CANCER is the 2nd leading cause of death, a heart attack being the first one and Cancer prevention is, therefore, a new challenge. Lung cancer accounts for the third and fifth cause of death in developed and developing countries respectively. Cancer forms over 200 kinds. Cancer cells are characterized by uncontrolled growth and spread abnormal cells, losing the power of self-destruction even after worn out, thus leading to crowding over healthy cells. It takes 2-6 weeks for cancer cells to duplicate (i.e. doubling time). One million cells together become a size of a pinhead and 1 billion that of a small grape. Thirty doubling time i.e. 230 = 10 73741824 cells (around 1 billion cells). Hence after 30 times multiplications (doubling), the cells will make a size to that of a small grape.
Five cancers universally causing leading deaths are cancers of lung, stomach, liver, colorectal and breast. Cancers account for 12% of all deaths. Every year 8 lakh new cases are detected, and 5.5 lakhs deaths, occurs due to cancer (accounting for 12% of all deaths).
It is rightly said that -Prevention is better than cure,which is so very opt in case of cancer.
Approximately 65% (30% tobacco + 35% diet) of cancers can be prevented by lifestyle modification, leaving tobacco and good healthy balanced diet. Other cancers may be due to infection (Human Papilloma Virus etc.), occupation, alcohol, pollution, radiation, drugs, industrial products, food addictive, ultraviolet light and some being, unknown. These factors which amount to approximately 25%, also can be modified to prevent cancers. Inherited cancers by gene mutation, amount to approximately 10%. Colon, breast, ovarian, prostate and skin cancers are inherited. By change in diet, environment and positive thinking inherited cause also may be modified up to some extent.
Hence approximately 90% of causes of cancers, are modifiable. If sincere steps are taken, cancers can be prevented to a larger extent.
Some simple lifestyle changes can make a big difference, as below –
- Smoking (tobacco) itself a very strong modifiable risk for at least 15 types (proven) of cancers. Among this lung oropharynx, larynx, esophagus, stomach, pancreas, kidney and bladder are distinct. Approximately 80% of lung cancers are smoker. Smoking 1-2 cigarettes daily, doubles the risk for oral and esophageal cancer.
Despite, after cessation of smoking, carcinogen-induced gene mutation, persists for years. Hence smoker has to leave smoking for > 15 years to become equal to non-smoker, as per risk of cancer is concerned. Smoking cessation may halt the early stages of carcinogenic process (i.e. – Metaplasia) but has no effect on Late Carcinogenesis.
- Diet Modification: In western culture where fat constitutes more than 30% of the total calories consumption, were seen to be having high prevalence of cancers. One should consume balanced diet. More than 5 fruits with high vegetable diet with more fiber, reduces cancer risk by 20%. Antioxidants, flavonoids, whole grain, beans and fibrous diet are associated with a reduction in colonic polyp and invasive colonic cancers. The metabolism producing oxygen free radical that can damage the cell’s fat, protein and DNA. Unrepaired DNA damage can turn into a mutation, which can later promote cancer. Hence, antioxidants are helpful. Mediterranean diet reduces risk of Breast Carcinoma. They also choose healthy fats like olive oil, over butter and fish instead of red meat. Ethyl alcohol 10 grams daily intake increase risk of breast cancer by 7.2%. Alcohol can cause cancers of head and neck, liver and esophagus.
- Vaccine: HPV (Human Papillomavirus Vaccine- Tetra) should be taken by females aged 9 to 26 years, to prevent from cervical, vulval, vaginal, anal, head and neck cancers. HPV 16 oral infection (additive affect with Smoking/Alcohol) acquired sexually, causes oropharynx cancer. In male also head and neck cancers may be prevented by this vaccine. In 1975, US rates of cervical cancers were 14.8/ million which declined to 6.5/ million in 2006, due to possibly by effective HPV vaccine. Now even HPV – Nano vaccine is on way to come to market.
Hepatitis B vaccine can save from liver cancer. This virus may be transmitted through sexual contact, infected blood and secretions. Hence, this vaccine is recommended for certain high-risk groups, such as – health workers, intravenous drug users and sex workers etc.
