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60 Histological subtypes of ovarian cancer: worldwide distribution and comparison of survival (CONCORD-3)

Objectives Ovarian cancer comprises several histologically distinct subtypes. The distribution of these subtypes varies worldwide. Survival differs between the subtypes. The CONCORD programme is the largest population-based study of global trends in cancer survival. We aimed to explore international variation in survival for each subtype, to help interpret international differences in survival from all ovarian cancers combined. Methods The third cycle of the CONCORD programme (CONCORD-3) includes data on 812,783 adult (15–99 years) women diagnosed with ovarian cancer during 2000–2014 in 61 countries. We defined six histological groups: type I epithelial, type II epithelial, germ cell, sex cord-stromal, other specific non-epithelial and non-specific morphology. Only microscopically verified tumours were included. Borderline tumours were excluded. We estimated age-standardised 5-year net survival for each country by histological group. Results Type II tumours were the commonest histological group worldwide (70%), followed by type I tumours (22%). Non-specific, other specific non-epithelial, germ cell and sex cord-stromal tumours were rare (8% of all tumours). Survival for each histologic subtype varied widely between countries. Survival from sex-cord stromal tumours was highest (80–90%). Survival ranged from 40% to 70% for type I tumours, but was much lower for type II (20–40%). Survival from germ cell tumours was generally 70–80%. Conclusions Type I, germ cell and sex cord-stromal tumours generally showed higher survival than type II tumours. The proportion of these tumours may influence survival estimates for all ovarian cancers combined. International comparisons of survival should focus on survival for each histological subtype rather than for all ovarian cancers combined.