Cancer Screening

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Symposium on Cancer - September 2010  


Cancer Screening: Controversies and Opportunities

Tex Med . 2010;106(9):41-49.

By Lewis Foxhall, MD; Rebecca Garcia, PhD; and Karen Torges

In 2010, more than 98,000 Texans are predicted to be diagnosed with cancer. 1 Yet many of the expected 36,000 deaths from cancer in Texas this year are potentially avoidable with better use of evidence-based screening interventions. More consistent application of screening recommendations can increase the proportion of newly diagnosed individuals with early-stage disease and who can benefit from potentially lifesaving, more effective, and less toxic treatment options. Nationally, death rates from cancers at the most common anatomic sites continue to decline, except that for lung cancer in women, which has stabilized. The impact of cancer varies across racial, ethnic, socioeconomic, and educational attainment groups, and these differences have changed little over recent years. A combination of prevention, screening, and more effective treatment has contributed to the avoidance of approximately 650,000 cancer deaths from 1992 through 2005. Cancer screening is considered a significant factor in this dramatic change in the natural history of cancer in the United States.

Despite the clear advantages of screening, recommendations about how and when to implement it to achieve the most beneficial outcomes (Table 1) are under continual scrutiny and refinement, which can lead to confusion and concern. Cancer screening recommendations have been featured prominently in media coverage over the last year, especially in relation to the national debate over health system reform. In addition, the U.S. Preventive Services Task Force (USPSTF), one of several organizations that participate in developing accepted recommendations for breast cancer screening, unexpectedly altered its statements regarding the age to start screening and the interval at which to perform mammography. 3 Likewise, the American College of Obstetricians and Gynecologists (ACOG) issued new recommendations related to cervical cancer screening. 4 The latter change, while less controversial than the former, is a departure from the generally accepted approach to screening for this largely avoidable cancer. More recently, the American Cancer Society (ACS) updated its recommendations for prostate cancer screening, with increased emphasis on shared decision making with patients. 5 What is the basis for these changes? How will they impact clinical practice? Will these changes lead to policy decisions that affect coverage for screening services by governmental and private payers?

On top of the confusion that may be caused by shifts in recommendations is the persistent problem of underutilization of screening services in Texas and the rest of the country6 (Table 2). As a result, unnecessary deaths and excess morbidity from cancer are a continued burden on Texans. As clinicians, how can we better appreciate and assess the risk our patients face for developing and potentially dying from cancer? What can we do to increase the adoption of these important interventions? Where should we concentrate our efforts to gain the maximum benefit? How can we work with our patients to achieve better understanding of the potential benefits and possible harms associated with the use of screening services in asymptomatic individuals? What is the clinician's role in addressing differences that exist in the incidence and mortality of cancer across racial, ethnic, socioeconomic, and educational attainment groups?

The following highlights of recent controversies related to screening and changes in recommendations by major authorities may help us begin to deal with these questions.


Breast Cancer Screening

In the midst of the health system reform debate this past summer, USPSTF announced a change in its recommendation statements for breast cancer screening. This led to a firestorm of controversy and prompted numerous articles and newscasts in the lay media. Many were concerned that the recommendations would lead to a limitation in insurance coverage for mammography in women aged 40 to 49 years. USPSTF has long been recognized as an authority that bases its decisions on a thorough review of the scientific evidence. Where evidence is available, USPSTF will recommend for or against a clinical preventive service. Where the evidence is lacking, the group will state that no recommendation can be made either way.

In the case of breast cancer screening, USPSTF downgraded its recommendation for screening women in their 40s, stating that it did not support "routine screening." A closer reading of the group's position revealed that it was not opposed to screening in this age group if the screening was preceded by shared decision making and discussion with the patient of the potential benefits and possible harms. Its assessment was that the documented benefit of screening in this age group (approximately 17% reduced mortality from breast cancer annually) did not outweigh the possible harms of anxiety, biopsies, and possible diagnosis and treatment of indolent cancers. Additionally, USPSTF recommended lengthening the interval between screenings to 2 years for women of all ages. Further, the group stated that the evidence was insufficient to make a recommendation for screening women aged 75 and older, for the routine use of clinical breast examination by a health professional, or for digital or magnetic resonance imaging (MRI) for screening.

Other authorities involved in developing guidelines and many patient advocacy groups argued that the changes were unwarranted and that the methodology used to develop the new recommendations had significant limitations.7 USPSTF eventually revised its statement by removing the recommendation against routine screening for women in their 40s, while still supporting the benefit of individualized, informed decision making regarding screening.

