Mapping local recurrence after radical resection of pancreatic body and tail cancer for target volume design

Background To construct a three-dimensional (3-D) mapping model of local recurrence in patients with pancreatic body and tail cancer (PDTC) after radical resection, and to assess the coverage of clinical target volume (CTV) defined by Radiation Therapy Oncology Group (RTOG) consensus guidelines for PDTC on local recurrence lesions. Methods Patients who experienced local recurrence after radical resection of PDTC between January 2013 and March 2024 were retrospectively analyzed. The geometric center of each local recurrence focus was marked as a point to determine its spatial location relative to the celiac artery (CA) or superior mesenteric artery (SMA). And a 3-D local recurrence map model was constructed based on the CT template image of a patient who underwent radical resection. Subsequently, the coverage of the postoperative CTV, as defined by RTOG consensus guidelines, on local recurrence sites was evaluated. Results A 3-D local recurrence map with 59 local recurrence points of 41 PDTC patients was generated. The mean distance from all local recurrence points to the CA was 3.14 cm (range, 0.67 - 8.68 cm), and the mean distance to the SMA was 3.23 cm (range, 0.66 - 8.59 cm). A total of 24 recurrence points were not covered by the CTV RTOG . Specifically, among the 24 recurrence points closer to the CA, 15 were not covered by CTV RTOG . Among the 35 recurrence points closer to the SMA, 9 were not covered by CTV RTOG. Among patients who received chemotherapy, 12 recurrence points were not covered by CTV RTOG , including 9 near the CA and 3 near the SMA. Among patients who did not receive chemotherapy, 12 recurrence points were not covered by CTV RTOG , including 6 near the CA and 6 near the SMA. There was no statistically significant difference in the coverage of recurrence points by CTV RTOG between the two groups (P = 0.400). Conclusions We constructed a 3-D anatomical recurrence map for PDTC following radical resection and demonstrated that 40.68% of local recurrence sites fall outside the CTV RTOG . These findings may provide valuable insights into optimizing the design of target volumes for postoperative radiotherapy in PDTC.