Fishing for Benefits:  Do Bone Drugs Prevent Breast Cancer?

Drugs companies and their well-paid physician representatives have found a new passion -- finding new benefits for old drugs.  Now  it is claimed that a popular class of drugs used to prevent or improve bone loss may also prevent breast cancer.

At the recently held San Antonio Breast Cancer Symposium, it was announced that bisphosphonates (example: alendronate) reduce incidence of breast cancer by 32%, a number that sounds  pretty good, right?  Study authors analyzed data from the 151,592 database of Women's Health Initiative (WHI).   Adjustments were made for baseline bone density, since women at risk for osteoporosis have a lower risk of breast cancer, probably due to lower lifetime estrogen exposure. 

Researchers found that of the 2216 women on bisphosphnates, only 64 developed breast cancer over an average follow-up of eight years.   Dr. Rowan Chlebowski, a medical oncologist at Harbor-University of California, Los Angeles Medical Center declared at a press conference preceding his podium presentation: "Oral bisphosphanate use may directly inhibit breast cancer incidence."  Dr. Chlebowski has been a consultant for, or served on the speakers bureaus for drug giants AstraZeneca, Amgen, Novartis, Pfizer and Eli Lilley. It is remarkable that this sort of conflict of interest is accepted as routine.

THE USUAL NUMBERS GAME

So a 32% reduction in breast cancer incidence sounds pretty good.  What I find so interesting about such announcements is that they focus on the relative risk reduction (RRR), always the highest, best sounding number.   

In this case, a few simple calculations show an absolute risk reduction of 1.35% and a number needed to treat (NNT) of 75.  In plain English, of 75 people treated with with bisphosphantes, one will avoid breast cancer over an eight year period by taking the drug.  

Bisphosphonates don't work that well for the main purpose -- reducing the key hard outcome of hip fracture, with NNT figures in the 70 to 80 range, and worse, for this end point.  The use of these drugs also raises all sorts of uncomfortable questions.  We have no idea of the their half-lives, so we don't know how long they last. What does it mean for these durable molecules to hang out for 20, 30 years or more in the human body?   Will we ever know?  Should we be concerned that by retarding bone resporption, these drugs accumulate old bone?  What about the studies that suggest a subset of women treated with these drugs actually experience a disturbance of normal bone turnover and may be placed in harm's way?  Why don't we hear more about these problems?  They are all published in the literature.  Why don't we read about press conferences on the dangers of these drugs rather on their supposed benefits? 

The assumption here is that the drugs work really well, although critics from within mainstream medicine argue their overuse is just another case of drug company disease mongering. 

Dr. Theresa Guise, a professor of medicine and oncology at the University of Indiana stated that the possibility a "simple oral drug" could prevent osteoporosis and breast cancer represents a "step forward in the prevention of . . . common health problems of women today."  Dr. Guise has been a consultant for Amgen, Novartis, Eli Lilly and Roche Pharmaceuticals.

LOTS OF MONEY SPENT ILL ADVISEDLY 

Thirty million people are treated with bisphosphonates every year.  A year's worth of alendronate, now available in generic form, costs $600 a year at the local CVS.  This adds up to $18 billion a year.

Study authors conceded that this particular study suggests association, but fails to establish proof.  More research is warranted.  Given the ability of Big Pharma to finance such research, we will no doubt see more studies.  Whether or not this is a good use for our health care dollars remains to be seen.  We're all paying the price.

From Internal Medicine News, January 2010