Breast cancer in women is the major public health problem throughout the world. Collectively India, US, and China account for almost one-third of the global breast cancer
burden. It is the most common cancer among the women both in developed and developing countries. Inspite of advancement for diagnosis and treatment, cancer is still a big threat to our society. Cancer is the second most common disease after lung cancer, accounting for a maximum death in the world. One in ten of all new cancers diagnosed worldwide each year is a cancer of the female breast. More than 1.1 million cases are diagnosed and more than half a million people die of it worldwide. The prevalence of cancer in India is estimated to be 2.5 million with about 5, 50,000 deaths per annum. About 55% of the global burden is currently experienced in developed countries, but its incidence is rapidly rising in developing countries. Due to advancement in globalization, physical activity has reduced to a greater extent, which is in turn giving rise to various bodily disorders. Increasing incidence of cancer in women is heading towards psychosocial problems affecting family thus burdening the nation.
Adequate physical activity is most essential for both physical and mental well-being. Many cancer survivors who have a good prognosis are at higher risk of dying from other causes,
such as cardiovascular diseases, and could possibly reap the same benefits of exercise as individuals without a cancer diagnosis. Furthermore, the physical and mental stresses of the side effects of treatments is an additional challenge. Some aspects of a Western lifestyle, primarily a high caloric intake and little physical activity, resulting in a positive energy balance, weight gain and, ultimately, obesity, are suspected to play a role. Physical activity, both at work and during leisure time, has consistently been inversely associated with this disease. Physical exercise has consistently been identified as a central element of rehabilitation for many chronic diseases and has been successful in improving quality of life and reducing all-cause mortality. Recent observational evidence suggests that moderate levels of physical activity may even reduce the risk of death from breast cancer, and therefore exercise may prove to be a valuable intervention to improve not only quality of life but overall survival. Most cancer therapies to date focus on killing the tumor, physical activity may offer two complementary roles for standard cancer therapy. First, cancer-specific mortality, although generally attributed to the destructive behavior of the tumor, is also dependent on the general health of the patient.
Overall health status is inherently integrated and substantially influenced by factors such as physical activity. For example, diabetics who develop cancer have increased overall mortality and, perhaps, cancer-specific mortality compared with nondiabetics with cancer, and physical activity is one of the strongest protective factors against diabetes. Even the attribution of cause of death in a cancer patient can be fraught with difficulties. Second, physical activity could have direct effects on the tumor that are mediated through alterations of various hormones, including insulin, insulin like growth factor 1, estrogen, and adiponectin. Many of these hormones, and others, have been associated with cancer risk and prognosis, which indirectly supports a causal role of physical activity on cancer-specific death. These factors may promote or inhibit tumor cell growth, and thus directly affect tumor progression. Exercise also has immune-modulating effects, which theoretically could affect cancer development or progression. Cancers have a number of molecular abnormalities related to metabolic and energy balance–related pathways.
Am I at risk?
The incidence of breast cancer increases with age, doubling about every 10 years until the menopause when the rate of increase slows dramatically. Compared with lung cancer, the incidence of breast cancer is higher at younger ages.
Age at menarche and menopause
Women who start menstruating early in life or who have a late menopause have an increased risk of developing breast cancer. Women who have a natural menopause after the age of 55 are twice as likely to develop breast cancer as women who experience the menopause before the age of 45. At one extreme, women who undergo surgical removal of ovum before the age of 35 have only 40% of the risk of breast cancer of women who have a natural menopause.
Age at first pregnancy
Nulliparity and late age at first birth both increase the lifetime incidence of breast cancer. The risk of breast cancer in women who have their first child after the age of 30 is about twice that of women who have their first child before the age of 20. The highest risk group are those who have a first child after the age of 35; these women appear to be at even higher risk than nulliparous women. An early age at birth of a second child further reduces the risk of breast cancer.
Up to 10% of breast cancer in Western countries is due to genetic predisposition. It can be transmitted through either sex and that some family members may transmit the abnormal gene without developing cancer themselves. It is not yet known how many breast cancer genes there may be. Two breast cancer genes, BRCA1 and BRCA2, have been identified and account for a substantial proportion of very high risk families—i.e. those with four or more breast cancers among close relatives.
Obesity is associated with a twofold increase in the risk of breast cancer in postmenopausal women whereas among premenopausal women it is associated with a reduced incidence.
Some studies have shown a link between alcohol consumption and incidence of breast cancer, but the relation is inconsistent and the association may be with other dietary factors rather than alcohol.
While women are taking oral contraceptives and for 10 years after stopping these agents, there is a small increase in the relative risk of developing breast cancer. There is no significantly increased risk of having breast cancer diagnosed 10 or more years following cessation of the oral contraceptive agent. Cancers diagnosed in women taking the oral contraceptive are less likely to be advanced clinically than those diagnosed in women who have never used these agents. Duration of use, age at first use, dose and type of hormone within the contraceptives appear to have no significant effect on breast cancer risk. Women who begin use before the age of 20 appear to have a higher relative risk than women who begin oral contraceptive use at an older age. This higher relative risk applies at an age when the incidence of breast cancer is however very low.
Hormone replacement therapy
Among current users of HRT and those who have ceased use 14 years previously have the relative risk of having breast cancer. This increase is consistent with the effect of a delay in the menopause. The risk of breast cancer appears higher with combined oestrogen and progestogen combinations.