Dr Shyam Kishore Shrivastava, Director of Radiation Oncology, HCG Cancer Centre Mumbai
Cancer is emerging as a major issue among the non-communicable diseases in our country. In India head and Neck, cervical and breast cancers are very common. As per recent data from National Cancer Registry Program (NCRP 2016), 1.7 million cases and 0.88 million deaths from cancers were expected in 2020. Among cancers, only 5-10% cancers have roots in genetic defects; however, 90-95% of cases can be attributed to the lifestyle and environment. Lifestyle factors including tobacco, alcohol, diet, environmental pollutants, infection, stress, and physical activity etc. have a profound influence on the development of cancer. Although the hereditary factors cannot be modified, however, the lifestyle and environment are potentially modifiable. Cancers like Head & neck, cervical, lung, colorectal, liver, skin, prostate, the breast is considered preventable cancers.
The use of tobacco as smoking was identified as a primary cause of lung cancer in 1964, further tobacco use has been attributed to nearly 15 types of cancers. According to studies the tobacco use in developing countries is increasing and using over 70% of world tobacco consumption. Alcohol is associated with an increased risk of oesophageal cancers, was known since 1910. Further studies revealed that chronic alcohol consumption is a risk factor for cancers of the upper aerodigestive tract including oral cavity, pharynx, larynx, and esophagus as well as liver, pancreas, and breast. There is evidence of synergistic effect between alcohol consumption and hepatitis C virus (HCV) and Hepatitis B virus (HBV). This possibly increases the risk of cirrhosis of the liver.
Diet also plays a significant role in cancer, red meat is considered as a risk factor for several cancers such as gastrointestinal tract, colorectal, gastric, pancreatic, and prostate, bladder, and oral cancers. Obesity is known for increased mortality and is attributed to cancer of the colon, breast, endometrium, renal cell carcinoma, etc. Increased modernization and western lifestyle and diet have been associated with increased prevalence of disruption of neurochemicals leading to inflammatory signalling pathways linked with obesity and cancer.
Nearly 15% of cancers are associated with infection such as Human Papilloma Virus (HPV), Epstein Barr Virus (EBV), HIV, HBV, HCV with risk of cervical, anogenital, skin cancer, nasopharyngeal cancer, Burkitt’s lymphoma, Kaposi sarcoma, and liver cancer. Even environmental pollution is linked to cancer including outdoor air pollution by carbon particles, hydrocarbons, smoke, and volatile compounds such as benzene. Food pollution by food additives, pesticides, carcinogenic metals and metalloids, pharmaceutical compounds, and cosmetics also contribute to cancer. Cervical cancer is associated with hygiene and socioeconomic status of the population, if the hygiene is improved the can be prevented to some extent. A small percentage of cancers may also be induced by ionizing or non-ionizing radiations typically from radioactive substances, ultraviolet, and pulsed electromagnetic radiation, these may include leukaemia, lymphoma, thyroid, skin cancers, sarcomas, lung, and breast cancers.
Prevention of cancer:
The fact that 5-10% of cancers are due to a genetic defect and the remaining 90-95% are due to lifestyle and environmental factors provide an opportunity for cancer prevention. Majority of cancers are related to tobacco and alcohol consumption, the avoidance of tobacco and minimizing alcohol consumption would likely have a major effect on reduction in cancer incidence.
Vaccination for certain viral causes such as cervical cancer, Hepatocellular carcinoma, would help prevent these cancers. Diet derived from natural products will potentially be helpful for a healthy lifestyle. Obesity and metabolic syndromes are linked to cancer mortality, thus modifying the diet, and having fruits and vegetables will prevent such instances. Several phytochemicals (such as carotenoids, vitamins, resveratrol, quercetin, sulforaphane, etc.) have been identified and may have potential against various cancers. These will have the advantage of being safe and targets for multiple cell signalling pathways to prevent cancers. Whole grain food does contain chemo-preventive antioxidants such as vitamin E, tocotrienols, phenolic acids, lignans, and phytic acids. A sedentary lifestyle has been associated with most chronic illnesses. Physical activities and regular exercise may reduce the incidence of various cancers.
For cancer prevention, a multi-prong approach is needed to tackle the growing burden of cancer in India. Therefore, cancer prevention requires smoking cessation, increased ingestion of fruits and vegetables, moderate use of alcohol, caloric restriction, exercise, minimal meat consumption, use of whole grains, use of vaccinations, and regular check-ups. World Health Organisation (WHO) has initiated a program for cancer cervix elimination, which is a great initiative at the global level. In India, the lack of nationwide screening guidelines and vaccination strategies is a hurdle for proper preventable cancers. Apart from the governmental initiative, the efforts by non-governmental organizations and advocacy by civil societies are needed to promote it. Cost-effective strategies for screening the high-risk population for sustainable long-term control of cancer. In addition, we provide evidence that cancer is a preventable disease that requires major lifestyle changes.