In vivo dosimetry using radiochromic films during intraoperative electron beam radiation therapy in early-stage breast cancer.

BACKGROUND AND PURPOSE: To check the dose delivered to patients during intraoperative electron beam radiation therapy (IOERT) for early breast cancer and also to define appropriate action levels. PATIENTS AND METHODS: Between December 2000 and June 2001, 54 patients affected by early-stage breast cancer underwent exclusive IOERT to the tumour bed using a Novac7 mobile linac, after quadrantectomy. Electron beams (5, 7, 9 MeV) at high dose per pulse values (0.02-0.09 Gy/pulse) were used. The prescribed single dose was 21 Gy at the depth of 90% isodose (14-22 mm). In 35 cases, in vivo dosimetry was performed. The entrance dose was derived from the surface dose measured with thin and calibrated MD-55-2 radiochromic films, wrapped in sterile envelopes. Films were analysed 24-72 h after the irradiation using a charge-coupled-device imaging system. Field disturbance caused by the film envelope was negligible. RESULTS: The mean deviation between measured and expected doses was 1.8%, with one SD equal to 4.7%. Deviations larger than 7% were found in 23% of cases, never consecutively, not correlated with beam energy or field size and with no evidence of linac daily output variation or serious malfunctioning or human mistake. The estimated overall uncertainty of dose measurement was about 4%. In vivo dosimetry appeared both reliable and feasible. Two action levels, for unexplained observed deviations larger than 7 and 10%, were preliminary defined. CONCLUSIONS: Satisfactory agreement between measured and expected doses was found. The implementation of in vivo dosimetry in IOERT is suggested, particularly for patients enrolled in a clinical trial.     

In vivo dosimetry and radiation therapy of breast cancer]

INTRODUCTION: Verification of absorbed dose in target volume is a key factor for quality assurance in radiotherapy. In vivo measurements allow evaluation of the variations in dose with time and variations between measured doses and calculated doses by TPS. The aim of this work were to evaluate reproducibility of patient positioning and to compare calculated doses by 2 different TPS. PATIENTS AND METHODS: Twenty patients were divided in 2 groups according to the thickness of their breast (mean SSD = 92.9 cm). In vivo measurement was performed within the first two sessions. RESULTS: Reproducibility of SSD evaluation was made on 12 beams between 2 fractions. With a tolerance margin of 0.5 cm, positioning errors were present in 33% (4/12). The 2 TPS were in agreement in 75% (30/40). CONCLUSION: In vivo dosimetry can be a very interesting tool to assess patients positioning variations and TPS dose calculation.     

Recurrence in the breast following conservative surgery and radiation therapy for early-stage breast cancer.

This report summarizes the experience of the Joint Center for Radiation Therapy (JCRT) in treating patients with clinical stage I and II breast cancer with conservative surgery and radiation therapy. The study population consisted of 1396 patients treated between 1968 and 1985. All patients underwent a gross excision of the tumor and received breast irradiation (with or without nodal irradiation) including a "boost" to bring the primary tumor site to a total dose of at least 60 Gy. The method of treatment evolved over the study-time period. During the interval from 1968 to 1982, patients typically underwent a limited gross excision of the tumor without regard to the microscopic margins of resection. During the period 1983 to 1985, film-screen mammography, inking of specimen margins, and reexcisions for inevaluable or involved margins were more commonly performed. With a median follow-up of 80 months, the 5-year crude rate of failure in the breast (as the first site of failure) was 8% (106/1396) and the crude rate of regional nodal/distant failure (as the first site of failure) was 16% (228/1396). The time-course of failures in the breast was protracted, occurring at a fairly constant rate over the first 7 years after treatment, but still seen beyond that point. Most recurrences in the breast (75%) developed at or near the original tumor site. The most important risk factor for developing a breast recurrence was the presence of an extensive intraductal component in the tumor. The cosmetic results following treatment were excellent or good in the majority of patients (87%) and were most adversely affected by extensive surgery.(ABSTRACT TRUNCATED AT 250 WORDS)     

乳腺癌Intrabeam系统术中放射治疗临床操作指南

正目前乳腺癌已成为中国女性发病率最高的恶性肿瘤~([1])。随着诊疗技术的提高,能行保留乳房(简称保乳)手术的早期乳腺癌患者也越来越多,经过综合治疗的保乳手术可以取得与乳房切除相同的临床疗效~([2])。保乳手术辅以放射治疗已成为早期乳癌患者的首选标准化治疗方式~([3-4])。研究表明,乳腺癌保乳手术治疗后85%～90%的复发位于原发灶附     

In vivo dosimetry during tangential breast treatment.

