The Importance of Verification CT-QA Scans in Patients Treated with IMPT for Head and Neck Cancers.

Purpose: To understand how verification computed tomography-quality assurance (CT-QA) scans influenced clinical decision-making to replan patients with head and neck cancer and identify predictors for replanning to guide intensity-modulated proton therapy (IMPT) clinical practice.
Patients and Methods: We performed a quality-improvement study by prospectively collecting data on 160 consecutive patients with head and neck cancer treated using spot-scanning IMPT who underwent weekly verification CT-QA scans. Kaplan-Meier estimates were used to determine the cumulative probability of a replan by week. Predictors for replanning were determined with univariate (UVA) and multivariate (MVA) Cox model hazard ratios (HRs). Logistic regression was used to determine odds ratios (ORs). P  < .05 was considered statistically significant.
Results: Of the 160 patients, 79 (49.4%) had verification CT-QA scans, which prompted a replan. The cumulative probability of a replan by week 1 was 13.7% (95% confidence interval [CI], 8.82-18.9), week 2, 25.0% (95% CI, 18.0-31.4), week 3, 33.1% (95% CI, 25.4-40.0), week 4, 45.6% (95% CI, 37.3-52.8), and week 5 and 6, 49.4% (95% CI, 41.0-56.6). Predictors for replanning were sinonasal disease site (UVA: HR, 1.82, P  = .04; MVA: HR, 3.64, P  = .03), advanced stage disease (UVA: HR, 4.68, P  < .01; MVA: HR, 3.10, P  < .05), dose > 60 Gy equivalent (GyE; relative biologic effectiveness, 1.1) (UVA: HR, 1.99, P  < .01; MVA: HR, 2.20, P  < .01), primary disease (UVA: HR, 2.00 versus recurrent, P  = .01; MVA: HR, 2.46, P  = .01), concurrent chemotherapy (UVA: HR, 2.05, P  < .01; MVA: not statistically significant [NS]), definitive intent treatment (UVA: HR, 1.70 versus adjuvant, P  < .02; MVA: NS), bilateral neck treatment (UVA: HR, 2.07, P  = .03; MVA: NS), and greater number of beams (5 beam UVA: HR, 5.55 versus 1 or 2 beams, P  < .02; MVA: NS). Maximal weight change from baseline was associated with higher odds of a replan (≥3 kg: OR, 1.97, P  = .04; ≥ 5 kg: OR, 2.13, P  = .02).
Conclusions: Weekly verification CT-QA scans frequently influenced clinical decision-making to replan. Additional studies that evaluate the practice of monitoring IMPT-treated patients with weekly CT-QA scans and whether that improves clinical outcomes are warranted.
Competing Interests: Conflicts of Interest: Robert L. Foote, MD, declares a patent with royalties from Bionix and a named professorship with Hitachi, and Chris J. Beltran, PhD, declares grant funding from Varian medical; all are outside the submitted work. The authors have no relevant conflicts of interest to disclose.
(©Copyright 2020 The Author(s).)