Over the last several decades there has been a progressive modification (generally a decrease) in the recommended intervals for Pap smear screening in the general population. Recently, the U.S. Preventive Services Task Force (USPST) published their latest Pap smear screening guidelines in the Annals of Internal Medicine and a multidisciplinary partnership among the American Cancer Society/American Society for Colposcopy and Cervical Pathology/American Society for Clinical Pathology (ACS/ASCCP/ASCP) published their updated guidelines in Ca: A Cancer Journal for Clinicians.
The guidelines were independently derived but are quite similar in their conclusions, a reassuring point for both patients and physicians. In general, they recommend that most patients get screened for cervical cancer no more often than every 3 to 5 years.
Principal recommendations include:
•Women between ages 21 and 65 without risk factors (such as DES exposure or immunodeficiency) should undergo cytologic screening every 3 years.
•Those aged 30 to 65 wishing to extend the screening interval could undergo screening with both cytologic exam and human papillomavirus testing every 5 years.
•Women younger than 21 should not be screened.
•Women older than 65 who have been adequately screened previously should not be screened.
The complete guidelines with comments from the American College of Obstetricians and Gynecologists (ACOG)
can be found here:
The following is taken from the ACOG comments (found above) regarding the guideline changes.
What is new about these guidelines?
This is the first time that USPSTF has recommended the combined use of cervical cytology and high-risk human papillomavirus (HPV) DNA testing (“co-testing”). The previous USPSTF guidelines had indicated that evidence was insufficient to make a recommendation regarding the use of co-testing. USPSTF now recommends that women age 30–65 years should be screened by either cytology every 3 years or co-testing every 5 years.
In contrast, ACS/ASCCP/ASCP finds that co-testing every 5 years is preferred to cytology alone but that cytology alone every 3 years is an acceptable strategy. In choosing to make co-testing the preferred strategy, ACS/ASCCP/ASCP focused on evidence from multiple randomized trials showing that co-testing has improved performance compared with cytology alone. Specifically, co-testing has increased sensitivity for detecting cervical intraepithelial neoplasia grade 3 or greater (CIN3+), and women who have undergone co-testing have a lower risk of CIN3+ and invasive cancer after the first screening round. Because of this improved performance, co-testing can be used for screening at less frequent intervals than cytology alone. In addition, co-testing offers greater risk reduction than cytology alone for adenocarcinoma of the cervix and its precursors.
What is the ACOG's position on these new guidelines?
The College applauds the work of these organizations in integrating the significant new evidence that has become available into the revised guidelines. Each set of recommendations was developed under a separate work plan, with its own policies and procedures for evidence collection and analysis. The very similar recommendations are reassuring because although they were developed independently and by different methodology, they drew on a common evidence base, which was interpreted the same way by different groups of experts. The College encouraged and facilitated collaboration among the groups, urging that consistency of message would benefit American women and the clinicians who care for them. This message was clearly heard.
The College now moves to its final phase of evaluating the recommendations. They will be evaluated by committees that make the College’s recommendations on screening for cervical cancer. Any new guidelines from the College will be published in Obstetrics & Gynecology.
Why do all these organizations—including the College—discourage annual cervical cancer screening?
Cervical cancer is typically slow growing, and most cancers are found in women who have never been screened or who have not been screened in the past 5 years. Recommending less frequent screening for cervical cancer is not new. The ACS has recommended less frequent screening for some women since 1980. The College has made similar recommendations since 1989. Note that the new guidelines from USPSTF and ACS/ASCCP/ASCP are for women at average risk. More frequent testing may be appropriate for women with conditions that place them at an increased risk of cervical cancer, such as immunocompromise or human immunodeficiency virus (HIV) infection.
These recommendations reflect a balance between benefits and harms. Both cervical cytology and testing for high-risk types of HPV DNA can detect cervical cancer and its precursors, but each will detect many abnormalities that will not go on to become cancer. Annual screening with cytology alone has been shown to lead to a very small increase in cancers prevented but greatly increases the number of unnecessary procedures and treatments. The prevalence of transient HPV infections and associated low-grade lesions is high, but most of these will regress within 1 to 2 years. The small fraction of lesions that do not regress will, on average, require many years to progress to cancer. Identifying and treating lesions that will likely regress on their own does not provide a benefit large enough to outweigh the harms. These harms may include anxiety associated with a “positive” cancer screening test, potential stigmatization from the diagnosis of a sexually transmitted infection, discomfort from additional diagnostic and treatment procedures, bleeding from treatment, and, longer term, an increased risk of pregnancy complications such as preterm delivery in women previously treated with excisional procedures for precancerous lesions.
While cost was explicitly not considered in the guideline development, increased testing and treatment clearly has associated cost and may be an additional potential harm for some women. Extending the interval for screening strikes the most appropriate balance between benefits and harms.
As noted in the ACS/ASCCP/ASCP guidelines, no screening test has perfect sensitivity, and preventing all cervical cancer is unrealistic. Even with annual cervical cancer screening, a small risk of cancer would remain after screening.
In their comments, ACOG is careful to note that not needing a yearly Pap smear does not mean that women should not have yearly physician visits, since the Pap smear is only one small component of a yearly physician evaluation.
Given the current availablity of effective vaccines against HPV, one wonders how this will ultimately figure into Pap screening recommendations as the vaccinated population grows. Will vaccinated patients even need routine Pap smear studies in the absence of any symptomatology? For the moment the recommendations clearly state that vaccination status should NOT affect screening, but we'll see how this changes as the efficacy of the vaccine continues to be documented.
If you're engaged in long-term planning for a pathology department it seems reasonable to assume that Pap smear volume will continue to decrease (assuming a stable patient population base) over the next few years. HPV testing, however, is likely to continue to increase.