Adaptive/Nonadaptive Proton Radiation Planning and Outcomes in a Phase II Trial for Locally Advanced Non-small Cell Lung Cancer

Abstract

Purpose To analyze dosimetric variables and outcomes after adaptive replanning of radiotherapy during concurrent high-dose protons and chemotherapy for locally advanced non-small cell lung cancer (NSCLC). Methods and Materials Nine of 44 patients with stage III NSCLC in a prospective phase II trial of concurrent paclitaxel/carboplatin with proton radiation [74 Gy(RBE) in 37 fractions] had modifications to their original treatment plans after re-evaluation revealed changes that would compromise coverage of the target volume or violate dose constraints; plans for the other 35 patients were not changed. We compared patients with adaptive plans with those with nonadaptive plans in terms of dosimetry and outcomes. Results At a median follow-up of 21.2 months (median overall survival, 29.6 months), no differences were found in local, regional, or distant failure or overall survival between groups. Adaptive planning was used more often for large tumors that shrank to a greater extent (median, 107.1 cm3 adaptive and 86.4 cm3 non-adaptive; median changes in volume, 25.3% adaptive and 1.2% non-adaptive; p<0.01). The median number of fractions delivered using adaptive planning was 13 (range, 4–22). Adaptive planning generally improved sparing of the esophagus (median absolute decrease in V70, 1.8%; range, 0–22.9%) and spinal cord (median absolute change in maximum dose, 3.7 Gy; range, 0–13.8 Gy). Without adaptive replanning, target coverage would have been compromised in 2 cases (57% and 82% coverage without adaptation vs. 100% for both with adaptation); neither patient experienced local failure. Radiation-related grade 3 toxicity rates were similar between groups. Conclusions Adaptive planning can reduce normal tissue doses and prevent target misses, particularly for patients with large tumors that shrink substantially during therapy. Adaptive plans seem to have acceptable toxicity and achieve similar local, regional, and distant control and overall survival, even in patients with larger tumors, versus non-adaptive plans.

Proton dose calculation on scatter‐corrected CBCT image: Feasibility study for adaptive proton therapy

“…10 Although APT is not yet widespread due to the limited deployment of volumetric imaging systems at proton centers, dose adaptation of proton treatments promises improved target coverage and normal tissue sparing. 11 Daily volumetric imaging with CBCT is a good candidate for APT as well as for image-guided proton therapy. However, there have been few studies on CBCT imaging for APT.…”

Clinical Implementation of Intensity Modulated Proton Therapy in Thoracic Malignancies

“…Proton therapy for lung cancer may be better able to spare critical structures than intensity modulated photon radiation therapy (IMRT) (1)(2)(3)(4)(5)(6). Passive scattering proton therapy (PSPT), however, relies on 3-dimensional treatment planning (with its inherent limitations) and requires typically 0.5 to 1 cm smearing plus other uncertainty margins (7).…”

The use of proton-beam therapy in the treatment of non-small-cell lung cancer

“…Over a long treatment period for advanced NSCLC, tumor shape and volume may change and replanning is useful. Koay et al showed improvement of target coverage and sparing of the esophagus and spinal cord after adaptive planning especially for large tumors [52].…”