Magnetic resonance imaging-based validation of the 2018 FIGO staging system in patients treated with definitive radiotherapy for locally advanced cervix cancer.

OBJECTIVE: To validate the revised 2018 International Federation of Gynecologic and Obstetrics (FIGO) staging system in patients who underwent diagnostic magnetic resonance imaging (MRI) and radiotherapy (RT) for locally advanced cervix cancer. METHODS: We analyzed 677 patients who were diagnosed with pelvic MRI and treated with definitive (chemo-)RT for locally advanced cervix cancer (stage IB2/IIA2-IVA or N+) between 1992 and 2018. Patients were classified according to 2009 and 2018 FIGO staging, and survival outcomes were compared. We developed a nomogram to improve prediction of progression-free survival (PFS). RESULTS: Pelvic and paraaortic lymph nodes were positive in 331 (48.9%) and 78 (11.5%) patients, respectively. At a median follow-up of 77.9 months, the 5-year PFS was 83.5%, 65.2%, 71.0%, 60.6%, 37.6% and 38.9% for IB, IIA, IIB, IIIA, IIIB and IVA according to FIGO 2009 and 88.9%, 60.0%, 73.8%, 66.7%, 36.3%, 68.9%, 43.6%, and 38.9% for IB, IIA, IIB, IIIA, IIIB, IIIC1, IIIC2, and IVA according to FIGO 2018, respectively. Survival of stage IIIC cervix cancer depended on the local extent of the tumor: the 5-year PFS of T1, T2, and T3 stages were 80.3%, 73.9%, and 45.5% for IIIC1 and 100%, 44.9%, and 23.4% for IIIC2. Histology, tumor size, node metastasis, FIGO 2009, and treatment modality were independent prognostic factors in the Cox regression analysis, and the nomogram incorporating these factors outperformed FIGO 2009 and FIGO 2018 (AUC 0.718 vs. 0.616 vs. 0.594). CONCLUSIONS: FIGO 2018 revision was associated with heterogenous outcomes among stage III cervix cancer patients. Our nomogram can assist the FIGO system in predicting PFS after definitive RT.