Threshold dose–response in radiation carcinogenesis: an approach from chronic β-irradiation experiments and a review of non-tumour doses

Purpose : To discuss the threshold dose problem in radiation carcinogenesis after a review of the present author's experimental data on mouse tumour induction by chronic β -irradiation and other relevant data. Conclusions : A threshold dose-response in radiation carcinogenesis appears in certain tissues and under certain conditions. The optimum condition for demonstrating an apparent threshold is with partial-body chronic or repeated radiation rather than with acute whole-body radiation. Its possible mechanism is host tolerance, involving DNA repair, apoptosis and an immune response activated by low radiation doses. This tolerance level was examined by a survey in the literature of non-tumour-inducing doses, D nt, the highest dose at which no significant increase of tumours was observed above the control level.     

An MRI-based dose–response analysis of urinary sphincter dose and urinary morbidity after brachytherapy for prostate cancer in a phase II prospective trial

PurposeTo compare dose–volume histogram variables for the internal and external urinary sphincters (IUS/EUS) with urinary quality of life after prostate brachytherapy.Methods and MaterialsSubjects were 42 consecutive men from a prospective study of brachytherapy as monotherapy with ¹²⁵I for intermediate-risk localized prostate cancer. No patient received hormonal therapy. Preplanning constraints included prostate V₁₀₀ higher than 95%, V₁₅₀ lower than 60%, and V₂₀₀ lower than 20% and rectal R₁₀₀ less than 1 cm³. Patients completed the Expanded Prostate Cancer Index Composite quality-of-life questionnaire before and at 1, 4, 8, and 12 months after implantation, and urinary domain scores were analyzed. All structures including the IUS and EUS were contoured on T2-weighted MRI at day 30, and doses received were calculated from identification of seeds on CT. Spearman's (nonparametric) rank correlation coefficient (ρ) was used for statistical analyses.ResultsOverall urinary morbidity was worst at 1 month after the implant. Urinary function declined when the IUS V₂₈₅ was 0.4% (ρ = ?0.32, p = 0.04); bother worsened when the IUS V₃₅ was 99% (ρ = ?0.31, p = 0.05) or the EUS V₂₄₀ was 63% (ρ = ?0.31, p = 0.05); irritation increased when the IUS V₃₅ was 95% (ρ = ?0.37, p = 0.02) and the EUS V₂₆₅ was 24% (ρ = ?0.32, p = 0.04); and urgency worsened when the IUS V₃₅ was 99.5% (ρ = ?0.38, p = 0.02). Incontinence did not correlate with EUS or IUS dose.ConclusionsDoses to the IUS and EUS on MRI/CT predicted worse urinary function, with greater bother, irritative symptoms, and urgency. Incorporating MRI-based dose–volume histogram analysis into the treatment planning process may reduce acute urinary morbidity after brachytherapy.     

Henry S. Kaplan Distinguished Scientist Award 2003The crooked shall be made straight; dose–response relationships for carcinogenesis

Estimates of radiation‐induced malignancies come principally from the atomic (A)‐bomb survivors and show an excess incidence of carcinomas that is linearly related to dose from about 5?cGy to 2.5?Gy. Above and below this dose range there is considerable uncertainty about the shape of the dose–response relationship. Both the International Commission of Radiation Protected (ICRP) and the National Council of Radiation Protection (NCRP) suggest that cancer risks at doses lower than those at which direct epidemiological observations are possible should be obtained by a linear extrapolation from higher doses. The demonstrated bystander effect for irradiation exaggerates the consequences of small doses of radiation and implies that a linear extrapolation from high doses would underestimate low dose risks. It is possible to make estimates of the cancer risk of diagnostic radiological procedures. Helical computed tomography in children is of particular interest since it is rapidly increasing in use and the doses involved are close to the lower limit of significance in the A‐bomb survivors. For example, an abdominal computed tomographic scan in a 1‐year‐old child can be estimated to result in a lifetime cancer risk of about 1:1000. In the context of radiotherapy, some normal tissues receive 70?Gy, while a larger volume receives a lower dose, but still far higher than the range for which data are available from the A‐bomb survivors. Data are available for the risk of radiation‐induced malignancies for patients who received radiotherapy, e.g. for prostate or cervical cancer. New technologies such as intensity modulated radiation therapy could result in a doubling of radiation‐induced second cancers since the technique involves a larger total‐body dose due to leakage radiation and the dose distribution obtained involves a larger volume of normal tissue exposed to lower radiation doses.     

