Validation of FIGO 2018 staging for cervical cancer: Insights from a Japanese multicenter cohort.

126 Background: The International Federation of Gynecology and Obstetrics (FIGO) updated its staging system for cervical cancer in 2018, introducing major changes such as the establishment of stage IIIC based on lymph node metastasis (LNM), which has been reported to provide a better reflection of prognosis. However, stage IIIC has been reported to be heterogeneous, with prognoses varying depending on LNM extent and local tumor factors. In Japan, where various imaging tests are extensively performed, this revision is expected to lead to numerous cases of stage migration due to LNM. However, there have been few reports on the impact of this revision in Japan. Therefore, this multicenter study aims to assess the validity of FIGO 2018 in a Japanese cohort, focusing on LNM, local tumor factors, and histological types. Methods: Using a unified registry for gynecological malignancies developed by The Japanese Society of Obstetrics and Gynecology, this study involved 1,468 cervical cancer patients treated between 2011 and 2019 across eight designated cancer treatment hospitals. The registry used the FIGO 2009 staging system, and patients with stage IA to IIIB disease were restaged according to the FIGO 2018. Stage IIIC cases were further classified into substages IIIC-T1, IIIC-T2, and IIIC-T3AB based on local tumor factors. Results: After restaging process, A total of 347 cases (27.6%) were upstaged to stage IIIC according to LNM. Survival analysis showed that stage IIIC had a poorer prognosis than stage II (HR, 2.09; 95% CI, 1.27-3.44; p=0.004), but a significantly better prognosis than stage IIIAB (HR, 0.46; 95% CI, 0.27-0.77; p=0.004). There was also a clear difference between subclasses stage IIIC1 and IIIC2, with IIIC2 having a worse prognosis (HR, 2.13; 95% CI, 1.23-3.67; p=0.007). A survival analysis focusing on stageIIIC1 subdivisions (T1, T2, and T3AB) showed varied prognosis among them. Furthermore, IIIC1-T1 and IIIC1-T2 had significantly worse prognoses compared to stages I and II (I vs IIIC1-T1, HR, 3.21; 95% CI, 1.64-6.30; p<0.001. II vs IIIC1-T2, HR, 1.82; 95% CI, 1.03-3.21; p=0.04), while the prognosis of IIIC1-T3AB was similar to stage IIIAB. In the analysis by histological type, there was little difference between IIIC1-T1 and IIIC1-T2 in squamous cell carcinoma, but there was significant difference between IIIC1-T1 and IIIC1-T2 in adenocarcinoma (HR, 5.12; 95% CI, 1.10-23.74; p=0.04). On the other hand, for IIIC2, prognosis was similar across T1, T2, and T3AB, all showing uniformly poor outcomes. Conclusions: We were able to concretely clarify the current situation in Japan and validate the usefulness of FIGO 2018. The comprehensive examination of LNM, local tumor factors, and histological type may further reinforce and complement FIGO 2018.