The risk of people with multiple sclerosis developing cancer is higher if they have used immunosuppressants than if they haven’t, according to a study that followed more than 1,000 patients for a decade.
The findings indicate that the often discussed association between MS and cancer may stem from older types of MS treatments rather than from the disease itself.
MS patients not treated with immunosuppressants had similar cancer risks as people in the general population, according to the study, “Association between multiple sclerosis, cancer risk, and immunosuppressant treatment: a cohort study.” It was published in the journal BMC Neurology.
Before the development of newer disease-modifying therapies, patients who failed to respond to interferons or Copaxone (glatiramer acetate) were often offered harsher treatments.
Modern disease-modifying treatments target selected immune system players. In contrast, immunosuppressant drugs — such as azathioprine, mitoxantrone, and cyclophosphamide — eliminate an entire spectrum of immune cells. They also permanently alter the activity of cancer-causing genes, researchers have discovered.
To gain insight into immunosuppressants’ role in MS patients developing cancer, researchers at the University of Palermo in Italy recruited 531 people with MS who had used the therapies. The group was composed of 346 women and 185 men.
As controls, the research team recruited 531 MS patients who had never been treated with immunosuppression. They compared both groups to people of the same age in the general population from the same area.
Researchers followed patients who used immunosuppressants an average of nine years, and untreated patients about 10 years.
They discovered that the risk of the immunosuppressant group developing cancer was 11 times higher than that of the untreated patients during the follow-up period. The younger a patient began taking an immunosuppressant, and the longer they took them, the higher the risk, the team found.
Gut cancers, breast cancer in women, and leukemia were the most common types of cancer among these patients.
Looking at the specific drugs used, no patients treated with cyclophosphamide developed cancer, although researchers noted that the study included few patients treated with it.
Those who took azathioprine and mitoxantrone were four times more likely to develop cancer than non-immunosuppressant patients. And patients treated for longer periods were at higher risk than those treated for a short time.
Another finding was that MS patients who had never been treated with immunosuppressants did not have higher cancer rates than the general population.
Researchers concluded that doctors should watch for cancer in patients treated with immunosuppressants so they tumors can be detected early.