RIO GRANDE, P.R. – Malignancy rates in psoriasis patients treated with ustekinumab did not increase significantly over 4 years of follow-up, based on pooled data from 3,117 patients enrolled in ustekinumab clinical trials.

Ustekinumab has shown effectiveness for treating moderate to severe psoriasis, but due to the potential of increased risk for cancer associated with its use, patients from several clinical trials (including PHOENIX I, PHOENIX II, and ACCEPT) are still being followed, said Dr. Kim A. Papp, director of research at Probity Medical Research, Waterloo, Ont., and colleagues.

The cumulative rates for nonmelanoma skin cancer in patients treated with ustekinumab for psoriasis remained low and stable throughout the follow-up period. A total of 0.57 cancer events per 100 person-years were reported in 2009 and 0.62 cancer events per 100 person-years were reported in 2010. The findings were presented at the annual Caribbean Dermatology Symposium.

In the complete analysis that included 6,791 patient-years of follow-up, 41 patients treated with any dose of ustekinumab developed at least one nonmelanoma skin cancer, and 3 patients developed both basal cell carcinoma and squamous cell carcinoma.

Another 42 patients developed at least one other malignancy, including 4 patients with melanoma in situ. However, no cases of invasive melanoma were observed during the study period. The other most common malignancies were prostate cancer (12 patients), colorectal cancer (4 patients) and breast cancer (3 patients).

By comparison, 39 individuals in the general population (based on the National Cancer Institute’s Surveillance, Epidemiology, and End Results database) developed at least one malignancy.

The findings were limited by the inclusion of several studies of varying lengths and by the inclusion criteria that can make comparison with the general population difficult, the researchers noted. The results suggest that rates of nonmelanoma skin cancer and other malignancies in psoriasis patients taking ustekinumab do not increase over time.

However, "additional long term data from clinical trials, observational registries, and postmarketing reporting databases will continue to define the ustekinumab malignancy risk profile," they wrote.

The study was sponsored by Centocor, which manufactures ustekinmab.