Purpose: There is an important and growing concern about the potential elevated risk of radiationâinduced second cancers associated new forms of radiation treatments. Concurrently with the recently formed AAPM Task Group 158 we have developed a framework to calculate volumeâaveraged organ doses to patients using the Monte Carlo method. Using previously calculated organ doses from selected 3DâCRT and IMRT treatments of prostate cancer, this study calculates radiationâinduced second cancer risks from these treatments utilizing the BIER VII report methodology. Method and Materials: A detailed model of a Varian Clinac 2100C was combined with the RPI Adult male computational phantom to calculate volumeâaveraged organ doses from a 3DâCRT 4âfield box treatment, a box treatment plus a 6âfield boost treatment, as well as a 7âfield IMRT treatment. Based on these organ doses, organâspecific excess relative risks (ERR) and lifetime attributable risks (LAR) were determined using the methodology outlined in the recently published BEIR VII report. The total wholeâbody LAR was determined for each treatment using arbitrary but clinically relevant monitor unit (MU) values of 10,000 and 40,000 for the 3DâCRT and IMRT treatments. Results: For organs closest to the primary beam the ERR/MU is higher for the IMRT treatment compared to the 3DâCRT treatments, resulting from an increase in the number of fields needed for IMRT treatments. For organs further away from the treatment volume the ERR/MU appears slightly higher for the 3DâCRT treatments, as a consequence of the added neutron component of the 18âMV primary beam. The total wholeâbody LAR for the IMRT treatment was 2%, compared to about 0.4% from the box treatment and 0.9% from the box plus boost treatment. Conclusion: The tools presented in this study improve upon previous methodologies by using the most accurate dosimetry methods as well as the most practical second cancer risk models.