PV QA 3 - Poster Viewing Q&A 3
TU_32_3052 - Prospective dosimetric evaluation of three radiation delivery techniques for spinal metastases and dosimetric predictors of gastrointestinal toxicity
Tuesday, October 23
1:00 PM - 2:30 PM
Location: Innovation Hub, Exhibit Hall 3
Prospective dosimetric evaluation of three radiation delivery techniques for spinal metastases and dosimetric predictors of gastrointestinal toxicity
S. Skamene1, D. Shi2, M. S. Krishnan3, R. Shiloh3, L. Warren3, J. Brown3, D. Apkon3, K. Roper3, Y. H. Chen2,4, T. A. Balboni3, and L. M. Hertan5; 1McGill University Health Centre, Montreal, QC, Canada, 2Harvard Medical School, Boston, MA, 3Brigham and Women's Hospital/Dana-Farber Cancer Institute, Boston, MA, 4Dana-Farber Cancer Institute, Boston, MA, 5Beth Israel Deaconess Medical Center, Boston, MA
Purpose/Objective(s): Radiation therapy (RT) is standard in the management of spine metastases. Techniques have evolved from AP-PA beams to more conformal techniques with the aim of reducing dose to organs at risk (OAR) and toxicities. However, it is unclear if more conformal planning techniques result in a clinically significant reduction in gastrointestinal (GI) toxicities. The aims of this study are to compare RT dosimetric parameters across three modalities of delivery [AP-PA, 3D conformal (3DCRT), and SBRT] and to identify dosimetric predictors of GI toxicities. Materials/Methods: From 12/2016-4/2017, patients undergoing RT for metastatic spinal tumors were enrolled in this prospective cohort study. RT technique (AP-PA, 3DCRT, SBRT) was determined prior to enrollment. GI OARs (esophagus, stomach, and bowel bag) were delineated on the planning CT scan using established RTOG guidelines. Mean dose, max dose, V5, V10, V15, V20, V25, V30, D5cc, D2cc, D1cc, and D0.035cc were recorded from dose-volume histogram data; field length was also recorded. Patient-reported GI symptoms were assessed by the validated MD Anderson Symptom Inventory (MDASI) 1 week after RT start, at RT completion, 1 and 4 weeks post-RT. The Kruskal-Wallis test assessed differences in OAR dosimetric parameters by treatment technique. Spearman correlations assessed relationships of dosimetric parameters to GI toxicities. Results: In total, 68 patients enrolled; the esophagus received RT in 28. Significant reductions in esophageal mean dose and V20 were noted for SBRT compared to AP-PA and 3DCRT. Mean esophageal dose correlated significantly with max change in dysphagia [r=0.41 (p=0.03)], odynophagia [0.60 (0.0007)], and GERD [0.46 (0.01)]. The stomach received RT in 26 patients and significant differences were seen in nearly all dose parameters comparing APPA, 3DCRT, and SBRT. Max change in GERD correlated with stomach D0.035cc [0.43 (0.03)]. 48 patients received RT to the bowel; when comparing RT techniques, significant differences in all dose parameters were found except mean dose and V5%. Significant correlations were noted between mean bowel dose and max change in vomiting [0.33 (0.02)] and diarrhea [0.29 (0.05)]. Conclusion: Significant differences were noted in the dose to GI OARs when comparing treatment techniques (AP-PA, 3DCRT, and SBRT). Mean organ dose and maximal point dose were most predictive of GI toxicities.
Author Disclosure: S. Skamene: None. D. Shi: None. M.S. Krishnan: None. R. Shiloh: None. J. Brown: None. Y. Chen: Employee; Constellation Pharmaceuticals. T.A. Balboni: Employee; Dana-Farber Cancer Institute. Research Grant; Templeton Foundation. Steering Committee Member; ASCO Palliative Care Steering Committee Member. L.M. Hertan: Employee; Brigham and Womens Hopsital.