Study: No significant link between diabetes Tx, bladder Ca

Author(s):

A new study reports no statistically significant increase in the risk of bladder cancer among patients treated with the diabetes drug pioglitazone (Actos), despite previous studies suggesting an association.

However, the authors, led by Assiamira Ferrara, MD, PhD, of Kaiser Permanente Northern California, Oakland, did find a possible link between pioglitazone and prostate and pancreatic cancer. They reported their findings in JAMA (2015; 314:265-77).

To explore the relationship between pioglitazone and bladder cancer, the investigators performed a cohort analysis of 193,099 diabetic patients and a nested case-control analysis of 464 bladder cancer patients and 464 matched controls. The patients, who were all 40 years of age or older in 1997 through 2002 and from Kaiser Permanente Northern California, were followed until December 2012.

A second cohort analysis of 236,507 patients, also from Kaiser Permanente and 40 years of age or older in 1997 through 2005, considered pioglitazone in relation to 10 additional cancers (prostate, female breast, lung/bronchus, endometrial, colon, non-Hodgkin lymphoma, pancreas, kidney/renal pelvis, rectum, and melanoma). It followed the patients until June 2012.

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Of the 34,181 patients (18%) in the bladder cancer cohort who received pioglitazone for a median of 2.8 years (range, 0.2 to 13.2 years), 1,261 (0.65%) were diagnosed with bladder cancer during the study. The crude incidence of bladder cancer was 89.8 per 100,000 person-years in pioglitazone users and 75.9 in nonusers. The authors found no association between ever use of pioglitazone and bladder cancer (hazard ratio 1.06) after taking potential confounding factors into account.

Case-control analyses also showed no significant association between pioglitazone and bladder cancer (odds ratio, 1.18) after adjusting for self-reported race and ethnicity, smoking history, occupations linked to bladder cancer, urinary tract infection, and glycosylated hemoglobin. The authors conclude that although pioglitazone use wasn’t associated with a statistically significant increased risk of bladder cancer, “a small increased risk, as previously observed, could not be excluded.”

The second cohort analysis, of pioglitazone and 10 other cancers, found that 38,190 (16%) patients had ever used the drug and 15,992 (6.8%) had been diagnosed with cancer. Analysis revealed no significant relationship between pioglitazone and eight of the 10 cancers, but showed an increased risk of prostate and pancreatic cancer.

For prostate cancer, the hazard ratio was 1.13 with a crude incidence of 453.3 per 100,000 person years for pioglitazone users and 449.3 for nonusers. For pancreatic cancer, the hazard ratio was 1.41 with a crude incidence of 81.1 for users compared with 48.4 for nonusers.

“The increased prostate and pancreatic cancer risks associated with ever use of pioglitazone merit further investigation to assess whether the observed association are causal or due to chance, residual confounding, or reverse causality,” the authors noted.

The study was funded by a grant from Takeda Development Center Americas, Inc.