The mean absolute dose deviation–A common metric for the evaluation of dose-volume histograms in radiation therapy

Radiation therapy needs to balance between delivering a high dose to targets and the lowest possible dose to the organs at risk. Dose-volume histograms (DVHs) summarize the distribution of radiation doses in the irradiated structures. The interpretation can however be a challenge when the number of structures is high. We propose the use of a simple summary metric. We define the mean absolute dose deviation (MADD) as the average of absolute differences between a DVH and a reference dose. The properties are evaluated through numerical analysis. Calculus trivially shows the identity of the MADD and the area between curves, between DVH and reference dose. Computation of the MADD is the same regardless of structures' designation, whether organ at risk or target, on the same dose scale. Basic calculus properties open the perspective of applying the MADD to the evaluation of treatment plans.     

Intensity-modulated radiation therapy for pancreatic and prostate cancer using pulsed low–dose rate delivery techniques

Reirradiation of patients who were previously treated with radiotherapy is vastly challenging. Pulsed low–dose rate (PLDR) external beam radiotherapy has the potential to reduce normal tissue toxicities while providing significant tumor control for recurrent cancers. This work investigates treatment planning techniques for intensity-modulated radiation therapy (IMRT)-based PLDR treatment of various sites, including cases with pancreatic and prostate cancer. A total of 20 patients with clinical recurrence were selected for this study, including 10 cases with pancreatic cancer and 10 with prostate cancer. Large variations in the target volume were included to test the ability of IMRT using the existing treatment planning system and optimization algorithm to deliver uniform doses in individual gantry angles/fields for PLDR treatments. Treatment plans were generated with 10 gantry angles using the step-and-shoot IMRT delivery technique, which can be delivered in 3-minute intervals to achieve an effective low dose rate of 6.7 cGy/min. Instead of dose constraints on critical structures, ring structures were mainly used in PLDR-IMRT optimization. In this study, the PLDR-IMRT plans were compared with the PLDR-3-dimensional conformal radiation therapy (3DCRT) plans and the PLDR-RapidArc plans. For the 10 cases with pancreatic cancer that were investigated, the mean planning target volume (PTV) dose for each gantry angle in the PLDR-IMRT plans ranged from 17.6 to 22.4 cGy. The maximum doses ranged between 22.9 and 34.8 cGy. The minimum doses ranged from 8.2 to 17.5 cGy. For the 10 cases with prostate cancer that were investigated, the mean PTV doses for individual gantry angles ranged from 18.8 to 22.6 cGy. The maximum doses per gantry angle were between 24.0 and 34.7 cGy. The minimum doses per gantry angle ranged from 4.4 to 17.4 cGy. A significant reduction in the organ at risk (OAR) dose was observed with the PLDR-IMRT plan when compared with that using the PLDR-3DCRT plan. The volume receiving an 18-Gy (V₁₈) dose for the left and right kidneys was reduced by 10.6% and 12.5%, respectively, for the pancreatic plans. The volume receiving a 45-Gy (V₄₅) dose for the small bowel decreased from 65.3% to 45.5%. For the cases with prostate cancer, the volume receiving a 40-Gy (V₄₀) dose for the bladder and the rectum was reduced significantly by 25.1% and 51.2%, respectively. When compared with the RapidArc technique, the volume receiving a 30-Gy (V₃₀) dose for the left and the right kidneys was lower in the IMRT plans. For most OARs, no significant differences were observed between the PLDR-IMRT and the PLDR-RapidArc plans. These results clearly demonstrated that the PLDR-IMRT plan was suitable for PLDR pancreatic and prostate cancer treatments in terms of the overall plan quality. A significant reduction in the OAR dose was achieved with the PLDR-IMRT plan when compared with that using the PLDR-3DCRT plan. For most OARs, no significant differences were observed between the PLDR-IMRT and the PLDR-RapidArc plans. When compared with the PLDR-3DCRT plan, the PLDR-IMRT plan could provide superior target coverage and normal tissue sparing for PLDR reirradiation of recurrent pancreatic and prostate cancers. The PLDR-IMRT plan is an effective treatment choice for recurrent cancers in most cancer centers.     

Dose–response relationship of locally applied nimodipine in an ex vivo model of cerebral vasospasm

Introduction

Cerebral vasospasm is a severe complication of subarachnoid hemorrhage (SAH). The calcium channel inhibitor nimodipine has been used for treatment of cerebral vasospasm. No evidence-based recommendations for local nimodipine administration at the site of vasospasm exist. The purpose of this study was to quantify nimodipine's local vasodilatory effect in an ex vivo model of SAH-induced vasospasm.

