Abstract
Background/Objective: India is the
world's most biodiverse region and is undergoing a
period of dramatic social and economic change. Due
to population's explosion, climate change and lax
implementation of environmental policies, the
incidence of breast cancer is increasing. From
population-based cancer registry data, breast
cancer is the most common cancer in women in urban
registries where it constitutes more than 30% of
all cancers in females. We conducted a
meta-analysis of all breast cancer case–control
studies conducted in India during 1991–2018 to
find pooled estimates of odds ratio (OR).
Materials and Methods: Eligible studies were
identified through a comprehensive literature
search of PubMed, EMBASE, and HINARI databases
from 1991 to January 2018. This analysis included
24 observational studies out of 34 that reported
the case–control distribution of reproductive
factors, body mass index (BMI) and type of
residence. The analysis was performed using RevMan
5.3 (Review Manager, 2017) applying the
random-effects model. Results: A total of 21,511
patients (9889 cases and 11,622 controls) were
analyzed, resulting in statistically significant
association between breast cancer and the
following reproductive factors: never breastfeed
(OR: 3.69; 95% confidence interval [CI]: 1.70,
8.01), menopausal age >50 years (OR: 2.88; 95%
CI: 1.85, 3.85), menarche age <13 years (OR:
1.83; 95% CI: 1.34, 2.51), null parity (OR: 1.58;
95% CI: 1.21, 2.06), postmenopause (OR: 1.35; 95%
CI: 1.13, 1.62), and age at the 1st pregnancy
>25 years (OR: 1.57; 95% CI: 1.37, 1.80).
Family history (FH) of breast cancer (OR: 5.33;
95% CI: 2.89, 9.82), obesity (OR: 1.19; 95% CI:
1.00, 1.42), and urban residence (OR: 1.22; 95%
CI: 1.03, 1.44) were also found to be significant
risk factors. Conclusion: The results of this
meta-analysis are indicative of significant
associations between reproductive factors and
breast cancer risk, profoundly so among women
experiencing menopause after the age of 50, women
who never breastfeed and FH of breast
cancer.
Genetic analysis of the vitamin D receptor gene in two epithelial cancers: melanoma and breast cancer case-control studies
