SU‐E‐T‐385: Comparison of Breast Radiotherapy Induced Secondary Cancer Risk for 3D‐Conformal Therapy, IMRT and VMAT

Purpose: The objective of this study was to evaluate the secondary cancer risk of various organs due to the radiation treatment of breast cancer. Methods: The organ doses were measured with photoluminescent dosimeter (PLD) in anthropomorphic phantom for the treatment of breast cancer with 3D conformal radiation therapy (3D), intensity‐modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT). The cancer risk based on measured dose was calculated using the BEIR (Biological Effects of Ionizing Radiation) VII models which yield lifetime attributable risks (LAR) for radiotherapy techniques. Results: The secondary dose per treatment dose (50.4 Gy) from 3D‐CRT in various organs ranged from 0.02 to 0.36 Gy. The secondary doses per treatment dose from IMRT and RapidArc, however, ranged between 0.07 and 8.48 Gy, indicating that IMRT and RapidArc are associated with higher doses of secondary radiation than 3D‐CRT. The organ specific LARs of the thyroid, contralateral breast and ipsilateral lung were 0.02, 19.76, 0.74 per 100,000 population in 3D‐CRT which is much lower compared with IMRT (0.11, 463.6, 10.2) or RapidArc (0.11, 290.37, 11.71). Conclusion: The overall estimation of LAR indicated that the radiation‐induced cancer risk due to the beast radiation therapy was lower with 3D‐CRT than with IMRT or RapidArc.