Task Group 85
Practical Radiological Protection Recommendations on Mitigating Secondary Cancer Risks in Modern Radiation Oncology

Since the early days of radiotherapy it was observed an increase in the number of tumours arising in the irradiated bed, and high dose volumes after the initial treatment, those tumours were more frequently seen with longer observation time. Due to the fact that cancer treatment has become more successful with time, and more patients survive after the initial treatment, it is felt that this risk should be re-assessed. Currently 50-60% of the cancer patients receive radiotherapy as a part of their oncologic treatment and due to the evolution of radiotherapy techniques a larger number of treatment beams is used, increasing the total number of MU (monitor units) used and also increasing the total volume to be irradiated. This issue is particularly important in the actual oncological scene in which combined modality approach (radio-chemotherapy) is commonly used.  Thus the risk could be increased. Theoretical radiobiological calculation are suggesting that because the low dose volume region treated has also increased due to the use of the above mentioned techniques, this increase could mean an increased risk of secondary cancer induction. It is felt pertinent then to examine the current literature in order to access the risk (or lack of it) and current models predicting it. This TG will continue to build the final report based upon on the work already done by the ICRP/ICRU TG conducted by J-M Cosset and also consider NCRP & AAPM work in this area. The aim is to provide practical radiological protection recommendations for the practising clinician on mitigating secondary cancer risks in modern radiation oncology.