Methods

SAH-induced vasospasm was modeled by contracting isolated segments of rat superior cerebellar arteries with a combination of serotonin and a synthetic analog of prostaglandin A₂. A pressure myograph system was used to determine vessel reactivity of spastic as well as non-spastic arteries.

Results

Compared to the initial vessel diameter, a combination of serotonin and prostaglandin induced considerable vasospasm (55?±?2.5 % contraction; n?=?12; p?<?0.001). Locally applied nimodipine dilated the arteries in a concentration-dependent manner starting at concentrations as low as 1 nM (n?=?12; p?<?0.05). Concentrations higher than 100 nM did not relevantly increase the vasodilatory effect. Nimodipine's vasodilatory effect was smaller in spastic than in non-spastic vessels (n?=?12; p?<?0.05), which we assume to be due to structural changes in the vessel wall.

Conclusion

The described ex vivo model allows to investigate the dose-dependent efficacy of spasmolytic drugs prior to in vivo experiments. Low concentrations of locally applied nimodipine have a strong vasodilatory effect, which is of relevance when considering the local application of nimodipine in cerebral vasospasm.     

Analysis of dose–volume parameters predicting radiation pneumonitis in patients with esophageal cancer treated with 3D-conformal radiation therapy or IMRT

Purpose  

Multimodality therapy for esophageal cancer can cause various kinds of treatment-related sequelae, especially pulmonary toxicities. This prospective study aims to investigate the clinical and dosimetric parameters predicting lung injury in patients undergoing radiation therapy for esophageal cancer.     

The potential use of ultra-low radiation dose images in digital mammography—a clinical proof-of-concept study in craniocaudal views

Objective:

To estimate the potential of low-dose images in digital mammography by analysing the effect of substantial dose reduction in craniocaudal (CC) views on clinical performance.

Methods:

At routine mammography, additional CC views were obtained with about 10% of the standard dose. Five radiologists retrospectively read the standard [mediolateral oblique (MLO) + CC] and combination low-dose mammograms (standard MLO + low-dose CC). If present, lesion type, conspicuity and suggested work-up were recorded. Final diagnoses were made by histology or follow up. A t-test or χ² test was used to compare results.

Results:

421 cases were included, presenting 5 malignancies, 66 benign lesions and multiple non-specific radiologic features. Using MLO with low-dose CC, all lesions were detected by at least one reader, but altogether less often than with standard mammography (sensitivity, 73.9% vs 81.5%). Missed lesions concerned all types. Lesions detected with both protocols were described similarly (p = 0.084) with comparable work-up recommendations (p = 0.658).

Conclusion:

Mammography with ultra-low-dose CC images particularly influences detection. While sensitivity decreased, specificity was unaffected. In this proof-of-concept study a lower limit was to be determined that is not intended nor applicable for clinical practice. This should facilitate further research in optimization of a low-dose approach, which has potential in a relatively young and largely asymptomatic population.

Advances in knowledge:

