This PDF is available for free download from a site hosted by Medknow Publications (www.medknow.com). Original Article - Clinical Free full text available from www.cancerjournal.net Radiation dose to contra lateral breast during treatment of breast malignancy by radiotherapy ABSTRACT Aims: External beam radiotherapy is being used regularly to treat the breast malignancy postoperatively. The contribution of collimator leakage and scatter radiation dose to contralateral breast is of concern because of high radio sensitivity of breast tissue for Incharge Telemedicine, carcinogenesis. This becomes more important when the treated cancer breast patient is younger than 45 years and therefore the SMS Medical College contralateral breast must be treated as organ at risk. Quantification of contralateral dose during primary breast irradiation is helpful to and Hospital, Jaipur - estimate the risk of radiation induced secondary breast malignancy. Materials and Methods: In present study contralateral breast dose was measured in 30 cancer breast patients undergoing For correspondence: external beam therapy by Co-60 teletherapy machine. Postoperative radiotherapy was delivered by medial and lateral tangential fields on alternate days in addition to supraclavicle field daily with 200 cGy/F to a total dose of 5000 cGy in 25 fractions. CaSO Jaipur - 302 015, India. themoluminescence dosimeter discs were employed for these measurements. Three TLD discs were put on the surface of skin of arunchougule@sancharnet.in contra lateral breast, one at the level of nipple and two at 3 cms away from nipple on both side along the midline for each field. At the end treatment of each filed, TLD discs were removed and measured for dose after 24h on Thelmador - 6000 TLD reader. Results: The dose at the contra lateral breast nipple was to be 152.5 to 254.75 cGy for total primary breast dose of 5000 cGy in 25 equal fractions which amounted to 3.05-6.05% of total dose to diseased breast. Further it was observed that the maximum contribution of contralateral breast dose was due to medical tangential half blocked field. Conclusion: CaSO 4 ; Dy thermoluminescence dosimetry is quite easy, accurate and convenient method to measure the contra lateral breast dose. KEY WORDS: Breast malignancy, contralateral breast dose, secondary cancer, thermoluminescence INTRODUCTION supra clavicle field is quite high and some times of the order of 500 cGy for 5000 cGy primary breast The age of incidence of breast malignancy is dose. The quantification of the contralateral breast decreasing and because of awareness and availability especially during treatment of diseased breast by of treatment options, most women prefer lumpectomy cobalt external beam is very important, as the scatter rather than radical mastectomy, which is followed by contribution will be more. At our center about 9% of Arun Chougule Department of Radiotherapy, 302004, India Dr. Arun Chougule, II - 38, Gandhinagar, : Dy 4 E-mail: radiotherapy. During external beam therapy of malignant breast, the contra lateral breast receives radiation due to leakage from collimator and scatter from primary. Breast is highly radiosensitive tissue for radiation induced second malignancy and is of more concern for female younger than 45 years of age receiving radiotherapy for breast malignancy. Boice et al [1] have reported that incidence of radiation induced breast cancer is a linear function of dose received by the contra lateral breast and the latent period is over 10 years. Several investigators [2-4] have measured the contra lateral breast dose either on Anderson female phantom/ Rando phantom and on actual patients and observed that the scatter dose to contra lateral breast during medial tangential and all the cancer patients are cancer breast treated after modified mastectomy of lumpectomy. In present study measurement of contralateral breast dose is done using CaSO4: Dy themoluminescence discs because of small size, very high sensitivity ability to record very small doses and its small size, very high sensitivity, ability to record very small doses and energy independent response for energy of about 150 to 1250 KeV, its many other advantages were reported by author elsewhere. [5,6] MATERIALS AND METHODS Measurement of contralateral breast dose was done in 30 patients undergoing external beam J Cancer Res Ther - March 2007 - Volume 3 - Issue 1 8