Assessment of radiation-induced second cancer risks in proton therapy and IMRT for organs inside the primary radiation field.

There is clinical evidence that second malignancies in radiation therapy occur mainly within the beam path, i.e. in the medium or high-dose region.

Adjuvant radiation therapy for early stage seminoma: proton versus photon planning comparison and modeling of second cancer risk.

Purpose: Given concerns of excess malignancies following adjuvant radiation for seminoma, we evaluated photon and proton beam therapy (PBT) treatment plans to assess dose distributions to organs at risk and model rates of second cancers.

Materials And Methods: Ten stage I seminoma patients who were treated with conventional para-aortic AP-PA photon radiation to 25.5 Gy at Massachusetts General Hospital had PBT plans generated (AP-PA, PA alone).

Comparison of second cancer risk due to out-of-field doses from 6-MV IMRT and proton therapy based on 6 pediatric patient treatment plans.

Background And Purpose: This study compared 6-MV IMRT and proton therapy in terms of organ specific second cancer lifetime attributable risks (LARs) caused by scattered and secondary out-of-field radiation.

Materials And Methods: Based on simulated organ doses, excess relative and excess absolute risk models were applied to assess organ-specific LARs. Two treatment sites (cranium and central spine) were considered involving six treatment volumes and six patient ages (9-month, 4-year, 8-year, 11-year, 14-year, and adult).

Comparison of out-of-field photon doses in 6 MV IMRT and neutron doses in proton therapy for adult and pediatric patients.

The purpose of this study was to assess lateral out-of-field doses in 6 MV IMRT (intensity modulated radiation therapy) and compare them with secondary neutron equivalent dose contributions in proton therapy. We simulated out-of-field photon doses to various organs as a function of distance, patient's age, gender and treatment volumes based on 3, 6, 9 cm field diameters in the head and neck and spine region. The out-of-field photon doses to organs near the field edge were found to be in the range of 2, 5 and 10 mSv Gy(-1) for 3 cm, 6 cm and 9 cm diameter IMRT fields, respectively, within 5 cm of the field edge.

Neutron equivalent doses and associated lifetime cancer incidence risks for head & neck and spinal proton therapy.

In this work we have simulated the absorbed equivalent doses to various organs distant to the field edge assuming proton therapy treatments of brain or spine lesions. We have used computational whole-body (gender-specific and age-dependent) voxel phantoms and considered six treatment fields with varying treatment volumes and depths. The maximum neutron equivalent dose to organs near the field edge was found to be approximately 8 mSv Gy(-1).