiation were found to be increased in some publications. However, after age adjustment and correction for follow-up duration no clear increase was detectable. DISCUSSION: Up to now, all available data are highly heterogeneous. Thus, a low risk for secondary cancer cannot be ruled out completely. Nevertheless, it seems very unlikely that there is a relevant risk for secondary cancer since the largest of the published series did not document an increased risk for any secondary cancer. CONCLUSION: Only very large prospective studies which are designed to minimize the influence of possible confounders will be able to address the real risk of prostate irradiation-related cancer induction. The available data are clearly not valid and helpful for guiding any treatment decision.     

Estimation of lifetime attributable risks (LARs) of cancer associated with abdominopelvic radiotherapy treatment planning computed tomography (CT) simulations

Purpose: The present study attempts to calculate organ-absorbed and effective doses for cancer patients to estimate the possible cancer induction and cancer mortality risks resulting from 64-slice abdominopelvic computed tomography (CT) simulations for radiotherapy treatment planning (RTTP).

Material and methods: A group of 70 patients, who underwent 64-slice abdominopelvic CT scan for RTTP, voluntarily participated in the present study. To calculate organ and effective doses in a standard phantom of 70?kg, the collected dosimetric parameters were used with the ImPACT CT Patient Dosimetry Calculator. Patient-specific organ dose and effective dose were calculated by applying related correction factors. For the estimation of lifetime attributable risks (LARs) of cancer incidence and cancer-related mortality, doses in radiosensitive organs were converted to risks based on the data published in Biological Effects of Ionizing Radiation VII (BEIR VII).

Results: The mean?±?standard deviation (SD) of the effective dose for males and females were 13.87?±?2.37 mSv (range: 9.25–18.82 mSv) and 13.04?±?3.42 mSv (range: 6.99–18.37 mSv), respectively. The mean?±?SD of LAR of cancer incidence was 35.34?±?13.82 cases in males and 34.49?±?9.63 cases in females per 100,000 persons. The LAR of cancer mortality had the mean?±?SD value of 15.38?±?4.25 and 16.72?±?3.87 cases per 100,000 persons in males and females respectively.

Conclusion: Increase in the LAR of cancer occurrence and mortality due to abdominopelvic treatment planning CT simulation is noticeable and should be considered.     

Efficacy of dose escalation on TCP,recurrence and second cancer risks: a mathematical study

Objective:

We investigated the effects of conventional and hypofractionation protocols by modelling tumour control probability (TCP) and tumour recurrence time, and examined their impact on second cancer risks. The main objectives of this study include the following: (a) incorporate tumour recurrence time and second cancer risks into the TCP framework and analyse the effects of variable doses and (b) investigate an efficient protocol to reduce the risk of a secondary malignancy while maximizing disease-free survival and tumour control.

Methods:

A generalized mathematical formalism was developed that incorporated recurrence and second cancer risk models into the TCP dynamics.

Results:

Our results suggest that TCP and relapse time are almost identical for conventional and hypofractionated regimens; however, second cancer risks resulting from hypofractionation were reduced by 22% when compared with the second cancer risk associated with a conventional protocol. The hypofractionated regimen appears to be sensitive to dose escalation and the corresponding impact on tumour recurrence time and reduction in second cancer risks. The reduction in second cancer risks is approximately 20% when the dose is increased from 60 to 72 Gy in a hypofractionated protocol.

Conclusion:

Our results suggest that hypofractionation may be a more efficient regimen in the context of TCP, relapse time and second cancer risks. Overall, our study demonstrates the importance of including a second cancer risk model in designing an efficient radiation regimen.