Tungsten/silver-acquired mammography images might facilitate substantial dose reduction. Ultra-low-dose CC images reduce sensitivity, but not specificity. Low-dose images have potential in a largely young and asymptomatic population; a baseline is set for further research in optimization of a low-dose approach.Mammography is the most widely used modality in breast imaging. An increasing number of females throughout the world undergo mammography frequently, either in the diagnostic or screening setting. With the growing incidence of breast cancer, and the decreasing age of onset, the demand for mammography, particularly in the younger population, is still rising. Also, a considerable number of high-risk females are identified and advised to have annual mammograms, as part of a multimodality approach, preceding regular screening. With this development, in a relatively young and largely asymptomatic population, every opportunity to lower radiation dose in mammography should be investigated.Standard mammography is gradually being extended to tomosynthesis. When used with synthetic two-dimensional (2D) mammography, the mean radiation dose might be comparable to standard mammography,¹ but lower doses are not to be expected. Moreover, implementation of a new technology, in screening and diagnostic imaging practices, takes both time and money. Therefore, in low-income countries and countries in transition, 2D mammography will continue to play a significant role for many years. Hence, ongoing research in radiation protection in this field is of undiminished importance.Since digitization of radiology, low-dose imaging is receiving increased attention. In digital mammography, radiation dose can be easily adapted. Owing to image processing, the unfavourable effect of dose reduction on image quality can be compensated for to a certain level. This has the potential to decrease dose level with different X-ray spectra without impairing lesion detectability. Mammography studies on dosimetry suggested that the radiologists'' performance in detecting abnormalities with standard radiation dose images and markedly dose-reduced images (33–55%) does not differ significantly.^2–4These results motivated us to perform a small-scale study on breast specimen with the objective to determine a threshold dose level for single views. The results of this experimental study show that application of a tungsten/silver (W/Ag) beam quality for low-dose imaging permits a substantial reduction of the average glandular dose (AGD), possibly up to 90%, in single digital mammographic images, irrespective of breast thickness, particularly in combination with post-process noise reduction.⁵In the present study, the potential of these low-dose images in a clinical setting was assessed. Physical image quality is not synonymous to perceived image quality or the clinical value of an image. The current information on this aspect of mammography is mainly based on phantom studies. As degradation of clinical performance caused by dose reduction is unacceptable, mammography systems use radiation dose levels that are set on the safe side. However, it is unclear at what point dose reduction starts to influence clinical performance negatively. Our study was set up to find information on this cross-over point, where dose reduction meets performance degradation. To investigate this, we set up a clinical observer study, evaluating the potential of low-dose imaging in digital mammography by analysing the effect of substantial dose reduction in craniocaudal (CC) views on clinical performance. We considered the CC view to be the most suitable candidate for this trial. As, in general, the CC view is most valuable for differentiation, for example, to distinguish suspect lesions from summation artefacts that concern as many as 83% of the one-view-only lesions,⁶ but much less so for detection, particularly when microcalcifications are concerned.⁷To determine the lower limit in dose reduction, we obtained additional images with an extremely low radiation dose. These images are meant to be compared with regular images and are not intended to set a baseline for clinical practice. Instead, this proof-of-concept study is intended to pave the way for further research. With data on both ends of the spectrum, intermediate dose levels can be simulated, generating a potential clinical alternative for the current protocols under specific circumstances. With this, we aim to do evidence-based and justified assessments of pragmatic dose reduction in mammography in the future. To our knowledge, this is the first clinical study dedicated to dose reduction in digital mammography.     

Computed tomography scout views vs. conventional radiography in body-packers – Delineation of body-packs and radiation dose in a porcine model

Objective

To compare abdominal computed tomography (CT) scout views with conventional radiography regarding radiation dose and delineation of drug packages in a porcine body-packer model.

Materials and methods

Nine samples of illicit drugs packed in ovoid plastic containers were consecutively placed in the rectum of a 121.5 kg pig cadaver. Antero-posterior and lateral scout views were obtained at 120 kVp and 80 mA, 150 mA and 200 mA, respectively, using a 64-row MDCT. Scout views were compared with conventional abdominal antero-posterior radiographs (77 kV and 106 ± 13 mAs). Visibility of three body pack characteristics (wrapping, content, shape) was rated independently by two radiologists and summarized to a delineation score ranging from 0 to 9 with a score ≥6 representing sufficient delineation. Mean delineation scores were calculated for each conventional radiography and single plane scout view separately and for a combined rating of antero-posterior and lateral scout views.

Results

Even the lowest single plane scout view delineation score (5.3 ± 2.0 for 80 mA lateral; 0.4 mSv; sensitivity = 44%) was significantly higher than for conventional radiographs (3.1 ± 2.5, p < 0.001; 2.4 ± 0.3 mSv; sensitivity = 11%). Combined reading of antero-posterior and lateral scout views 80 mA yielded sufficient delineation (6.2 ± 1.4; 0.8 mSv; sensitivity = 56%).

Conclusions

All CT scout views showed significantly better delineation ratings and sensitivity than conventional radiographs. Scout views in two planes at 80 mA provided a sufficient level of delineation and a sensitivity five times higher than conventional radiography at less than one third of the radiation dose. In case of diagnostic insecurity, CT can be performed without additional logistical effort.     

The cohesion–performance relationship in sport: a 10-year retrospective meta-analysis

The purposes of this meta-analysis were to: (a) examine the direction and magnitude of the cohesion–performance relationship in studies published between 2000 and 2010 and (b) explore moderators of this relationship. A total of 118 effect sizes were calculated. Results revealed a statistically significant (a) moderate relationship between overall cohesion and performance (r = 0.34, p < 0.01), (b) large relationship between task cohesion and performance (r = 0.45, p < 0.01), and (c) small relationship between social cohesion and performance (r = 0.11, p < 0.01). Gender, athletes’ skill level, sport type, and performance were found to be significant moderators of the cohesion–performance relationship. These results are interpreted in relation to previous research and theoretical frameworks on cohesion and performance in sports.     

