Controlling Insulin Is Good for Diabetes -- and Breast Cancer?

Doctors have long encouraged patients with diabetes to exercise regularly to help control their insulin levels and to maintain a healthy weight. Now, breast oncologists at Dana-Farber Cancer Institute in Boston are studying the relationship between exercise, weight, and insulin levels and the risk of breast cancer recurrence.

“We know that women who are overweight at the time of breast cancer diagnosis have a higher risk of recurrence than lean women, but the reasons for this are not clear,” says Jennifer Ligibel, MD. “Recent evidence suggests that high insulin levels, which are common in overweight women, may be involved in the increased risk of breast cancer recurrence.”

Based on these findings, Ligibel and her colleagues are conducting several studies to examine the potential benefits of regular exercise, diet modification and other weight-control activities in breast cancer survivors. The Active After Cancer Trial explores whether a telephone-based program can motivate patients to start an exercise program after completing treatment for early stage breast cancer.

The team is also conducting an exercise study for patients with metastatic breast cancer, designed to determine whether regular exercise can increase energy and physical fitness in women living with advanced disease. Finally, Dana-Farber is participating in the LISA trial, an international study that will examine whether losing weight after breast cancer diagnosis helps to reduce recurrence rates and improve survival in postmenopausal patients with estrogen receptor positive breast cancer.

Ligibel is quick to note that while finding the energy to exercise can be a challenge for many, it can be especially difficult for cancer patients in active treatment. “Unfortunately, chemotherapy decreases a person's energy during treatment, and many people stop exercising completely,” she explains. “Often, patients don’t return to good exercise patterns after chemotherapy is completed, even if they once had them.” This inactivity can lead to weight gain and higher insulin levels, which might also increase the risk of the cancer coming back.

Source: Dana-Farber Cancer Institute