Advances in knowledge:

The impact of various fractionation protocols on TCP and relapse in conjunction with second cancer risks is an important clinical question that is as yet unexploredClinically, it is observed that over half of all cancer patients undergo radiotherapy over the course of their treatment, either as a primary treatment modality or in an adjuvant or a neoadjuvant context. In current radiotherapy treatments, tumours are often irradiated with a heterogeneous dose distribution throughout the treatment volume. The probability that all cancerous cells are removed from the system immediately post treatment is known as tumour control probability (TCP).¹ The design and complexity of any treatment regimen in terms of improving therapeutic efficacy can be deduced (to some extent) from TCP values. Although a given heterogeneous dose distribution to the target volume locally controls the disease to a large extent (for a given radiation regimen), there are still shortcomings associated with the currently used radiation protocol. Of these, side effects are of great importance and can be classified based on the time to clinical presentation, with shorter-acting side effects arising from irritation of the skin or mucosa, or irradiation of tissues with sensitive adjacent structures. Late toxicities of radiation are known to manifest after a period of 10–15 years, and one of the major late toxicities is the appearance of a secondary malignancy. Moreover, owing to the gains made in cancer care and patient management, there has been a marked increase in the number of survivors of childhood cancers, or cancers at young ages, and these patients are therefore at increased risk for the delayed consequences of radiotherapy. Several clinical studies have reported tumour recurrence or relapse within a span of 5 years² and late toxicities in the form of secondary malignancies within 5–20 years^3–7 post irradiation. These clinical investigations have been carried out on several types of tumours across a variety of treatment regimens and have also indicated that tumour relapse is a leading cause of death along with radiation-induced second cancers.Several pre-treatment factors such as age at diagnosis, gender and stage of tumour may impact tumour relapse. Relapse probability and time may vary depending on the treatment modality. In our work, for simplicity, we consider the effect of single treatment modality, namely, radiotherapy on TCP along with analysis of time to relapse. Also, escalating the dose to the target volume will eliminate tumours^8–10 and may have an impact on the relapse time (either very long ideally or an increase in the recurrence time) depending on the radiation protocol. Moreover, dose escalation may elevate radiation-induced second cancer risks, but the degree to which it increases these risks remains to be determined.Clinically, it is widely believed that radiotherapy-induced cancer risks are owing to scattered doses and radiation leakage from the linear accelerator, as well as irradiation to the healthy tissues adjacent to the target volume. Several systematic clinical investigations have indicated that radiation therapy is a significant causative factor of second cancers. Numerous case–control and cohort–control studies have also suggested that there is an increased risk of secondary malignancies with young cancer survivors, for example, survivors of Hodgkin''s lymphoma (HL).^11–13 Therefore, it is of paramount importance to reduce radiation doses to healthy tissue, while at the same time improve dose conformity to the target volume. The critical organs that get irradiated can be located in-beam (known as serial organs) or out-beam (also known as parallel organs) to the radiation beams and occasionally also receive the same integral dose. It is therefore critical to minimize radiation dosage and schedule radiation doses such that there is minimal impairment of delivery to the critical organs around the primary treatment volume, a probable increase in the relapse time (or with a long relapse time ideally), but also with the goal of reducing the risk of a secondary malignancy. It should be noted that in this work, we concentrated on modelling late complications due to radiotherapy, that is, radiation-induced second cancers only and not on normal tissue complication probability (NTCP) modelling.The main objective of this work is to develop a generalized mathematical framework that can incorporate relapse dynamics into a TCP model in conjunction with a second cancer risk model. This was carried out to understand the effects of dose escalation on recurrence and second cancer risks. Our minimal model also proposes an efficient paradigm in terms of regimen that may provide insights to be confirmed by future clinical investigations.     

Effects of low level radiation-what's new?

