ESTRO 2024 - Abstract Book

S171

Brachytherapy - GI, paediatric, miscellaneous

ESTRO 2024

219

Digital Poster

Outcome of intraoperative radiotherapy as a salvage treatment for locally recurrent rectal cancer

Raluca Stoian 1 , Hannes Neeff 2 , Mark Gainey 1 , Michael Kollefrath 1 , Constantinos Zamboglou 1 , Jan-Philipp Harald Exner 1 , Dimos Baltas 1 , Anca Ligia Grosu 1 , Tanja Sprave 1

1 University of Freiburg, Radiationoncology, Freiburg, Germany. 2 University of Freiburg, Surgery, Freiburg, Germany

Purpose/Objective:

Locally advanced recurrent rectal cancer (RRC) requires a multimodality approach. Intraoperative high-dose radiotherapy (HDR-IORT) as a treatment option may reduce the risk of local recurrence. However, the optimal therapeutic regimen remains unclear. The aim of this retrospective monocentric study was to evaluate the toxicity and oncologic outcomes of HDR-IORT after resection of the RRC.

Material/Methods:

Between 2018 and 2022, 17 patients with an RRC received the resection and HDR-IORT. HDR-IORT was delivered solely or as an intentional boost with a median dose of 13 Gy (range 10-13 Gy) using iridium-192 HDR remote afterloader (Elekta AB, Sweden). The prescription dose (range 10-13 Gy) was applied to the 5 mm depth from the applicator surface. All participants were followed for assessment of acute and late adverse events (using the Common Terminology Criteria for Adverse Events version 5.0 and the modified Late Effects in Normal Tissues criteria (subjective, objective, management, and analytic, LENT-SOMA) at three- to six-month intervals. Overall survival (OS) and progression-free survival (PFS) were calculated using the Kaplan-Meier method.

Results:

Most patients (47%) had cT3-4 N0 tumor stage of RRC. At the time of diagnosis of RRC, eight (47 %) patients had visceral metastases (hepatic, pulmonary, or peritoneal) in terms of oligometastatic disease. The median interval between primary tumor resection and diagnosis of RRC was 17 months (range 1-65 months). In addition to HDR IORT, two patients received long-course CRT up to 50.4 Gy in 1.8 Gy and two other patients received short-course CRT up to 36 Gy in 2 Gy. For concomitant CRT, all patients received 5-FU or capecitabine. The most common acute toxicity grade 1-2 was pain in seven (41.2 %) patients, wound healing disorder in three (17.6 %), and lymphedema in two (11.8%) patients. Chronic toxicities were almost the same grade 1-2 as pain in seven (41.2 %) patients, wound healing disorder in three (17.6 %), and incontinence in two (11.8%) cases. No patient experienced a higher grade ≥ 3 event. The median follow up was 13 months (range 1-38). The 1-, 2-, and 3-year OS was 87%, 65%, and 65% respectively. The 1-, 2-, and 3-year PFS was 67%, 57%, and 22% respectively. Gender, chemotherapy, dose escalation by EBRT, and presence of oligometastatic disease had no significant impact on OS and PFS (log-rank p>0.05 for all).

Conclusion: