Abstract

Background and purpose:We conducted a trial of adaptive radiotherapy (RT) for limited stage small cell lung cancer (LS-SCLC) to quantify the dosimetric advantages, toxicity, survival and failure patterns associated with this technique. Material and methods:Study patients underwent planning CT scans before treatment (CT-1), after fractions 5 (CT-2) and 10 (CT-3). RT plans were adapted to measured tumor volume changes. Tumors were treated to the maximum safe dose based on critical structure dosimetry. Non-adapted mock RT plans were created using each CT-1 to determine maximum non-adapted dose. Adapted and mock non-adapted plans were compared for tumor and normal tissue doses. Patients were followed for toxicity, failure patterns and survival. Results:Ten patients were accrued. All patients completed protocol RT. Median total adapted dose was 60 Gy versus 47 Gy in the mock non-adapted plans. Adapted plans provided significantly reduced V20 (mean 31% vs. 36%, p = 0.009), mean lung dose (14.7 vs. 17.3 Gy, p = 0.009), and dose to 1/3 of esophagus (median 35 vs. 49 Gy, p = 0.03) compared to non-adapted plans. Maximal acute RT toxicity was grade 2 esophagitis. There were 2 thoracic and 5 distant failures. Median progression-free and overall survival was 13.4 and 16.1 months. Conclusion:Adaptive radiotherapy facilitates RT dose escalation for LS-SCLC without overdosing normal structures.

Authors and Affiliations