05/01/2007Cancer Screening

Eudoro Coello, MD, FRCP (C)

The goal of screening is to detect cancer at an early stage when it is treatable and curable.  There should be evidence that earlier diagnosis results in an improved outcome.  Only cancers of the breast, cervix, colorectal and prostate have widely accepted screening interventions, and only breast, colorectal and cervical cancer have met the criteria of the US Preventive Services Task Force.  Listed below are current recommendations.

Breast Cancer Screening

Acceptable techniques include mammogram, clinical breast examination, and breast self-examination.  The breast cancer screening trials provide clear evidence of benefit for women over the age of 50, and increased evidence of a small but statistically significant benefit for women 40-49 years of age.  Both the American Cancer Society and the National Cancer Institute advise yearly mammograms for women 40 or older based on a reduced mortality which is most pronounced in women in their 50’s.  Additional benefit is observed with high quality yearly clinical breast examination.

Cervical Cancer Screening

A steady declining mortality was observed after the initiation of widespread PAP testing, and this has resulted in a major success in cancer control.  Cancer of the cervix is accessible and has a long pre-clinical detectable phase.  Guidelines are continuing to recommend annual screening.  Because mortality increases with advanced age and 40—50% of all women who die from cancer of the cervix are older than 65 years, it seems prudent to screen older women.

For women who have had hysterectomies, the practice of screening with vaginal smears is still common; however, the likelihood of detecting vaginal dysplasia is extremely low and the false positive rate is high, suggesting that the practice is unnecessary.

Colorectal Cancer Screening

The efficacy of fecal occult blood testing and endoscopy has been well documented.  A slow decrease has been seen in both the incidence and mortality since the 1970’s.

As in cancer of the cervix, a long pre-clinical and detectable phase make colorectal carcinoma ideal for screening.  Increased risk for colorectal cancer is found with personal history of colorectal cancer, adenomatous polyps or inflammatory bowel disease as well as those with family history of adenomas, colorectal cancer or colorectal cancer syndromes.

Two tests that are currently in use for colorectal cancer screening; fecal occult blood testing, and sigmoidoscopy—colonoscopy.  Digital rectal examination is not useful in preventing mortality from rectal cancer.  A decreased mortality of 30% is observed with having had at least one fecal occult blood test in previous five years.

The advantage of sigmoidoscopy, colonoscopy over fecal occult blood testing in that it frequently includes removal of cancer or a pre-cancerous lesion, thus combining prevention (removal of polyps), screening and treatment in one step.  It needs to be performed infrequently and perhaps only every five to ten years.  A 60% reduction in mortality has been reported.

Prostate Cancer Screening

Consensus is lacking concerning recommendations for prostate cancer screening.  First, no definitive evidence suggests that prostate cancer screening results in reduction in mortality or improved clinical outcomes,  Second, the incidence is rising due to detection of latent asymptomatic cases with uncertain clinical relevance.

Lung Cancer Screening

Screening is not currently recommended due to evidence that screening procedures cannot identify tumors early enough to reduce mortality.

It is imperative to have regular cancer screening and to follow-up with your physician with any questions.

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