The Link Between Psoriasis and Malignant Lymphoma Risk

Among many cancers, there are certain factors that may increase risk. These may be broad, such as age, or specific, like an infection. A new study that looked into the 5-year risk for new-onset lymphoma found that one of the heightened risks for malignant lymphoma is psoriasis.

About the study

A large population study was recently conducted in Denmark and found that psoriasis is associated with a higher risk of malignant lymphoma. In other words, those who have psoriasis are more likely than others to have a diagnosis of malignant lymphoma throughout their lifetime.

There have been other chronic inflammatory and autoimmune diseases that pose risks for lymphoma, such as Sjögren's syndrome and rheumatoid arthritis. However, many have questioned if psoriasis could be a risk for malignant lymphoma due to its immunologic nature, resulting in some controversy. Studies aiming to determine the answer have found varying results, which is why a need for a larger for study was present - and now, it's here.

More about psoriasis

Psoriasis is common, and affects around 2-3% of adults. The pathophysiology of the condition results in abnormal immune responses, which often revolve around heightened activity among T-cells, antigen-presenting cells, and Th-1 cytokines. On certain occasions, it has also been shown that B lymphocyte activity can increase as well, suggesting immune activation. A further confusion revolves around treatment. Patients who have extensive psoriasis are often treated with cyclosporine and methotrexate, or other systemic therapies that have presented an association with the development of lymphoma. To treat psoriasis, it is becoming more common to use biologic therapies that attack T-cells or cytokines, like tumor necrosis, and many worry that these therapies are increasing the risk of lymphoma due to the manner in which they attack the disease.

There is added difficulty in assessing the connection between psoriasis and lymphoma due to the cancer's statistical rarity. Therefore, the sample sizes need to be very large to yield informative results. Even so, it is important to analyze as non-Hodgkin lymphoma is the fifth most common cancer in the United States, and affects approximately 19/100,000 people per year, which is around the same rate as melanoma. The incidence has increased between three and four percent per year since 1973, and unfortunately, the five year survival rate is only 53 percent, which is why added risk factors are crucial to be aware of.

Discovery

One of the largest studies in this field of study, the Danish investigation into the link between psoriasis and malignant lymphoma has been able to quantify the risk of new-onset Hodgkin lymphoma (HL), non-Hodgkin lymphoma (NHL), and cutaneous T-cell lymphoma (CTCL) within those who have psoriasis. These results were made available during the Psoriasis: From Gene to Clinic International Congress in London on November 30th.

The abstract of the study explained, "psoriasis is a common, chronic, inflammatory disease. Psoriasis has been hypothesized to be associated with an increased risk of lymphoma due to its pathophysiology, its treatments, or a combination of these factors. We performed a large population-based cohort study of the risk of lymphoma in psoriasis patients using the General Practice Research Database."

Patients who were eighteen years and over between 2008 and 2012 who had been diagnosed with psoriasis, or were using a topical vitamin D derivative presented data to the study. Vitamin D is usually the first line of treatment for psoriasis in Denmark, and it is not commonly used to treat anything else.

Read on to learn about the results of this study and what they mean for lymphoma diagnosis in people with psoriasis.