Tumour histology, age at diagnosis, body mass and smoking are also strongly linked with ovarian cancer survival, according to the analysis led by Oxford Population Health.
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.
According to the research team, a possible explanation for why survival rates varied according to the tumour histotype may be differences in how these respond to treatment. For instance, some ovarian cancer histotypes (eg mucinous cancers) are resistant to conventional chemotherapy, whereas others respond well.
Dr Kezia Gaitskell (CEU), a lead author of the study, said: ‘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.’
*The Million Women Study is a population-based prospective study. The study includes one in four of all UK women born between 1935 and 1950, recruited through 66 NHS breast screening centres in England and Scotland in 1996-2001. Participants completed a questionnaire regarding health, sociodemographic, and lifestyle factors, and are being followed up for health outcomes by linkage to national databases.
**Body mass index (BMI) is a measure of weight relative to a person’s height. It is calculated by dividing a person’s weight (in kilograms) by the square of their height (in metres). A BMI between 18.5 and 24.9 kg/m² is considered a healthy weight; a BMI between 25 and 29.9 kg/m² is classed as overweight; and a BMI greater than 30 kg/m² is classed as obese.