Lack of effect of small high-dose volumes on the dose–response relationship for the development of fibrosis in distant parts of the ipsilateral lung in mini-pigs

Purpose : Multi-field radiation therapy for intrathoracic tumours results in a heterogeneous dose distribution in lung tissue. This study investigated whether irradiation of small lung volumes with high fibrogenic doses affects the dose–response relationship for development of fibrosis in distant parts of the ipsilateral lung of mini-pigs. Materials and methods : The whole right lung of 26 ’Mini-Lewe? pigs was irradiated with homogeneous doses of between 25 Gy and 40 Gy given in five equal fractions using opposing anterior–posterior portals and a linear accelerator. Another 32 animals were irradiated with a constant dose of 35 Gy to a small house-shaped high-dose field (base 3.0 cm, height 4 cm) located 3 cm caudolateral to the right hilus, while the surrounding right lung received either no irradiation or homogeneous doses of between 20 Gy and 30 Gy. The radiation fields were simulated and port films were obtained for each of the 10 fields in all pigs. Fibrosis was quantified 9 months after irradiation by determination of the hydroxyproline (HP) content of the 32 high-dose volumes and in the lung apex and the basolateral lung of all 58 pigs. Based on the reference value for the HP-ratio, i.e. the HP-concentration of the right lung over the left lung, obtained in 12 unirradiated control animals, the experimental results were converted into quantal data for probit analysis, a responder being an animal with an HP-ratio > 1.33. Results : A dose–response relationship for the HP-ratio was obtained in the different lung sites and irradiation groups. For a given dose level the mean HP-ratios and response rates did not differ systematically between the lung apex and the basolateral lung. Probit analysis of the pooled data produced ED 50 values of 21.8 Gy (95% CI 12–37) for irradiation without a high-dose volume and 25.9 Gy (24–28) for irradiation with a high-dose volume. These values are not significantly different. The results from both irradiation groups could be well fitted by a common dose–response curve with an ED 50 value of 26.1 Gy. Unexpectedly, the response rates in the high-dose volume increased with increasing dose to the surrounding right lung. Analysis of the port films provided an explanation for this finding: inaccuracies in daily field positioning. When this error was corrected for by use of the mean dose to the high-dose volume, a dose–response curve with an ED 50 of 25.2 Gy (22–29) was determined for the high-dose volume. Conclusions : The results of the study indicate that the irradiation of a small lung volume with high fibrogenic doses does not affect the dose–response relationship for development of fibrosis in distant parts of the ipsilateral lung.     

Magnetic resonance imaging response in patients treated with definitive radiation therapy for medically inoperable endometrial cancer—Does it predict treatment response?

PurposeMany patients with endometrial cancer cannot undergo surgery and instead receive definitive radiation therapy (RT). We investigate the correlation between MRI response to RT and clinical outcomes.Methods and MaterialsWomen with inoperable, clinical Stage I endometrial cancer were treated with definitive brachytherapy (BT) with/without pelvic RT (PRT). Patients underwent MRI with functional diffusion-weighted imaging before and after RT. A radiologist retrospectively classified cases as complete, partial, or indeterminate response (CR, PR, or IR, respectively) vs. disease progression. Local control was clinicopathologically defined.ResultsFrom 2007 to 2017, 50 women underwent definitive RT. Thirty-five (70%) received BT alone (median dose 37.5 Gy). For combined therapy, the median PRT and BT doses were 45 and 25 Gy, respectively. Median gross tumor volume and high-risk clinical target volume were 7.1 cc and 90.0 cc, respectively. Median followup among living patients was 20 months. All patients underwent post-RT MRI with T1/T2 sequencing at a median of 3.2 months after RT; 40 patients (80%) underwent functional diffusion-weighted imaging sequences. On initial post-RT MRI, CR was documented in 42 patients (84%), IR in 1 patient (2%), and PR in seven patients (14%). At median followup of 16.3 months, no CR patients had uterine failure. Among eight patients with initial PR/IR, all were found to be clinicopathologically no evidence of disease at the uterus on further evaluation.ConclusionsDefinitive RT with BT or BT + PRT is associated with high response rates on MRI. Overall, initial CR predicted for excellent outcome with no infield failure.     

