Switching Disease-Modifying Treatments May Enhance Cancer Risk in Multiple Sclerosis

Patients with multiple sclerosis (MS) who switch disease-modifying treatments (DMTs) more frequently may be at an increased risk of developing cancer, according to a new study published in Frontiers in Neurology.

Previous studies have indicated that MS and cancer may share some aberrant functions of the immune system, the researchers wrote; however, this relationship has not been fully understood.

For the study, the authors aimed to better understand the incidence of cancer in patients with MS and evaluate the impact of DMTs on cancer risk. They compared a database of patients with MS between 2003 and 2013 in Catania, Italy, with the Integrated Cancer Registry of Catania-Messina-Siracusae-Enna. During the study period, 2730 individuals were diagnosed with MS and 1180 were enrolled in the study.

Of the patients in the study, there were a total of 36 incidences of cancer. According to the data, the global standardized incidence ratio (SIR) was 1.18 (CI 95% 0.78-1.58), with a significantly higher risk observed in men aged 20 to 50 years and in women over 50 years of age.

The researchers also analyzed the effects of different MS treatment strategies on the relative risk of developing cancer based on 4 subgroups: patients not treated with any DMT, treated with 1 DMT, treated with 2 DMTs, and treated with more than 2 DMTs.

The relative risk for developing cancer was not significantly higher in the group treated with no DMTs, but slightly increased in the group treated with 1 DMT. However, the relative risk was 1.99 (CI 95% 1.14-3.45) in patients with MS switching 1 DMT and 3.38 (CI 95% 1.83-6.22) in those who switched at least twice.

Of the 36 cancers observed, the most common cases (22.2%) were primarily located in the genitourinary system. Patients with cancer were older than those who did not have cancer, with a higher age at onset of MS. Additionally, the researchers noted that patients with both MS and cancer had longer MS disease duration and worse disability.

Overall, the researchers concluded that incidence of cancer in patients with MS was not higher than in the general population, although there was a significantly higher incidence in certain subpopulations of patients. This included men aged 20 to 50 years old and women over 50 years, as well as patients who experienced at least 2 therapeutic switches of DMTs.

The researchers hypothesized as to what may drive higher risk of cancer in patients with MS. They indicated that the dysregulation of the immune system typically responsible for the pathogenesis of MS disease and the immunological consequences of using drugs with different mechanisms of action may be a factor.

“Furthermore, the findings of higher cancer risk in patients who switched at least twice may have significant implications on MS management, influencing treatment decision making process,” the researchers wrote.

Reference

D’Amico E, Chisari CG, Arena S, et al. Cancer risk and multiple sclerosis: evidence from a large Italian cohort. Frontiers in Neurology. 2019. https://doi.org/10.3389/fneur.2019.00337