Feasibility of Proton Beam Therapy for Para-Aortic Lymph Node Recurrence in Patients With Gynecologic Cancer After Pelvic Irradiation: A Case Series.

Aim: Irradiation of para-aortic lymph node recurrences in patients with prior pelvic irradiation raises concerns about overlapping irradiated fields, which should be minimized to reduce severe adverse events. We report six gynecologic cancer patients treated with proton beam therapy for para-aortic lymph node recurrence after pelvic irradiation.

Methods: Six patients who received proton beam therapy for para-aortic lymph node recurrence after pelvic irradiation between 2010 and 2022 were included. Overlapping fields were assessed using the 50% dose distance between the initial and proton therapy fields.

Results: A 5- to 10-mm overlap was observed in three patients. Grade 2 rectal hemorrhage occurred in three patients, grade 3 hematuria in two, and grade 4 sigmoid perforation in one. These adverse events were linked to pelvic irradiation and peritoneal dissemination. Among five patients who died, the median survival after proton therapy was 13 months (range: 9-34). One patient survived with disease at 34 months. Re-enlargement of treated para-aortic lymph nodes was not observed in four patients.

Conclusions: Proton beam therapy was well-tolerated and achieved favorable local control in para-aortic lymph node recurrence after pelvic irradiation. It may be a useful option for gynecologic cancer patients with overlapping irradiated fields.