Published: January 2009
Early diagnosis and detection of cancer profoundly affect survival rates and maximize positive outcomes. Major screening guidelines exist for the most common cancers: colon, breast, cervical, and prostate. Advanced imaging techniques, biomarkers, and multimodal approaches are providing promising strategies for detecting and diagnosing cancer at its earliest and most treatable stages. However, a large fraction of the population does not undergo appropriate screening or is screened inconsistently. For example, in 2004, among adults older than 50 years, the prevalence of having an endoscopic procedure within the past 5 years for colorectal cancer screening was 52.1%, and the prevalence of doing an at-home fecal occult blood test (FOBT) within the past year was only 19%. Overall, among adults older than 50 years, the prevalence of having had either an FOBT or endoscopic procedure was 52.1%. In addition, compared with persons with health insurance, the uninsured nonelderly group was significantly less likely to have had a colorectal cancer screening.1 Access, insurance coverage, and patient discomfort are all barriers to obtaining these preventive procedures. Physicians should discuss these cancer screening guidelines and recommend which test is most appropriate to increase patient awareness and follow-through and in turn promote long-term health.
As of 2008, prostate cancer, lung and bronchus cancer, and colon cancer remain the top three leading new cancer cases in men. Breast, lung and bronchus, and colon cancers remain the top three cancers in women. Lung and bronchus cancer remains the leading cause of cancer-related deaths in both men and women, with the 5-year survival rate averaging 15%.2
In 2008, about 10% of new cancer cases in both men and women in the United States were colorectal cancer. The diagnosis will be made in approximately 77,250 men and 71,560 women in the United States, and approximately 49,960 will die from it.1
Screening measures for colorectal cancer include colonoscopy, flexible sigmoidoscopy, and FOBT. Most organizations recommend that screening start at age 50 years. The standard screening procedure is the colonoscopy every 10 years, which allows a complete examination of the entire colon. The procedure is both diagnostic and preventive, especially when an adenomatous polyp or precancerous polyp is removed. Flexible sigmoidoscopy and double-contrast barium enemas (DCBEs) should be done at 5-year intervals.
A thorough discussion of the specific modalities of colon cancer screening is discussed in “Treatment of Colorectal Cancer,” elswhere in this text. The role of the primary care physician is to educate and provide reassurance that these cancer-screening procedures are relatively safe. Newer technologies, such as computed tomography (CT) colonography and stool DNA testing, need further study before being accepted as part of the preventive approach to detect colon cancer in the average-risk patient.
Breast cancer is the leading cause of new cancer in women in the United States (approximately 26% of all new cancer cases).1 In 2008, approximately 182,460 women in the United States learned they had breast cancer, and 40,480 died from it. Most organizations agree that breast cancer screening should start at age 40 years for the average-risk woman.
Physicians should discuss with their patients the benefits of regular screening, the limitations of mammography, and the need for further testing, including breast biopsy, for false-positive results. The U.S. Preventive Services Task Force (USPSTF)3 recommends a mammography every 1 to 2 years, and the American Cancer Society (ACS) recommends one annually. Decisions on when to stop mammography screening should be individualized and based on a patient's life expectancy and comorbid conditions.
Advanced screening modalities such as breast ultrasound, full-field digital mammography, and breast magnetic resonance imaging (MRI) may be more appropriate for women who are at higher risk for breast cancer. The breast MRI procedure has been found to be highly sensitive but less specific than conventional mammography. Breast MRI may be most useful in women with a family history of breast cancer or those who test positive for the breast cancer gene (BRCA). Protein biomarkers for breast cancer, which include inflammatory markers, cell-cell contact, and tissue repair processes, a re still under investigation but might be able to differentiate normal breast tissue from malignant breast tissue.
The USPSTF currently recommends against routine use of tamoxifen or raloxifene for the primary prevention of breast cancer in women at low or average risk for breast cancer. They recommend that physicians discuss chemoprevention with women at high risk for breast cancer and at low risk for adverse effects of such treatment. A more detailed discussion on breast disorders and breast cancer screening is found in the “Women's Health” section of this text.
Recommendations for cervical cancer screening have changed because of advances in cervical cancer screening that uses liquid-based cytology and advances in human papillomavirus (HPV) testing. The American College of Obstetricians and Gynecologists (ACOG) and the USPSTF recommend initial testing with either the traditional Papanicolaou (Pap) smear or liquid-based cytology starting by age 21 years or approximately 3 years after the first sexual intercourse.4,5 Future screenings should occur every year with a traditional Pap smear or every 2 years with liquid-based cytology. At or after age 30 years and with three normal test results, intervals can be increased to every 2 to 3 years with traditional Pap smear or every 3 years with HPV assay testing plus cervical cytology. Screening can be discontinued at age 70 years for women who have had three or more normal Pap test results in the previous 10 years or who have had a total hysterectomy. A more detailed discussion, including the new HPV vaccination and management of abnormal Pap smears, is found in the chapter “Cervical Cancer Screening and Prevention.”
