According to previous research, the overall risk of cancer in patients treated with TNF inhibitors seems not to be increased; there have however been concerns over an increased risk of melanoma. Most observational studies have reported no increased risk of melanoma in patients with rheumatoid arthritis (RA) who are not treated with biological drugs, whereas there have been case reports and at least one observational study suggesting a possible link between TNF inhibitors and risk of melanoma.
An interim analysis based on the Swedish biologics register previously reported as an abstract (and based on a small number of events) found an excess risk of melanoma in RA patients treated with TNF inhibitors, and the current publication is an extension of this previous analysis. The bottom line of the presented results is that RA patients treated with TNF inhibitors had an increased risk of first invasive melanoma compared to patients with RA who were not receiving such treatment (20 additional cases per 100,000 person years). The overall burden of cancer in this population was not however increased.
The authors note the following limitations of the study, which need to be considered when interpreting the results:
• Although they adjusted for several risk factors, confounding by indication is a possibility • There was no information on personal history of dysplastic or multiple naevi, which are known risk factors for melanoma• The median follow-up from start of TNF inhibitor treatment was 4.8 years (maximum 10 years), which might be insufficient to detect long term effects on cancer risks.
The authors discuss their findings in relation to other studies and conclude that they may not markedly shift the overall risk-benefit balance of TNF inhibitor treatment, as the absolute increase in melanoma risk was small. However this balance may be shifted in those patients who are at a high risk of melanoma for other reasons (such as those with a personal history), and increased clinical vigilance is advisable in such patients, if treatment with TNF inhibitors is considered.