The 3-dimensional (3-D) dose distribution as calculated in clinical practice for tangential breast treatment was verified by means of in vivo dosimetry. Clinical practice in our institution implies the use of 8 MV X-ray beams, a 2-D treatment planning system, collimator rotation and a limited set of patient data for dose calculations. By positioning diodes at the central beam axes as well as in the periphery of the breast the magnitude of the dose values at the isocentre and in points situated in the high-dose regions behind the lung could be assessed. The position of the diodes was verified by means of an on-line portal imaging device. The reproducibility of these in vivo dose measurements was better than 2% (1 SD). Our study showed that on the average the dose delivery at the isocentre is 2% less and at the points behind the lung, 5.7% higher with respect to the calculated dose values. Detailed analysis of these in vivo dosimetry results, based on dose measurements performed with a breast shaped phantom, yielded the magnitudes of the errors in the predicted dose due to several limitations in the dose calculation algorithms and dose calculation procedure. These limitations are each introducing an error of several percent but are compensating each other for the dose calculation at the isocentre. We concluded that the dose distribution in a patient for our treatment technique and dose calculation procedure can be predicted with a 2-D treatment planning system in an acceptable way. A more accurate prediction of the dose distribution can be performed but requires an estimation of the lack of scatter due to missing tissue, the change in the dose distribution due to oblique incident beams and the incorporation of the actual output of the treatment machine in the assessment of the number of monitor units.     

Quality control in the conservative treatment of breast cancer: patient dosimetry using silicon detectors.

Twenty patients with early breast cancer were treated with external irradiation, delivered with two tangential beams (6 MV X-rays) using a half-beam block (HBB) and 3-D compensating filters. All patients were immobilized with individualized cellulose acetate casts. Patient dosimetry was performed using p-type silicon detectors. Midline doses were calculated by combined entrance and exit dose measurements. The mean ratio of the measured and the prescribed doses was 96.6 +/- 3.8% at the reference point, 96.8 +/- 4.3% at off-axis points on the central plane and 96.8 +/- 7.6% at off-plane points.     

The use of TL detectors in dosimetry of systemic radiation therapy

A method for determining absorbed doses to organs in systemic radiation therapy (SRT) is evaluated. The method, based on thermoluminescent (TL) dosimeters placed on the patient's skin, was validated and justified through a phantom study showing that the difference between measured (TL dosimeters in the phantom) and derived (TL method) values is within 10%. Six radioimmunotherapy (RIT) patients with widespread intraperitoneal pseudomyxoma were also studied. In dose evaluations, special emphasis was on kidneys. In addition to the TL method, the absorbed doses to kidneys were calculated using MIRD formalism and a point dose kernel technique. We conclude that in SRT the described TL method can be used to estimate the absorbed doses to those critical organs near the body surface within 50% (1 SD).     

The potential of proton beam radiation therapy in breast cancer

A group of Swedish oncologists and hospital physicists have estimated the number of patients in Sweden suitable for proton beam therapy. The estimations have been based on current statistics of tumour incidence, number of patients potentially eligible for radiation treatment, scientific support from clinical trials and model dose planning studies and knowledge of the dose-response relations of different tumours and normal tissues. In primary breast cancer, it is estimated that about 300 of the annually 3 425 irradiated patients can potentially be candidates for proton beam therapy to reduce late toxicity, mainly from the heart and lungs.     

Feasibility study of using MOSFET detectors for in vivo dosimetry during permanent low-dose-rate prostate implants

PURPOSE: To investigate the feasibility of using new micro-MOSFET detectors for QA and in vivo dosimetry of the urethra during transperineal interstitial permanent prostate implants (TIPPB). METHODS AND MATERIALS: This study involves measurements for several patients who have undergone the implant procedure with iodine-125 seeds. A new micro-MOSFET detector is used as a tool for in vivo measurement of the initial dose rate within the urethra. MOSFETs are calibrated using a single special order calibration seed. The angular response is investigated in a 100 kVp X-ray beam. RESULTS: micro-MOSFETs are found to have a calibration factor of 0.03 cGy/mV for low energy X-rays and a high isotropic response (within 2.5%). Prostate volume and shape changes during TIPPB due to edema caused by the trauma of needle insertion, making it difficult to achieve the planned implant geometry and hence the desired dose distribution. MOSFET measurements help us to evaluate the overall quality of the implant, by analyzing the maximum dose received by urethra, the prostate base coverage, the length of the prostatic urethra that is irradiated, and the apex coverage. CONCLUSIONS: We demonstrate that ease of use, quick calibration and the instantaneous reading of accumulated dose make micro-MOSFETs feasible for in vivo dosimetry during TIPPB.     