A comprehensive review of the effects of exposure to low levels of ionizing radiation, BEIR VII-Phase 2: Health Risks From Exposure to Low Levels of Ionizing Radiation, was published in 2006. The BEIR (Biological Effects of Ionizing Radiation) reports are a series of publications by the National Academy of Sciences. The last BEIR report on the effects of low level radiation, BEIR V, was published in 1990. To update the risk estimates for exposure to low levels of ionizing radiation, the BEIR committee reviewed recent epidemiologic studies of the atomic bomb survivors, as well as recent studies of populations exposed to radiation from diagnostic and therapeutic medical studies, from occupational exposures and from exposure due to releases of radioactive materials into the environment. Additional increasingly sophisticated epidemiologic studies continue to be published. BEIR VII reconfirmed that the linear no threshold model is the most practical model to estimate radiation risks, especially for radiation protection purposes. The updated risk estimates have not changed significantly from the BEIR V estimates, but the confidence intervals have narrowed as the result of the availability of additional data. The effects of low doses of radiation should be of particular interest to medical professionals because radiation exposure from diagnostic medical studies is, by far, the largest source of radiation exposure from human activity. One recommendation of the BEIR VII report is to perform epidemiologic studies of patients, especially children, who have been exposed to radiation as part of their care. A large, sophisticated epidemiologic study will likely be able to detect an increase in cancer risk. The purpose of this article is to highlight the contents of this important publication with particular emphasis on what is new.     

Left-sided breast cancer and risks of secondary lung cancer and ischemic heart disease

Purpose

Modern breast cancer radiotherapy techniques, such as respiratory-gated radiotherapy in deep-inspiration breath-hold (DIBH) or volumetric-modulated arc radiotherapy (VMAT) have been shown to reduce the high dose exposure of the heart in left-sided breast cancer. The aim of the present study was to comparatively estimate the excess relative and absolute risks of radiation-induced secondary lung cancer and ischemic heart disease for different modern radiotherapy techniques.

Methods

Four different treatment plans were generated for ten computed tomography data sets of patients with left-sided breast cancer, using either three-dimensional conformal radiotherapy (3D-CRT) or VMAT, in free-breathing (FB) or DIBH. Dose–volume histograms were used for organ equivalent dose (OED) calculations using linear, linear–exponential, and plateau models for the lung. A linear model was applied to estimate the long-term risk of ischemic heart disease as motivated by epidemiologic data. Excess relative risk (ERR) and 10-year excess absolute risk (EAR) for radiation-induced secondary lung cancer and ischemic heart disease were estimated for different representative baseline risks.

Results

The DIBH maneuver resulted in a significant reduction of the ERR and estimated 10-year excess absolute risk for major coronary events compared to FB in 3D-CRT plans (p = 0.04). In VMAT plans, the mean predicted risk reduction through DIBH was less pronounced and not statistically significant (p = 0.44). The risk of radiation-induced secondary lung cancer was mainly influenced by the radiotherapy technique, with no beneficial effect through DIBH. VMAT plans correlated with an increase in 10-year EAR for radiation-induced lung cancer as compared to 3D-CRT plans (DIBH p = 0.007; FB p = 0.005, respectively). However, the EARs were affected more strongly by nonradiation-associated risk factors, such as smoking, as compared to the choice of treatment technique.

Conclusion

The results indicate that 3D-CRT plans in DIBH pose the lowest risk for both major coronary events and secondary lung cancer.

     

Radiation risks potentially associated with low-dose CT screening of adult smokers for lung cancer

PURPOSE: To estimate the radiation-related lung cancer risks associated with annual low-dose computed tomographic (CT) lung screening in adult smokers and former smokers, and to establish a baseline risk that the potential benefits of such screening should exceed. MATERIALS AND METHODS: The estimated lung radiation dose from low-dose CT lung examinations corresponds to a dose range for which there is direct evidence of increased cancer risk in atomic bomb survivors. Estimated dose-, sex-, and smoking status-dependent excess relative risks of lung cancer were derived from cancer incidence data for atomic bomb survivors and used to calculate the excess lung cancer risks associated with a single CT lung examination at a given age in a U.S. population. From these, the overall radiation risks associated with annual CT lung screening were estimated. RESULTS: A 50-year-old female smoker who undergoes annual CT lung screening until age 75 would incur an estimated radiation-related lung cancer risk of 0.85%, in addition to her otherwise expected lung cancer risk of approximately 17%. The radiation-associated cancer risk to other organs would be far lower. If 50% of all current and former smokers in the U.S. population aged 50-75 years received annual CT screening, the estimated number of lung cancers associated with radiation from screening would be approximately 36,000, a 1.8% (95% credibility interval: 0.5%, 5.5%) increase over the otherwise expected number. CONCLUSION: Given the estimated upper limit of a 5.5% increase in lung cancer risk attributable to annual CT-related radiation exposure, a mortality benefit of considerably more than 5% may be necessary to outweigh the potential radiation risks.     

