Does Psoriasis Increase the Risk of Lymphoma?

Psoriasis is one of the most common skin diseases, and some evidence suggests a link to lymphoma.

A recent study found a small but statistically real increased risk for lymphoma and two other cancers in patients with psoriasis, but there may be more to this story than meets the eye.

Psoriasis

Psoriasis is one of the most common skin diseases, associated with symptoms such as itch, pain or bleeding.

The involved areas of skin appear as red, raised areas called plaques, which may be covered with a coarse silvery scaling.

Different forms of psoriasis can have differing appearances and different patterns of involved skin.

Psoriasis is considered a systemic inflammatory condition, which may have implications for -- and shared risk factors with -- other diseases, including certain malignancies.

People with psoriasis seem to contract other, potentially related diseases at a greater rate than would be expected based on numbers from the general population. These include the following:

  • Psoriatic arthritis
  • Crohn’s disease
  • Certain malignancies
  • Depression
  • Nonalcoholic fatty liver disease
  • Metabolic syndrome and cardiovascular disorders

Lymphoma

Lymphoma is a cancer that affects the lymphocytes, a kind of white blood cell located in the circulation, but also in the bone marrow and in the lymph nodes.

Hodgkin’s lymphoma, or HL, and non-Hodgkin’s lymphoma, or NHL, are the two main categories of lymphoma.

Because lymphocytes are a part of the immune system, researchers have wondered about connections between immune diseases and lymphoma, and they continue to try to understand relationships between the two.

Psoriasis and Lymphoma

The American Cancer Society (ACS) does not currently list psoriasis specifically as a risk factor for lymphoma. They do, however, include autoimmune diseases in their list of risk factors for NHL, mentioning rheumatoid arthritis and systemic lupus erythematosus as examples. Rheumatoid arthritis, psoriasis, and inflammatory bowel disease (IBD) have all been shown to be associated with an increased risk of lymphoma in some, but not all studies.

An overactive immune system in autoimmune diseases may make lymphocytes grow and divide more often than normal, potentially increasing the risk of lymphoma developing. As the ACS points out, however, people who get NHL may have few or no known risk factors; and even if a person with NHL has one or more risk factors, it is often very hard to know how much these factors might have contributed to the lymphoma.

Examining the Link

Increased rates of lymphoma have been reported in a number of studies of patients with psoriasis, and the risk of lymphoma with biological agents, in general, has been a topic of debate. Biologic agents have a role in the treatment of diseases like rheumatoid arthritis and psoriasis, and they have been demonstrated to be relatively safe; however they work by suppressing the immune system, so there is concern that this could raise the risk for certain cancers.

There may be an increase in the risk of cancers such as lymphoma in people with psoriasis, but there are a number of challenges in studying this kind of link.

  • First of all, even though lymphoma is of great public health importance, statistically it is relatively rare compared to psoriasis, which as made it difficult to get high enough numbers to analyze.
  • Second, having psoriasis is statistically associated with a number of factors -- like smoking, obesity, ultraviolet therapy and drugs that suppress the immune system – and these factors may increase the risk of lymphoma and other cancers, independent of the psoriasis, itself.

The JAMA Oncology Study

Recently, researchers analyzed records from 198,366 patients with psoriasis and 937,716 without psoriasis using a database in the United Kingdom.

Results showed that there was a small but "statistically real" increased risk for non-melanoma skin cancer, lymphoma and lung cancer in people who had psoriasis.

These researchers found that cancer risk was slightly higher for patients who were classified as having moderate-to-severe psoriasis as opposed to mild disease. There was no significant association between psoriasis and cancer of the breast, colon, prostate, or leukemia, however.

Journal of the American Academy of Dermatology Study

Even more recently, doctors from the Center for Dermatology Research at Wake Forest School of Medicine in Winston-Salem, North Carolina, conducted a related study. They noted that psoriasis is associated with many, many other varied health conditions, or comorbidities.

They also felt the measurement of risk from psoriasis—often reported to doctors and patients as the relative risk—might not be the best measurement. While relative risk can be useful, the authors felt that thinking about risks in relative terms, rather than absolute terms, would tend to lead people to overestimate the effect of psoriasis.

Thus, the research group set out to calculate the absolute risk attributable to psoriasis for the various diseases. The conditions linked to psoriasis most strongly (with the highest relative risk) were nonmelanoma skin cancer, melanoma, and lymphoma.

Their calculations:

Disease            Relative Risk     Psoriasis-Risk       Number of Patients

Skin cancer         7.5                         0.64                         1,551

Melanoma           6.12                       0.05                         29,135                              

Lymphoma          3.61                       0.17                         5,823


Interpretation of the above calculations:

In order to attribute 1 case of lymphoma to psoriasis, a doctor would have to see 5,823 patients with psoriasis.

Sources

Saleem M, Kesty C, Feldman S. Relative versus absolute risk of comorbidities in patients with psoriasis. J Am Acad Dermatol. 2016 Dec 13. pii: S0190-9622.

Fuxench ZC, Shin DB, Beatty AO, Gelfand JM. The risk of cancer in patients with psoriasis: a population-based cohort study in the Health Improvement Network [published online ahead of print December 16, 2015]. JAMA Oncol.

Boehncke WH, Boehncke S. More than skin-deep: the many dimensions of the psoriatic disease. Swiss Med Wkly. 2014;144:w13968.

Continue Reading