Older AS patients may be at greater risk for some blood cancers
Risk similar among AS patients who have inflammatory bowel disease, study finds
Ankylosing spondylitis (AS) patients 65 and older may be at an increased risk of certain blood cancers compared with older adults in the general population, according to a recent study.
The risk for these cancers, however, was similar among AS patients and people with another inflammatory condition called inflammatory bowel disease (IBD).
The study, “Risk of Hematologic Malignancies in Elderly Patients With Ankylosing Spondylitis: A Cohort Study and Systematic Review,” was published in Mayo Clinic Proceedings.
A number of autoimmune and inflammatory diseases have been linked to an increased risk of blood cancers, or hematologic malignancies, which usually is attributed to high levels of inflammation and immune system abnormalities.
Few studies have found an increased risk of blood cancer among people with AS, an inflammatory form of arthritis affecting the joints of the spine. However, most of these studies have focused on young or middle-aged adults with AS, consistent with a typically young age of onset for the disease.
Yet, older age is a known risk factor for blood cancers. “If hematologic malignancies result from chronic inflammation, we might expect these risks to manifest only after decades of cumulative exposure to inflammation,” the researchers wrote.
Moreover, elderly patients with IBD, a condition that shares some underlying pathological features with AS, are at an increased risk of blood cancers, but the risk isn’t seen in younger patients.
A pair of researchers in the U.S. now evaluated Medicare claims data from AS patients, IBD patients, and the general population to examine the potential risk of blood cancers among older adults.
Medicare is a federally-funded insurance program available to adults 65 and older in the U.S. The team retrospectively examined medical files from patients who enrolled in Medicare from January 1999 to December 2010 to identify people with an AS diagnosis.
Patients treated with TNF-alpha inhibitors were not included in the study due to the potential association between these medications and cancer.
Ultimately, 12,451 AS patients, 234,905 IBD patients and 10,975,340 people unaffected by either AS or IBD (a control group) were identified and followed in the database until September 2015 for medical claims relating to blood cancer.
A total of 297 cases of blood cancer were identified in the AS group over a mean follow-up of 9.9 years and 4,538 cases were observed in the IBD group over a 9.3-year follow-up. In the general population, 128,239 incidents of blood cancer were reported over an average 8-year follow-up period.
Non-Hodgkin’s lymphoma was the most common type of blood cancer in all three groups.
Standard incidence ratio
Researchers generated a standard incidence ratio (SIR) for each cancer type in the disease groups relative to the general population. Data took into account the number of blood cancer cases and the total number of observation years in each group, while also controlling for age, sex and race.
Simply put, an SIR above 1 reflects a higher incidence in the AS or IBD groups than the general population.
The analysis found a significantly higher incidence of three types of cancers in older AS patients: non-Hodgkin’s lymphoma, multiple myeloma, and chronic lymphocytic leukemia. The SIRs for these three cancer types were 1.39, 1.52, and 1.5, respectively.
The incidence of blood cancers in AS was comparable to that observed in the IBD group.
To learn more, the researchers conducted a systematic review of 21 studies that previously reported on the risks of blood cancer in AS, focusing specifically on potential age associations.
While most of these studies, involving young or middle-aged patients, did not find an association between blood cancer and AS, a few of the studies identified some type of risk.
For example, two studies identified about a two times higher risk of multiple myeloma in AS patients, regardless of age. Moreover, one study found an age-related increased risk of lymphoma, with patients 75 and older being 1.5 times more likely to develop that cancer than the general population.
Altogether, “clinicians who care for older patients with AS should be aware of the elevated risk,” the researchers wrote, noting that, “additional large cohort studies are needed to evaluate further the risks in younger patients.”
Moreover, if an AS patient using a TNF-alpha inhibitor develops one of these blood cancers, it “should not necessarily be attributed to [TNF-inhibitor] treatment,” the team concluded.