J.H.J. Roelofzen

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.

DNA adducts in skin biopsies and 1-hydroxypyrene in urine of psoriasis patients and healthy volunteers following treatment with coal tar.

Coal tar ointments (CTO) are frequently used in the treatment of psoriasis and eczema, but CTO contain carcinogenic polycyclic aromatic hydrocarbons (PAH). PAH are absorbed and metabolized in the skin. In psoriasis, the skin barrier is altered and therefore, absorption and metabolism of PAH may differ from healthy skin. In this study, levels of urinary 1-hydroxypyrene and PAH-DNA adducts in the skin were studied in psoriatic patients and healthy volunteers. Three punch biopsies were taken from the lower back of 10 male volunteers and from a psoriatic plaque in 10 male patients. A surface of 6.25 cm(2) was treated with CTO. After 96 h CTO was removed and another three skin biopsies were collected from the treated area. DNA was isolated from skin biopsies and urine was collected during and after the exposure period. After 24h, a twofold lower 1-hydroxypyrene urinary excretion was observed in patients compared to healthy volunteers and after 48 h, this difference reached statistical significance (p<0.05). Over 96 h the median level of the sum of PAH-DNA adducts, analyzed by (32)P-post-labeling, increased from 3.5 before CTO administration to 21.1 adducts per 10(8) nucleotides in volunteers, and from 1.0 to 3.6 adducts per 10(8) nucleotides in patients. At 96 h, PAH-DNA levels were higher in healthy volunteers than in patients (p<0.05). Biomarkers for uptake, bioavailability and bioactivation of PAH were lower in patients compared to volunteers. These data suggest a lower risk of carcinogenic effects of CTO in psoriatic skin compared to healthy skin.

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.

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

Abstracts: Frontiers in Cancer Prevention Research 2008 A114 Background 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. Methods 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. Results 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). Conclusion 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.