Ovarian cancer is the fifth leading cause of death from cancer for UK women, with a five-year survival rate below 50%. A key reason for this poor survival is that many women (two-thirds in the UK) are first diagnosed when they have advanced disease (stage III or IV). However, it is unclear whether other factors also influence survival, such as age, lifestyle factors, and the microscopic structure of the cancer (histotype).
In a new study published today in Cancer Epidemiology, researchers from Oxford Population Health’s Cancer Epidemiology Unit (CEU) explored the association between ovarian cancer survival and a range of personal characteristics and lifestyle factors, using data from The Million Women Study. 1.3 million UK women completed a detailed health questionnaire in 1996–2001 and were followed up for around 18 years through linking to national databases.
- During the follow-up period, 13,222 women were diagnosed with ovarian cancer, of whom 8,697 (66%) died from the disease.
- More advanced tumours were strongly associated with worse survival, even after adjusting for other factors. Compared to women diagnosed at stage I, women diagnosed at stage III had a seven-fold higher risk of death overall, and women diagnosed at stage IV had a ten-fold higher risk.
- Older age at diagnosis was also associated with poorer survival. Overall, each five-year increase in age was associated with a 19% increased risk of death from ovarian cancer.
- Tumour histotype also had a strong impact on survival. Five-year survival was good for serous and mucinous borderline tumours (95% and 97% respectively); intermediate for endometrioid (69%), mucinous (63%), and clear cell carcinomas (54%); and poor for serous carcinomas (31%), carcinosarcomas (21%), and tumours of other/ unspecified type (21%).
- There was also suggestive evidence of worse survival in women who reported higher body mass index (BMI) and smoking, though evidence for these associations was less strong than for stage, age and histotype. There was an overall 6% higher risk of death for each five unit increase in BMI, and women who smoked had a 17% higher risk of death compared with those who had never smoked.
- There was little or no evidence that survival was affected by the other factors investigated, including alcohol intake, oral contraception use, menopausal hormone therapy, and family history of breast cancer.
This analysis represents one of the largest studies to date on how ovarian cancer survival is affected by anthropometric factors, in addition to stage at diagnosis, tumour histotype and grade. The results indicate that tackling obesity and smoking could be one strategy to improve survival, however the stronger association with stage suggests that earlier diagnosis would have a greater impact. - Dr Kezia Gaitskell (CEU), a lead author of the study