M. Yoshimura1, T. Iwai1, Y. Ono1, M. Kanai2,3, A. Fukuda4, K. Nagai5, H. Isoda6, and T. Mizowaki1; 1Department of Radiation Oncology and Image-applied Therapy, Kyoto University Graduate School of Medicine, Kyoto, Japan, 2Department of Therapeutic Oncology, Kyoto University Graduate School of Medicine, Kyoto, Japan, 3Cancer Treatment Center, Kansai Medical University Hospital, Osaka, Japan, 4Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan, 5Department of Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan, 6Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
Purpose/Objective(s): The purpose of this study was to retrospectively analyze the outcomes of moderately-hypofractionated IMRT (MHF-IMRT) for unresectable locally advanced pancreatic cancer (UR-LAPC). Materials/
Methods: Patients with UR-LAPC who underwent MHF-IMRT with a total prescribed dose of 45-51 Gy in 15 fractions between Oct 2010 and March 2023 at our hospital were analyzed. As for radiotherapy planning, GTV consisted of the primary tumor and metastatic lymph nodes. CTV was defined as GTV with a margin 5 mm in all directions plus the prophylactic area, which included the retropancreatic para-aortic lymph nodes between the celiac axis and the superior mesenteric artery. PTV was CTV with a margin of 5 mm in all directions. PTV-PRV was the volume that subtracted the stomach plus 5-10 mm, and the duodenum plus 3-5 mm margins, the small intestine and colon plus 0-5 mm from PTV. The prescription dose was specified as D95% to PTV-PRV= 45-51 Gy and D98% to PTV=36 Gy using simultaneous integrated boost (SIB)-IMRT technique. Overall survival (OS), local control (LC), progression-free survival (PFS), distant disease-free survival (DDFS) based on the treatment start date, and gastrointestinal adverse event rates were examined. Data was analyzed using the Kaplan-Meier method, and the toxicities were scored by CTCAE ver. 4.0. Results: Eighty-seven patients were analyzed. Forty-six patients were male, and performance status was 0/1/2 in 68/18/1, respectively. Median age was 69 years (42-86), and the primary tumor was located at pancreatic head/body/tail in 45/36/2, respectively. The median maximum tumor diameter was 32 mm (10-70), and T/N stage was T4N0/T4N1 in 75/12 (UICC 8th edition), respectively. Prescribed doses were 45/48/51 Gy in 5/77/5, and concurrent chemotherapy was gemcitabine/S-1/none in 80/6/1, respectively. As respiratory motion management, expiratory breath-hold/dynamic tumor tracking/shallow-breathing were used in 46/37/4 patients, respectively. The first recurrence site was the locoregional recurrence/distant metastasis/both in 13/47/7, respectively. Median survival time/2-year OS/LC/PFS/DDFS were 21.4 months/45.2%/66.1%/24.4%/57.3%, respectively. No recurrence was observed in 4 patients at more than 2 years after the last administration of maintenance chemotherapy. As for GI adverse events =grade 3, acute grade 3 appetite loss was observed in 3 patients, and late grade ¾ gastrointestinal bleeding were observed in 3/2 patients, respectively. No grade 5 adverse events were observed. Conclusion: The outcomes of MHF-IMRT for UR-LAPC were favorable with tolerable toxicities. While this treatment approach has enabled a small number of long-term survivors without chemotherapy, there is a risk of some gastrointestinal bleeding, and careful attention is required.