Because USPSTF released its revised recommendations just as the health system reform debate was heating up, task force members suddenly found themselves called to legislative hearings to explain their position. Additionally, the secretary of Health and Human Services proclaimed that the recommendations would not be used to limit provision or payment for services by government programs. Many are still concerned, though, that the issuance of the original revised recommendations may lead to restricted access for mammography screening according to other established guidelines. Although it has now stabilized, the use of mammography had declined for several years. While multiple factors contribute, this decline may be explained in part by a decrease in health professional contact since the Women's Health Initiative led to a reduction in the use of hormone replacement therapy and concomitantly fewer follow-up visits where mammography could be recommended. 8 This issue raises the need for health professionals to maintain regular follow-up for screening examinations.


Cervical Cancer Screening

A less controversial change was announced by ACOG in 2009 regarding cervical cancer screening. These changes were proposed by the specialty society on the basis of improved knowledge of the course of precancerous disease and the impact of screening and treating abnormalities in younger women. The new recommendations would increase the age to start screening to 21 years rather than 3 years after the initiation of vaginal intercourse, as in the current, generally accepted guidelines. Additionally, the interval between screenings would be extended to 2 years for women younger than 30 years. ACOG recommends women aged 30 years and older be screened every 3 years if the results of their last three Pap tests have been normal. Finally, women aged 65 to 70 years with a history of three normal Pap tests in the last 10 years could stop screening unless they had a history that would suggest increased risk.

While these changes are significant, they do not represent a dramatic departure from the current recommendations. It is estimated that the rate of cervical cancer is 1 to 2 cases for every 1 million women younger than 21 years. It is now thought that many of the premalignant lesions detected in younger women will resolve without treatment, while screening for and treating such premalignant lesions in this age group may increase the risk of premature births. Increasing the screening interval is based on evidence indicating the lower risk of positive results on a Pap test in women who have had normal results previously. Differences in these recommendations and the existing guidelines will likely be resolved in the near future.


Prostate Cancer Screening

An additional area of controversy is related to prostate cancer screening. Disagreement over the value of screening for this type of cancer type has existed for several years. The currently available screening test, the prostate-specific antigen (PSA), has been available for more than two decades. While not developed initially as a screening tool, the PSA test has been used as such without scientific evidence of benefit based on well-designed randomized trials.

The incidence of prostate cancer increased dramatically in the late 1980s and early 1990s, along with the increase in treatment of prostatic hypertrophy with transurethral resection and the rapid adoption of the PSA test for screening. This increased incidence has declined subsequently, and mortality rates are now below prescreening era level. 2 Additionally, diagnoses of early-stage disease have increased, and diagnoses of late-stage disease have decreased.9

Several observational and case-control studies are cited as an indication of the value of screening.10-12  While PSA screening can detect early-stage disease,13 it is uncertain that its use and the subsequent treatment of screen-detected disease are associated with a reduction in mortality from prostate cancer. The challenge of using screening to reduce death rates for this cancer revolves around the presence of indolent prostate cancers that will not grow significantly in a man's lifetime. Currently, the PSA test cannot distinguish these indolent cancers from aggressive, life-threatening tumors. Furthermore, the various modalities of treatment for either form of prostate cancer carry significant risk for long-term adverse effects in a significant proportion of men.14-16

Much anticipation has surrounded the completion of two large randomized trials comparing prostate screening with usual care. Unfortunately, the results of these trials differ: the European Randomized Study of Screening for Prostate Cancer (ERSPC)17 demonstrated that screening was associated with a 20% reduction in the annual mortality rate, but the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO)18 showed no benefit. Important methodological differences between the trials may explain the conflicting outcomes; such differences include screening intervals, PSA cutoff points leading to biopsy, the number of men who followed advice to receive a biopsy, levels of contamination of intervention and control groups, and the duration of follow-up, among others. Continued analysis of results after a longer period may provide some clarification. Meanwhile, we are still left with clinical uncertainty as to the value of PSA screening.

ACS recommends that clinicians share this uncertainty with patients and inform them of the possible benefits and potential harmful effects of screening and subsequent treatment of screen-detected disease. Numerous decision aids have been developed that may help clinicians in this process. Additional changes include the initiation of discussion earlier for higher risk groups, such as African-Americans and men with a family history of prostate cancer, especially those with an earlier-than-average age of diagnosis. Also, the use of lower PSA level cut points for biopsy (2.5 vs. 4.0 mg/mL) and individualized risk assessment is advised. Screening intervals for men of average risk may be extended to 2 years if the PSA level is less than 2.5 mg/mL. The use of digital rectal examination is now considered optional except in those patients with hypogonadism, for whom the PSA level is a less sensitive indicator of prostate cancer.


