Patients who take five or more medications in the six months before beginning IV chemotherapy for a cancer diagnosis are more likely to be hospitalized after their chemotherapy treatment, according to the findings from a new study published in the Journal of Geriatric Oncology.

In a retrospective, population-based study, researchers looked at data from 13,959 patients with prostate, lung, or breast cancer in a Medicare database and categorized the patients based on the number of medications they were taking in the six months before starting IV chemotherapy. Patients with lung cancer were taking a median of 11 medications, those with prostate cancer were taking 10, and those with breast cancer were on 6 therapies.

They found that compared to patients taking fewer than five medications, hospitalization rates increased by 114% in patients who were on 15 or more medications, 75% for those taking 10–14 therapies, and 45% of those on 5–9 different medications.

“Most chemotherapy regimens are based on data from clinical trials, which often exclude or under-represent patients with multiple comorbidities. Therefore, little is known about the outcomes of older adults with cancer treated with chemotherapy while taking numerous medications,” the authors wrote. “Our research findings highlight a significant area of concern and a research area ripe for quality improvement.”