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 CancerAdnexal 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) Chapter 078. Prevention and Early Detection of Cancer (Part 10) Lung Cancer Chest x-ray and sputum cytology have been evaluated in randomized lungcancer screening trials. No reduction in lung cancer mortality has been seen,although all the controlled trials have had low statistical power. Even screening ofhigh-risk subjects (smokers) has not proven beneficial. Spiral CT can diagnoselung cancers at early stages; however, false-positive rates are high. Spiral CTscreening increases the number of lesions detected and increases the number ofdiagnostic and therapeutic procedures. However, its capacity to save lives isunproven. Ovarian Cancer Adnexal palpation, transvaginal ultrasound, and serum CA-125 assay havebeen considered for ovarian cancer screening. These tests alone and incombination do not have sufficiently high sensitivity or specificity to berecommended for routine screening of ovarian cancer. The risks and costsassociated with the high number of false-positive results is an impediment toroutine use of these modalities for screening. Most expert panels have concludedthat routine screening for ovarian cancer is not indicated for standard-risk womenor those with single affected family members, but might be worthwhile in familieswith genetic ovarian cancer syndromes. Prostate Cancer The most common prostate cancer screening modalities are DRE and serumprostate-specific antigen (PSA) assay. Newer serum tests, such as measurement ofbound to free serum PSA, have yet to be fully evaluated. An emphasis on PSAscreening has caused prostate cancer to become the most common non-skin cancerdiagnosed 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 iseffective. Some experts are concerned that prostate cancer screening, more thanscreening for other cancers, may cause net harm. Prostate cancer screening clearlydetects many asymptomatic cancers, but the ability to distinguish tumors that arelethal 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 insignificantprostate cancers. No trial has yet demonstrated the benefit of prostate cancerscreening and treatment. The placebo arm of the Prostate Cancer Prevention Trial showed thatrigorous screening of low-risk men for 7 years leads to the diagnosis of prostatecancer in >12% of patients. In addition, 15% of men who had normal DRE andPSA levels after 7 years were found to have prostate cancer on biopsy despite thenormal 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 understudy. However, both surgery and radiation therapy may cause significantmorbidity, such as impotence and urinary incontinence. Comparison of radicalprostatectomy to watchful waiting in clinically diagnosed (not screen-detected)prostate cancers showed a small decrease in prostate cancer death rate in thesurgery arm. One life was saved for every 18–20 men treated with radicalprostatectomy. Urinary incontinence and sexual impotence were more common inthe surgery arm. One current screening recommendation is that men over age 50be offered screening and allowed to make a choice after being informed ofpotential risks and benefits (Table 78-3). A man should have a life expectancy ofat least 10 years to be eligible for screening. The USPSTF has found insufficientevidence to recommend prostate cancer screening. Endometrial Cancer Transvaginal ultrasound and endometrial sampling have been advocated asscreening tests for endometrial cancer. Benefit from routine screening has not beenshown. Transvaginal ultrasound and endometrial sampling are indicated forworkup of vaginal bleeding in postmenopausal women but are not considered asscreening tests in symptomatic women. Skin Cancer Visual examination of all skin surfaces by the patient or by a health careprovider is used in screening for basal and squamous cell cancers and melanoma.No prospective randomized study has been performed to look for a mortalitydecrease. Observational epidemiologic evidence from Scotland and Australiasuggests that screening programs have caused a stage shift in melanomasdiagnosed. Screening may reinforce sun avoidance and other skin cancerprevention behaviors. Further Readings Bach PB et al: Computed tomography screening and lung cancer outcomes.JAMA 297:953, 2007 [PMID: 17341709] Barrett-Connor ...