ESTRO 2023 - Abstract Book

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ESTRO 2023

Between January 2021 and August 2022, 44 cervical cancer patients were treated with at least one ICB session with the conventional technique of using RR alone with TR applicators (Figure 2A), followed by at least one with the modified technique of using a combination of radiopaque VP and a RR, repeating the same applicator set and loading pattern (Figure 2B). The remaining ICB sessions, if any, were done using that applicator-type and packing technique, which gave the best dosimetric parameters during previous sessions in that particular patient. Out of total 111 ICB sessions with TR applicators, 44 in which RR alone was used constitutes conventional group and 67 in which a combination of radio-opaque VP and RR was used for rectum displacement constitutes modified group.

Results For the same dose (100%) prescribed to point A in both groups, the mean dose to the ICRU rectal point was 44.1% of the prescription dose (range, 23.8-77.8%; median 42.5%) in the RR+VP group and 55.5% (range, 36.4-73.1%; median 56.5%) in the RR group. There was 11.5% reduction in mean dose to the ICRU rectal point (p<0.001). The mean dose to the ICRU bladder point was 55.5% of the prescription dose (range, 14.8-127.2%; median 55.5%) in the RR+VP group and 49.8% (range 11.6-95.6%; median 51.5%) in the RR group. There was 5.7% increase in the mean dose to the ICRU bladder point (p=0.21). The other point doses and volume parameters were similar between groups. Conclusion Modified technique of combining radio-opaque vaginal packing and a rectal retractor, significantly reduced the ICRU rectal point dose, compared to using a rectal retractor alone during brachytherapy with tandem-ring applicators.

PO-2138 Outcomes of postoperative vaginal brachytherapy in the early-stage endometrial cancer

H. Lim 1 , W. Park 2 , W.K. Cho 3

1 Samsung Medical Center, Radiation Oncology , Seoul, Korea Republic of; 2 Samsung Medical Center, Sungkyunkwan University School of Medicine, Radiation Oncology, Seoul, Korea Republic of; 3 Samsung Medical Center, Sungkyunkwan University School of Medicine, Radiation Oncology, Seoul, Korea Republic of Purpose or Objective The aim of this study is to investigate treatment outcomes and failure pattern of adjuvant vaginal brachytherapy for postoperative early-stage endometrial cancer and to identify significant clinicopathologic factors associated with prognosis. Materials and Methods A total of 142 patients with stage 1 and 2 endometrial cancer who underwent vaginal brachytherapy after surgery were retrospectively reviewed. The rate of locoregional recurrence and distant metastasis were analyzed by using Pearson’s χ 2 test or Fisher’s exact test to explore possible risk factors. The Kaplan-Meier method was used to assess locoregional recurrence-free survival (LRRFS), disease-free survival (DFS), and overall survival (OS). The Cox proportional hazard model was applied for univariate and multivariate analysis to determine relative importance of prognostic risk factors affecting LRRFS, DFS, and OS. Results During follow-up, 14 (9.9%) patients developed recurrences. The recurrence was locoregional in 8 cases (local: 3, regional: 5) and distant in 10 cases. The 5-year locoregional recurrence-free survival, disease-free survival and overall survival were 94.0%, 91.0%, and 97.8%, respectively. The univariate and multivariate analysis showed that grade (HR=9.96, p=0.002), largest mass (HR=6.16, p=0.012) and depth of invasion (HR=8.14, p=0.010) were significantly associated with DFS. Grade (HR=65.69, p=0.012) was also a predictive factor for OS. Based on this analysis, we classified the patients into low, intermediate, and high-risk group regarding the number of factors that patients had; 0 for low, 1 for intermediate, and 2 or more for high risk group. Five-year LRRFS was 100%, 96.2%, and 87.2% for low, intermediate, and high-risk group, respectively (p=0.178). Five-year DFS was significantly different among the risk groups, presenting as 100%, 96.2%, and