|
Screening for skin cancer |
Helfand M, Mahon S, Eden K |
|
|
Authors' objectives The authors aimed to review studies about the effectiveness and accuracy of routine skin cancer screening by primary care providers.
Searching MEDLINE was searched from January 1994 to June 1999; the search terms were listed in the report. Studies published prior to 1994 were identified using other reviews and the Guide to Clinical Preventive Services (see Other Publications of Related Interest). Additional articles were located from the reference lists of identified studies and through recommendations made by experts.
Study selection Study designs of evaluations included in the reviewStudies of any design were eligible for inclusion.
Specific interventions included in the reviewStudies were eligible for inclusion in the review if they assessed routine skin cancer screening by a primary care provider. Two methods of screening were eligible: total body skin examination in all people seen in primary care; and assessing skin cancer risk in all patients, followed by total body skin examination in people at high risk.
Both mass screening and case-finding programmes to detect squamous cell carcinoma, basal cell carcinoma and malignant melanoma were included.
Reference standard test against which the new test was comparedThe authors did not pre-specify a 'gold' standard as an inclusion criterion. Skin biopsy was the gold standard used to assess the accuracy of total body skin examination in studies included in the review. In some studies, longitudinal follow-up was used to assess mortality and morbidity.
Participants included in the reviewStudies were eligible for inclusion if they examined screening in the general adult population or in the elderly.
Outcomes assessed in the reviewStudies were eligible for inclusion if they included data on yield of screening, screening tests, risk factors, risk assessment, effectiveness of early detection, or cost-effectiveness. The main outcomes in the studies included in the review were mortality, morbidity, sensitivity and specificity. The authors calculated summary statistics from the extracted data.
How were decisions on the relevance of primary studies made?Two reviewers independently assessed a subset of 500 abstracts. Once consistency was established, one reviewer assessed the remaining abstracts for relevance.
Assessment of study quality The authors did not state that they assessed validity.
Data extraction The authors did not state how the data were extracted for the review, or how many reviewers performed the data extraction.
Data were extracted on the type of study, study design, population, recruitment, setting, screening test type, examiner, targeted or non-targeted strategy, participant risk factors, referral procedure, yield of screening, types of suspected skin cancers, biopsies, confirmed skin cancers, stages and thickness of skin cancers detected. Where possible, data were also extracted on definitions of suspicious lesions, gold standards, mortality, morbidity, positive and negative predictive values, likelihood ratios, sensitivity and specificity. The authors calculated odds ratios and likelihood ratios from the extracted data.
Methods of synthesis How were the studies combined?A narrative synthesis of the studies was presented. The authors calculated positive predictive values, likelihood ratios and odds ratios from the extracted data to facilitate comparisons between the studies.
How were differences between studies investigated?The authors did not report a formal method for assessing heterogeneity. They described sources of heterogeneity such as participant characteristics, examiner characteristics, setting, level of risk, intervention type, workup bias and methodological quality.
Results of the review The authors did not report the total number of studies included in the review. A total of 103 references were cited in the bibliography, of which 7 studies (n=571,928) assessed the accuracy of skin cancer screening. Twenty-four studies (n=358,416) were included on the consequences of screening: 12 focused on mass screening, 4 on population-based screening, 2 on case-finding methods, 2 on worksite screening and 4 on other screening.
Based on 5 prospective studies, the authors suggested that total body skin examination by primary care physicians has low accuracy. Skin cancer was suspected in between 4 and 28% of the participants, but biopsy confirmed cancer in only 1 to 6%. The authors found no evidence that screening for melanoma reduces morbidity or mortality. They also found no evidence that formal screening programmes increase the cure rate for basal cell carcinoma or squamous cell carcinoma. Mole counts and other factors predict an increased risk over time, but the authors found no study of risk stratification followed by total body skin examination. They also found little evidence on the adverse effects of screening, or the effectiveness of general screening for reaching people at high risk.
Cost information The authors identified one cost-effectiveness analysis of screening for malignant melanoma. The incremental cost-effectiveness ratio was US$29,170 per year of life saved.
Authors' conclusions Routine screening in primary care settings has low accuracy. There was no evidence that screening the general population reduces death from skin cancer, although there were few randomised trials or well-designed prospective observational studies on this topic.
CRD commentary This review addressed a defined research question, but the authors did not specify the inclusion and exclusion criteria clearly. Only one database was searched and unpublished literature was not included. It was unclear whether the review was restricted to English language studies. The procedures used to select the studies, assess validity and extract the data were not described in full. The total number of studies and participants from which the data were drawn was unclear. It is therefore not possible to judge the quality of the studies included in the review, or the quality of the review process.
The authors acknowledged the possibility of workup bias and other problems which could impact on their findings. Although an appropriate narrative synthesis was used to collate the findings, heterogeneity was not formally assessed.
Overall, the authors' conclusions are supported by the data they present, but the lack of detail about the included studies makes it difficult to assess the generalisability of the findings.
Implications of the review for practice and research Practice: The authors found that routine skin cancer screening in primary care may not be accurate or cost-effective. Routine screening may be best reserved for groups at higher risk of skin cancer. This lack of accuracy of total body skin examinations may need to be weighed against the possible benefits, however, especially given that the follow-up strategy of skin biopsy does not cause major discomfort or morbidity for most patients.
Research: The authors suggested that there is a need for more research on screening in the elderly, especially among elderly men who have a high incidence of melanoma. Prospective population-based studies that compare the incidence of lethal melanoma in screened and unscreened groups, and strategies to identify high-risk groups that may benefit from primary care screening, may also be useful.
Funding Agency for Healthcare Research and Quality, contract number 290-97-0018.
Bibliographic details Helfand M, Mahon S, Eden K. Screening for skin cancer. Rockville, MD, USA: Agency for Healthcare Research and Quality. Systematic Evidence Review; 2. 2001 Other publications of related interest 1. US Preventive Services Task Force. Screening for skin cancer (including counselling to prevent skin cancer). In: DiGuiseppi C, Atkins D, Woolf SH, Kamerow DB, editors. Guide to Clinical Preventive Services. 2nd ed. Washington (DC): US Government Printing Office, Office of Disease Prevention and Health Promotion; 1996. p. 141-52.
2. Wolff T, Tai E, Miller T. Screening for skin cancer: an update of the evidence for the U.S. Preventative Services Task Force. Evidence Synthesis Number 67. AHRQ Publication No. 09-05128-EF-1. Rockville, Maryland: Agency for Healthcare Research and Quality. 2009.
3. Wolff T, Tai E, Miller T. Screening for skin cancer: an update of the evidence for the U.S. Preventative Services Task Force. Annals of Internal Medicine. 2009;150(3):194-198. Indexing Status Subject indexing assigned by CRD MeSH Carcinoma, Basal Cell /diagnosis /epidemiology; Skin Neoplasms /diagnosis /epidemiology AccessionNumber 12002008075 Date bibliographic record published 30/06/2004 Date abstract record published 30/06/2004 Record Status This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn. |
|
|
|