Proton versus photon radiation therapy for patients with high-risk neuroblastoma: the need for a customized approach.

BACKGROUND: Proton therapy for treatment for high-risk neuroblastoma may offer sparing of organs at risk (OAR) when compared to intensity-modulated X-ray therapy (IMXT). PROCEDURE: Double-scattered proton plans and IMXT plans delivering 2,160 cGy to the primary tumor site and other residual disease were developed for 13 consecutive HR-NBL patients. Radiation doses to target volumes and OAR were calculated to determine the optimal modality for each.
RESULTS: All patients received radiation (5/13 ≥ 2 sites). No patient has experienced local recurrence or clinical organ toxicity. Coverage was excellent using both protons and IMXT: median % dose delivered to 95% clinical target volume was 99% and 100%, respectively. For nine patients with lateralized disease, proton therapy offered sparing of the contralateral kidney both with regard to median dose and dose to 20% (median <1 cGy vs. 362 cGy, P = 0.01; median 100 cGy vs. 634 cGy, P = 0.02, respectively). Proton therapy did not reduce ipsilateral kidney dose, and for 2 select patients with lateralized disease IMXT improved overall bilateral renal sparing. Proton therapy improved median bowel (median 33 cGy vs. 590 cGy, P = 0.01), total body (median <1 cGy vs. 30 cGy, P = 0.15), and liver dose (median <1 cGy vs. 529, P < 0.001). When chest RT was required, proton therapy decreased median heart dose and mean lung dose.
CONCLUSIONS: For most patients (11/13), proton therapy offered the optimal combination of target coverage and organ sparing, and is a feasible treatment for HR-NBL. We recommend a customized approach with careful evaluation of renal dosimetry; IMXT may be preferred for select patients.