Abstract A114: No increased risk of cancer after coal tar treatment in patients with psoriasis or eczema

Coal tar is an effective topical treatment for psoriasis and eczema, but it contains several carcinogenic polycyclic aromatic hydrocarbons (PAHs), such as benzo(a)pyrene, benz(a)antracene and dibenz(a,h)anthracene. Occupational and animal studies showed an increased risk of cancer after exposure to coal tar. Many dermatologists have abandoned this effective treatment for safety reasons, although the risk of cancer after dermatological coal tar therapy is unclear. To study the risk of cancer after coal tar treatment and other therapies, the LATER study (Late effects of coal tar treatment in eczema and psoriasis; the Radboud study) was conducted.

A large historical cohort study was performed including 13,200 patients diagnosed with psoriasis and eczema between 1960 and 1990 at three large hospitals in the Netherlands. Specific information on skin disease and treatment, risk factors and cancer occurrence was retrieved from medical files, postal questionnaires, the Netherlands Cancer Registry and Causes of Death Registry. Cox Proportional Hazard regression models were used to evaluate differences in cancer risk by treatment modality.

Coal tar treatment did not increase the risk of non-skin malignancies (HR=0.92; 95%CI=0.78-1.09), nor the risk of skin cancer (excluding basal cell carcinoma) (HR=1.09; 95%CI=0.69-1.72). Alternative therapies, such as PUVA and systemic therapies appeared to be associated with an increased risk of skin cancer (HR=1.17; 95%CI=0.75-1.82 and HR=2.33; 95%CI=1.60-3.40, respectively), but no increased risk of non-skin cancer was observed (HR=0.91; 95%CI=0.75-1.10 and HR=1.12; 95%CI=0.95-1.32).

This study is the first study with sufficient numbers of patients and follow-up to reliably estimate the risk of cancer after coal tar treatment. The use of coal tar was not associated with an increased risk of cancer. PUVA and systemic therapies showed an increased risk of skin cancer, but no increased risk of tumours at other sites was observed. After considering the risks and benefits of coal treatment against the risks and benefits of other therapies, we conclude that coal tar coal tar can be maintained as a safe and effective treatment within dermatological practice.

Citation Information: Cancer Prev Res 2008;1(7 Suppl):A114.