The Problem with Some Breast Cancer Drugs: High Blood Sugar

Original Article: https://www.medscape.com/viewarticle/hyperglycemia-risky-side-effect-certain-cancer-drugs-2025a1000a05

Why Cancer Treatments Cause Blood Sugar Problems

Some new breast cancer drugs, such as inavolisib, alpelisib, and capivasertib, can cause a serious side effect: hyperglycemia, (high blood sugar). These drugs block the PI3K/Akt pathway, which is important to prevent cancer growth — but it’s also important for controlling blood sugar with insulin. Blocking it can make blood sugar spike, which is dangerous and hard to manage. Because of this, some doctors are choosing not to prescribe these drugs.

How Bad is the Risk?

In clinical trials, some patients develop high blood sugar after taking these drugs — up to 85% of patients on inavolisib. Some even had to stop their cancer treatment because their blood sugar got too high. In rare cases, patients developed diabetic ketoacidosis, a life-threatening condition. This serious risk is making some doctors switch to other cancer treatments that don’t cause these blood sugar problems.

Managing the Side Effects

Doctors now should check patients’ blood sugar before and during treatment and sometimes give them diabetes medicine e.g., metformin. But many cancer doctors aren’t experts in diabetes care, and there’s a shortage of endocrinologists (diabetes doctors) to help. There may be benefits for using newer diabetes medicines or helping patients change their diet to lower carbohydrates. Planning ahead — such as improving blood sugar early before starting these cancer drugs — can help make treatment safer and more successful.