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Implications of the Biology of Cancer

Correcting defective oncogene function at this point is possible in theory only. Thus the major strategies for cancer control become:

• The disease is best prevented by avoiding exposure to radiation, chemicals and viruses which produce the genetic changes;

• The next best is early detection of the disease treat the disease early while it is still potentially curative. Examples include the use of the PAP smear for cervical cancer, mammography for breast cancer, the identification of dysplastic nevi or leukoplakia for melanoma and oral cancer respectively, or the detection of colonic polyps for colon cancer. Differentiation agents are being examined experimentally to see whether neoplastic transformation can be reversed.

Screening is important since early diagnosis of common tumors means that they are more likely to be curable as small local lesions. But screening is inextricably linked to treatment. It is sometimes forgotten that a screening program can only work if the detected tumors can be promptly and effectively treated. In this way screening downstages (more tumors are diagnosed at early stage) and eventually reduces mortality. But even incidence may also be reduced since some of the lesions detected (for example with PAP smears) will be premalignant.

New data were presented at the 1997 American Medical Association’s Science Reporters Conference which suggested that by the year 2000 one in every two Americans will be diagnosed with cancer during the course of his or her lifetime, but only one in five will actually die of the disease. The most recent U.S. data show for the first time a decline in the overall cancer death rate by 2 to 3%. Although some see the gains as small, it means that there are more cancer survivors even though cancer rates may be swelling. Many patients diagnosed today with several forms of cancer will live longer and with a greater quality of life than if the diagnosis had been made even 10 years ago.

Less than one in four patients survived more than five years after treatment in the 1940s. The number increased to one in three in the 1960s, and today the adjusted cure rate is slightly above 50% in a developed country. This is important for cancer control programming because it means a heavier load of active patients in the treatment system.

A number of factors are thought to be responsible for these changes:

• The quickening pace of our fundamental understanding of the cellular, biochemical and genetic basis of cancer;
• Better prospects for prevention and earlier diagnosis;

• A wider array of effective therapies;
• A greater emphasis on quality of life with less aggressive therapies being developed which place as much emphasis on patient comfort as on the eradication of disease;
• The appearance of new drugs which reduce side effects of chemotherapy like nausea, vomiting, diarrhea and anemia, as well as new agents which protect the heart and kidneys from chemotherapy damage, and which stimulate appetite and reduce cancer pain;
• Improved surgical techniques for breast conservation, limb preservation for bone and soft tissue sarcomas, sphincter-sparing procedures to replace colostomies for rectal cancer, and preservation of the larynx in advanced laryngeal carcinoma. Combined modality treatment with surgery plus adjuvant radiotherapy and chemotherpy create less morbidity and improved results.
• The use of psychosocial support, support groups, and behavioral modification such as smoking cessation, alcohol moderation, good nutrition, regular exercise and stress reduction.

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