ESTRO 2025 - Abstract Book

S776

Clinical - Gynaecology

ESTRO 2025

Purpose/Objective: We aim to examine the trends in second primary malignancies (SPMs) among cervical cancer (CC) over the past 40 years, in conjunction with advancements in radiotherapy techniques, and assess whether brachytherapy increases the risk of SPMs. Material/Methods: Data from 27,565 CC survivors with over two years of follow-up were analyzed using SEER registries (1975-2019). Poisson and Fine-Gray competing risk regression calculated relative risks (RRs) and subdistribution hazard ratios (sHRs) for radiotherapy-related malignancies. Results: External beam radiotherapy (EBRT) (43%) was associated with an increased risk of pelvic SPMs (adjusted RR = 2.06; 95% CI, 1.80-2.36; P < 0.001). No significant differences were observed in extra-pelvic SPMs (adjusted RR = 1.01; 95% CI, 0.92-1.11; P = 0.888) or hematologic malignancies (adjusted RR = 0.85; 95% CI, 0.68-1.06; P = 0.225). Compare to 1975-1994, patients treated after 1995 had a significantly reduced incidence of pelvic SPMs within 15 years (sHR = 0.72; 95% CI, 0.53-0.98; P = 0.036). This incidence further declined after 2002, compared to those treated between 1975 and 2001 (sHR = 0.59; 95% CI, 0.36-0.95; P = 0.030). Brachytherapy alone increased the risk of pelvic malignancies (adjusted RR = 2.00; 95% CI, 1.14-3.46; P = 0.041), but combining EBRT with brachytherapy did not further raise the risk of pelvic SPMs (adjusted RR = 1.24; 95% CI, 0.91-1.70; P = 0.250). Conclusion: The risk of pelvic SPMs post-EBRT has declined over the past 40 years, and the addition of brachytherapy did not elevate the risk of SPMs. Poster Discussion Prevalence of Sarcopenia during and after Pelvic Radiotherapy in Gynecological Cancer Patients J. J. Laan 1 , G. H. Westerveld 1 , K. A. Hinnen 1 , B. R. Pieters 1 , Z. van Kesteren 1 , L. Ewals 1 , I. M. Dekker 2 , L. J. Stalpers 1 , L. R. van Lonkhuijzen 3 1 Radiation Oncology, AmsterdamUMC, Amsterdam, Netherlands. 2 Nutrition and Dietetics, AmsterdamUMC, Amsterdam, Netherlands. 3 gynaecologic oncology, AmsterdamUMC, Amsterdam, Netherlands Purpose/Objective: Patients undergoing pelvic radiation therapy for gynecological cancers are at risk of experiencing muscle loss, a condition known as sarcopenia. Sarcopenic gynecologic cancer patients treated with surgery or chemotherapy have demonstrated worse oncological outcome 1,2 . However, longitudinal data on body composition and the prevalence of sarcopenia in gynecological cancer patients treated with radiotherapy are limited. Our study aims to determine whether women undergoing pelvic radiation therapy develop sarcopenia before, during, and shortly after treatment, and whether this can be reliably assessed by bioelectric impedance analysis (BIA) as a bedside alternative to CT 3 . Material/Methods: This prospective cohort study included women aged ≥18 years with histologically confirmed primary cervical-, endometrial-, vulvar-, or vaginal cancer scheduled for external beam radiotherapy (EBRT) with curative intent. Sarcopenia was assessed at baseline, last week of EBRT, and 3 and 6 months follow-up. Sarcopenia was assessed by two methods: muscle mass area measured on lumbar CT scan (gold standard), and by BIA. Keywords: second cancers, radiotherapy, cervical cancer 263