This study examines the state-wise burden of female breast cancer in India in 2016 using data from 28 population-based cancer registries under NCRP across the country. In 2018, the age-standardized breast cancer incidence among women in South Central Asia was 25.9 per 100,000 women, according to the GLOBOCAN study [8, 19]. According to the Global Burden of Diseases (GBD) study, the age-standardized rate in South Central Asia in 2016 was 21.6 per 100,000 women [20]. These studies estimated the national and subnational burdens using a wide range of data sources. However, our study only used data from population-based cancer registries under NCRP, which are mainly in urban areas. Rural women are less likely to develop breast cancer than their urban counterparts, and age-standardized incidence rates are higher in urban and metro areas, with Hyderabad, Chennai, Bangalore, and Delhi as leading Indian cities [21, 22]. Urban factors such as a sedentary lifestyle, high obesity rates, delayed age at marriage and childbirth, and minimal breastfeeding have been attributed to a higher burden of breast cancer in urban areas compared to their rural counterparts [23]. This is supported by our study's findings, which indicate that urban registries such as Chennai, Bangalore, and Delhi had higher incidence rates than rural registries. This can explain why our study found a higher incidence of breast cancer (32.0 per 100,000 women) than the GBD and GLOBOCAN estimates.

The study found that the breast cancer burden is higher in the state of Telangana. The relatively low literacy rate among females, higher life expectancy than the national average, high tobacco use, and alcohol consumption among women contributed to the increase in cancer burden in the state [24, 25]. In addition, one in three women were found to be overweight/obese, ranking 6th among the states of India, which is an important risk factor for breast cancer [26]. This was attributed to changing lifestyles, sedentary behaviour, unhealthy eating, and inadequate physical activity [27]. An average delay of 271 days (as noted in a study from neighboring state of Odisha) in disclosing symptoms to loved ones before taking steps toward diagnosis contributes to the late diagnosis of cancer [28].

The GBD also looked at regional variations in female breast cancer. The crude DALYs were found to be higher in states such as Kerala, Punjab, Tamil Nadu, Delhi, Maharashtra, Karnataka, and Haryana [20]. With the exception of Maharashtra, these states have higher DALYs in our study as well. However, the female breast cancer burden estimate for Maharashtra was simply an average of a number of registries that included both urban and rural registries. In our study, we may have underestimated the burden for Maharashtra. However, the majority of these burden differences between states can be explained by their socio-economic development.

Socio-economic factors significantly shape the cancer burden, affecting access to healthcare, preventive measures, and treatment outcomes. Individuals with lower socio-economic status encounter barriers to timely and quality healthcare, leading to delayed cancer detection, compounded by limited resources and health literacy. Occupational exposures and financial strain heighten cancer risks and impact treatment accessibility. Geographical and psychosocial disparities further complicate the issue. Research priorities may inadvertently overlook cancers prevalent in lower socio-economic groups. Recognizing and addressing these disparities is crucial for equitable cancer control, ensuring universal access to prevention, early detection, and treatment. In India, the correlation between cancer prevalence and socio-economic inequalities is evident, emphasizing the need to reevaluate resource allocation and enhance access to healthcare and social support systems [29,30,31,32].

Even global studies have found that developed countries have a higher incidence of breast cancer than developing and underdeveloped countries [19]. This can be applied to India, where more developed states like Tamil Nadu, Telangana, Karnataka, and Delhi have a much higher burden of breast cancer than states in the eastern and north-eastern regions. This is due to known risk factors such as delayed first childbirth, lower parity, higher levels of obesity, a shorter duration of breastfeeding, and physical inactivity, all of which are linked to a region's socio-economic development [33]. Another possible explanation is that states with more advanced healthcare infrastructure have higher levels of awareness, screening, and diagnosis rates.

In developing Asian countries, the incidence of breast cancer peaked in the forties during the early twenty-first century, whereas it peaked in the sixties in developed countries [34, 35]. Our finding that breast cancer incidence peaked after the age of 50 suggests that the age of onset in India has changed since the previous decade, moving from the forties to fifty and above. This is a positive finding despite the rising incidence of breast cancer, as the prognosis for breast cancer in younger women is typically worse [36]. The results of the projection indicated a significant increase in the burden of female breast cancer in India from 2016 levels. Several studies in India have found that the age-standardized incidence of breast cancer is significantly increasing [36,37,38].

The increasing incidence of breast cancer in India underscores the urgent need for comprehensive awareness campaigns and screening programs [39]. A significant concern is that a majority of women diagnosed with breast cancer in the country present with advanced stages or metastatic disease, suggesting a lack of awareness [36]. India faces remarkably low rates of breast cancer screening, encompassing self-breast examination and mammography [40]. Numerous barriers contribute to this, including personal factors (lack of awareness about screening services, methods, lack of prioritization of health, and inadequate education), economic constraints, social stigma around the disease, distrust in the healthcare systems and professionals, inadequate health infrastructure, fears regarding surgical procedures like mastectomy [31, 41,42,43,44,45].

Recognizing the need for intervention, mandatory screening, incentivization, and awareness creation emerge as crucial factors facilitating breast cancer screening. Hence, adopting a multidisciplinary approach that not only raises awareness but also promotes screening and facilitates treatment becomes imperative. Strengthening screening, diagnostic, and treatment facilities for breast cancer patients in India could potentially reduce premature mortality, prevent catastrophic health expenditures, and enhance overall survival rates.