What is New in Screening for Malignancy
A systematic review of screening mammography in women concluded that the pooled relative risks for breast cancer mortality with screening at ages 39 to 49, 50 to 59, and 60 to 69 were 0.85, 0.86, and 0.68 respectively [1]. This same review found that the effectiveness of clinical breast examination has not been proven by well-designed large trials.
The U. S. Preventive Services Task Force (USPSTF) published updated screening guidelines for breast cancer in November 2009, recommending screening every two years for women aged 50 to 74 years [2]. In December 2009, after professional and public reaction, the USPSTF revised their November 2009 recommendation not to routinely screen women aged 40 to 49 with mammography [3], and recommends that patients' values regarding benefits and harms be taken into account in deciding whether to start regular biennial mammography before the age of 50. The USPSTF recommends against teaching women how to perform breast self-examination, but finds evidence insufficient to make recommendations regarding benefits of clinical breast examination in any women or mammographic screening for women 75 years or older.
The NELSON trial, an ongoing randomized CT-based lung cancer trial, reported results of the first two rounds of screening [4]. The trial protocol limits follow-up for identified nodules to those with initial nodule volume >0.5 cm or subsequent change in size. Using this protocol, 0.3 percent (20 in 7361) of high-risk subjects with initial negative screening had lung cancers detected after two years of follow-up. These findings suggest that specified criteria for follow-up of CT findings may reasonably limit invasive testing for false positive examinations.
In a case-control study using stored serum samples collected periodically from women who later developed ovarian cancer and from controls, three tumor markers (CA 125, mesothelin, and HE4) began to increase three years before the diagnosis of ovarian cancer, but adequate discrimination between normal and cancer cases was achieved only one year before diagnosis [5]. CA125 was most strongly predictive of ovarian cancer. It is unclear whether detection at one year before clinical diagnosis would be sufficiently early to impact mortality.
A randomized trial involving almost 90,000 women [6] confirmed findings of a prior meta-analysis [7] that conventional Pap smears and liquid-based cytology perform equivalently in the detection of cervical abnormalities.
The benefits of screening sexually active adolescents for cervical cancer may be offset by potential harms [8]. The American College of Obstetrics and Gynecology (ACOG) released new guidelines in 2009, recommending initiating Pap smear screening at age 21 [9]. While high quality evidence is not available to define the appropriate age to initiate testing, now it has been suggested that screening be initiated no earlier than age 21, regardless of the age of initiation of sexual activity. They also now suggest that Pap smear screening in average risk women less than 30 years old be initiated at intervals of one to two years, lengthening the screening interval to two to three years after three consecutive negative smears or at age 30, whichever comes first.
The effectiveness of colonoscopy in detecting proximal lesions has been called into question. A community-based study of participants undergoing screening colonoscopy found a significantly lower incidence of left-sided, but not right-sided, advanced colorectal neoplasia comparing participants who had a prior colonoscopy within the previous ten years with those who had not [10]. This finding may reflect bias in this nonrandomized study, incomplete colonoscopic examination of the right colon, or biologic differences in right-sided tumors, such as more flat or rapidly growing neoplasms.
REFERENCES
3. www.ahrq.gov/clinic/USpstf/uspsbrca.htm
8. Sawaya, GF. Cervical-Cancer Screening -- New Guidelines and the Balance between Benefits and Harms. N Engl J Med 2009; 361:2503.
9. ACOG Practice Bulletin No. 109: Cervical Cytology Screening. Obstet Gynecol 2009; 114:1409.
