USPSTF: Insufficient evidence to estimate benefit, harm of skin cancer screening

Issue: March 10, 2009

In an update on the evidence for skin cancer screening, the U.S. Preventive Services Task Force has concluded that the benefits and harms of whole-body skin examination — by a clinician or patient self-examination — for the early detection of skin cancer cannot be assessed due to lack of data. The guidelines were published in Annals of Internal Medicine.

In 2001, the task force concluded that they could not recommend for or against routine screening with whole-body skin examination due to insufficient evidence. For their current statement the task force reviewed studies published since 2001 on screening efficacy, stage of detection by screening and the accuracy of whole-body examination by primary care physicians and self-examination by patients.

Studies have reported physician accuracy in diagnosing melanoma with high sensitivity (46% to 100%) and specificity (70% to 98%). However, according to the task force, most accuracy studies evaluated the primary care physician’s ability to identify melanoma from images of lesions with a known diagnosis, thus compromising the applicability of evidence to whole-body skin examination.

In addition, the efficacy of clinician screening on clinical outcomes such as reduced morbidity and mortality have not been examined in randomized trials, according to the task force. Instead, only indirect evidence exists to demonstrate how earlier treatment due to screening may improve health outcomes. According to the systematic review, studies to assess whether screening improves outcomes in basal cell and squamous cell carcinomas do not exist.

Weighing harms and benefits

Though the task force states that little evidence on the harms of screening exists, they do note that false-positive results can often lead to biopsies and unnecessary treatment. The detection of non-melanomas and thin lesions that result from screening are also problematic due to the potential for overtreatment. Based on this, the task force was unable to estimate the degree of harm associated with screening.

Similarly, the task force was unable to estimate the degree of net benefit due to a lack of studies comparing the health outcomes among screened vs. unscreened populations. Due to limited evidence on the overall harms of screening, the task force could not make necessary assessments.

In addition, the task force states that although early-stage lesions likely detected during screening have increased the incidence of melanoma, mortality from the disease has not changed considerably.

Practice recommendations

Due to the lack of evidence, the task force did not recommend for or against screening in their guidelines. However, they do suggest that if physicians continue to apply skin cancer screening to their practice, patients should be informed of the uncertainty about the balance of benefits and harms.

The task force also recommends that clinicians remain watchful for skin lesions with malignant features observed during physical exams performed for other reasons. Such features include asymmetry, border irregularity, color variability, diameter greater than 6 mm or rapidly changing lesions; suspicious lesions warrant biopsy.

Clinicians should also be aware of those patients known to be at an increased risk for melanoma, including: fair-skinned men and women aged 65 years or older, patients with atypical moles and those with more than 50 moles. Family history and a considerable history of sun exposure and sunburn are also risk factors. However, the task force notes that even in high-risk patients the benefits from screening are uncertain.

Previously reviewed evidence for counseling to prevent skin cancer and interventions designed to reduce skin cancer are also available from the task force at the AHRQ website. – by Stacey L. Adams

Ann Intern Med. 2009;150:188-193.

This is a very interesting update of the 2001 U.S. Preventive Services Task Force recommendation statement on screening for skin cancer. [The task force] reviewed published studies since 2001 on screening effectiveness, the stage of detection by screening, and the accuracy of whole-body examination by primary care clinicians and self-examination by patients. Unfortunately, because of lacking of large scale prospective studies to address the important issues of effectiveness of early detection, and the morbidity and mortality outcomes, it is not surprising that the task force issued the exact same statement (insufficient evidence) recommendation as they did in 2001.

The incidence of melanoma and skin cancer has increased in the last two decades; the lifetime risk for melanoma has been increasing dramatically since 1935. The death rate from melanoma is rising linearly while the incidence is increasing exponentially. This is not due to early diagnosis or better cancer-counting methods, but primarily due to a true increase in incidence. Melanoma is now the most frequent cancer in women 25 to 29 years of age and the second most frequent (after breast cancer) in women 30 to 34 years of age. Thickness of the melanoma is the most important prognostic factor on the outcome of patients. Patients with thin melanoma (<1 mm) have a 15-year survival rate of 80% to 90% vs. 30% to 50% for patients with thick melanoma (>4 mm). If the incidence of melanoma is increasing primarily because of an increase in late-stage lesions (thick lesions), I am afraid that the death rate from melanoma would be rising exponentially, not linearly.

In the article they quote, 'The first 15 years of the American Academy of Dermatology Skin Cancer Screening Programs: 1985-1999,' published in 2003. The free skin cancer screening coupled with melanoma/skin cancer education is provided by dermatologists. From 1985 to 1999, 639,835 individuals were screened through this program, 80% did not have a regular dermatologist, 60% had never had their skin checked by any doctor, 51% would not have seen a doctor for skin cancer without the free screening, and 30% had a presumptive diagnosis of skin cancer or a precursor lesion. Sustained commitment by the American Academy of Dermatology to the screening program is critical to reducing the morbidity and mortality of skin cancer.

– Wen-Jen Hwu, MD, PhD

HemOnc Today Editorial Board Member