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    Thursday, May 14, 2009

    Does Cancer Screening Really Help All?

    No evidence so far that it helps with certain cancers reports Robert W. Rebar, MD [Journal Watch General Medicine, 2009].

    As much one would like to believe that early detection for all automatically leads to better care, that is not always the case. Although it is true that finding and treating cancer at an early stage will help in some cases — such as colon cancer and Pap smears that reduce deaths from cervical cancer — the data are less conclusive for at least three other cancers.

    Ovarian carcinoma
    Ovarian carcinoma is the leading cause of death from gynecologic malignancies in the U.S., reports Robert W. Rebar, MD largely because diagnosis usually is not made until disease is advanced.

    In a study funded by the National Cancer Institute, of more than 30,000 women in the study’s screening arm who underwent at least one annual screen, 11.1% had at least one positive test result. The positive predictive value of the tests ranged from 1.0% to 1.3% during different screening rounds, and 4.7 to 6.2 cancers per 10,000 women were identified with screening. The ratio of surgeries to detected invasive ovarian cancer cases was 19.5 to 1.

    Unfortunately 72% of cancers were late stage. Because the prevalence of ovarian cancer is low, false positives are numerous and screening leads to surgery for many women who do not have cancer. The benefits of screening will outweigh the harms seems unlikely.

    Prostate cancer
    In an op-ed in USA Today (4/23/09), Kevin Pho, MD, a primary-care physician in New Hampshire, questions whether "early screening" is "always in the patient's best interest." Dr. Pho cited two studies appearing in the New England Journal of Medicine that examine "the effects of prostate cancer screening."

    In one study, "sponsored by the National Institutes of Health," researchers "found that such screening did not decrease deaths." Meanwhile, "the second study showed that for every death prevented, 50 men would suffer from over-diagnosis." To put the problem in context: Only 3% of men die from prostate cancer; 97% will die from something else.

    Almost one-third of those treated for prostate cancer suffer from significant side effects, including impotence and urinary incontinence. Taken together, the study found that the benefit was minimal, and far from definitive.

    Breast Cancer[see Part II in my series of article on Mammagraphy]

    Dr. K.Pho notes that "similar issues influence breast cancer screening decisions" and that physicians "cannot be sure of which cancers are dangerous." As a result, "for every life saved from breast cancer, 10 more lives will be affected by" biopsy or breast surgery. He concludes, There cannot be a one-size-fits-all approach" to preventive care.Because doctors cannot be sure of which cancers are dangerous, every woman with a suspicious finding is subjected to a biopsy or breast surgery. For every life saved from breast cancer, 10 more lives will be affected by the ensuing procedures.

    Other cancers
    The uncertainty surrounding tests is true of other cancers, including lung, skin (malignant melanoma), testicular and pancreatic (pancreatic adenocarcinoma), where little compelling evidence has shown that early screening is beneficial.

    My opinion
    The problem associated with these studies showing questionable or no benefit to a longer life for cancer victims is the statistics themselves. Statistics are still statistics and you are you. Some lives have been saved from early screening. But for every inspiring story of a person cured from cancer made possible by early detection, there are untold stories of many more who suffer from the side effects of unnecessary invasive procedures stemming from false positive test results.

    But when only 1% of a certain population of 100 benefits that 1% may be you-and as far as you’re concerned you are 100% of the study.

    Another example is that mammograms detect a number of slow-growing tumors that will never be harmful. But because doctors cannot be sure of which cancers are dangerous, every woman with a suspicious finding is subjected to a biopsy or breast surgery. Although it’s true that for every life saved from breast cancer, 10 more lives will be affected by the ensuing procedures, yours may be the life that’s saved.

    Unless you believe with Gilbert Welch, professor of medicine at the Dartmouth Institute for Health Policy and Clinical Practice, who says, "I place considerable value on not suffering the side effects of treatment" and "death is not the only outcome that matters," you may choose not to undergo these uncertain screening procedures.

    But at least you will be making an informed decision. As Dr. Pho states “patients must be better informed of the potential consequences either choice can bring.”

    Please remember, as with all our articles we provide information, not medical advice.

    For any treatment of your own medical condition you must visit your local doctor, with or without our article[s]. These articles are not to be taken as individual medical advice.

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