2788 - Recurrence Sites of FIGO Stage III Endometrial Cancer after Postoperative Radiotherapy
Presenter(s)
C. Li1, H. Shi2, L. Chen3, and R. Cai4; 1Department of Radiation Oncology, Ruijin Hospital, Shanghai Jiaotong University, Shanghai, China, 2Department of Breast Surgery, Shanghai Jiaotong University School of Medicine, Shanghai, China/Shanghai, China, 3Department of Radiation Oncology, Ruijin Hospital of Shanghai Jiaotong University, Shanghai, China, 4Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, Shanghai, China
Purpose/Objective(s): Postoperative radiotherapy (RT) is a cornerstone in the management of stage III endometrial cancer (EC). However, recurrence site and their implications for treatment optimization remain poorly characterized.
Materials/Methods: We retrospectively analyzed stage III EC patients treated at our institution from 2017 to 2022, comparing those who received postoperative RT with those who did not. Recurrence sites were categorized as pelvic or para-aortic, and histology was classified as endometrioid carcinoma or special types. KM curves and Fisher’s exact test was used to compare recurrence rates, and Cox regression was performed to identify risk factors for para-aortic lymph node (PALN) recurrence.
Results: Among 65 eligible patients, 50 received postoperative RT and 15 did not. Median follow-up was 39.5 vs. 48.00 months in RT and non-RT groups respectively. The two groups had similar median ages (60.5 vs. 59 years) and stage IIIC distribution (76% vs. 80%), but the non-RT group had a higher proportion of special histologic types (19.6% vs. 53.3%, p=0.03). The 5-year local-regional recurrence rate was significantly lower in the RT group (46.7% vs. 80.4%, P=0.013). The pelvic recurrence significantly reduced in the RT group (2.4% vs. 53.3%, P<0.001). Notably, recurrence patterns shifted after postoperative RT. In the RT group, a total of 5 recurrences occurred, all of which 100% (5/5) involved the PALN region with one case also exhibiting pelvic recurrence, compared to only 14.3% (1/7) recurrence of PALN region in the non-RT group (P=0.02). No vaginal recurrences were observed in two groups. Among PALN recurrences, 80% (4/5) occurred at the target volume margin. Special histologic type was an independent risk factor for PALN recurrence (HR, 18.7; 95% CI, 1.91–183.44; P=0.012, P-interaction >0.99 between RT and histology).
Conclusion: PALN recurrence is the dominant failure site in stage III EC after postoperative RT, highlighting the need to optimize target volumes to include the para-aortic region. Histological type is a key predictor of PALN recurrence.
Abstract 2788 - Table 1: Recurrence in radiotherapy vs. non-radiotherapy groups for local-regional, para-aortic, and pelvic sites (Fisher exact test)| Recurrence Type | Radiotherapy Group | Non-Radiotherapy Group | OR (95% CI) | p-value |
| Local-Regional Recurrence | 10% (5/50) | 46.67% (7/15) | 0.13 (0.03–0.62) | 0.004* |
| Absolute Pelvic Recurrence | 2% (1/50) | 46.67% (7/15) | 0.03 (0.001–0.24) | <0.001* |
| Absolute Para-aortic Recurrence | 10% (5/50) | 6.67% (1/15) | 1.55 (0.15–78.73) | 1 |
| Relative Para-aortic Recurrence | 100% (5/5) | 14.3% (1/7) | Inf (0.69–Inf) | 0.02* |