Colorectal Cancer Screening

While colorectal cancer screening guidelines have not undergone any major revisions, the ongoing challenge associated with screening for colorectal cancer deserves consideration. Although rates of utilization of colorectal cancer screening have increased, available screening services are still substantially underutilized. This is particularly troubling for colorectal cancer because screening has the potential to reduce the mortality and even the incidence of this cancer to very low levels. Because adenomatous polyps were discovered to function as precursor lesions, identifying and removing significant polyps can greatly lower a patient's risk for developing colon cancer.19 The use of fecal occult blood testing and the subsequent evaluation of the colon with optical endoscopy have been documented to reduce the mortality and incidence of colon cancer in randomized controlled trials.20 Newer screening modalities such as computed tomography colonography (virtual colonoscopy)21 and DNA screening of stool specimens22 are recommended by some authorities, but not others. Coverage by government and some private payers also varies with respect to these technologies.

Pros and cons can be assigned to any of the screening modalities, and these should be passed along to patients as they share in the decision making about which modality to use in an individual situation. Because all the recommended screening approaches are effective, the best test to use is sometimes said to be "the one that gets done." In clinical practice, identifying those individuals who may be at higher risk for the development of colon cancer and thus may benefit from more intensive interventions is important.23 Those at increased risk include persons with a history of adenomatous polyps; personal history of curative-intent surgical resection of colon cancer; family history of colon cancer or adenomas in first-degree relatives, especially at younger ages; inflammatory bowel disease of the colon lasting 8 years or longer; or the identification or suspicion of hereditary syndromes, including hereditary nonpolyposis colon cancer or familial adenomatous polyposis.

Of note is the fact that only about half of those who are eligible have been screened. There is still a great opportunity to avert death from colorectal cancer for our patients through higher rates of adoption of colorectal screening tests.


Future Directions

These ongoing controversies have led some to question the value of screening, particularly for breast and prostate cancer.24 They argue that the natural course of these diseases should have been altered significantly with a greater decline in advanced disease and that many of the screen-detected cancers are indolent and may not require treatment. Others counter that the predicted population response to screening is diminished by real-world experience and that despite the dissemination of evidence-based guidelines, not everyone in the eligible population gets screened or uses the screening tests at the prescribed intervals. Those who are not screened because they fall outside the screening eligibility limits, have no access to screening because of financial or other reasons, or refuse screening recommendations also are diagnosed with cancer and add to the reported incidence rates. These areas need further attention if we are to achieve the full benefit of screening.

Additional research leading to improved ability to distinguish indolent from aggressive lesions could significantly improve the benefit of screening in prostate cancer and, to a lesser degree, in breast cancer. Personalized risk assessment using genomic or proteomic markers of risk or existing disease holds the promise of more targeted interventions for prevention, screening, and subsequent treatment. Such risk assessment would also reduce the need to treat those cancers that are not life-threatening and better enable aggressive treatment of those that are. Better support tools to aid shared decision making are also needed. Allowing our patients to better understand the potential benefits of a given screening intervention as well as the potential ill effects will lead to more optimal use of screening tests and a patient-centered approach that considers each patient's values related to screening and treatment for cancer.

One action already undertaken is almost certain to have a profound effect on the utilization of screening services. The Patient Protection and Affordable Care Act, which was signed into law on March 23, 2010, could potentially have a great impact on the delivery of health care, including clinical preventive services. The inclusion of many currently uninsured and underinsured persons into employer-sponsored insurance or government programs (primarily Medicaid) may eliminate one of the major barriers to the use of screening tests. The uninsured generally follow screening recommendations at about half the frequency of insured populations. Coverage of preventive services with the elimination of cost sharing for Medicare and Medicaid should improve utilization. Additionally, services related to behavior modification will now be required to be covered by health plans. Provisions supporting the primary care workforce may lead to better access to health professionals offering clinical preventive services; however, this support may be of limited duration.

The inclusion of an additional 32 million people into various coverage plans may combine with the existing shortage of primary care physicians and a predicted shortage of oncologists to have the unintended effect of limiting access for many.

An additional area of concern is that only cancer screening services recommended by USPSTF at its two highest levels, A and B,25 will be included in health plan requirements. In light of the recent controversy concerning breast cancer screening in younger women, the possibility that this concern may become reality is troubling, even though government officials have stated the concern is unwarranted. Finally, challenges will continue for those not included in the provisions of the health system reform legislation, such as undocumented aliens. This is a particular concern in border states such as Texas.