- One should also avoid unprotected, multi partner and unhealthy sex. Risk for cancer is also believed to increase with early age of sex exposure. Human Papillomavirus (HPV) infection gets transmitted due to intercourse with multiple partners, high risk sexual behavior and early multiple pregnancies. This HPV is responsible for cancer of cervix, vulva, anal and head & neck. In India: 134000 people get cervical cancer every year, which is 29% of overall world incidence. Approximately 72825 die every year because of cervical cancer, 30% of World rate. It is reported that one woman dies of cervical cancer in every 7 minutes (TOI 13.3.13).
Hepatitis B, Hepatitis C and HIV are also transmitted through sexual contact. Hepatitis B & C causes liver cancer, whereas HIV causes Kaposi’s Sarcoma, Cervical cancer and B-Cell non-Hodgkin’s Lymphoma.
- Exercise: If 75 minutes/ week (Minimum 4 days/ week) of vigorous exercise or 150 minutes/ week of moderate exercise is proved beneficial for few cancers like colon, breast etc. Breast cancer is believed to decrease by 18% with daily brisk walking.
- Protection from Ultraviolet (UV) light of sun, may protect from squamous/ basal cell carcinomas and melanoma. Exposure to UV -B rays which is emitted between 10am to 4pm, causes skin cancers. Hence protecting from this by using sun screening agents, wide brim hats, goggles, umbrella and protective clothes, may help. Clothes should be tightly woven, loose fitting that covers most of the skin. Bright and Dark colors reflect most of the UV radiation than bleached cotton. Avoid sunlamps and tanning beds, since they are as damaging as natural sunlight.
- Obesity is another risk factor for cancer. BMI for Indian should be between 18 kg/m2 to 23 kg/ m2. Risk increases as BMI increased beyond 25 kg/m2, for colon, breast, endometrial, esophagus cancers. Women aged over 50 years, if overweight, increased 50% risk for breast cancer. To decrease weight, avoid refined carbohydrates, high salt, high non – vegetarian diet.
- Aspirin or NSAID (Non-Steroidal Anti-Inflammatory Drug) are found to reduce the risk of Colorectal cancer. Diet high in calcium lower colon cancer risk, by binding with Bile & fatty acid. Bile and fatty acid are responsible for colonic epithelium proliferation. Avoid use of estrogen (for menopause etc.) and progesterone, prevents from cancers of Breast, Endometrial and Uterine. Women who begin menstruating early or who start menopause late, produce more estrogen over their lifetimes and have a higher risk of Breast cancer. After the Estrogen binds to its receptors in a cell, it turns on hormone – responsive gene that promotes DNA synthesis and self-proliferation. If the cell happens to have cancer producing mutations, this cell will also proliferate and has a chance to grow into tumor.
By help of Mass people, individual, Government, NGO, and mass media etc., we can tackle the below risk factors also.
- Air pollution (Sulphate, Nitrate, Ammonia, Carbon, Mineral dust, Nickel, Cadmium, Mercury, Arsenic etc.): a lot of toxic gases and metals contribute towards an unsafe value of air quality index (AQI). AQI<50 is ideal for inhalation. With each 10 ㎍ increase of these particles, per cubic meter of air, the risk of lung cancer increases by around 10 – 12%. It has been observed that the residential areas near to main ring roads have multi fold increase in lung cancer than those which are away from main roads.
- Industrial pollution: chemical exposures and pesticides have also been proved to cause cancers.
- Second hand smoke exposure also contributes as the causal agent because it is the smoke exiting out of the lungs of primary smoker after various harmful reactions and metabolization thus causing harm to the second hand (passive) smokers.
Gene mutation are the basis of inherited cancers, which amounts to about 10% of all cancers.
This is needed for early detection and cure of the patient.
Be cautious from cancer by remembering the below Mnemonic (CAUTION) for detection of majority of cancer.