Dose–effect response in image-guided adaptive brachytherapy for cervical cancer: A systematic review and meta-regression analysis

PurposeThis study aimed to integrate and update the dose–effect relationship between volumetric dose and local control for cervical cancer brachytherapy.Methods and MaterialsWe identified studies that reported high-risk clinical target volume (HR-CTV) D₉₀ and local control probability by searching PubMed, Web of Science, and the Cochrane Library databases through Oct 27, 2019. The regression analyses were performed using a probit model between HR-CTV D₉₀, D₁₀₀, intermediate-risk clinical target volume (IR-CTV) D₉₀, and dose to Point A vs. local control probability. Subgroup analyses were performed according to stratification: time of local control, income level of the country or region, stage of cancer, pathology, mean volume of HR-CTV, dose rate, image modality, concurrent chemoradiotherapy proportion, interstitial proportion, and mean overall treatment time.ResultsThirty-three studies encompassing 2893 patients were included. The probit model showed a significant relationship between the HR-CTV D₉₀ value and the local control probability, p < 0.0001. The D₉₀ corresponding to a probability of 90% local control was 83.7 Gy_EQD2,10 (80.6–87.8 Gy_EQD2,10). Of the 33 studies included in our analysis, eight studies, including 1172 patients, reported the IR-CTV D₉₀ value, ranging from 59.1 Gy_EQD2,10 to 72.3 Gy_EQD2,10. The probit model also showed a significant relationship between the IR-CTV D₉₀ value and the local control probability, p = 0.0464. The 60 Gy_EQD2,10 for IR-CTV D₉₀ corresponded to an 86.1% local control probability (82.0%–89.8%).ConclusionsA significant dependence of local control on HR-CTV D₉₀ and IR-CTV D₉₀ was found. A tumor control probability of >90% can be expected at doses >84 Gy_EQD2,10 and 69 Gy_EQD2,10, respectively, based on an updated meta-regression analysis.     

Accumulated dose to the rectum,measured using dose–volume histograms and dose-surface maps,is different from planned dose in all patients treated with radiotherapy for prostate cancer

Objective:

We sought to calculate accumulated dose (D_A) to the rectum in patients treated with radiotherapy for prostate cancer. We were particularly interested in whether dose–surface maps (DSMs) provide additional information to dose–volume histograms (DVHs).

Methods:

Manual rectal contours were obtained for kilovoltage and daily megavoltage CT scans for 10 participants from the VoxTox study (380 scans). Daily delivered dose recalculation was performed using a ray-tracing algorithm. Delivered DVHs were summated to create accumulated DVHs. The rectum was considered as a cylinder, cut and unfolded to produce daily delivered DSMs; these were summated to produce accumulated DSMs.

Results:

Accumulated dose-volumes were different from planned in all participants. For one participant, all D_A levels were higher and all volumes were larger than planned. For four participants, all D_A levels were lower and all volumes were smaller than planned. For each of these four participants, ≥1% of pixels on the accumulated DSM received ≥5 Gy more than had been planned.

Conclusion:

Differences between accumulated and planned dose-volumes were seen in all participants. DSMs were able to identify differences between D_A and planned dose that could not be appreciated from the DVHs. Further work is needed to extract the dose data embedded in the DSMs. These will be correlated with toxicity as part of the VoxTox Programme.

Advances in knowledge:

DSMs are able to identify differences between D_A and planned dose that cannot be appreciated from DVHs alone and should be incorporated into future studies investigating links between D_A and toxicity.     

Using a thermoluminescent dosimeter to evaluate the location reliability of the highest–skin dose area detected by treatment planning in radiotherapy for breast cancer

Acute skin reaction during adjuvant radiotherapy for breast cancer is an inevitable process, and its severity is related to the skin dose. A high–skin dose area can be speculated based on the isodose distribution shown on a treatment planning. To determine whether treatment planning can reflect high–skin dose location, 80 patients were collected and their skin doses in different areas were measured using a thermoluminescent dosimeter to locate the highest–skin dose area in each patient. We determined whether the skin dose is consistent with the highest-dose area estimated by the treatment planning of the same patient. The χ² and Fisher exact tests revealed that these 2 methods yielded more consistent results when the highest-dose spots were located in the axillary and breast areas but not in the inframammary area. We suggest that skin doses shown on the treatment planning might be a reliable and simple alternative method for estimating the highest skin doses in some areas.