Through the use of evidence-based screening, we can help many of our patients avoid death and unnecessary suffering from cancer. We know some patients will eventually develop cancer, and a significant number may already have asymptomatic cancer today. Our challenge is to consistently use the tools available to assess risk factors for cancer, such as smoking and obesity, and identify potential problems through screening as early in the course of disease as possible. Simple things such as obtaining and regularly updating a thorough personal and family history for cancer and its precursors can help us identify persons likely to have an inherited predisposition to cancer. A current cancer screening history can also help us assess our patients' screening status and need for further testing. Risk calculation algorithms and risk assessment tools are available and should be used to encourage the use of risk-appropriate screening strategies by our patients.

One of our most powerful tools is our advice as trusted health professionals to follow screening recommendations, a strategy that has been shown to improve screening uptake across multiple preventive services. The use of patient decision aids will further facilitate the discussion of screening options and meaningful, shared decision making. Organizing our practice settings to systematically initiate discussions about screening recommendations and to follow and recall patients to maintain screening intervals can significantly improve screening rates.

Using knowledge of barriers to screening for those populations disparately impacted by cancer is equally important. Focusing on those racial and ethnic groups that carry an increased risk of cancer mortality compared with other groups is necessary to address these differences. Persons who face additional challenges because of low socioeconomic status or educational attainment also deserve closer attention. Finally, concentrating on the promotion of underutilized and highly effective interventions, such as those for colorectal, breast, and cervical cancers, can increase the magnitude and impact of our efforts.

Cancer screening has the potential to greatly reduce the number of cancer deaths in our patient populations. It can give our patients the option for treatments that are more effective and have fewer adverse effects. Cancer screening interventions can even reduce the number of persons who develop cancer.

Regardless of our political leanings, we must be prepared for changes in health care delivery that may result from the recently enacted legislation. We should try to capitalize on those elements that give us the opportunity to improve access to cancer screening services for our patients. Maintaining current knowledge and competencies in the delivery of these services is critical to reducing the burden of cancer on Texans.

Lewis Foxhall, MD, is vice president for health policy at The University of Texas M.D. Anderson Cancer Center in Houston and chair of the TMA Physician Oncology Education Program. Rebecca Garcia, PhD, is the chief prevention officer of the Cancer Prevention and Research Institute in Austin. Karen Torges is the director of strategic collaborations with the American Cancer Society-High Plains Division in Austin.


