BERLIN – Use of the long-acting insulin glargine (Lantus) doesn't appear to carry an increased risk of breast cancer, according to a large but short-term study.
In a case-control study, there was no difference in breast cancer risk whether patients took glargine or a host of other short-acting insulins, including lispro (Humalog) or aspart (NovoLog), Lucien Abenhaim, MD, of the London School of Hygiene and Tropical Medicine, and colleagues reported at the European Association for the Study of Diabetes meeting.
"We see very little difference between those exposed to glargine versus other insulins," Abenhaim said during an oral presentation.
He cautioned, however, that the mean duration of insulin use was only 3.2 years and longer term trials are needed to better assess risk of breast cancer with insulin use.
Helen Colhoun, PhD, of the University of Dundee in Scotland, noted that this duration of exposure to insulin "is quite short."
"It isn't possible to really say that there is or there isn't any risk associated with much longer exposure to glargine," she said during the oral session at which the findings were presented.
Still, she concluded on the whole that the study was "painstaking" and "reassuring."
Several recent studies, including the randomized controlled ORIGIN trial, have failed to find an increased risk of cancer with insulin use. Concerns have traditionally stemmed from the fact that insulin is a growth factor, which could fuel tumor growth.
In addition, some have questioned whether newer, long-acting insulins given once daily, such as glargine – in contrast to more rapid acting formulations that are taken with meals – could confer additional risk.
So Abenhaim and colleagues conducted the International Study of Insulin and Cancer (ISICA), which was sponsored by Sanofi, maker of glargine. They conducted a systematic case-control study among 92 large centers the U.K., France, and Canada.
Among 39,958 breast cancer cases, 6.2% were diabetic, and 41.3% of these patients participated in the trial.
They were matched to diabetic controls from 582 general practices based on similarities in age, date, country, region, type of diabetes, and diabetes management – bringing the study total to 775 cases and 3,050 controls.
All were contacted via a telephone interview that involved a recall of medications, as well as verification with prescription records, Abenhaim said.
The majority of cases had primary invasive breast cancer, mostly in stage 1 or 2, and the mean age was about 66 in both groups.
Both cases and controls had been diagnosed with diabetes around age 53, the majority used oral antidiabetic drugs, and about a quarter used insulin.
Abenhaim and colleagues found no increased risk of breast cancer with glargine use compared with other insulins:
- Glargine: OR 1.04, 95% CI 0.76 to 1.44
- Lispro: OR 1.23, 95% CI 0.79 to 1.92
- Aspart: OR 0.95, 95% CI 0.64 to 1.40
- Human: OR 0.81, 95% CI 0.55 to 1.20
Results did not change in a series of sensitivity analyses, he added.
The only factor that appeared to be related to breast cancer was having a duration of diabetes of longer than 10 years, Abenhaim reported (OR 1.31, 95% CI 1.10 to 1.56).
Colhoun said a "major weakness" of the study was its reliance on patient recall of diabetes therapy.
"Recall from patients and practitioners seems to me to be a difficult way to do a study in an era when we have so many really good drug databases that give you almost perfect capture of drug exposures," she said.
The study was supported by Sanofi.
The researchers reported relationships with Sanofi.
Primary source: European Association for the Study of Diabetes meeting
Source reference:
Abenhaim L, et al "The International Study of Insulin and Cancer" EASD 201; DOI: 10.1016/S0140-6736(10)61374-8.
Source reference:
Abenhaim L, et al "The International Study of Insulin and Cancer" EASD 201; DOI: 10.1016/S0140-6736(10)61374-8.
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