Prostate cancer is the leading type of new cancer cases in men in the United States and accounts for about 25% of all new cancers. In 2008, prostate cancer was diagnosed in approximately 186,320 men, and about 28,660 died as a result of it. If prostate-specific antigen (PSA) testing and digital rectal examination (DRE) can diagnose early stages of moderate- to high-grade prostate cancer, then mortality rates from prostate cancer can be reduced. No major medical organization in the United States endorses universal screening for average-risk men. In August 2008, the USPSTF concluded that the current evidence is insufficient for screening men younger than 75 years. For the first time, the task force recommended against routine prostate screening in men 75 years or older. However, all organizations recommend that for men, starting at age 50 years, physicians should discuss the risks and potential benefits of PSA testing, consider patient preferences, and individualize the decision to test.6
The controversy of PSA testing lies in its poor specificity (high false-positive findings), which leads to unnecessary biopsy. There are no specific guidelines regarding cutoff values to recommend prostate biopsy. An increase of more than 0.75 ng/mL per year (PSA velocity) can indicate the need for a prostate biopsy. It is generally accepted to stop screening for prostate cancer if the man's life expectancy is less than 10 years. A more extensive discussion of prostate cancer takes place in the chapter “Prostate Cancer.”
In 2008, approximately 161,840 people died from lung cancer–related causes. This is greater than colorectal, breast, and prostate cancers combined.2 To date, no screening modalities have been shown to reduce mortality rates. The benefit of screening for lung cancer with sputum cytology, chest x-rays, or low-dose CT has not been established in any group, including asymptomatic high-risk populations such as older smokers. Although sensitivity of low-dose CT for detecting lung cancer is four times greater than the sensitivity of chest x-ray, the low-dose CT is associated with higher false-positive results, more radiation exposure, and increased costs compared with chest x-ray.3
Current large randomized, controlled trials to evaluate the effect of lung cancer screening on mortality, such as the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial (PLCO), are ongoing. This is a large-scale clinical trial to determine whether certain cancer screening tests reduce deaths from prostate, lung, colorectal, and ovarian cancers.7 The underlying rationale for the trial is that screening for cancer might allow doctors to discover and treat the disease earlier. Numerous epidemiologic and ancillary studies are included to answer related crucial questions. A more detailed discussion on lung cancer occurs in the chapter “Lung Cancer.”
Several organizations recommend a number of cancer screening guidelines. However, recommendations for screening for colon, breast, cervical, and prostate cancers are very similar. Table 1depicts an overall summary of screening guidelines for these four most common cancers. Every effort should be made to educate and reduce the barriers to screening. Physicians need to take a more proactive approach. They should discuss these cancer screening guidelines and recommend which test is most appropriate to increase patient awareness and promote long-term health. Patients must also take greater responsibility for their own proper nutrition and exercise to lower their risk for cancer.8
|American Cancer Society1||U.S. Preventive Services Task Force3|
|Age ≥20 yr||Age ≥40 yr|
|BSE optional||Mammography every 1-2 yr ± CBE|
|Age 20-30 yr|
|CBE every 3 yr|
|Age ≥18 yr||Recommendations|
|Conventional Pap test annually, or||Screening for cervical cancer in women who have been sexually active and have a cervix|
|Liquid-based cytology every 2 yr after first sexual intercourse or by age 21 yr||Optimal age to begin screening is unknown|
|Age ≥30 yr with 3 normal consecutive Pap tests||No routine screening for cervical cancer in women >65 yr who have had adequate recent screening with normal Pap smears and are not otherwise at high risk for cervical cancer|
|Conventional Pap test or liquid-based prep every 2-3 yr, or||No routine Pap smear screening in women who have had a total hysterectomy for benign disease|
|Conventional Pap test or liquid-based prep with HPV assay every 3 yr||Conclusions|
|Age ≥70 yr with ≥3 normal Pap tests and no abnormal Pap tests in the past 10 yr||The evidence is insufficient to recommend for or against routine use of new technologies to screen for cervical cancer|
|May stop||The evidence is insufficient to recommend for or against routine use of HPV testing as a primary screening test for cervical cancer|
|Women with hysterectomy|
|Age ≥50 yr:||Age ≥50 yr|
|FOBT or FIT annually, or||FOBT annually, or|
|Flex sig every 5 yr, or||Flex sig every 5 yr, or|
|FOBT or FIT annually plus flex sig every 5 yr, or||FOBT annually plus flex sig every 5 yr, or|
|DBCE every 5 yr, or||DBCE every 5 yr, or|
|Colonoscopy every 10 yr||Colonoscopy every 10 yr|
|Women at menopause||No mention|
|Inform about risks and symptoms of endometrial cancer and strongly encouraged to report any unexpected bleeding or spotting|
|Age ≥50 yr|
|PSA blood test plus DRE offered annually||Evidence is insufficient to recommend for or against routine screening for prostate cancer using PSA or DRE for men <75 yr. Recommend against screening for men ≥75 yr.|
|Include examination for cancers of the thyroid, testicles, ovaries, lymph nodes, oral cavity, and skin cancer||Evidence is insufficient to recommend for or against routine screening for lung, oral, and skin cancers|
|Health counseling about tobacco, sun exposure, diet and nutrition, risk factors, sexual practices, and environmental and occupational exposures||Recommends against screening for bladder, ovarian, pancreatic, and testicular cancers in asymptomatic adults|
BSE, breast self-examination; CBE, Clinical breast examination; DBCE, Double contrast barium enema; DRE, Digital rectal examination; FIT, fecal immunochemical test; flex sig, flexible sigmoidoscopy; FOBT, Fecal occult blood test (at-home procedure for collecting two samples from three consecutive specimens); HPV, human papilloma virus; Pap, Papanicolaou; prep, preparation; PSA, prostate-specific antigen test.