References

  1. Cancer Facts & Figures 2009, American Cancer Society. http://www.cancer.org/Research/CancerFactsFigures/cancer-facts-figures-2009?from=fast . Accessed 4/10/2010.
  2. Jemal A, Siegel R, Ward E, Hao Y, Xu J, Thun MJ.    Cancer Statistics, 2009. CA Cancer J Clin. 2009;59(4):225-249.
  3. US Preventive Services Task Force. Screening for breast cancer: US Preventive Services Task Force recommendation statement. Ann Intern Med . 2009;151(10):716-726.
  4. American College of Obstetricians and Gynecologists Committee on Practice Bulletins-Gynecology. ACOG Practice Bulletin no. 109: Cervical cytology screening. Obstet Gynecol. 2009;114(6):1409-1420.
  5. Wolf AM, Wender RC, Etzioni, RB, et al.  American Cancer Society guideline for the early detection of prostate cancer: update 2010. CA Cancer J Clin. 2010;60(2);70-98.
  6. Centers for Disease Control and Prevention Behavioral Risk Factor Surveillance System.  http://www.cdc.gov/brfss . Accessed April 14, 2010.
  7. Smith RA, Cokkinides V, Brooks D, Saslow D, Brawley OW. Cancer screening in the United States, 2010: a review of current American Cancer Society guidelines and issues in cancer screening. CA Cancer J Clin. 2010;60(2):99-119.
  8. Ravdin PM, Cronin KA, Howlader N, et al.  The decrease in breast-cancer incidence in 2003 in the United States. N Engl J Med. 2007;356(16):1670-1674.
  9. Tarone RE, Chu KC, Brawley OW. Implications of stage-specific survival rates in assessing recent declines in prostate cancer mortality rates. Epidemiology. 2000;11(2):167-170.
  10. Catalona WJ, Smith DS, Ratliff TL, Basler JW. Detection of organ-confined prostate cancer is increased through prostate-specific antigen-based screening. JAMA. 1993;270(8):948-954.
  11. Brawer MK, Chetner MP, Beatie J, Buchner DM, Vessella RL, Lange PH.  Screening for prostatic carcinoma with prostate specific antigen. J Urol . 1992;147(3 Pt 2):841-845.
  12. Kvåle R, Auvinen A, Adami HO, et al.  Interpreting trends in prostate cancer incidence and mortality in the five Nordic countries. J Natl Cancer Inst. 2007;99(24):1881-1887.
  13. Stamey TA, Yang N, Hay AR, McNeal JE, Freiha FS, Redwine E. Prostate-specific antigen as a serum marker for adenocarcinoma of the prostate. N Engl J Med . 1987;317(15):909-916.
  14. Stanford JL, Feng Z, Hamilton AS, et al.  Urinary and sexual function after radical prostatectomy for clinically localized prostate cancer: the Prostate Cancer Outcomes Study. JAMA. 2000;283(3):354-360.
  15. Schover LR, Fouladi RT, Warneke CL, et al.  Defining sexual outcomes after treatment for localized prostate carcinoma. Cancer. 2002;95(8):1773-1785.
  16. Gore JL, Kwan L, Lee SP, Reiter RE, Liwin MS.  Survivorship beyond convalescence: 48-month quality-of-life outcomes after treatment for localized prostate cancer. J Natl Cancer Inst. 2009;101(12):888-892.
  17. Schröder FH, Hugosson J, Roobol MJ, et al. Screening and prostate-cancer mortality in a randomized European study. N Engl J Med. 2009;360(13):1320-1328.
  18. Andriole GL, Crawford ED, Grubb RL III, et al.  Mortality results from a randomized prostate-cancer screening trial. N Engl J Med. 2009;360(13):1310-1319.
  19. Winawer SJ, Zauber AG, Fletcher RH, et al.  Guidelines for colonoscopy surveillance after polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer and the American Cancer Society. CA Cancer J Clin. 2006;56(3):143-159.
  20. Mandel JS, Bond JH, Church TR, et al. Reducing mortality from colorectal cancer by screening for fecal occult blood. Minnesota Colon Cancer Control Study. N Engl J Med. 1993;328(19):1365-1371.
  21. Johnson CD, Chen MH, Toledano AY, et al. Accuracy of CT colonography for detection of large adenomas and cancers. N Engl J Med. 2008;359(12):1207-1217.
  22. Imperiale TF, Ransohoff DF, Itzkowitz SH, Turnbull BA, Ross ME; Colorectal Cancer Study Group. Fecal DNA versus fecal occult blood for colorectal-cancer screening in an average-risk population. N Engl J Med. 2004;351(26):2704-2714.
  23. Levin B, Lieberman DA, McFarland B, et al.  Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. CA Cancer J Clin. 2008;58(3):130-160.
  24. Esserman L, Shieh Y, Thompson I. Rethinking screening for breast cancer and prostate cancer. JAMA. 2009;302(15):1685-1692.
  25. Agency for Healthcare Quality and Research, US Preventive Services Task Force. Grade Definitions After May 2007. http://www.ahrq.gov/clinic/uspstf/gradespost.htm#brec . Accessed April 2, 2010.


SIDEBAR

Internet Resources

American Cancer Society  (www.cancer.org)

Baylor College of Medicine, Dan L. Duncan Cancer Center, Houston (www.bcm.edu/cancercenter)

Agency for Healthcare Research and Quality  (www.ahrq.gov)

Cancer Prevention and Research Institute of Texas (www.cprit.state.tx.us)

National Cancer Institute  (www.cancer.gov)

Texas Cancer Information Website  (www.texascancer.info)

University of Texas Health Science Center, San Antonio, Cancer Therapy and Research Center  (www.ctrc.net/ctrc_home.cfm?db_content=home&CFID=218059&CFTOKEN=42788060)

University of Texas M.D. Anderson Cancer Center, Houston  (www.mdanderson.org)


SIDEBAR

Steps to Improved Cancer Screening

  • Refresh your memory of the current screening recommendations by reviewing the included summary of recommendations from the American Cancer Society.
  • Familiarize yourself with recommendations of other authorities, such as the American College of Obstetricians and Gynecologists and the U.S. Preventive Services Task Force.
  • Request a Physician Oncology Education Program pocket guide to screening recommendations for easy reference.
  • Familiarize yourself with tools that facilitate shared decision making.
  • Consider implementing changes in your office systems to improve the consistent delivery of cancer screening recommendations to your patients.
  • Use the Texas Cancer Information website to access information about cancer services, care options for the uninsured, and the most recent cancer statistics for your area.
  • Be familiar with and apply for funding opportunities for research, screening, and other cancer prevention programs and services available through the Cancer Prevention and Research Institute of Texas. 

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