Impact of patient distance to radiation therapy on mastectomy use in early-stage breast cancer patients.

PURPOSE: Treatment access underlies quality cancer care. We hypothesize that mastectomy rates in a rural state are independently influenced by distance to radiation therapy (XRT) and by changing XRT access through opening new facilities. PATIENTS AND METHODS: Early-stage breast cancer patients diagnosed from 1996 to 2000 were identified in the Virginia state registry. Distance from patient zip code to nearest XRT facility was calculated with geographical software. Distance to XRT facility (< or = 10, > 10 to 25, > 25 to 50, and > 50 miles), American Joint Committee on Cancer tumor stage, age, race, and diagnosis year were evaluated for influencing mastectomy rate. Mastectomy use within 15 miles of five new facilities was assessed before and after opening. RESULTS: Among 20,094 patients, 43% underwent mastectomy, 53% underwent lumpectomy, and therapy of 4% of patients is unknown. Twenty-nine percent of patients lived more than 10 miles from XRT facility. Mastectomy increased with distance to XRT facility (43% at < or = 10 miles, 47% at > 10 to 25 miles, 53% at > 25 to 50 miles, and 58% at > 50 miles; P < .001). Among 11,597 patients with T1 (< 2 cm) tumors, mastectomy also varied by distance (31% at < or = 10 miles, 36% at > 10 to 25 miles, 41% at > 25 to 50 miles, and 49% at > 50 miles; P < .001). In multivariate analysis, mastectomy use was independently influenced by XRT distance after adjusting for age, race, T stage, and diagnosis year. Over the study period, mastectomy rates declined from 48% to 43% across Virginia, and there were similar declines in a 15-mile area around four new radiation facilities in urban settings. However, mastectomies decreased from 61% to 45% around a new XRT facility in a rural setting. CONCLUSION: Distance to XRT facility significantly impacts mastectomy use. Opportunities for increasing breast-conservation rates through improved XRT access exist.     

Impact of concurrent versus sequential tamoxifen with radiation therapy in early-stage breast cancer patients undergoing breast conservation treatment.

PURPOSE: To assess the impact of sequencing of tamoxifen and radiation therapy (RT) on outcomes in early-stage breast cancer. PATIENTS AND METHODS: This retrospective study evaluates the effect of the sequence of tamoxifen with RT on outcomes in stage I to II breast cancer patients who underwent breast-conservation treatment (BCT) and received adjuvant tamoxifen, with or without adjuvant chemotherapy. Patients were grouped as concurrent (tamoxifen given during RT followed by continued tamoxifen; 174 patients) and sequential (RT followed by tamoxifen; 104 patients). RESULTS: Median follow-up after RT was 8.6 years for both groups. The pathologic T and N stage, race, estrogen and progesterone status, number of positive nodes, and RT were comparable between the two groups (all P >/= .08). More women age 49 years or younger and women who received chemotherapy were in the sequential group than the concurrent group (6% and 25%, respectively; P < .0001). The sequence of tamoxifen therapy did not influence 10-year local recurrence rates (sequential, 7%; concurrent, 3%; P = .52), overall survival (sequential, 86%; concurrent, 81%; P = .64), or relapse-free survival (sequential, 76%; concurrent, 85%; P = .35). When adjusting age and chemotherapy use in the multivariable Cox model, hazard ratios comparing sequential versus concurrent tamoxifen therapy were 1.56 (95% CI, 0.87 to 2.79), 1.23 (95% CI, 0.63 to 2.41), and 1.22 (95% CI, 0.33 to 4.49) for the overall survival, relapse-free survival, and local recurrence, respectively. CONCLUSION: The therapeutic regimens of tamoxifen given concurrently or sequentially with RT both appear to be reasonable options for patients treated with BCT.     

