Health Letter, April 2013
Routine screening of women for cervical cancer with Papanicoulaou (Pap) smears, also called Pap tests, has helped saved numerous lives since it was introduced into clinical practice in the U.S. in 1941. However, a recent study conducted by the Centers for Disease Control and Prevention (CDC) revealed that as many as 22 million women who had previously had a hysterectomy may have undergone unnecessary Pap tests over the past decade. The CDC data also suggest that millions of other women older than 65 years who have not had a hysterectomy likewise underwent unnecessary Pap tests during this same time period.
The CDC’s data on Pap tests once again highlight a pervasive problem within the U.S. health care system: the frequent use of unnecessary medical tests and treatments. In addition to wasting money, time and clinical resources, unnecessary medical tests and treatments expose patients to risks of complications and adverse events directly caused by the procedure or treatment without offering sufficient benefits to offset the risks.
As noted in past issues of Health Letter, unwarranted diagnostic tests can also lead to misdiagnosis or overdiagnosis, both of which can result in patient anxiety as well as more needless medical procedures and treatments that present additional risks of harm and unnecessary costs. Misdiagnosis may occur when a patient undergoes a diagnostic test and has a false-positive result. In this case, the test result is abnormal, but the patient does not have the disease for which he or she is being tested. Overdiagnosis occurs when a test result shows a true abnormality, but one that will never cause symptoms or result in death.
Overview of cervical cancer
The cervix is the lowest part of the uterus (womb) that opens into the top of the vagina. Cancer of the cervix, or cervical cancer, occurs when cells within the outermost lining of the cervix become malignant.
Cervical cancer is the third most common type of gynecologic cancer in the U.S. (ranking behind uterine cancer and ovarian cancer). U.S. women have a less than 1 percent chance of being diagnosed with cervical cancer during their lifetimes, with the average age at the time of diagnosis being 48 years. In 2013, approximately 12,000 U.S. women are expected to be diagnosed with invasive (advanced-stage) cervical cancer, and about 4,000 will die from the disease.
Because infection with the human papilloma virus (HPV) is detected in more than 99 percent of cervical cancer cases, it is considered the cause of most such cancers. However, only a very small minority of the 75 to 80 percent of sexually active adult women who contract HPV infection develop cervical cancer.
Well-established risk factors for cervical cancer include:
- Early onset of sexual activity;
- Multiple sexual partners;
- A high-risk sexual partner (e.g., a partner with multiple sexual partners or known HPV infection);
- A history of sexually transmitted infections (e.g., syphilis, chlamydia or genital herpes);
- History of vulvar or vaginal squamous epithelial cancers (other cancers also caused by HPV); and
- Immunosuppression (due to, for example, chemotherapy, organ transplantation, or human immunodeficiency virus infection).
Most of these risk factors are the same as those for developing HPV infection.
The development of cervical cancer is preceded by precancerous changes to cells within the outer lining of the cervix. In many patients, these abnormal changes will regress and not progress to cervical cancer, whereas in others, the precancerous cells will progress to the early, noninvasive stage of cervical cancer over many months to years.
What are Pap tests?
At both the precancerous and the early, noninvasive stages of cervical cancer, patients are asymptomatic. The Pap test is a screening test designed to detect these early stages of the disease when it can be easily treated, thus preventing progression to actual cervical cancer in women with precancerous lesions and curing the disease in those who have early stage cancer.
Pap tests are usually done as part of routine pelvic exams. A small brush, special spatula or both are used to gently remove cells from the lining and opening of the cervix. These cells are transferred to a glass slide and examined under a microscope by a pathologist. Results typically are available after a few weeks. If precancerous or cancerous cells are found, the patient will be asked to undergo additional tests to examine the cervix and, in most cases, take biopsies. If precancerous or cancerous lesions are confirmed upon further testing, appropriate treatment is then offered.
It is important to understand that Pap tests are not perfect. Some patients have false negative results (in which the test results are normal but the patient has precancerous cervical lesions or cervical cancer), and others have false positive results (in which the results show abnormal cervical cells but the patient does not have precancerous cervical lesions or cervical cancer).
Recommendations for screening for cervical cancer
Over the past two decades, the U.S. Preventive Services Task Force (USPSTF), the American Cancer Society (ACS), and the American College of Obstetricians and Gynecologists (ACOG) have issued and periodically updated separate recommendations regarding when women should undergo screening for cervical cancer and how frequently. Currently, all three groups recommend that women ages 21 to 29 years undergo Pap tests every three years and that women over age 30 undergo these tests either every three years or every five years if combined with simultaneous testing for HPV infection.