Radiation risks of medical imaging: separating fact from fantasy

During the past few years, several articles have appeared in the scientific literature that predict thousands of cancers and cancer deaths per year in the U.S. population caused by medical imaging procedures that use ionizing radiation. These predictions are computed by multiplying small and highly speculative risk factors by large populations of patients to yield impressive numbers of "cancer victims." The risk factors are acquired from the Biological Effects of Ionizing Radiation (BEIR) VII report without attention to the caveats about their use presented in the BEIR VII report. The principal data source for the risk factors is the ongoing study of survivors of the Japanese atomic explosions, a population of individuals that is greatly different from patients undergoing imaging procedures. For the purpose of risk estimation, doses to patients are converted to effective doses, even though the International Commission on Radiological Protection warns against the use of effective dose for epidemiologic studies or for estimation of individual risks. To extrapolate cancer incidence to doses of a few millisieverts from data greater than 100 mSv, a linear no-threshold model is used, even though substantial radiobiological and human exposure data imply that it is not an appropriate model. The predictions of cancers and cancer deaths are sensationalized in electronic and print public media, resulting in anxiety and fear about medical imaging among patients and parents. Not infrequently, patients are anxious about a scheduled imaging procedure because of articles they have read in the public media. In some cases, medical imaging examinations may be delayed or deferred as a consequence, resulting in a much greater risk to patients than that associated with imaging examinations. ? RSNA, 2012.     

Interspecies scaling of risk for radiation-induced bone cancer

The induction of bone cancer in mice, dogs and humans, due to protracted alpha-irradiation from skeletal burdens of radium, was found to be represented by a single dose-rate/time/response function, when time was normalized with respect to species natural life-span. In the absence of other causes of death, the median time to death from bone cancer after 226Ra intake is given by tm* = 790-d*-0.29, based on the dog data, with -d* the time-weighted average absorbed dose rate in cGy/mLSF to skeleton and where time is measured as milli-life-span-fraction. On the basis of life-span scaling of the time dimension, data on cancer induction from studies with laboratory animals can be scaled to estimate human risks in a three-step process involving a three-dimensional analysis. The overall cancer risk distribution is shown to be a mountain-like surface rising from a Euclidean plane formed by the dose rate and survival time co-ordinates. At lower dose rates the time required for cancer induction may exceed the natural life-span yielding a quasi-threshold for cancer risk. For intakes of 226Ra in young adults this quasi-threshold is predicted to occur at a cumulative life-time alpha-radiation dose to the skeleton of about 1 Gy.     

Blood Hemoglobin Level and Treatment Outcome of Early Breast Cancer

BACKGROUND AND PURPOSE: To determine whether the blood hemoglobin concentration correlates with the prognosis of patients with early breast cancer and, if so, whether this is restricted to treatment modality. PATIENTS AND METHODS: Data were collected retrospectively from patients with early breast cancer (T1,2 N0-2 M0) who underwent either breast-conserving surgery followed by adjuvant radiotherapy (BCS-RT; n=96) or a modified radical mastectomy (MRM; n=194). The effect of preoperative blood hemoglobin level, nodal status, histological grading and hormone receptor status on disease-free survival was determined for both treatment modalities using a Cox regression model and visualized by Kaplan-Meier plots. RESULTS: The blood hemoglobin concentration significantly correlated with disease-free survival of patients receiving BCS-RT (relative risk [RR]: 0.67 per g/dl; p=0.007). This was independent of other known risk factors for breast cancer patients, as determined by multivariate analysis. By contrast, the blood hemoglobin level had no prognostic significance when patients were treated with MRM. CONCLUSION: Blood hemoglobin concentration seems to affect the prognosis of patients with early breast cancer when a treatment schedule that includes radiotherapy is applied. Reduced radiosensitivity due to diminished tumor oxygenation may be the underlying cause. Confirmative trials and studies intended to elucidate the underlying mechanism are warranted.     

