NEW YORK (Reuters Health) – While angiotensin receptor blockers (ARBs) as a class do not appear to be associated with an increased malignancy risk in patients with diabetes, losartan seems to lower the risk while telmisartan and candesartan may increase it, according to a Taiwanese study reported in the Journal of Clinical Oncology online June 20th.
“The underlying mechanism certainly requires further investigation,” the authors suggest.
ARBs are a mainstay of hypertension treatment in patients with diabetes, note Dr. Mei-Shu Lai, with the National Taiwan University in Taipei, and colleagues, but a recent meta-analysis raised alarm with the finding that ARBs were associated with a modestly increased risk of a new cancer diagnosis.
Earlier this month, the US Food and Drug Administration announced the results of its review of ARBs versus other antihypertensives, finding no increased cancer risk with ARBs.
Meanwhile, the Taipei team conducted a nationwide case-control study to assess the incidence of malignancies associated with ARBs among the diabetic population in Taiwan, using the national health insurance database that covers 99% of the 23 million residents of Taiwan.
From a population of over half a million diabetics, some 22,000 were identified as having newly diagnosed type 2 diabetes and as starting antihypertensive drug treatment after July 2000. As of December 2007, 1281 patients in the cohort had developed cancer and were matched to 5104 controls by age and sex.
The investigators found that 333 (26.0%) of the individuals with cancer and 1,341 (26.3%) of the controls had received ARBs (odds ratio, 0.98). After adjustment, there was no statistically significant association between ARBs as a class and cancer incidence (OR, 0.94)
Furthermore, “In those who had >3 years of exposure to ARBs, we found no evidence of increased risk for late cancer occurrence (OR, 1.00),” the team reports. “In the cumulative dose analysis, there was a trend toward a decreased risk of cancer in those with the higher cumulative dose.”
However, the risk of cancer varied with individual ARBs, the findings indicate. Losartan was associated with decreased risk (OR, 0.78), valsartan (OR, 0.90) and irbesartan (OR, 0.97) were neutral, while candesartan (OR, 1.79) and telmisartan (OR, 1.54) possibly increased the risk of malignancy. The data set did not provide information about olmesartan and eprosartan.
“Well-designed epidemiologic studies that examine large computerized health databases may provide useful information, although the current analysis for a single-drug effect must be considered exploratory,” Dr. Lai and colleagues caution.
They add, “Further investigation is required to demonstrate the relative risk between ARBs and specific types of cancer.”
Angiotensin Receptor Blockade and Risk of Cancer in Type 2 Diabetes Mellitus: A Nationwide Case-Control Study
J Clin Oncol 2011;29.