NEW YORK (Reuters Health) – Women who use bisphosphonates may not have a decreased risk of colon cancer, a new study finds — despite prior evidence suggesting the drugs might offer some protection.
This latest study, reported online May 29th in the Journal of Clinical Oncology, focused on more than 86,000 U.S. nurses followed for over a decade. Overall, 801 developed colon cancer. The risk was no different among women who didn’t use bisphosphonates, versus users — regardless of how many years they had been on the medications.
“It is not clear whether bisphosphonates have any role in treatment of colorectal cancer, and our data does not support its routine use as a (prevention) agent for colorectal cancer,” lead researcher Dr. Hamed Khalili, a gastroenterologist at Massachusetts General Hospital in Boston, said in an email.
Since evidence suggests bisphosphonate users have a lower risk of certain cancers, researchers have been interested in whether the drugs might help prevent those tumors in people who are particularly at risk.
One study last year found women who used bisphosphonates had a 59% lower chance of developing colon cancer than non-users (see Reuters Health story of February 14, 2011).
But that study was designed differently than the current one, Dr. Khalili pointed out. In the earlier report, researchers compared colon cancer patients with a group of women who were free of the disease.
Dr. Khalili’s study, in contrast, followed a large group of initially cancer-free women over time. Thus, the researchers were able to collect information on women’s health and lifestyle habits before their cancer diagnosis.
That’s important because women on bisphosphonates may, for example, be more likely than other women to get screened for colon cancer.
Bisphosphonate users are also likely to be taking vitamin D and calcium, which themselves have been linked to lower colon cancer risk, Dr. Khalili added.
When his team first looked at the data, there was in fact some weak evidence that women on bisphosphonates might have a slightly lower colon cancer risk than non-users.
But the link got even weaker when the researchers accounted for colon cancer screening and which women were taking calcium and vitamin D.
According to the American Cancer Society, one in 19 men develops colorectal cancer at some point, and slightly fewer women do. The disease is the third-leading cause of cancer deaths in the U.S.
J Clin Oncol 2012.