Dermatological exposure to coal tar and bladder cancer risk: a case-control study.

OBJECTIVE: Coal tar ointments are used as treatment of various skin diseases, especially psoriasis and eczema. These ointments contain several carcinogenic polycyclic aromatic hydrocarbons. Metabolites of these polycyclic aromatic hydrocarbons are excreted in the urine and therefore, dermatological use of coal tar may be associated with an increased risk of bladder cancer. The objective of this study was to evaluate the association between dermatological use of coal tar ointments and bladder cancer. MATERIAL AND METHODS: A population-based case-control study was conducted including 1,387 cases diagnosed with bladder cancer and 5,182 population controls. Information on the use of coal tar, history of skin disease, and known risk factors for bladder cancer was obtained through postal questionnaires. Logistic regression analyses were performed to estimate the risk of bladder cancer after coal tar treatment, adjusted for age, gender, smoking status, duration of smoking, and intensity of smoking. RESULTS: The use of coal tar ointments was approximately equal among cases and controls (3.8% vs. 3.0%, respectively). Dermatological application of coal tar was not significantly associated with bladder cancer (adjusted odds ratio = 1.37, 95% CI: 0.93-2.01). An inverse association between bladder cancer and a history of skin disease was observed (adjusted odds ratio = 0.74, 95% CI: 0.61-0.90). CONCLUSION: This is the first study with a specific aim to study the association between the use of coal tar preparations and bladder cancer. The results suggest that there is no reason for safety concerns with respect to the risk of bladder cancer after the use of coal tar preparations in dermatological practice.

No increased risk of cancer after coal tar treatment in patients with psoriasis or eczema.

Coal tar is an effective treatment for psoriasis and eczema, but it contains several carcinogenic compounds. Occupational and animal studies have shown an increased risk of cancer after exposure to coal tar. Many dermatologists have abandoned this treatment for safety reasons, although the risk of cancer after coal tar in dermatological practice is unclear. This large cohort study included 13,200 patients with psoriasis and eczema. Information on skin disease and treatment, risk factors, and cancer occurrence was retrieved from medical files, questionnaires, and medical registries. Proportional hazards regression was used to evaluate differences in cancer risk by treatment modality. Patients treated with coal tar were compared with a reference category of patients treated with dermatocorticosteroids (assumed to carry no increased cancer risk). The median exposure to coal tar ointments was 6 months (range 1-300 months). Coal tar did not increase the risk of non-skin malignancies (hazard ratio (HR) 0.92; 95% confidence interval (CI) 0.78-1.09), or the risk of skin cancer (HR 1.09; 95% CI 0.69-1.72). This study has sufficient power to show that coal tar treatment is not associated with an increased risk of cancer. These results indicate that coal tar can be maintained as a safe treatment in dermatological practice.

Coal tar in dermatology.

Coal tar is one of the oldest treatments for psoriasis and eczema. It has anti-inflammatory, antibacterial, antipruritic and antimitotic effects. The short-term side effects are folliculitis, irritation and contact allergy. Coal tar contains carcinogens. The carcinogenicity of coal tar has been shown in animal studies and studies in occupational settings. There is no clear evidence of an increased risk of skin tumors or internal tumors. Until now, most studies have been fairly small and they did not investigate the risk of coal tar alone, but the risk of coal tar combined with other therapies. New, well-designed, epidemiological studies are necessary to assess the risk of skin tumors and other malignancies after dermatological use of coal tar.

Treatment policy for psoriasis and eczema: a survey among dermatologists in the Netherlands and Belgian Flanders.

Today, many therapies are available for the treatment of psoriasis and eczema. One of the oldest topical therapies is coal tar. Coal tar has been used for decades, but over the past years, the use of coal tar has decreased for several reasons, including the supposed carcinogenicity of coal tar. We investigated the current and past treatment policies for psoriasis and eczema with special emphasis on the use of tar products; a postal survey was conducted among all dermatologists in two European countries: the Netherlands (n = 360) and the Flemish speaking part of Belgium (Flanders) (n = 328). This study was conducted as part of the ongoing LATER-study ("Late effects of coal tar treatment in eczema and psoriasis; the Radboud study"). All practising dermatologists received a questionnaire. Dermatologists were asked to describe their treatment policies in mild/moderate psoriasis, severe psoriasis, mild/moderate eczema and severe eczema. The response rate to the questionnaire was 62.5% for the Dutch dermatologists and 45.7% for the Flemish dermatologists. Almost all dermatologists prescribe topical corticosteroids. In eczema, most of the dermatologists prescribe the recently introduced calcineurin inhibitors (95%). Coal tar is a second choice topical therapy. Dutch dermatologists mainly use tar in the treatment of eczema (72% vs. 48% in Flanders), whereas in Flanders, tar is mainly prescribed in psoriasis (60% vs. 41% in Holland). Flemish dermatologists very frequently prescribe PUVA in psoriasis (93% vs. 63%). Topical treatment, especially topical corticosteroids, is the mainstay in psoriasis and eczema. Coal tar still is an important (second choice) therapy for the topical treatment of psoriasis and eczema, but its use varies from country to country. Despite the carcinogenicity of PUVA, this photochemotherapy is frequently prescribed by dermatologists, mainly in Flanders.