Blood Sugar Levels May Affect Cancer Outcomes in Patients With Diabetes

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When it comes to high blood sugar, cancer and diabetes can create a “vicious cycle,” as one expert explained.

Image of a blood sugar test.

"The inflammation and tumor markers could be causing the varying blood sugar, or it could be vice-versa,' an expert told CURE®. "It's kind of a vicious cycle in a way with the physiology."

An association has been found between inflammatory markers and blood sugar fluctuation among patients with diabetes and lung cancer. However, as one expert noted, the relationship between the two diseases remains unclear. Still, patients with diabetes can work with their health care team to promote the best possible outcomes.

In an analysis of 60 patients with type 2 diabetes and lung cancer, researchers found, “the greater the [blood glucose] fluctuation in [patients with lung cancer] after chemotherapy, the more unfavorable the therapeutic effect of chemotherapy; the higher the level of tumor markers and inflammatory cytokines [and] the more adverse reactions the patient experiences.” These findings were published in the World Journal of Diabetes.

However, Dr. Amanda C. Leiter, assistant professor of Endocrinology, Diabetes and Bone Disease for the Mount Sinai Health System, explained that while an association between inflammation and high blood sugar is clear, any cause-and-effect relationship is harder to pin down.

“I think this confirms what we already know about diabetes and inflammation, and dysglycemia [blood sugar dysregulation] and high blood sugars being linked to inflammation,” she said. “The study does show an association between inflammatory markers and the blood sugar fluctuations. But since this was an observational study [where patients’ data was retrospectively analyzed], it's unclear which one is causing the other.

“The inflammation and tumor markers could be causing the varying blood sugar, or it could be vice-versa. It's kind of a vicious cycle in a way with the physiology. So, we know that blood sugar fluctuations can make inflammation worse, as well as vice-versa, that inflammation can also make blood sugars worse. So, it's hard to draw any causal relationship between the two, but they do establish an association and link between those two things.”

Leiter discussed the importance of blood sugar control for patients with diabetes and cancer, how cancer and its treatments can contribute to blood sugar complications and more.

What is the importance of blood sugar control for patients with cancer?

It's very well-established that diabetes and high blood sugar are linked to more complications with cancer treatment. In general, in the context of a cancer diagnosis, diabetes can often fall to the wayside and there is data showing that the treatment and management of diabetes is suboptimal in the cancer treatment setting.

[It’s important to] inform patients that their underlying health conditions, especially diabetes, are really important to manage when they’re undergoing cancer treatments and that these high blood sugars may contribute to some complications of therapy down the road.

How can these treatments contribute to blood sugar complications?

Diabetes itself can increase the risk of a few cancer treatment-related complications, and then actual cancer treatment can contribute to high blood sugar. So, all of this is a little bit of a vicious cycle.

And so, just starting with how high blood sugar is bad for cancer treatments, we know that hyperglycemia, or high blood sugar, is linked to more complications with cancer surgeries, these patients tend to have more side effects with their chemotherapy and are also more likely to be hospitalized from the side effects of their chemotherapy. And then in general, patients who are undergoing cancer treatment are also more likely to get high blood sugars for a number of reasons.

So one [reason is] just stress in general can cause high blood sugar. There's a big link between inflammation, which is related to stress, and high blood sugar. And then also, a lot of the treatments that patients get for cancer can also contribute to this. A lot of patients, especially with their chemotherapy, get steroid treatments. And steroids can really cause high blood sugar.

And then underlying all of this is that a lot of patients with cancer already have risk factors for high blood sugar, like diabetes, or higher body mass index. The combination of all those things is a recipe for blood sugars to go up during the course of cancer treatment.

Say there is someone with diabetes who receives a cancer diagnosis, what can they do to give themselves the best chance at good outcomes?

That's a great question. I think [a good plan would include] just working with either their endocrinologist or primary care physician to come up with a plan to manage high blood sugars during the course of treatment — and this, of course, will depend on what the treatment is and what the overall goals of care are.

… And then on top of that, too, a lot of studies have been showing that — as hard as it is to exercise [during cancer treatment] — exercise is very good in the context of cancer treatment, for patient mental health, as well as for managing blood sugars. [Patients should] also make sure to adhere as much as possible to a healthy diet and working with a nutritionist either at the cancer center or with their diabetes or primary care provider.

Transcript has been edited for clarity and conciseness.

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