Introduction/Background Uterine carcinosarcoma (CS) is a rare cancer with poor prognosis. CS without myometrial invasion (MI), such as limited to the endometrial lining/polyp or with no residual uterine disease at the time of hysterectomy is extremely uncommon. The oncologic outcomes of these patients are poorly understood and there is no consensus on standard of care. Therefore, the study aims to evaluate the long-term outcomes of CS patients without MI.

Methodology Patients with FIGO stage IA CS limited to the endometrial lining/polyp or without residual uterine disease were identified from 9 centers worldwide between 12/1998 and 1/2023. Patients who underwent surgical staging (hysterectomy, bilateral salpingo-oophorectomy, bilateral lymph node assessment (sentinel or systematic lymphadenectomy)) were included. Patients were excluded if adjuvant therapy was unknown. Survival analysis follow-up was limited to the first 10 years after surgery.

Results Of 84 patients included, 21 (25.0%) had disease confined to a polyp, 50 (59.5%) to the endometrial lining, and 13 (15.5%) had no residual disease in the hysterectomy specimen. Patients received observation (n=12 [14.3%]), vaginal brachytherapy (VB) alone (n=13 [15.5%]), EBRT±VB (n=4 [4.8%]), or chemotherapy ±EBRT±VB (n=55 [65.5%]). Twenty-seven patients (32.1%) recurred. Five-year recurrence-free survival (RFS) was 63.9% (95% CI, 53.2–76.7%); median follow-up for patients without recurrence was 4.6 years (interquartile range, 1.9–6.1). No significant difference was observed in RFS between patients in the three groups (p=0.60, figure 1A). Five-year overall survival (OS) was 73.0% (95% CI, 62.9–84.8%), and was also not significantly different between groups (p=0.12, figure 1B). Univariate analysis showed no significant differences in RFS and OS by postoperative treatment.

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Abstract #534 Figure 1

Recurrence-free survival (A) and overall survival (B) Kaplan Meier curves stratified by tumor location: no residual in the uterine specimen, confined to polyp, limited to endometrium.

Conclusion Patients with stage IA CS without MI have a relatively high recurrence rate. Even in patients with no MI or no residual tumor at the time of hysterectomy, prognosis is unfavorable. While caution must be exercised in withholding adjuvant therapy, the optimal treatment remains unclear.

Disclosures NO disclosures