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Doctors Prescribe Caution With Insulin's Cancer Ties
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By Michelle Fay Cortez and Trista Kelley
Oct. 1 (Bloomberg) -- Insulin and the medicines that increase the hormone may boost cancer risk in people with diabetes, while drugs that make the body more sensitive to insulin may lower the danger, said researchers at a diabetes conference in Europe.
A review of studies presented by half-a-dozen doctors, involving thousands of patients, wasn't able to prove the safety of Sanofi-Aventis SA's long-acting insulin Lantus, the investigators said. The problem may be that patients don't fully respond to the insulin they already have, said Edwin Gale, professor of diabetes at the University of Bristol in the U.K.
European scientists startled medical professionals in June when they reported that Lantus, the world's biggest-selling insulin, may increase the risk of cancer. More research is needed, according to a panel of doctors convened yesterday at the European Association for the Study of Diabetes in Vienna. The diabetes group, based in Dusseldorf, Germany, said it would spend 3 million euros ($4.4 million) in the next three years funding studies into the topic.
"I'm not changing my clinical practice because we're not at that stage yet, but I'm certainly aware of the potentially negative effect," said Ulf Smith, EASD president and professor of internal medicine at Goeteborg University in Sweden. "We need to understand more."
Unanswered Question
In the U.K., about half of patients with Type 2 diabetes use Lantus, said Gale, who is editor-in-chief of EASD's medical journal Diabetologia. About 200 million people worldwide have diabetes, primarily the type 2 form that typically develops in overweight, sedentary adults.
"What has emerged in the past few months is a whole new area of research," Gale said. "People need to know there is an unanswered question" about the Lantus risk. "Physicians ought to at least think about this as they prescribe it."
An internal analysis of all Sanofi studies on Lantus, involving more than 10,000 patients, found no increased risk, said Riccardo Perfetti, senior medical director for Sanofi's metabolism unit. The company is conducting three additional studies to confirm its findings, he said in an interview.
"We do not see a signal of cancer risk, we do not see it," Perfetti said. "We need to address this specifically" with large studies led by independent researchers. "We're going to do it the way it should be done."
Rival Levemir
The question raised about Lantus may benefit Novo Nordisk A/S's rival long-acting insulin, Levemir. An analysis of studies from the Bagsvard, Denmark-based company found Levemir patients had fewer tumors than those getting traditional human insulin, said David Russell-Jones, from the University of Surrey. The trials lasted an average of six months. Studies that compared Levemir and Lantus had too few tumors to see any differences.
Unlike Lantus, Levemir doesn't bind tightly to the receptor for insulin-like growth factor I, or IGF-I, which can trigger cell proliferation, said Chief Science Officer Mads Krogsgaard Thomsen in an interview. It also stimulates cell growth significantly less, while having the same or better metabolic potency as Lantus or older human insulin, he said.
"We can say for Levemir there isn't any case or hypothesis for why it might increase cancer risk that we have to answer," Thomsen said. "No one has ever argued Levemir has an issue with carcinogenicity. It was designed to not have that."
Benefits Seen
Diabetes causes blood sugar levels to be higher than normal. Insulin, a hormone made in the pancreas, helps convert blood sugar into energy. Diabetics don't produce enough insulin naturally or their bodies have trouble using it properly.
The revelations at the meeting weren't just about insulin. Metformin, sold by Bristol-Myers Squibb Co. as Glucophage and now available in inexpensive generic formulations, may reduce cancer risk, researchers said. There are similar suggestions of protection with GlaxoSmithKline Plc's Avandia and Takeda Pharmaceuticals Co.'s Actos.
The drugs, all pills, treat diabetes by making patients more sensitive to insulin, rather than boosting levels of the hormone. They are being studied as cancer treatments in people who don't have diabetes, the researchers said.
Data presented at the conference from 300 doctors in the U.K. included 31,421 patients getting metformin alone, 5,035 given insulin and metformin, and 4,829 given insulin only.
Research Findings
The more insulin used by patients with type 2 diabetes, the greater the chance they were to be diagnosed with cancer, said Craig Currie, a researcher at the University of Wales in Cariff. Metformin, a staple of diabetes care, lessened the risk in everyone except those getting the most insulin, he said.
"This is not definitive, it just alerts us to the possibility" that insulin bolsters cancer risk, Currie said at a press conference. Future studies should compare the use of insulin, including Sanofi's Lantus and Novo Nordisk A/S's Levemir, with oral treatments, he said.
Insulin may be fanning the flame of small cancers, helping them grow faster, said Jeffrey Johnson, professor of public health sciences at the University of Alberta in Canada, who has studied the topic for the past three years. There is only a signal now, and the scientific world is still investigating the link, he said.
"People feel very confident with insulin because it's been used for 80 years and they know how it affects sugars," Johnson said. "We need to be more attentive to the collateral impact. With early and aggressive insulin therapies, we might be more cautious in pushing that."
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