Change in bowel / bladder habit
A sore that does not heal
Unusual bleeding or discharge
Thickening of lump in breast / elsewhere
Indigestion of difficulty in swallowing
Obvious change in wart / mole
Nagging coughing or hoarseness of voice
For few cancers (American Cancer Society), screening has been recommended for general population even if there are no obvious symptoms; like in cancers of the breast, cervical, colon, prostate, lung, ovary and skin etc. Its treatment is most successful when it is detected as early as possible, often before symptoms occur. Early stages of breast cancer usually do not produce symptoms but may show up on a Mammogram. Breast cancer when grows to a point where physical symptoms appear, which may be a painless mass, skin thickening/swelling / irritation/distortion, or nipple changes like erosion, inversion, tenderness or discharge needs emergent intervention. The ‘Modified Gail Model’ can predict the 5-year risk for breast cancer. If 5-year Gail risk is < 1.66% = low risk. If 5-year Gail risk is > 1.66% = high risk
For Breast Cancer:
- Self-breast examination after age 20 years
- Breast examination by a physician is needed after age 20 years, at every 3 years; and after 40 years, annually.
- Mammogram: American cancer society (ACS) recommends, female aged 40 years should undergo Mammography every year till in good health. Whereas United States Preventive Service Task Force (USPSTF) recommends female after 50 years, mammography should be done biennially.
- MRI Breast screening should be done in women with > 20% lifetime risk of breast cancer. In these, MRI breast plus Mammography was recommended annually.
For Cervical Cancer:
In Age > 21 years, Papanicolaou (Pap) test is recommended 3 yearly.
In Age> 30 years, Pap Smear combined with HPV testing is done every 5 years, till age 65 years.
For Colon Cancer:
Screening is recommended after 50 years (at a younger age, if there is any family history present). Fecal occult blood test (FOBT) is on yearly basis, Flexible sigmoidoscopy every 5 years or double contrast barium enema every 5 years, or colonoscopy every 10 yearly, are recommended for colonic cancer.
For Prostate Cancer:
In men over 50 years, PSA (Prostate-specific Antigen) and DRE (Digital Rectal Examination) is recommended.
Chemoprevention are specific natural or synthetic chemical agents to reverse, suppress, or prevent carcinogenesis before the development of invasive malignancy. Cancer can be prevented by interference with the factor that causes cancer initiation, promotion or progression. Influences that cause the initiated cell & its surrounding tissue microenvironment to progress through the carcinogenic process & change phenotypically are called promoters. Promoters include androgen, linked to prostate cancer & estrogen, linked to breast and endometrial cancers.
Oral Leucoplakia, a premalignant lesion, if treated with Isotretinoin cause regression of leucoplakia. Post-menopausal women taking estrogen plus progesterone have a 44% lower relative risk of colorectal cancer compared to placebo. This positive effect is mitigated by the modest increase in cardiovascular & breast cancer risk.
Tamoxifen (Antiestrogenic with partial estrogenic agonistic activity), upregulates Transforming Growth Factor β, which decreases breast cell proliferation thereby decreasing the risk of developing breast cancer by 49%.
Raloxifene is a chemopreventive drug especially for postmenopausal women for breast cancer.
Aromatase inhibitors are even more effective than Tamoxifen in adjuvant breast cancer therapy, as well as prevention for invasive cancers.
Angelina Jolie, Sharon Osbourne (who had genetic predisposition) got their breast removed as a preventive measure against breast cancer in order to lead a healthy life. Females with severe cervical dysplasia are treated with electrosurgical excision or conisation or hysterectomy. Colectomy is used to prevent colon cancer, is in patient with familial polyposis or ulcerative colitis. Prophylactic oophorectomy may also be employed for prevention of ovarian and breast cancer among high risk women.
How far have we come?
Five-year survival rate, in 1913 was 10% whereas in 2013 is 66%. We thrive to fight and will continue to do so since cancer still remains the second leading cause of death worldwide.
Around 90% of cancers can be prevented by general awareness, lifestyle modifications, healthy dietary habits, cessation of smoking and alcohol, maintaining environmental hygiene with good air quality index, vaccination, regular health care check-ups and last but not the least positive thinking!
The author, Dr. Srikant Sharma is a Senior consultant in internal medicine at Moolchand Medicity, New Delhi.