Meta-analysis finds no definitive link between tanning bed use and malignant melanoma

Robyn Boyle, RPh, for MDLinx | February 19, 2018

A meta-analysis from an international team of investigators has found that while there is a slightly increased risk of melanoma in tanning bed users, the studies had significant shortcomings that render their results incomplete, unbalanced, and uncritical.

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Most solarium devices emit UV-A radiation. Only a small fraction of radiation is emitted in the UV-B range.

The authors of the new study, led by Barbara Burgard, Dr. med., from the Saarland University in Hamburg, Germany, stated that, “Current scientific knowledge is mainly based on observational studies with poor quality data, which report associations but do not prove causality. At present, there is no convincing evidence that moderate/responsible solarium use increases melanoma risk.”

The findings were published in Anticancer Research. The analysis was based on two cohort and 29 case-control studies found during a systematic literature search of the scientific databases MEDLINE and ISI Web of Science.

Although the association of ultraviolet (UV) light, specifically UV-B, in promoting non-melanoma skin cancers and melanoma is generally accepted, tanning bed use and the risk of malignant melanoma is still a matter of debate. Most solarium devices emit UV-A radiation, only a small fraction of radiation (<5%) is emitted in the UV-B range.

Previous meta-analyses that assessed melanoma risk and solarium use have been criticized for errors, limitations (including unobserved or unrecorded confounding), and not conforming to standard guidelines of evidence-based medicine.

To incorporate new studies and to improve comparability between studies, the investigators took a different approach in this meta-analysis and used crude risk estimates in a random-effects model. Individual studies were also evaluated for quality using a standard quality assessment scale. Studies were then graded according to the recommendations of the Oxford Centre for Evidence-based Medicine (CEBM).

The studies were analyzed based on four outcomes: ever exposure, high and low exposure, and first exposure at a young age (

Studies were conducted in Europe (64.5%), North America (29%), and Australia (6.5%); most participants were recruited before 2000 (80%), and differed in age and gender distributions. The studies included 11,706 malignant melanoma cases and 93,236 controls. The authors noted that the quality of the studies varied, and they felt that the resulting evidence levels were low due to unobserved or unrecorded confounding, lack of interventional trials, and a high risk of bias.

This meta-analysis showed a statistically significant weak association for ever-exposure compared to non-exposure to UV radiation from a tanning bed. The overall risk of melanoma was 1.19.

Although 13 studies included in the meta-analysis reported a possible association between melanoma risk and the age of first use of a solarium, only four studies used the same age threshold (

Fifteen studies evaluated dose-response relationships between UV radiation exposure from a solarium and risk of melanoma but only seven defined exposure as >10 sessions in a lifetime. The pooled results indicated a statistically significant association for melanoma risk and high exposure to UV radiation from a tanning bed (OR = 1.43); however, a meta-analysis of the seven studies did not show an association (OR = 1.13). The authors felt that differences are probably due to a high risk of bias found in most (85.7%) of the pooled studies.

The authors explained that there are numerous confounding factors that are difficult to control, including UV exposure from the sun, technical differences in tanning beds, length of exposure, time period of recruitment, and other factors the influenced the use of tanning beds over time.

They also emphasize that interventional trials are lacking, and results of cohort and case-control studies do not prove causality. Moreover, the level of evidence and grade of recommendation of studies in this meta-analysis are weak.

According to the Oxford CEBM, all outcomes in this meta-analysis indicated poor quality cohort and case-control studies and a grade D recommendation (defined as troublingly inconsistent or inconclusive studies of any level).

“Present scientific knowledge does not support the hypothesis of an increased melanoma risk due to solarium use,” concluded the authors.

Recently, the European Commission’s Scientific Committee on Health, Environment, and Emerging Risks (SCHEER) and the World Health Organization (WHO) released reports that recommend that, due to evidence of carcinogenic effects of tanning beds, there is no safe limit for UV irradiation, and no indication for use.1

In a critical appraisal that accompanied the meta-analysis in Anticancer Research, author Jorg Reichrath, Dr. med., also from Saarland University, along with other investigators from around the world, refuted the conclusions of SCHEER and WHO because the recommendation fails to take into account the beneficial health effects of UV radiation as well as the flawed scientific quality of the studies supporting their conclusions.

Accepted benefits of UV radiation include preventing and treating vitamin D deficiency, as well as dermatological phototherapy. Dr. Reichrath and colleagues concluded that “present scientific knowledge does not support the notion that tanning bed use per se may increase melanoma risk.”

To read more about this study, click here

References:

  1. Reichrath J, et al. Anticancer Research, 2018;38(2):1111-1120.

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