Comparative Risk Predictions of Second Cancers After Carbon-Ion Therapy Versus Proton Therapy

Abstract

The purpose of this work was to propose a theoretical framework that enables comparative risk predictions for second cancer incidence after particle-beam therapy for different ion species for individual patients, accounting for differences in relative biological effectiveness (RBE) for the competing processes of tumor initiation and cell inactivation. Our working hypothesis was that using carbon-ion therapy instead of proton therapy would show a difference in the predicted risk of second cancer incidence in the breast for a sample of Hodgkin lymphoma (HL) patients. We generated biologic treatment plans and calculated relative predicted risks of second cancer in the breast using two proposed methods: a full model derived from the linear-quadratic model and a simpler linear-no-threshold model. For our reference calculation, we found the ratio of predicted risk of breast cancer incidence for carbon-ion versus proton plans <Rc/Rp> to be 0.75±0.07 but not significantly smaller than 1 (p=0.180). Our findings suggest that second cancers risks are, on average, comparable between proton therapy and carbon-ion therapy.

Radiation Therapy and Cardiac Death in Long-Term Survivors of Esophageal Cancer: An Analysis of the Surveillance, Epidemiology, and End Result Database

“…[ 40 ] Furthermore, the worldwide expansion of carbon ion RT has also generated a phase I/II trial demonstrating its safety and efficacy in esophageal cancer [ 41 ]. Although this trial did not examine cardiac toxicities, a recent dosimetric study of cardiac doses in patients with mediastinal Hodgkin lymphoma treated with protons versus carbon ions demonstrated decreased cardiac doses with the latter, potentially owing to a smaller lateral penumbra [ 42 ]. A major question for clinicians to now address is which patients benefit most from these new (and expensive) technologies to spare cardiac dose—in other words, the patients most likely to be long-term survivors may be the same patients for which these new technologies may be most cost-effective [ 43 ].…”

High control rates of proton‐ and carbon‐ion–beam treatment with intensity‐modulated active raster scanning in 101 patients with skull base chondrosarcoma at the Heidelberg Ion Beam Therapy Center

“…An even stronger result has been described with carbon ions and a spot scanning delivery method. When a possible difference between carbon ions and protons was considered, a theoretical study by Eley et al 27 showed comparable risks with the 2 methods. The researchers observed 1 secondary malignancy 6.7 years after radiotherapy.…”

“…8 Nevertheless, regarding the interval of 6.7 years until the observation of a secondary malignancy in the aforementioned study, further investigations with a longer follow-up need to be performed for a significant evaluation. When a possible difference between carbon ions and protons was considered, a theoretical study by Eley et al 27 showed comparable risks with the 2 methods.…”

Carbon Ion Radiobiology

“…Due to the high uncertainty on the shape of the dose-response curve, it is hard to develop realistic mathematical models of radiation carcinogenesis. Comparative model studies of second cancer risk in patients exposed to C-ions and volumetric arc radiotherapy [ 312 ] or proton therapy [ 313 ] show only small predicted changes, that can change for different patients.…”