Why cancer strikes more women than men in India
For oncologists worldwide, India can look like a puzzling outlier when it comes to cancer.
For one, despite reporting more than 1.5 million new cases every year, India's cancer rate remains lower than, say, the economically advanced US. That's about 100 cases per 100,000 people compared with 300 in the US.
This may be easier to explain: Indians are a vastly younger people and as people get older, the chances of getting cancer get higher. But survival rates are poor - barely a third of patients survive beyond five years or more after being diagnosed with the disease.
What is more difficult to explain is why more women in India are diagnosed with cancer than men, according to a new study published in The Lancet Oncology. Men report a 25% higher incidence of cancer than women all over the world, but India bucks this trend.
Having said that, more men die of cancer in India than women.
But that is because breast, cervical, ovarian and uterine cancer, that account for more than 70% of the cancers in women in India, allow higher chances of survival on treatment. Indian men suffer largely from lung or oral cancer - both related to smoking and ingesting tobacco - which are more virulent with lower survival rates.
Breast cancer is now the most common cancer among women in India, accounting for 27% of all cancers among women. Oncologists say there has been a sharp uptick in cases in the last six years.
At 45-50 years, the peak age of onset of breast - and ovarian cancer - in India appears to be a decade younger than the peak age (above 60 years) in high-income countries. This could be due to genetic and environmental factors.
Cancer is, at times, a genomic disease. Studies have shown the BRCA1 and BRCA2 genes usually increase a woman's risk of breast cancer four to eightfold and can explain why some families have lots of relatives diagnosed with breast cancer.
But less than 10% of the breast cancers in India are inherited, so genomic screening may not be very useful to find out the cause in the vast majority of female cancers.
Then there are regional variations.
The incidence of breast cancer is the highest, for example, in the capital, Delhi, but oncologists are not sure why. They can only speculate about increased awareness and higher rates of diagnosis, and not much more.
Dr Ravi Mehrotra, director of the National Institute of Cancer Prevention and Research and one of the authors of the study, believes that known risk factors for breast cancer - high-fat diet, obesity, late marriage, fewer children, inadequate breast feeding - may be leading to more cases in what is a rapidly urbanising country.
Also, he says, many women may be diagnosed late because of lack of awareness and reluctance to go to doctors.
In the US, for example, 80% of breast cancers are diagnosed relatively early in the first and second stages. In India, most of the breast cancers are diagnosed in the third and fourth stages.
The only silver lining, say oncologists, is that 60% of those with breast cancer in India survive for five years.
"But we still don't know fully why women are reporting such a high rate of breast cancer," says Dr Mehrotra.
What can be more easily tackled is cervical cancer, mainly caused by the human papilloma virus (HPV), and accounting for nearly 23% of all cancers among women in India.
Since 2008, HPV vaccines have been offered to girls aged 11 to 13, and cases of the cancer caused by this virus have fallen sharply worldwide. In India, only Punjab and Delhi have HPV vaccination programmes.
But cervical cancer is still the second most common cancer among women in India, and accounts for a quarter of deaths among women suffering from cancer.
"It is one of the most preventable of all cancers," says Dr Mehrotra. "No women should be dying of cervical cancer."
India needs a louder and more transparent conversation about reproductive sexual health. It also needs to include the HPV vaccine in the bouquet of free mass vaccinations provided by the government.
According to the Lancet paper, India - a country of more than a billion people and 4,000 anthropologically distinct groups - needs genomic studies to identify country-specific genetic biomarkers. It also needs cancer prevention strategies that work for its people.
For example, the Lancet suggests parallel studies of women cancer patients in the Punjab region of India and the Punjabi diaspora in the UK. "This might offer an unique opportunity to study the genetic and environmental influences on cancer development in genetically related populations that have been subjected to different environmental factors."
India launched a cancer control programme in 1976, but there's not enough funds because the government spends a mere 1.2% of GDP on healthcare. But sometime this year, the government will launch free cancer screening for oral, breast and cervical cancer in 165 of the country's 700 districts.
"Things are looking up," says Dr Mehrotra. "But we have a long way to go. We still have a long way to go before we solve the many riddles."