2800 - MRI-Guided Interstitial Brachytherapy for Vaginal Recurrence of Endometrial Cancer Using 2 vs. 3 or More Fractions
Presenter(s)
J. N. Maina1, M. Milosevic2, J. M. Croke3,4, Z. Liu5, J. Lukovic5, N. Malik6, A. Rink7, A. Beiki-Ardakani8, R. A. Weersink9, M. Serban10, J. Skliarenko11, S. J. Rauth12, J. Conway4, and K. Han5; 1Department of Radiation Oncology, Princess Margaret Hospital, University of Toronto, Toronto, Canada, 2Princess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, ON, Canada, 3Department Radiation Oncology, University of Toronto, Toronto, ON, Canada, 4Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada, 5Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada, 6Division of Radiation Oncology, Princess Margaret Cancer Centre, Toronto, ON, Canada, 7Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Canada, Toronto, ON, Canada, 8Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada, 9Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, ON, Canada, 10Department of Radiation Oncology, Princess Margaret Hospital, Toroto, ON, Canada, 11Trillium Health Partners, Mississauga, ON, Canada, 12Credit Valley Hospital, Mississauga, ON, Canada
Purpose/Objective(s): Vaginal recurrences of endometrial cancer can be salvaged with external beam radiotherapy and brachytherapy, but the optimal brachytherapy dose-fractionation is unclear. We hypothesized that a 2-fraction (Fr) MRI-guided interstitial brachytherapy regimen would provide comparable outcomes as a more fractionated regimen. This study aimed to compare disease and toxicity outcomes of patients treated with 2 vs 3 or more Fr MRI-guided interstitial brachytherapy for vaginal recurrence of endometrial cancer.
Materials/Methods: Patients who received salvage MRI-guided interstitial brachytherapy for vaginal recurrence of endometrial cancer between 2018-2023 were retrospectively reviewed. Overall survival (OS) and disease-free survival (DFS) were estimated using the Kaplan-Meier method and compared between groups using the log rank test. Toxicities were assessed using the Common Terminology Criteria for Adverse Events (version 5).
Results: Thirty-nine patients were included in the analysis, of which most (97%) had endometrioid adenocarcinoma histology, and 4 (10%) also had pelvic lymphadenopathy. Only 2 patients were not treated with pelvic radiation due to prior radiation. Twenty-one (53.8%) patients were treated with 2 Fr (8-9 Gy/Fr) of brachytherapy and 18 patients (46.2%) with 3 or 4 Fr (mostly 7–8 Gy/Fr). There was no significant difference in mean high-risk clinical target volume (CTVHR) D90% (82.9 Gy vs 82.6 Gy, respectively). With a median follow up of 36 months, there was 1 isolated local failure (LF), 1 LF and regional failure (RF), 1 LF and distant failure (DF) and 1 RF in the 2-Fr group; and 1 isolated LF, 1 RF and DF, and 3 DF in the 3+ Fr group. No significant differences were found between the 2 Fr and 3+ Fr groups in 2-year DFS (83% vs 77%, p = 0.90) or OS (91% vs 94%, p = 0.81). Treatment was well-tolerated, with the highest late toxicity grade being grade 2 (0 gastrointestinal, 1 genitourinary and 5 vaginal), and no significant difference between the 2 groups.
Conclusion: Patients with vaginal recurrence of endometrial cancer treated with 2 Fr of MRI-guided interstitial brachytherapy had similar DFS, OS and toxicity rates as those treated with 3+ Fr. A 2-Fr MRI-guided interstitial brachytherapy regimen may be an alternative to 3+ Fr for patients with recurrent endometrial cancer.