A retrospective study for investigating the relationship between old and new staging systems with prognosis in ovarian cancer using gynecologic cancer registry of Japan Society of Obstetrics and Gynecology (JSOG): disparity between serous carcinoma and clear cell carcinoma

OBJECTIVE: International Federation of Gynecology and Obstetrics (FIGO) staging for ovarian, fallopian tube, and peritoneal cancers was revised in 2014. The aim of this study is to clarify whether the revised FIGO2014 staging reflects the prognosis of patients with ovarian cancer by histological type in Japan. METHODS: We extracted 9,747 patients who were diagnosed with ovarian cancer since 2004 until 2008 and who could be classified into appropriate stages from the Gynecologic Cancer Registry of Japan Society of Obstetrics and Gynecology. These cases were analyzed after revision to FIGO2014 based on the pTNM classification. RESULTS: Among stage I, the 5-year overall survival rate (5y-OS) in FIGO2014 was 94.9% in stage IA, 92.3% in stage IC1, 86.1% in IC2, and 84.9% in IC3 with significant differences between stages IA and IC1 (p=0.012), IC1 and IC2 (p<0.001). There was a significant difference between stages IA and IC1 in clear cell and mucinous carcinoma but not in serous and endometrioid carcinoma. Among stage III, the 5y-OS was 75.6% in stage IIIA1, 68.9% in IIIA2, 58.6% in IIIB, and 44.4% in IIIC, with significant differences between stages IIIA2 and IIIB (p=0.009), IIIB and IIIC (p<0.001). Among stage IV, the 5y-OS was 43.1% in stage IVA(*) and 32.1% in IVB with a significant difference (p=0.002). CONCLUSION: The results suggest that changes in classification for stage III and stage IV are appropriate, but the subclassification for stage IC might be too detailed. There was a discrepancy of prognosis by histological type between stage IA and IC1.