Since 2003, all three groups have recommended against screening for cervical cancer in women who have had a total hysterectomy (which includes removal of the cervix) if the following two conditions are met:
- The hysterectomy was for a benign (not cancererous or precancerous) condition (for example, uterine fibroids).
- The patient has no prior history of precancerous cervical changes or cervical cancer.
(Of note, approximately 95 percent of all hysterectomies in the U.S. are total hysterectomies.)
Ten years ago, the USPSTF recommended against routinely screening women older than age 65 for cervical cancer if they had undergone adequate recent screening with normal Pap test results and were not otherwise at high risk for cervical cancer. ACS made a similar recommendation for women older than age 70, whereas ACOG did not have an upper age limit for discontinuing such screening.
All three groups now recommend against screening women older than age 65 if certain criteria are met regarding the absence of prior cervical cancer or precancerous cervical abnormalities and prior negative Pap test results. (The exact criteria vary somewhat between groups.)
The CDC study
In a study published in the Morbidity and Mortality Weekly Report on Jan. 4, 2012, CDC researchers analyzed data from the Behavioral Risk Factor Surveillance System (BRFSS), a state-based system of health surveys established by the CDC in 1984. The BRFSS surveyors call a random sample of civilian adults in all 50 states and the District of Columbia each month to ask questions regarding general health status, health risk behaviors (e.g., smoking, exercise), preventive health practices and access to health care, primarily related to chronic disease and injury. The system surveys more than 350,000 people each year. Every two years, the BRFSS survey includes a section on women’s health, asking women, among other things, whether they had ever had a Pap test, how long since their last Pap test and if they had undergone a hysterectomy.
The CDC researchers, interested in trends in screening women for cervical cancer, analyzed data from the women’s health section of surveys of women aged 30 years or older from 2000 to 2010. They found that among the women who reported having had a hysterectomy, the proportion who underwent a recent (within three years) Pap test decreased from 73 percent in 2000 to 59 percent in 2010. Among women age 30 to 64 who had had a hysterectomy, the percentage reporting a recent Pap test decreased significantly: from 81 percent in 2000 to 69 percent in 2010. For women 65 or older with a hysterectomy, there was a significant decline, from 62 percent to 45 percent over the same 10-year span. For women 65 or older with no prior hysterectomy, the proportion reporting a recent Pap test declined significantly, from 74 percent in 2000 to 65 percent in 2010.
The CDC noted several important limitations to its study, including:
- Prior studies of self-reported Pap test data have shown that women may overreport being screened with a Pap test and underreport the time since their last test.
- Information on the timing of recent Pap tests relative to the timing of hysterectomy in the women surveyed was not obtained; thus, a small number of hysterectomies may have been performed after the Pap test.
- The BRFSS survey did not ask about the reasons for hysterectomy, whether the cervix was removed, or reasons for which women might need continued screening after a hysterectomy (for example, having a high-grade, precancerous lesion before hysterectomy).
- Survey responses were low, ranging from 40 percent to 56 percent.
Despite these limitations, the study authors were able to make some reasonable general conclusions. In particular, they concluded that although expert recommendations regarding cervical cancer screening have resulted in significantly reduced unnecessary screening in women who have had a total hysterectomy or who are older than 65, many women in these groups are still undergoing unwarranted screening that provides no benefit. For women with hysterectomies, the researchers estimated that as many as 22 million may have received unnecessary Pap tests, contrary to the consistent recommendations of the USPTF, ACS and ACOG that have been in place for nearly a decade. The CDC data also suggest that millions of other women older than age 65 also underwent unnecessary cervical cancer screening during this same time period.
Advice for readers
Clearly, many physicians and other health care providers who perform Pap tests are not well-informed about, or fail to follow, the well-accepted guidelines for when such tests are no longer needed. If you have had a total hysterectomy with removal of the cervix and do not have a history of high-grade, precancerous cervical lesions or cervical cancer, or if you are older than 65, have had adequate prior screening and are not at high risk for cervical cancer, you should challenge any health care provider’s recommendation that you have a Pap test. In such circumstances, ask your health care provider to explain the basis for the recommendation and the justification for deviating from the current guidelines for such tests. If you are not satisfied with the explanation provided, you should decline to have the test and consider seeking a second opinion. Consider sharing and discussing this article with your doctor.