Evaluation of auto-contouring and dose distributions for online adaptive radiation therapy of patients with locally advanced lung cancers

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Pract Radiat Oncol


PURPOSE: Retrospective studies were performed to evaluate the accuracy of automatically mapped structures and dosimetric consequences of daily online adaptive radiation therapy (ART) for lung cancer treatments.

METHODS: Ten locally advanced lung cancer patients (prescription=2Gyx30) with 297 fractions of treatment were selected for this retrospective study on a research emulator (Ethos™, Varian Medical Systems). All adaptive treatments were simulated twice: Automatic-ART (A-ART) - automatic contours were utilized without modification, and Supervised-ART (S-ART) - automatic contours were modified manually by physicians and physicists. Dosimetric results were analyzed by relating supervised scheduled (S-SCH) dose (initial baseline reference (REF) plan delivered on daily anatomy and supervised contour correction without any adaptation), A-ART and S-ART to the REF dose.

RESULTS: Two hundred ninety (of 297) fractions were analyzed. Comparing target volumes between A-ART and S-ART, Dice similarity coefficient was 0.93±0.05, mean contour distance was 1.5±1.2 mm, and Hausdorff distance was 4.0±2.3 mm. Analysis of daily results over 290 fractions of treatment showed that average target coverage improved from 0.96±0.04 (S-SCH) to 1.00±0.02 (A-ART) and 1.02±0.04 (S-ART); average upper dose constraint was reduced from 1.01±0.11 (S-SCH) to 0.94±0.10 (A-ART) and 0.93±0.12 (S-ART). A-ART and S-ART improved PTV minimum doses by 4.85±3.03 Gy (p=0.049) and 4.46±8.99 Gy (p=0.058), respectively. Statistical analysis shows that A-ART and S-ART significantly improved cumulative target dose by 0.033 ± 0.087 (p = 0.002) and 0.032 ± 0.086 (p = 0.003) and reduced upper constraints by 0.033 ± 0.072 (p <0.001) and 0.032 ± 0.072 (p <0.001) relative to S-SCH dose results, respectively.

CONCLUSION: Accuracy of Ethos automatic contouring for lung cancer is considered clinically acceptable. The online adaptive radiation therapy improves target coverage and spares organs-at-risk significantly.

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ePub ahead of print