Prediction of Secondary Cancer in Pediatric, Adolescent, and Young Adult Patients Receiving Abdominal External Beam Radiotherapy
A Toltz1*, N Shin2, C Laude2, D Roberge3, C Freeman2, J Seuntjens1, W Parker2, (1) McGill University, Montreal, Quebec, Canada, (2) McGill University Health Centre, Montreal, Quebec, Canada, (3) Centre Hospitalier de l'Universite de Montreal, Montreal, Quebec, CanadaSU-E-T-282 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
Purpose: Evaluate the risk of induction of secondary lung cancer and any solid cancer for patients receiving external beam radiotherapy in the abdomen using intensity modulated photon therapy (IMRT) or 3D conformal radiotherapy (3D-CRT) as compared to intensity modulated proton therapy (IMPT).
Methods: Six patients (5 male, 1 female; ages 3-24; previously treated with IMRT or 3D-CRT in the abdomen) were re-planned for IMPT using commercially available treatment planning software. Plan dose volume histograms were used to assess the risk of induction of secondary cancer, specifically lung cancer and any solid tumor in the body. Excess Absolute Risk for lung cancer was predicted using the Schneider modified linear quadratic model. Risk for secondary solid cancer in the body was predicted using two methods: Excess Relative Risk (ERR) based on a linear relationship between risk and integral dose, and Excess Absolute Risk (EAR) and lifetime cumulative risk implementing the Schneider Organ Equivalent Dose using linear, linear-exponential, and plateau models. An estimate of risk due to neutron dose was calculated for each patient and included in IMPT risk calculations.
Results: EAR for lung cancer was on average reduced for IMPT by 49% and 48% as compared to 3D-CRT and IMRT respectively. ERR for secondary solid cancer was on average reduced for IMPT by 28% and 24% as compared to 3D-CRT and IMRT respectively. EAR for secondary solid cancer was on average reduced for IMPT by 32% and 36% as compared to 3D-CRT and IMRT respectively. Lifetime cumulative risk for secondary cancer induction was on average reduced for IMPT by 31% and 35% as compared to 3D-CRT and IMRT respectively.
Conclusions: Models predict the risk for induction of secondary lung cancer and any solid cancer is reduced for IMPT as compared to 3D-CRT and IMRT for all patients in this study.
Funding Support, Disclosures, and Conflict of Interest: This work is supported by a grant from the Fonds de recherche sante Quebec.