SSAT - SBRT AFTER NEOADJUVANT CHEMOTHERAPY (NAC) FOR LOCALLY ADVANCED PANCREATIC CANCER (LAPC): PRELIMINARY INSTITUTIONAL RESULTS.

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SBRT AFTER NEOADJUVANT CHEMOTHERAPY (NAC) FOR LOCALLY ADVANCED PANCREATIC CANCER (LAPC): PRELIMINARY INSTITUTIONAL RESULTS.
Aikaterini Dedeilia^*^¹, Georgios Kritselis^³, Nikiforos Ballian^², Nikolaos Giakoumakis^², Grigorios Tsiotos^²
^¹Surgery, Massachusetts General Hospital, Boston, MA; ^²Mitera-Hygeia Hospital, Department of Surgery, Marousi, Greece; ^³Mitera-Hygeia Hospital, Department of Radiation Oncology, Marousi, Greece

Background
NAC for tumor downstaging, better local/distal disease control, and higher R0 resection rate, followed by pancreatectomy are the two pillars of the management of LAPC. The potential additional role of SBRT remains controversial.

Materials and Methods
In our tertiary referral center, patients with LAPC undergo a complete course of NAC (mostly FOLFIRINOX), cross-sectional imaging reevaluation in 2 weeks and exploration for possible resection when the tumor looks resectable, en-block with the involved major vascular structure(s). Recently, when such a resection did not look feasible and there was no disease progression, we initiated a program of SBRT (5fr/8Gy per fraction/40Gy total dose), with no concurrent chemotherapy. A month after SBRT, patients were restaged (CT with pancreatic protocol) for possible resection.

Results
Twenty-six patients (10 males/16 females, median age: 59, ECOG-PS score: 0-1) with LAPC underwent SBRT a median of 27 days following NAC (Aug. 2019 – June 2023). No SBRT-related side effects occurred. Follow-up was complete (Dec. 2023) with a median of 18 months. Twelve patients (46%) were subsequently explored for possible resection, a median of 2 months after SBRT, and in 8 of them (75%, or 31% of the total) a pancreatectomy was performed. R0 resection was achieved in 7 (88%). Five patients are alive and well at 11, 14, 19, 21, and 31 months since diagnosis and three patients died at 13, 22, and 27 months. The 4 patients explored, but not resected, had complete encasement of the common and proper hepatic artery from its origin to its bifurcation (2 patients), or micrometastatic liver, or peritoneal disease (1 patient each). The 13 patients not subjected to pancreatectomy were followed closely and received further chemotherapy when appropriate. They had a median survival of 15 months since diagnosis. Local control was achieved in 9 (69%). Seven patients are alive for a median of 15 months and 6 patients died at a median of 15 months.

Conclusions
Our initial experience shows that SBRT following NAC for LAPC is safe, is associated with a high rate of local control and may render resectable about one third of patients considered unresectable after NAC alone.

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