Adherence to glucose-lowering drug therapy declines after cancer diagnosis

Last Updated: 2015-02-04

By Will Boggs MD

NEW YORK (Reuters Health) - After receiving a diagnosis of cancer, patients with diabetes decrease their adherence to glucose-lowering drug treatment, researchers from the Netherlands report.

"While our study revealed that cancers with worse prognosis and more advanced cancer stages resulted in substantially lower adherence at the time of cancer diagnosis, this was not seen for breast and prostate cancer," Dr. Marjolein M.J. Zanders, from Netherlands Comprehensive Cancer Organization, Eindhoven, told Reuters Health by email. "These two types of cancers are associated with better prognosis and are less life-threatening. Patients and physicians might pay more attention toward glycemic control in these patients, since they probably are less sick and long-term outcomes are more important."

A cancer diagnosis magnifies the already increased mortality of diabetic patients, and decreased medication adherence could lead to poor metabolic control, higher risk of diabetic complications, and, even worse, overall mortality.

Dr. Zanders and colleagues used data from the PHARMO Database Network and Eindhoven Cancer Registry to evaluate how a cancer diagnosis influences adherence to glucose-lowering drug regimens in 3281 patients with cancer, compared with 12,891 controls without cancer.

During an average of 6.5 years of follow-up, an increased number of controls used insulin or combination treatment, according to the February 1 Diabetologia online report.

Among patients with cancer, glucose-lowering drug use increased by 0.10% per month before their cancer diagnosis. At the time of cancer diagnosis, though, glucose-lowering drug use decreased by 6.3%. Thereafter, glucose-lowering drug use declined by 0.20% per month.

When analyzed by cancer type, there were no important declines in adherence among patients with prostate or breast cancer, but there were large drops in adherence in patients with esophageal, stomach, pancreas, liver, or pulmonary cancer.

Declines in adherence were more precipitous the higher the tumor, node, metastasis stage and with each extra month after cancer diagnosis.

Chemotherapy and radiotherapy did not influence the rate of decline in adherence, but patients who did not receive surgery were about four times more likely than those who did not receive surgery to stop taking their glucose-lowering drugs.

Given the limitations of their data, the researchers were unable to identify why these patients stopped taking their glucose-lowering drugs.

"In future studies," they write, "the reason for the decline in needs to be further elucidated among the different cancer types-is it the patient who prioritizes the fight against cancer or the advice of the physician to stop the treatment?"

"All medical specialists need to work with the patient for their overall health, and not just for one specific condition they are focused on - it is in the best interest of the patient's overall health," Dr. Zanders said.

"Also within cancer patients with more severe or advanced cancers, the adherence to glucose-lowering drug use might be important to prevent recurrent hyperglycemia or ketoacidosis," she said. "Both patients and medical professionals need to still pay attention to glucose-lowering drug use around a diagnosis of cancer."

This research was supported by the European Foundation for the Study of Diabetes. One author is employed by PHARMO Database Network; the other authors report no disclosures.

SOURCE: http://bit.ly/1I2llBs

Diabetologia 2015.