Chapter 078. Prevention and Early Detection of Cancer (Part 10)

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Lung Cancer Chest x-ray and sputum cytology have been evaluated in randomized lung cancer screening trials. No reduction in lung cancer mortality has been seen, although all the controlled trials have had low statistical power. Even screening of high-risk subjects (smokers) has not proven beneficial. Spiral CT can diagnose lung cancers at early stages; however, false-positive rates are high. Spiral CT screening increases the number of lesions detected and increases the number of diagnostic and therapeutic procedures. However, its capacity to save lives is unproven. Ovarian Cancer Adnexal palpation, transvaginal ultrasound, and serum CA-125 assay have been considered for ovarian cancer...

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Chapter 078. Prevention and Early Detection of Cancer (Part 10) Lung Cancer Chest x-ray and sputum cytology have been evaluated in randomized lung cancer screening trials. No reduction in lung cancer mortality has been seen, although all the controlled trials have had low statistical power. Even screening of high-risk subjects (smokers) has not proven beneficial. Spiral CT can diagnose lung cancers at early stages; however, false-positive rates are high. Spiral CT screening increases the number of lesions detected and increases the number of diagnostic and therapeutic procedures. However, its capacity to save lives is unproven. Ovarian Cancer
Adnexal palpation, transvaginal ultrasound, and serum CA-125 assay have been considered for ovarian cancer screening. These tests alone and in combination do not have sufficiently high sensitivity or specificity to be recommended for routine screening of ovarian cancer. The risks and costs associated with the high number of false-positive results is an impediment to routine use of these modalities for screening. Most expert panels have concluded that routine screening for ovarian cancer is not indicated for standard-risk women or those with single affected family members, but might be worthwhile in families with genetic ovarian cancer syndromes. Prostate Cancer The most common prostate cancer screening modalities are DRE and serum prostate-specific antigen (PSA) assay. Newer serum tests, such as measurement of bound to free serum PSA, have yet to be fully evaluated. An emphasis on PSA screening has caused prostate cancer to become the most common non-skin cancer diagnosed in American males. This disease is prone to lead-time bias, length bias, and overdiagnosis, and substantial debate rages among experts as to whether it is effective. Some experts are concerned that prostate cancer screening, more than screening for other cancers, may cause net harm. Prostate cancer screening clearly detects many asymptomatic cancers, but the ability to distinguish tumors that are lethal but still curable from those that pose little or no threat to health is limited. Men over age 50 have a high prevalence of indolent, clinically insignificant
prostate cancers. No trial has yet demonstrated the benefit of prostate cancer screening and treatment. The placebo arm of the Prostate Cancer Prevention Trial showed that rigorous screening of low-risk men for 7 years leads to the diagnosis of prostate cancer in >12% of patients. In addition, 15% of men who had normal DRE and PSA levels after 7 years were found to have prostate cancer on biopsy despite the normal screening tests. Thus, screening missed more disease than it found and >27% of normal-risk men in their late 60s were found to have prostate cancer. The effectiveness of treatments for low-stage prostate cancer are under study. However, both surgery and radiation therapy may cause significant morbidity, such as impotence and urinary incontinence. Comparison of radical prostatectomy to "watchful waiting" in clinically diagnosed (not screen-detected) prostate cancers showed a small decrease in prostate cancer death rate in the surgery arm. One life was saved for every 18–20 men treated with radical prostatectomy. Urinary incontinence and sexual impotence were more common in the surgery arm. One current screening recommendation is that men over age 50 be offered screening and allowed to make a choice after being informed of potential risks and benefits (Table 78-3). A man should have a life expectancy of at least 10 years to be eligible for screening. The USPSTF has found insufficient evidence to recommend prostate cancer screening.
Endometrial Cancer Transvaginal ultrasound and endometrial sampling have been advocated as screening tests for endometrial cancer. Benefit from routine screening has not been shown. Transvaginal ultrasound and endometrial sampling are indicated for workup of vaginal bleeding in postmenopausal women but are not considered as screening tests in symptomatic women. Skin Cancer Visual examination of all skin surfaces by the patient or by a health care provider is used in screening for basal and squamous cell cancers and melanoma. No prospective randomized study has been performed to look for a mortality decrease. Observational epidemiologic evidence from Scotland and Australia suggests that screening programs have caused a stage shift in melanomas diagnosed. Screening may reinforce sun avoidance and other skin cancer prevention behaviors. Further Readings Bach PB et al: Computed tomography screening and lung cancer outcomes. JAMA 297:953, 2007 [PMID: 17341709]
Barrett-Connor E et al: Effects of raloxifene on cardiovascular events and breast cancer in postmenopausal women. N Engl J Med 355:125, 2006 [PMID: 16837676] Fisher B et al: Tamoxifen for prevention of breast cancer: report of the National Surgical Adjuvant Breast and Bowel Project P-1 Study. J Natl Cancer Inst 90:1371, 1998 [PMID: 9747868] Freedland SJ, Partin AW: Prostate-specific antigen: Update 2006. Urology 67:458, 2006 [PMID: 16504254] Humphrey LL et al: Breast cancer screening: A summary of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med 137:347, 2002 [PMID: 12204020] Prentice RL et al: Low-fat dietary pattern and risk of invasive breast cancer. The Women's Health Initiative randomized controlled dietary modification trial. JAMA 295:629, 2006 [PMID: 16467232] Winawer SJ et al: Guidelines for colonoscopy surveillance after polypectomy: A consensus update by the Multi-Society Task Force on Colorectal
Cancer and the American Cancer Society. Gastroenterology 130:1872, 2006 [PMID: 16697750] References for Online The Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group. The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. N Engl J Med 330:1029, 1994 Baxter N, Canadian Task Force on Preventive Health Care: Preventive health care 2001 update: Should women be routinely taught breast self- examination to screen for breast cancer? CMAJ 164(13): 837, 2001 Cinciripini PM, Hecht S, Henningfield JE et al: Tobacco addiction: Implications for treatment and cancer prevention. J Natl Cancer Inst 89:1852, 1997 [PMID: 9414173] Greenwald P, Kramer BS, Weed DL. Cancer Prevention and Control. New York, Marcel Dekker, 1995 National Institutes of Health Consensus Development Panel: National
Institutes of Health Consensus Development Conference Statement: Breast Cancer Screening for Women Ages 40–49, January 21–23, 1997. J Natl Cancer Inst 89(14): 1015, 1997 Smith RA, Cokkinides V, Eyre HJ: American Cancer Society guidelines for the early detection of cancer, 2003. CA Cancer J Clin 53: 27, 2003 [PMID: 14756304] Stoutjesdijk M: Magnetic resonance imaging and mammography in women with a hereditary risk of breast cancer. J Natl Cancer Inst 93: 1095, 2001 [PMID: 11459871] Websites The Canadian Taskforce on Preventive Health Care http://www.ctfphc.org/ The National Cancer Institute Cancernet http://cancernet.nci.nih.gov/