Acute Gastrointestinal Toxicity and Bowel Bag Dose-Volume Parameters for Pre-Operative Radiotherapy for Retroperitoneal Sarcoma

Publication date: Available online 19 December 2015
Source:Practical Radiation Oncology
Author(s): Kimberley S. Mak, John G. Phillips, Constance M. Barysauskas, Leslie K. Lee, Edward G. Mannarino, Liam Van Benthuysen, Chandrajit P. Raut, John T. Mullen, Mark Fairweather, Thomas F. DeLaney, Elizabeth H. Baldini
PurposeAcute gastrointestinal (GI) toxicity has been studied in GI and gynecological (GYN) cancers, with V15<830 cc, V25<650 cc, and V45<195 cc identified as dose constraints for the peritoneal space [bowel bag (BB)]. There are no reported constraints derived from retroperitoneal sarcoma (RPS), and prospective trials for RPS have adopted some of the GI and GYN constraints. This study quantified GI toxicity during pre-operative RT for RPS, assessed toxicity using published constraints, and evaluated predictors for toxicity.Methods and MaterialsFrom 2003-2013, 56 patients with RPS underwent pre-operative RT at two institutions. Toxicity was scored using Radiation Therapy Oncology Group (RTOG) criteria for upper and lower acute GI toxicity. BB was contoured on planning CT scans per RTOG atlas guidelines with review by a radiologist. Relationships between toxicity, clinical factors and BB dose were analyzed.ResultsThree patients (5%) developed Grade ≥3 acute GI toxicity: two Grade 3 toxicities (anorexia and nausea) and one Grade 5 toxicity (tumor-bowel fistula). Thirty-six patients (64%) had Grade 2 toxicity (nausea, 55%; diarrhea, 23%; pain, 20%).Tumor size was the only significant clinical predictor of Grade ≥2 acute GI toxicity. Larger mean BB volumes predicted for Grade ≥2 toxicity (p=0.001). On ROC analysis, V30 was the best discriminator for toxicity (p=0.0001). Median BB V15 was 1,375 cc; 75% of patients had V15 ≥830 cc. Median V25 was 1,083 cc; 68% had V25 ≥650 cc. Median V45 was 575 cc; 82% had V45 ≥195 cc. V25 ≥650 cc was significantly associated with Grade ≥2 toxicity (p=0.01).ConclusionsAmong patients treated with pre-operative RT for RPS, significant acute GI toxicity was very low despite BB dose exceeding established constraints for most cases. Acceptable dose constraints for RPS may be higher than those for GI or GYN cancers. Further assessment of dose-volume constraints for RPS is needed.



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