DEGRO practical guidelines for radiotherapy of non-malignant disorders: Part I: physical principles, radiobiological mechanisms, and radiogenic risk.

PURPOSE: Synopsis of the introductory paragraph of the DEGRO consensus S2e-guideline recommendations for the radiotherapy of benign disorders, including physical principles, radiobiological mechanisms, and radiogenic risk. MATERIALS AND METHODS: This work is based on the S2e-guideline recommendations published November 14, 2013. The basic principles of radiation physics and treatment delivery, evaluation of putative underlying radiobiological mechanisms, and the assessment of genetic and cancer risk following low-dose irradiation will be presented. RESULTS: Radiation therapy of benign diseases is performed according to similar physical principles as those governing treatment of malignant diseases in radiation oncology, using the same techniques and workflows. These methods comprise usage of orthovoltage X-ray units, gamma irradiation facilities, linear accelerators (LINACs), and brachytherapy. Experimental in vitro and in vivo models recently confirmed the clinically observed anti-inflammatory effect of low-dose X-irradiation, and implicated a multitude of radiobiological mechanisms. These include modulation of different immunological pathways, as well as the activities of endothelial cells, mono- and polymorphonuclear leukocytes, and macrophages. The use of effective dose for radiogenic risk assessment and the corresponding tumor incidence rate of 5.5%/Sv are currently controversially discussed. Some authors argue that the risk of radiation-induced cancers should be estimated on the basis of epidemiological data. However, such data are rarely available at present and associated with high variability. CONCLUSION: Current radiobiological studies clearly demonstrate a therapeutic effectiveness of radiation therapy used to treat benign diseases and implicate various molecular mechanisms. Radiogenic risks should be taken into account when applying radiation treatment for benign diseases.

Why recent studies relating normal tissue response to individual radiosensitivity might have failed and how new studies should be performed.

PURPOSE: New insights into the kinetics of late complications occurring after radiation therapy indicated that all patients have a constant risk of developing late tissue complications. These observations might have a great impact on studies relating normal tissue complications to individual radiosensitivity. METHODS AND MATERIALS: Data previously published by Peacock et al. were used for analysis. In this study, 39 breast cancer patients with severe reactions (responders) were compared with 65 matched patients showing no reactions (nonresponders). Cellular radiosensitivity as measured in vitro in terms of D(0.01) did not show significant differences between the two groups, both for high-dose-rate (5.84 +/- 0.06 vs. 5.85 +/- 0.07 Gy) and low-dose-rate (7.44 +/- 0.10 vs. 7.56 +/- 0.09 Gy) irradiation. RESULTS: A theoretical distribution was calculated for the individual radiosensitivity of patients with Grade or=(MV + SD), a normal group with a sensitivity between MV - SD and MV + SD, and a sensitive group

Is there a life-long risk of brachial plexopathy after radiotherapy of supraclavicular lymph nodes in breast cancer patients?

BACKGROUND AND PURPOSE: To contribute to the question whether the risk of radiation-related brachial plexopathy increases, remains constant or decreases with time after treatment. PATIENTS AND METHODS: Between 12/80 and 9/93, 140 breast cancer patients received supraclavicular lymph node irradiation using a telecobalt unit. Total dose was 60 with 3Gy per fraction at a depth of 0.5 cm and 52 with 2.6Gy per fraction to the brachial plexus at a depth of 3 cm. Twenty-eight women received chemotherapy, 34 tamoxifen. Brachial plexopathy was graded using a modified LENT-SOMA score. Actuarial complication-free survival and overall survival were obtained from Kaplan-Meier analysis. The impact of chemotherapy or tamoxifen was tested using the chi2 test. The annual incidence of radiation-related brachial plexopathy was assessed by exponential regression as described by Jung et al. [Radiother Oncol 61 (2001) 233]. RESULTS: Actuarial overall survival was 67.1% after 5 years, 54.0% after 10 years, 49.9% after 15 years, and 44.0% after 20 years. In 19/140 patients, brachial plexopathy grade>/=1 occurred after a median interval of 88 (30-217) months. The percentage of patients being free from plexopathy was 96.1% after 5 years, 75.5% after 10 years, 72.1% after 15 years, and 46.0% after 19 years, respectively. A significant impact of type of surgery, chemotherapy or tamoxifen was not observed. The annual incidence of brachial plexopathy was 2.9% for grade>/=1 lesions and 0.8% for grade>/=3 lesions. The rates did not change significantly with time. CONCLUSIONS: The risk of brachial plexopathy after supraclavicular lymph node irradiation in breast cancer patients remains constant for a considerable portion of the patient's life.

Individual radiosensitivity measured with lymphocytes may be used to predict the risk of fibrosis after radiotherapy for breast cancer.

BACKGROUND AND PURPOSE: To analyse the relationship of individual cellular radiosensitivity and fibrosis after breast conserving therapy. A new model was used describing the percentage of patients developing fibrosis per year and per patient at risk. PATIENTS AND METHODS: In a retrospective study, 86 patients were included, who had undergone breast conserving surgery and irradiation of the breast with a median dose of 55 Gy (54-55 Gy) given at 2.5 Gy/fraction (n=57) or 2 Gy/fraction (n=29). Median age was 62 years (range 44-86) and median follow-up was 7.5 years (range 5-17). Patients were examined for fibrosis according to the LENT/SOMA score. For analysis, fibrosis was classified as grade 0 and grade 1 (G0-1) or present grade 2 and grade 3 (G2-3). The time to complete development of fibrosis was determined by analysis of yearly mammograms. Individual cellular radiosensitivity was determined by scoring lethal chromosomal aberrations in in vitro irradiated (6 Gy) lymphocytes using metaphase technique. Patients with low/intermediate cellular radiosensitivity were compared with patients with high cellular radiosensitivity using actuarial methods. RESULTS: Ten patients developed fibrosis at 1-8 years after radiotherapy. Individual cellular radiosensitivity was described by normal distribution of lethal chromosomal aberrations, the average was 5.47 lethal aberrations per cell (standard deviation (SD) 0.71). Cellular radiosensitivity was defined as low/intermediate (< or =6.18 lethal aberrations) in 73 patients and high (>6.18 lethal aberrations; mean+SD) in 13 patients. In both groups, the actuarial rate of fibrosis-free patients decreased exponentially with time after radiotherapy. Patients with high cellular radiosensitivity showed a 2.3-fold higher annual rate for fibrosis than patients with intermediate and low radiosensitivity (3.6 versus 1.6% per year). CONCLUSIONS: In breast cancer patients, high individual cellular radiosensitivity as determined by the number of lethal chromosome aberrations in in vitro irradiated lymphocytes might be associated with an enhanced annual rate of fibrosis.