11-17 January 2013 #638

Testing screens

Screening for cancer helps by identifying diseases early and give patients a better shot at a healthy life
Dhanvantari by Buddha Basnyat, MD

Screening tests for cancer leave big dents in peoples' wallets, but they help in the early detection of diseases and give patients a better shot at a healthy life. In this piece we will look at tests available for six of the most common cancers: breast, cervix, colon, lung, ovary, and prostate.

For breast cancer, mammography (which uses low energy X-rays) is the most common method to look for abnormal tissues. Doctors recommend mammograms every two years for women over 50.

In Nepal cervical cancer screening (Pap test) is still not widely used or available and as a result cervical cancer remains the most common cause of cancer-related death in women. Screening should ideally start at 21, regardless of the age of onset of sexual activity and repeated every three years until the age of 29. After that the test can be done every five years till the age of 65. Because the human papilloma virus triggers cervical cancer, vaccination against this virus is useful, but rather expensive.

Colon cancer is caused by polys (abnormal growth in the mucosal lining of the colon). Removing the polys can prevent cancer, so colonoscope screening is recommended at 50 and every 10 years thereafter till 75.

Out of all the tests, screening for prostate cancer is controversial to say the least. Many low risk prostate cancers are slow to grow and may outlive the patient. So what is the point of screening? Furthermore, once cancer in the prostate is detected, most people will want to do further tests and procedures which may not be risk-free.

After evaluating the risk-benefit ratio of prostate cancer screening, the US Preventive Service Task Force no longer supports the commonly used prostate-specific antigen (PSA) test which is a blood test. They suggest the digital (finger) rectal exam instead.

For heavy smokers screening for lung cancer with chest X-rays or sputum exam is not worthwhile, but the low-dose CT (LDCT) of the chest is a good alternative. Of course, giving up smoking would be the best way to avoid this leading cause of death.

For ovarian cancer, no screening appears to be beneficial for women with average-risk, keeping in mind the risk-benefit ratio.

For patients with special risks (for example, patients with a family history of ovarian cancer, colon cancer etc), the recommendations discussed above for all the different cancers may not apply.