Cancer incidence and mortality among flight personnel: a meta-analysis

BACKGROUND: Increased cancer risk among flight personnel have previously been noted, including breast cancer among flight attendants and acute myeloid leukemia among pilots. Hypothesis: Exposure to cosmic radiation and other physical or chemical agents may pose health risks for flight personnel. METHODS: We performed an exhaustive search for published and unpublished cohort studies of flight personnel from 1986-98. We combined relative risks (RR) for selected causes from four mortality and/or incidence studies of pilots and two incidence studies of flight attendants, using standard meta-analytic methods. Heterogeneity among the combined studies was explored and adjustments were made for possible confounding by socioeconomic status (SES), where indicated, using correction factors from published studies. RESULTS: SES-adjusted combined RRs were elevated (>1.2) among male pilots for mortality from melanoma 11.97 (95%, CI: 1.02-3.82)] and brain cancer [1.49 (0.89-2.20)], and for cancer incidence of the prostate [1.65 (1.19-2.29)] and the brain [1.74 (0.87-3.30)]. Among female flight attendants, increases were seen for incidence of all cancers [1.29 (0.98-1.70)], melanoma [11.54 (0.83-2.87)], and breast cancer [1.35 (1.00-1.83)]. CONCLUSIONS: Flight personnel appear to be at increased risk for several types of cancer. Both occupational exposures and well-established non-occupational risk factors may contribute to this increased risk. To better control for confounding factors and to identify exposures potentially amenable to preventive measures, future studies should compare risks within cohorts by flight routes, work history, and exposure to cosmic and UV radiation, electromagnetic fields, and chemical substances.     

Lymph node pathology. Benign proliferative, lymphoma, and metastatic disease

The evaluation of cervical lymph nodes is one of the main indications for performing CT and MR imaging of the neck. Imaging may be done for evaluation of an unknown neck mass, but more commonly the neck is imaged to evaluate potential metastasis from a known mucosal malignancy. CT and MR imaging characteristics of both malignant and nonmalignant nodal diseases are reviewed and the differential diagnosis of nodal pathologies for specific imaging findings are discussed. A recently proposed imaging-based nodal classification for metastatic nodal diseases from head and neck cancer is also described.     

Radiogenic risks from hysterosalpingography

The aim of this study was to determine ovarian dose, effective dose and associated radiogenic risks from hysterosalpingography (HSG), and to provide data for the estimation of radiogenic risks related to HSG studies performed in any laboratory. The fluoroscopy time, number of radiographs taken and entrance surface dose were measured in a series of 78 consecutive patients undergoing HSG as part of their infertility work-up. Organ-dose values per radiograph and per minute of fluoroscopy were separately determined using an anthropomorphic phantom and thermoluminescence dosimetry. The radiogenic risk for deleterious effects on a possible future embryo and the radiogenic risk for cancer induction on the patient undergoing HSG were estimated. The average HSG procedure in our laboratory involves a mean fluoroscopic time of 0.3 min and a mean number of radiographs of 3.2. The dose to female gonads from an average HSG procedure was 2.7 mGy and the patient effective dose was 1.2 mSv. The risk for radiogenic anomalies in a future embryo of the woman undergoing an average HSG procedure and the risk for radiogenic fatal cancer induction in the exposed woman were estimated to be less than 10^–3 of the correspondent nominal risks. Radiation risks from a typical HSG are low, but they may be elevated if fluoroscopic and/or radiographic exposures are prolonged for any reason. Present data allow the estimation of radiogenic risks associated with HSG procedures performed in other laboratories with use of different equipment, screening time and number of radiographs taken.