Not Enough Evidence to Balance Harms, Benefit of Visual Skin Cancer Exam

There is currently not enough evidence to assess the balance of benefits and harms of a visual skin examination by a clinician to screen for skin cancer in asymptomatic adults, according to a recommendation statement by the US Preventive Services Task Force (USPSTF) published recently in JAMA.

The published statement was an I statement indicating that there is insufficient evidence to balance benefits and harms-that evidence is lacking, of poor quality, or is conflicting.

Although basal and squamous cell carcinoma are the most common types of skin cancer in the United States, they are not associated with high rates of mortality. In contrast, in 2016, it is estimated that more than 75,000 people will develop melanoma, with more than 10,000 dying from the disease. In this update to its 2009 recommendation, the USPSTF reviewed available evidence on the effectiveness of screening for skin cancer with a visual examination in reducing morbidity or mortality, as well as the potential harms of this screening method.

In this review, the Task Force found “adequate” evidence that skin examination by a clinician has modest sensitivity and specificity for detecting melanoma, but evidence was limited and inconsistent for the detection of non-melanoma skin cancer. In addition, there is not enough evidence to conclude that early detection by skin examination reduces a patient’s morbidity or mortality.

When looking at the harms of clinician-conducted visual examinations, the Task Force found evidence that harms are small, “but current data are insufficient to precisely bound the upper magnitude of these harms.” Among the possible harms listed are misdiagnosis, overdiagnosis, and resulting cosmetic or functional adverse effects from biopsy or overtreatment.

The Task Force also discussed research needs and gap in its statement.

“The USPSTF recognizes the challenge of conducting a definitive randomized clinical trial (RCT) on primary screening, with cause-specific mortality as an endpoint, to provide clear evidence on the efficacy of the clinical visual skin examination in screening for skin cancer, given the comparatively low rate of death from melanoma in the population (even among persons at higher risk),” they wrote.

“If adequately powered RCTs are not possible, a high-quality case-control study could provide sufficient power without requiring a large sample size. However, this study design has limitations in the ability to create an appropriate comparison group, the ability to accurately measure the exposure of interest (because of recall bias and other sources of misclassification), healthy volunteer bias (persons receiving skin examinations likely have other good health habits), and other unmeasured sources of confounding. Studies would have to be carefully designed to avoid these threats to validity.”

In an editorial comment published with the recommendation, Hensin Tsao, MD, PhD, of Massachusetts General Hospital in Boston, and Martin A. Weinstock, MD, PhD, of Warren Alpert Medical School of Brown University and Veterans Affairs Medical Center in Providence, Rhode Island, noted that the statement of insufficient evidence is not the same as “evidence of no benefit.”

Based on this statement, Tsao and Weinstock said that the medical community should come together “in executing well-designed but feasible studies so future recommendations can be of greater public health benefit.”

The benefits and harms of self-examination for skin cancer screening will be addressed in a separate recommendation statement.