Insulin not associated with cancer

Despite some concerns to the contrary, the use of insulin glargine (Lantus) is not associated with an increased risk of any cancer in people with diabetes or prediabetes, according to a substudy of the prospective Outcome Reduction with an Initial Glargine Intervention (ORIGIN) trial.

After a median of 6 years, the risk of cancer was similar among patients taking insulin glargine and those given standard care (HR=0.94, P=0.52), Louise Bordeleau, MD, MSc, of McMaster University in Hamilton, Ontario, reported at the American Diabetes Association annual meeting.

While previous epidemiological studies have had mixed results, Bordeleau said that “as the only randomized trial to specifically address risk of cancer in patients on insulin glargine versus standard care, this is the best evidence we have so far [that insulin glargine does not raise cancer risk].”

Bordeleau said she suspected the findings could be extended to other forms of insulin, although that remains to be tested.

Session co-chair Bessie A. Young, MD, MPH, of VA Puget Sound Healthcare in Seattle, told reporters  that it “is very reassuring that after 5 years of follow-up, they did not find any increased incidence of cancer in a large randomized controlled study of patients on insulin glargine. Because insulin is a potential growth factor, physicians have been worried about it,” she said.

The ORIGIN study was an international, double-blind trial involving 12,537 patients with cardiovascular risk factors plus impaired fasting glucose, impaired glucose tolerance, or early type 2 diabetes who were randomized to insulin glargine or standard care. Standard care was defined as clinician judgment with no insulin until patients were uncontrolled on at least two oral medications and yearly screening for those with prediabetes.

The study was a 2 x 2 factorial design, with other arms randomized to omega-3 fatty acids or placebo.

At last year’s diabetes meeting, researchers reported that the main trial showed that insulin glargine has a neutral effect on cardiovascular outcomes.

The cancer substudy was designed to look at cancer incidence and cancer mortality by randomization allocation.

Cancer events were prospectively collected and all cancer outcomes were adjudicated. Time-to-event curves were compared using stratified log-rank tests, and hazard ratios were calculated with Cox regression models with factorial allocation, baseline diabetes status, and history of cardiovascular event before randomization as covariates.

A total of 953 (7.6%) patients developed a cancer event during the median follow-up period of 6.2 years.

The rate of cancer was 1.32 per 100 person-years both in the glargine and standard groups.

The unadjusted cancer death rates were 0.54 per 100 person-years in the standard group and 0.51 per 100 person-years in the glargine arm, also a nonsignificant difference.

Participants who developed cancer tended to be older, have a higher frequency of smoking, alcohol intake, previous cardiovascular event, new diagnosis of diabetes, and statin or aspirin use.

Adjusted models for key clinical subgroups remained neutral (P>0.17 for all).

HbA1c level, glucose-lowering therapies including metformin, and body-mass index did not modulate risk of a cancer event, Bordeleau said.

Disclosure: The study was supported by Sanofi.  Bordeleau disclosed no conflicts of interest. Young reported no conflicts of interest.

Reference: Bordeleau L, et al “Cancer outcomes in patients with dysglycemia on basal insulin: Results of the ORIGIN Trial” ADA 2013, Abstract 385-OR.