The debate as to whether or not these systemic treatments for psoriasis increase a patient’s risk of malignancy remains largely unresolved and has been further confounded by the premise that the disease itself, may also inherently place the patient at a higher likelihood of developing certain cancers. This review examines the risk of malignancy associated with therapies for moderate to severe psoriasis, including:

• Psoralen and ultraviolet A (PUVA)

• Narrowband and broadband ultraviolet B (UVB)

• Methotrexate (MTX)

• Cyclosporin (CsA)

• Mycophenolate mofetil (MMF)

• Biologic therapies: alefacept, efalizumab, infliximab, etanercept, adalimumab, and ustekinumab.

The following findings were reported:

• PUVA, when given long term, is associated with increased risks of cutaneous squamous cell carcinoma and malignant melanoma.

• UVB, both narrowband and broadband, have not been shown to increase risk of non-melanoma skin cancer or melanoma.

• MTX, CsA, and MMF may be associated with an increased risk of lymphoproliferative disorders during treatment, demonstrated in clinical trials in patients with rheumatoid arthritis and documented in case reports about psoriasis patients.

• The risk of malignancy with biologic therapy is still unclear. However, the majority of studies examining this carcinogenic risk suggest that TNF blockers may cause a slightly increased risk of cancer, including non-melanoma skin cancer and haematological malignancies.

The authors conclude “many of the therapies for moderate to severe psoriasis, including PUVA, traditional systemic therapies, and some biologic therapies, may increase the risk of malignancy. Appropriate patient counselling and selection, as well as clinical follow-up, are necessary to maximize safety with these agents.” They acknowledge that their findings are limited by the lack of power and randomisation of the majority of studies cited in their review, as well as the long-term follow-up periods which would further substantiate the hypothetical link. Furthermore, due to the substantial lack of clinical data, the majority of studies evaluated focus on the treatment of patients with rheumatoid arthritis. They also note that the increased risk of malignancy associated with psoriasis itself is a confounding factor. They call for further long-term study to more precisely quantify the risks associated with biologic therapies.