Patterns of locoregional failure following post-operative intensity-modulated radiotherapy to oral cavity cancer: quantitative spatial and dosimetric analysis using a deformable image registration workflow

• Main Authors: Abdallah S. R. Mohamed, Andrew J. Wong, Clifton D. Fuller, Mona Kamal, Gary B. Gunn, Jack Phan, William H. Morrison, Beth M. Beadle, Heath Skinner, Stephen Y. Lai, Sean R. Quinlan-Davidson, Abdelaziz M. Belal, Ahmed G. El-Gowily, Steven J. Frank, David I. Rosenthal, Adam S. Garden
• Format: Article
• Language: English
• Published: BMC 2017-08-01
• Series: Radiation Oncology
• Subjects: Patterns of failure; Post-operative intensity modulated radiation therapy; Oral cavity cancer; Deformable image registration; Quantitative spatial and dosimetric analysis
• Online Access: http://link.springer.com/article/10.1186/s13014-017-0868-y

Abstract Background We sought to identify spatial/dosimetric patterns of failure for oral cavity cancer patients receiving post-operative IMRT (PO-IMRT). Methods Two hundred eighty-nine OCC patients receiving PO-IMRT were retrospectively reviewed from 2000 to 2012. Diagnostic CT documenting recurrence (rCT) was co-registered with planning CT (pCT) using a validated deformable image registration software. Manually segmented recurrent gross disease (rGTV) was deformed to co-registered pCTs. Mapped rGTVs were compared dosimetrically to planned dose and spatially to planning target volumes using centroid-based approaches. Failures types were classified using combined spatial/dosimetric criteria: A (central high-dose), B (peripheral high-dose), C (central intermediate/low-dose), D (peripheral intermediate/low-dose), and E (extraneous-dose). Results Fifty-four patients with recurrence were analyzed; 26 local recurrence, 19 regional recurrence, and 9 both local and regional recurrence. Median time to recurrence was 4 months (range 0–71). Median rGTVs volume was 3.7 cm3 (IQR 1.4–10.6). For spatial and dosimetric analysis of the patterns of failure, 30 patients (55.5%) were classified as type A (central high-dose). Non-central high dose failures were distributed as follows: 2 (3.7%) type B, 10 (18.5%) type C, 1 (1.8%) type D, and 9 (16.7%) type E. Non-IMRT failure in the matching low-neck field was seen in two patients. No failures were noted at the IMRT-supraclavicular field match-line. Conclusions Approximately half of patients with local/regional failure had non-central high dose recurrence. Peripheral high dose misses were uncommon reflecting adequate delineation and dose delivery. Future strategies are needed to reduce types C and E failures.