Introduction/Background Gynaecologic carcinosarcomas (GCS) are rare cancers. From 2003 onwards, GCS are no longer considered sarcomas but epithelial carcinomas; thus, shifting their treatment approach. Hospital Clinico San Carlos (HCSC) is EURACAN referral centre for rare gynaecological malignancies since 2022. The objectives of this study are to analyse the behaviour of GCS in our institution, treatment time trends and its impact on survival.

Methodology Retrospective analysis of 57 GCS patients treated in HCSC from 1995 to 2022.

Results Median age at diagnosis: 65 years (range 30–90); postmenopausal (98.2%) and ECOG 0 (63%). Median CA125 at diagnosis: 48.4 U/mL (range 5.1- 2130). Primary disease: uterus (80.7%), ovary (17.5%) or vaginal stump (1.8%). Ascites at diagnosis (14%). FIGO staging at diagnosis: I 40.4%, II 14%, III 22.8% and IV 22.8%. 49/57 patients underwent primary surgery (R0 81.6%) including lymphadenectomy in 65.3%. 42/57 patients received chemotherapy: adjuvant 50.9%, neoadjuvant 8.8%, and first line 14%. Two cohorts: up to 2003: 15.8% (9/57) and from 2003 to 2022: 84.2% (48/57). Carboplatin and paclitaxel were used from 2003 in 47.6%. Sequential adjuvant radiotherapy administered in 20/42 (47.6%), only in uterine CS (UCS).

After a median follow-up of 20.67 months, median Progression Free Survival (mPFS) and median Overall Survival (mOS) were 16.03 and 25.23 months, respectively. Patients diagnosed from 2003 onwards, have better mOS than those diagnosed before 2003 (40.5 vs 9.7 months, p 0.034), not better mPFS (17.9 vs 7.8 months p 0.415). Ascites (p 0.046), CA125 at diagnosis (p 0.030), >50% of endometrial infiltration in UCS (p 0.041) and incomplete response in the first radiological evaluation (p 0.001) were identified as independent statistically significant poor prognostic factors.

Conclusion The change in treatment approach in GCS since 2003 has improved mOS, probably due to a multidisciplinary approach including surgery, chemotherapy, and radiotherapy.

Disclosures Aranzazu Manzano: Receipt of grants/research supports: ASTRA ZENECA (AZ), Receipt of honoraria or consultation fees: AZ, GSK, Participation in a company sponsored speaker’s bureau: AZ, MSD, PHARMAMAR, GSK, ROVI, SANOFI.