OBJECTIVES: Invasive serous adenocarcinomas may present as primary ovarian (POC), primary fallopian tube (PFC) or primary peritoneal (PPC) carcinomas. Whether they are variants of the same malignancy or develop through different pathways is debated.

METHODS: Population-based prospectively collected data on POC (n=1443), PPC (n=268) and PFC (n=171) cases was obtained from the Danish Gynecological Cancer Database (2005-2013). Chi-square, Fisher's or Wilcoxon-Mann-Whitney test, multivariate logistic regression, Kaplan-Meier and multivariate Cox-regression were used as appropriate. Statistical tests were 2-sided. P-values of <0.05 were considered statistically significant.

RESULTS: PPC cases were older (P<0.0001), had a later age at menarche (P=0.02), a higher percentage were multi-parous (≥two children vs. no children) OR 1.70 (1.01-2.49) and both PPC and PFC tended to have a higher BMI (>35 vs. >18.5-25) than POC cases. PFC cases were diagnosed in earlier stages (P<0.001). In advanced stages a lower proportion had preoperative carcinosis or ascites, and a higher percentage had macro-radical surgery or lymphadenectomy compared to POC. In contrast, more PPC cases had post-operative carcinosis; whereas a lower proportion had lymphadenectomy or macro-radical surgery compared to POC. PPC had a significantly lower overall survival than POC, HR=1.24 (1.04-1.47).

CONCLUSION: We found differences in risk pattern profiles among the three groups, especially for PPC. Furthermore, the severity of stage specific disease differed significantly according to location, resulting in a lower overall survival for PPC. These differences warrant further research to determine to what extent PPC is a distinct disease entity.