A recent study using Health 2020 data gives us a glimpse into the complex world of different types of cancer.
The study (3) sought to investigate the connection between weight and height, and the risk of breast cancer. To this end, the researchers analysed data from 1,061,915 women, 36,297 of whom developed breast cancer. These data were pooled together from 20 studies (Health 2020 among them) under the mantle of the Pooling Project of Prospective Studies of Diet and Cancer (DCPP). The DCPP is an international consortium established in 1991 to investigate associations between dietary and anthropometric factors and risk of cancer.
Body height and weight have been consistently reported to be associated with cancer risk, but the associations are not always straightforward, and this study is a good example.
The analysis confirmed that the taller a woman is, the higher her risk of breast cancer. It also found that a higher Body Mass Index (BMI) after menopause led to a higher risk of breast cancer. Women who were lean at a young age (18-20 years old) and gained weight later in their life also had an increased risk of post-menopausal breast cancer.
In another analysis looking at subtypes of breast cancer, height, weight, and weight gain showed stronger associations with the hormone receptor-positive subtype than with the hormone receptor-negative subtype (see text box).
These results are useful in themselves to researchers and clinicians, but they also show us how varied cancer types can be. Cancer is not one disease, but many, and even within breast cancer we can find many different subtypes, manifesting in different ways, affected by different factors in different ways, and responding in different ways to treatment plans.
In another recent paper using the DCPP platform and Health 2020 data (4), the researchers showed that weight loss (of at least 2 kilograms), in women aged 50 years or older, sustained over the long term, was associated with a lower risk of breast cancer compared with those of stable weight. This is important evidence for breast cancer prevention.
These findings highlight the importance of pooling projects such as the DCPP: it is only by combining data from multiple studies that researchers can get a sample size large enough to enable them to look at cancer subtypes and at detailed factors such as changes in body weight throughout life.
3. van den Brandt PA, Ziegler RG, Wang M, Hou T, Li R, Adami HO, et al. Body size and weight change over adulthood and risk of breast cancer by menopausal and hormone receptor status: a pooled analysis of 20 prospective cohort studies. Eur J Epidemiol. 2021;36(1):37-55.
4. Teras LR, Patel AV, Wang M, Yaun SS, Anderson K, Brathwaite R, et al. Sustained Weight Loss and Risk of Breast Cancer in Women 50 Years and Older: A Pooled Analysis of Prospective Data. J Natl Cancer Inst. 2020 Sep 1;112(9):929-937.
Text Box 1: Breast cancer and hormone receptors
A “hormone receptor” is a class of protein found in many types of human cells. Breast tumours are routinely tested to see whether their cells have receptors for the hormones oestrogen and progesterone. The presence or absence of these receptors can tell a clinician a lot about how to classify – and treat – that tumour.