Abstract P6-10-15: Lifelong vegetarianism and breast cancer risk in India: A multicentre case control study of 2101 women
Authors: Gathani T , Barnes I 
Published: May 2016

Background

Breast cancer is now the most commonly diagnosed malignancy in women in India with over 150,000 incident cases per year. Interest in the role of diet in the aetiology of breast cancer is stimulated by the observation of the lower incidence of breast cancer in Asian populations where the intake of animal products is lower than that of Western populations. Studies investigating this relationship to date in India have been of small size and provided conflicting results and therefore a large scale case-control study in India addressing this relationship is of interest.

Methods

Between 2011 and 2014 we conducted a multicentre hospital based case-control study in eight cancer centres in India. Eligible cases included women aged 30-70 years with a new diagnosis of primary invasive breast cancer (ICD10 C50). Eligible hospital based controls included the accompanying attendants of the women with breast cancer and patients in the general hospital without cancer. Information about diet, lifestyle, reproductive and socio-demographic factors were collected using interviewer administered structured questionnaires. Cases and controls were frequency matched on a age geography. Multivariate logistic regression models were used to estimate the odds ratio and 95% confidence intervals for the risk of breast cancer in relation to lifelong vegetarianism, following adjustment for other known risk factors for the disease.

Results

The study included 2101 cases and 2252 controls. The mean age at recruitment was similar for both cases (49.7 years) and controls (49.6 years). The mean number of children was similar for both cases (2.6) and controls (2.5) and 98% of the study population had ever breastfed. However significant differences were observed in the proportion of cases whose duration of breastfeeding was greater than six years compared to controls (22% versus 29%). Cases were significantly more likely to live in a town (23% versus 16%), have running water (84% versus 78%) and live in a permanent dwelling (88% versus 78%). The proportion of lifelong vegetarians among the cases was 29% compared to 25% amongst the controls. However, on multivariate analysis, with adjustment for known risk factors for the disease, the risk of breast cancer was the same amongst cases and controls (OR 1.01 (95% CI 0.87-1.19)).

Conclusions

The prevalence of the known reproductive and sociodemographic risk factors for breast cancer is similar in India as in other populations. To our knowledge, this is the largest study conducted in India investigating the relationship between lifelong vegetarianism and risk of breast cancer, taking into account known risk factors for the disease. These results show that lifelong exposure to a vegetarian diet does not decrease the subsequent risk of breast cancer.

Citation Format: Gathani T, Barnes I. Lifelong vegetarianism and breast cancer risk in India: A multicentre case control study of 2101 women. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-10-15.