Novel approaches to postoperative radiation therapy as part of breast-conserving therapy for early-stage breast cancer

Breast-conserving therapy (BCT) consists of segmental mastectomy followed by postoperative radiation therapy (RT) to the whole breast. At least 6 prospective randomized trials have proven the equivalence of BCT to mastectomy. However, BCT remains underused and, most importantly, a sizable proportion of patients with invasive breast cancer fail to complete the recommended protocol of breast preservation by omitting postoperative RT. The inconvenience of complying with the standard 6-week radiation regimen, which includes approximately 30 daily visits, at least partially explains this lack of adherence. New clinical studies have generated preliminary evidence that more convenient, shorter radiation regimens might reveal equivalence to the current standard. Moreover, the availability of modern technology to deliver and target ionizing radiation by improving homogeneity of radiation dose has made it possible to safely explore the use of greater radiation doses per fraction. Finally, currently ongoing research trials will enable the identification of specific subsets of patients who are likely to be safely treated by partial-breast radiation (instead of radiation to the whole breast) with more accelerated regimens. This article reviews the available data and the current ongoing research on novel RT techniques and fractionation schedules in BCT for early-stage breast cancer.     

Second nonbreast malignancies after conservative surgery and radiation therapy for early-stage breast cancer

PURPOSE: Breast cancer patients treated with conservative surgery and radiation therapy are at risk of developing second nonbreast malignancies (SNBMs). The purpose of this study was to determine the incidence of all SNBMs and SNBMs by specific location among long-term survivors and to compare the risk of these events to the age-specific incidence of malignancies as first cancers in the Surveillance Epidemiology and End-Results Program (SEER) population. METHODS AND MATERIALS: We analyzed the likelihood of SNBM development for 1884 patients with clinical Stage I or II breast cancer treated with gross excision and > or = 60 Gy (median 63) to the breast between 1970 and 1987. Fifty-seven percent received supraclavicular/axillary radiation (median dose 45 Gy, range 20-60) and 28% received systemic therapy. The median age at diagnosis was 52 years. The median clinical tumor size was 2 cm. Patients were considered at risk of an SNBM until the development of the first of distant metastases or contralateral breast cancer or death or, if alive and disease-free, until the last follow-up visit. The expected numbers of cancers were obtained from the SEER database, using the age-specific incidence for white women within 5-year age groups and 5-year calendar intervals. The median time at risk for an SNBM was 10.9 years (range 0.2-27.9). RESULTS: By 8 years of follow-up, 432 patients (23%) had developed distant metastases, 295 patients (16%) a local/regional recurrence, and 159 (8%) a contralateral primary. Of the 1884 patients in our cohort, 147 (8%) developed an SNBM compared with the 127.7 expected from SEER. This corresponds to an absolute excess of 1% of the study population and a relative increase of 15% greater than that expected from SEER (p = 0.05). Within the first 5 years, the observed and expected rates of SNBMs were identical (47 vs. 46.9). After 5 years, 24% more SNBMs were observed than expected (100 vs. 80.8, p = 0.02). Among patients <50 years old at breast cancer diagnosis, 43% more observed SNBMs occurred than expected (40 vs. 28, p = 0.02). For patients > or = 50 years, 7% more SNBMs were observed than expected (107 vs. 99.7, p = 0.25). Lung SNBMs were observed in 33 women, 52% more than the 21.67 predicted by SEER (p = 0.01). Most of the lung SNBMs occurred >5 years after treatment (n = 23) and in women who were >50 years at the time of their breast cancer diagnosis (n = 27). The observed incidence of ovarian cancer was significantly greater than expected among patients <50 years (7 vs. 1.96, p = 0.004) but was not different than expected for patients > or = 50 years (5 vs. 5.3, p = 0.61). Among the 7 sarcomas, 3 developed in the radiation field. CONCLUSIONS: SNBMs occur in a substantial minority (8%) of patients treated with conservative surgery and radiotherapy. However, the absolute excess risk compared with the general population is very small (1%). This excess risk is only evident after 5 years. In particular, a slightly increased incidence of lung SNBMs and a somewhat larger increase in ovarian cancer among younger patients was found. Our data suggest that preventive strategies to reduce the incidence of certain cancers (e.g., smoking cessation and prophylactic oophorectomy) and/or continued monitoring for SNBMs to increase the likelihood of early detection and treatment may be prudent in this population.