CHICAGO -- Rates of malignancy among patients with psoriasis outpaced national averages, irrespective of therapy in most cases, according to a study reported here.

Overall, psoriasis was associated with a 5-year malignancy rate of 115.5 cases per 10,000 person-years compared with 96/10,000 for the general population. Stratified by type of treatment, malignancy rates were in a relatively narrow range bounded by 94.6/10,000 for patients treated with adalimumab (Humira) and 138.1/10,000 for patients treated with infliximab (Remicade).

Action Points Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

Patients who received nonbiologic therapies had an overall malignancy rate of 116.8/10,0000, Alexa Kimball, MD, of Massachusetts General Hospital in Boston, and colleagues reported at the American Academy of Dermatology summer meeting.

"Patients with psoriasis had a higher rate for all malignancies, excluding nonmelanoma skin cancer, compared with the general population," the investigators concluded in a poster presentation. "Rates for all malignancies, excluding nonmelanoma skin cancer, were similar across treatment subcohorts."

Rates of lymphoma and nonmelanoma skin cancer varied by treatment group, but overall rates for both conditions exceeded rates in the general population.

A second report from the same investigators showed variation among psoriasis therapies with respect to infection-related hospitalizations, including a substantially higher rate among patients treated with infliximab.

Several studies have suggested that psoriasis is associated with an increased risk of certain malignancies, including non-Hodgkin lymphoma, nonmelanoma skin cancer, and cancers of the respiratory tract, urinary tract, and liver, the investigators pointed out in their background information. The malignancy risk might be related to chronic inflammation associated with psoriasis, and psoriasis therapies such as phototherapy, cyclosporine, and methotrexate may increase the risk as well.

To determine whether rates of cancer differ between treated and untreated psoriasis, investigators analyzed commercial claims data for 74 million covered lives and Medicare claims data for 5.3 million covered lives. The analysis focused on patients who had 12 months of continuous coverage from Jan. 1, 2005 through Dec. 31, 2006.

The psoriasis cohort comprised all adults who had a psoriasis diagnosis as of Dec. 31, 2006. Within that cohort, the investigators identified subgroups of patients who had at least one prescription claim for etanercept (Enbrel), adalimumab, infliximab, ustekinumab (Stelara), nonbiologic therapies for psoriasis, or phototherapy. Adults not meeting the psoriasis criteria served as a general population for comparison.

Follow-up continued until a first diagnosis of malignancy, disenrollment from the health plan, or 5 years from the index period.

The analysis included 5,857 patients who received nonbiologic psoriasis therapy, 6,856 treated with etanercept, 3,314 with adalimumab, 1,044 with infliximab, 526 with ustekinumab, and 5,156 with phototherapy.

Excluding nonmelanoma skin cancer, 508,929 malignancies occurred during 51,071,587 person-years of observation in the general population. The psoriasis cohort had 1,692 cases of cancer and 119,432 person-years of observation.

In the biologic subgroup, etanercept-treated patients had 205 cases malignancy in 19,792 person-years of observation (100.2/10,000), 70 malignancies and 7,774 person-years with adalimumab (94.6), 39 cases and 2,720 person years with infliximab (138.1), and seven cases during 558 person-years with ustekinumab (100.6). Additionally, 201 malignancies occurred during 14,148 person-years in the phototherapy group (117.3) and 234 cases during 15,707 person years with nonbiologic therapy (116.8).

Lymphoma rates varied more than did the rates for other malignancies. The rate in the general population was 6.6/10,000 versus 11.1/10,000 in the total population of psoriasis patients. The etanercept subgroup had the lowest lymphoma rate (6.9), followed by adalimumab (10.7), infliximab (18.1), and ustekinumab (25.1). The phototherapy subgroup had a lymphoma rate of 18.2, and the nonbiologic subgroup had a rate of 13.1.

The rate of nonmelanoma skin cancer was 94.2 in the general population versus 147.2 in the psoriasis cohort. Rates in the different treatment subgroups were 173.7 for nonbiologics, 155.9 for etanercept, 234.2 for adalimumab, 179.4 for infliximab, and 233.3 ustekinumab. Patients treated with phototherapy had a rate of 168.1.

The most striking finding in the study of infection-related hospitalization (involving the same databases) was the relative outlier status of patients treated with infliximab (554.7 events per 10,000 person-years). That compared with 261.5 for etanercept, 321.9 for adalimumab, 287.1 for ustekinumab, 341.4 for nonbiologics, and 261.2 for phototherapy.

The addition of systemic corticosteroid therapy to primary treatment substantially increased the rate of infection-related hospitalizations across all treatment groups. The rate ratio for patients who received steroids versus those who did not ranged from 1.36 for the phototherapy subgroup to 3.42 for the etanercept subgroup. Among patients treated with nonbiologic agents, the addition of systemic steroids more than doubled the rate ratio for infection-related hospitalization (RR 2.58).

Charles Bankhead is senior editor for oncology and also covers urology, dermatology, and ophthalmology. He joined MedPage Today in 2007. Follow