PV QA 4 - Poster Viewing Q&A 4
Purpose/Objective(s): Locoregional failure after definitive chemoradiotherapy for stage III non-small cell lung cancer (NSCLC) represents an important mode of failure for this population. Dose escalation did not lead to improved local control or overall survival on RTOG 0617. We hypothesized that dose escalation via the SIB technique could improve local control in patients with stage III NSCLC.
Materials/Methods: Review of patients with stage III NSCLC treated with an SIB technique between 2010 and 2017. Patient, tumor, treatment, patterns of failure, toxicity, and survival were analyzed.
Results: Twenty eight patients were treated with median age of 69.5 years. Forty-six percent were male. Sixty-four percent of patients were stage IIIA; 60.7% were squamous cell histology and 29.6% were adenocarcinoma. Ninety-three percent had concurrent chemotherapy, primarily carboplatin and paclitaxel. The SIB target was an inner margin on the GTV in all but two patients, in which the entire GTV was the target. Mean PTV volume was 491.4 cc; mean SIB volume was 96.2 cc. The majority of patients were treated with 60 Gy in 2 Gy fractions to the PTV; number of fractions ranged from 24 to 32 and total prescribed dose to the PTV ranged from 50 to 70 Gy. The SIB as a percentage of prescribed dose ranged from 10 to 25% (mean 16.7%). After median follow up of 19 months, median survival was 18 months (95% CI 4.1 – 31.9). Kaplan-Meier estimate of two year overall survival is 32.2%. Nine patients (32%) experienced a locoregional failure with a mean time to failure of 13.9 months. Treatment was generally well tolerated, though two patients expired during treatment likely due to complications from their cancer. One patient experienced a grade 3 esophageal stricture; there were no other grade 3 or higher toxicities.
Conclusion: Dose escalation via the SIB technique appears well-tolerated in this single institution experience. Control and survival outcomes may be biased due to selection of patients with bulky disease. Whether this method of dose escalation can improve outcomes may warrant further investigation.
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