Other cancers

Analyses of data from our two international collaborations, The Collaborative Group on Epidemiological Studies of Ovarian Cancer and The Collaborative Group on Epidemiological studies of Endometrial Cancer, and from the Million Women Study, have shown that hormones have important causal and preventive effects on both ovarian and endometrial cancer; use of hormonal contraceptives results in strong long-term protection (Collaborative Group on Epidemiological Studies of Endometrial Cancer, 2015; Collaborative Group on Epidemiological Studies of Ovarian Cancer, 2008), and menopausal hormones have the opposite effect on risk (Collaborative Group On Epidemiological Studies Of Ovarian Cancer, 2015; Beral et al, 2007; Beral et al, 2005).

Bringing together the worldwide epidemiological data on these cancers has shown that failure to take account of tumour subtype can mask important associations. For example, in our collaborative analyses, smoking was associated with little effect on the overall incidence of ovarian cancer, but with a large increase in mucinous ovarian cancers and a compensatory decrease in endometrioid and clear cell tumours (Collaborative Group on Epidemiological Studies of Ovarian Cancer, 2012).

Future work will focus on exploring the role of reproductive and other risk factors for both cancers, according to histological type. The Million Women Study is being used to address hypotheses about the aetiology of ovarian and endometrial cancers that cannot be answered by the international collaborations, for example about the effects of diet and certain environmental exposures. 

Colorectal cancer is the second most common cancer in the UK. Extremely low rates of colorectal cancer are found in first, but not second, generation British South Asians, suggesting that there may be large, but still unknown, effects of environmental exposures. We are conducting research to assess the relationships between colorectal and other gastrointestinal cancers and a wide range of risk factors including smoking, alcohol intake, sex hormones, obesity, physical activity, diet and genetics within the Million Women Study and other existing cohort studies such as UK Biobank. Results of our analyses suggest that hormonal factors are associated with the development of several gastrointestinal cancers (Green et al, 2012) and that the risk of oesophageal cancer may be increased in users of oral bisphosphonates (Green et al, 2010).

We have shown that the risk of colorectal cancer is increased with alcohol intake (Floud et al, 2023) and we have also published a diet-wide analysis for risk of colorectal cancer showing that eating red and processed meat is associated with higher risks of colorectal cancer and that eating dairy products could help to protect against colorectal cancer, largely due to the calcium they contain (Papier et al, 2025).  The Million Women Study cohort has also been linked to routinely collected data from the NHS bowel screening programme to examine the relationship between factors such as education, socio-economic status, smoking habits, diet, and reproductive history, and screening uptake and outcomes. 

The extremely large size of the Million Women Study means that we are uniquely placed to examine the aetiology of many relatively rare cancers. Brain cancers and other cancers of the central nervous system (CNS) are uncommon but typically have a poor prognosis. Hormonal factors are thought to play a role in the aetiology of CNS cancers and analyses of Million Women Study data suggest that current users of HRT may be at an increased risk for such tumours (Benson et al, 2010), a finding supported by corresponding analyses of data from the UK General Practice Research Database (Benson et al, 2015). Analyses looking at mobile phone use within the Million Women Study found no evidence of an association with brain tumour incidence (Schuz et al, 2022; Benson et al, 2013). As sizeable numbers of rare cancer types accrue in the cohort we plan to investigate their relationship with diet, smoking, and other factors. 

PAN-CANCER analyses

We have published comprehensive reports, based on Million Women Study data, comparing risk factors that have been implicated in the development of many different cancer sites, such as birthweight, being breastfed, height, adiposity, alcohol intake, blood transfusion, and rheumatoid arthritis, with their associations with a wide range of cancers (Green et al, 2011; Reeves et al, 2007; Sweetland et al, 2023; Allen et al, 2009; Floud et al, 2023; Yang et al, 2014; Yang et al 2017; Yang et al 2019; Yang et al, 2024).