Yes, to the extent we know the causes of it. If we know that a particular substance is responsible for causing a particular cancer, then it would be a fair assumption that avoidance of that substance will prevent that cancer. For example it has been established that tobacco causes lung cancer and people who do not smoke have a lesser chance of developing lung cancer. In fact the old adage prevention is better than cure is no better applied anywhere else. Early detection of cancer is also a form of prevention (secondary prevention) in the sense that early detection leads to cure and thereby prevent mortality and sufferings.
The proof comes from epidemiological observation. The cause and effect relation between cancer and some common substances in our environment was first noted amongst the chimney sweepers in London who used to develop cancers of the scrotum due to continuous exposure to chimney soot. Gradually many more such substances have been discovered and later verified through tests in laboratory animals and interventional studies in the community. It is true that often the proof is indirect but it is scientifically established that direct intervention or change in dietary habits and life style have caused a decline in incidences of stomach cancer, liver cancer, mouth cancers , and uterine cervical cancers in some communities.
Exposure to radiation and toxic chemicals that have the ability to cause direct cell damage and mutation of genes tops the list of such substances but the list is big and probably incomplete. We mention a few here :
They do, but to a much lesser degree. People, who smoke and indulge in excesses, are likely to develop cancers many more times than who do not.
People with history of certain types of cancers in the family are certainly at a higher risk. Family cancer syndromes have been identified in which people from the same family are found to be affected by certain types of adenocarcinomas. Medullary cancers of thyroid, breast, and ovarian cancers, cancers of colon and stomach, certain blood and lymph gland cancers, and retinoblastoma of the eye have genetic causes.
The steps can be taken at three levels as under,
1) Governmental level :- Along with the help of international agencies government can take steps to institute laws and monitoring systems to prevent hazards from radioactivity, toxic gas emissions and waste product from factories, use of known cancer causing substances like asbestos and certain chemicals, ban use of tobacco and products like pan masala to keep the environment safe and pollution free. It can also institute preventive measures like mass vaccination and screening programs for cancers endemic to a particular locality or community.
2) Community level: - Communities or large organizations can take up programs of awareness and early detection camps. ( See CROP )
3) Individual level : Three basic things to do are 1) avoidance of abuses like tobacco, excess of alcohol, fast life and fast food, 2) adoption of healthy diet without red meat, fat etc. and regular exercise 3) having regular check ups and be aware of the danger signals of cancer so that one seeks early medical consultation leading to early detection.
One must also assess his or her own cancer risk depending on family history of cancer and personal habits and be on the look out. It is possible to have preventive surgery against certain types of cancers,
Breast cancer ---- breast self examination every month after thirty, Mammography once at the age of forty, then every three years.
If family history positive, then genetic testing.
Uterine cervical cancer ----- Pap smear and gynecological examination at regular intervals after thirty five.
Colon cancer --- periodical examination of stool for occult blood. Colonoscopy in appropriate cases.
Oral cancers --- Mouth self examination, regular dental checkups
Prostate cancer--- periodical physical examination and PSA blood test for prostate cancer after sixty.
Lung cancer---- ( if strong H/O smoking ) Yearly x-ray chest.
Liver cancer--- ( if H/O serum hepatitis ) Blood test and USG scan.
Ovarian cancer --- USG scan, blood test, genetic testing if strong family historyHowever one must appreciate that there is no test which can be conclusively negative for all time to come and which can detect any and every cancer in the whole body. For each cancer a different test is necessary and needs to be repeated at periodical intervals.
A few drugs have passed trials, namely tamoxifen for breast cancer, aspirin and some other nonsteroidal anti inflammatory agents against colonic cancer, finesteride for prostate cancer, H. pylori infection curing drugs for gastric cancer, vitamin A derivatives for oral cancer.
Antioxidants have a special role. Antioxidants prevent damage to cells by free radicals, which are cells that have lost an electron and have become unstable cells. The free radicals try to steal electrons from other normal cells in order to become stable and thus create more new free radicals leading ultimately to the damage to DNA and development of mutated cells and possible development of a malignant or cancer cell.
Also diets deficient in vitamins and certain minerals can cause development of cancer like selenium deficiency cause esophageal cancer in certain areas and adequate intake of vitamins and minerals can prevent cancer. Although a large study in USA has shown that B-carotene treatment in smokers actualluy resulted in an increase in cancer incidence.
Amongst the common substances we intake, turmeric, carrot, tomato, leafy vegetables, garlic, and fish prevent cancer. In that respect simple Bengali diet is good for prevention of cancer but not perhaps the Chittagong type of diet that use heavily salted dried fish, excess of chili, and spices.
Several cancer treatment vaccines are under evaluation at present. They include vaccines for non-Hodgkin lymphoma, melanoma, kidney cancer, multiple myeloma, and prostate cancer. But as of today two vaccines are available for clinical use. They are hepatitis B virus for liver cancer and vaccine against human papillomavirus for cervical cancer.
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