Scanning Beam Proton Therapy versus Photon IMRT for Stage III Lung Cancer: Comparison of Dosimetry, Toxicity, and Outcomes

Abstract

There are limited clinical data on scanning-beam proton therapy (SPT) in treating locally advanced lung cancer, as most published studies have used passive-scatter technology. There is increasing interest in whether the dosimetric advantages of SPT compared with photon therapy can translate into superior clinical outcomes. We present our experience of SPT and photon intensity modulated radiation therapy (IMRT) with clinical dosimetry and outcomes in patients with stage III lung cancer. Methods and Materials: Patients with stage III lung cancer treated at our center between 2013 and May 2018 were identified in compliance with our institutional review board (64 patients Z 34 SPT þ 30 IMRT). Most proton patients were treated with pencil beam scanning (28 of 34), and 6 of 34 were treated with uniform scanning. Fisher exact test, c 2 test, and Mann-Whitney test were used to compare groups. All tests were 2-sided. Results: Patient characteristics were similar between the IMRT and SPT patients, except for worse lung function in the IMRT group. Mean dose to lung, heart, and esophagus was lower in the SPT group, with most benefit in the low-dose region (lungs, 9.7 Gy vs 15.7 Gy for SPT vs IMRT, respectively [P Z .004]; heart, 7 Gy vs 14 Gy [P Z .001]; esophagus, 28.2 Gy vs 30.9 Gy [P Z .023]). Esophagitis and dermatitis grades were not different between the 2 groups. Grade 2þ pneumonitis was 21% in the SPT group and 40% in the IMRT group (P Z .107). Changes in blood counts were not different between the 2 groups. Overall survival and progression-free survival were not different between SPT and IMRT (median overall survival, 41.6 vs 30.7 months, respectively [P Z .52]; median progression-free survival, 19.5 vs 14.6 months [P Z .50]). Conclusions: We report our experience with SPT and IMRT in stage III lung cancer. Our cohort of patients treated with SPT had lower doses to normal organs (lungs, heart, esophagus) than our IMRT cohort. There was no statistically significant difference in toxicity rates or survival, although there may have been a trend toward lower rates of pneumonitis.

Charged particle therapy for high-grade gliomas in adults: a systematic review

“…Previous studies have found that intensity-modulated proton therapy (IMPT) can provide more conformal target coverage than IMRT [19,41]. Similar outcomes with other malignant tumors found less toxicity after proton therapy than IMRT [42][43][44][45]. The different survival outcomes have not been produced by the same radiation dose of the two techniques, so the dose-escalation model for proton therapy will be applied to more prospective research.…”

Proton versus photon radiation therapy: A clinical review

“…Comparing uniform scanning proton therapy (USPT)/PBSPT with IMRT, a single institutional study reported no statistically significant differences in grade ≥ 2 pneumonitis and esophagitis rates, acute dermatitis, OS, progression-free survival, or locoregional control for stage III lung cancer patients without adjusting for potential confounders (28). Yu et al (29) also showed there were no statistically significant differences in the subacute (3 months post-treatment) grade 3 pneumonitis, esophagitis and dyspnea rates, 1-year OS, freedom from distant metastasis rate, or freedom from locoregional recurrence rate between IMPT and IMRT treated stage I-IV NSCLC patients using multivariable analysis.…”

Patient Derived Ex-Vivo Cancer Models in Drug Development, Personalized Medicine, and Radiotherapy

“…MRI-guided radiotherapy in gynecologic cancers can reduce exposure to adjacent organs by up to 59% [ 110 ]. Proton beam therapy also reveals marked reduction in an off-target dose due to its inherently confined Bragg peak distribution [ 111 , 112 ]. While this has reduced side effects of treatment, empiric dosing and fractionation are still cornerstones of the field.…”