A clinical study involving 1,000 prostate cancer patients was stopped this week by Southwest Oncology Group in Michigan due to concerns the treatment may have caused leukemia in three of the participants.The men in the study received the chemotherapy drug mitoxantrone, thought to possibly improve survival rates for those with poor prognoses following prostate surgery. But before results could be measured, leukemia struck and researchers halted the study, declaring the leukemia findings "an unacceptable risk to patients."
While the assumption is that the drug caused the leukemia -- a disease commonly associated with children and the elderly -- it's still unproved at this point.
Mitoxantrone is not a worthless drug, say some experts. Since its release a decade ago, it has been used to decrease bone pain for men with advanced prostate cancer and to treat multiple sclerosis and, ironically, adult leukemia.
1. Thanks for this blog.
This study raises the question "How much risk is too much?" Three men out of 488 in the arm of the study involving mitoxantrone developed leukemia. Three men equates to .6% - less than 1%, meaning that more than 99% did not develop leukemia. Of course, if these were the first three men in the study, that would make a difference, but the accompanying article did not address that level of information.
The men in the study all had poor prognoses following prostate cancer surgery. It's a reasonable assumption that many had positive surgical margins or positive lymph nodes. Therefore, it was a group that was willing to take some risks, to place some bets, because sitting still was not a great option. All the men had hormonal blockade as I understand it, which does quite well for most men at high risk for recurrence. Giving mitoxantrone might have upped their odds of success, but now we will not know if the added benefit, if any, was worth the added burden.
How much risk is too much is a tough question, one that clearly depends on the risks of not taking the extra step. My hunch is the researchers did the right thing in this case, but I have a strong impression that sometimes researchers are too gun-shy and pull back from a potentially useful tactic with substantial benefit just because it involves a risk that is truly miniscule.
This is what has happened so far on a broad scale with finasteride, a drug that has been proven to reduce prostate cancer incidence by 25%. A apparent possible one percent increase of more aggressive cancer spooked the media and most of the medical establishment. Fortunately, that increase is now understood to be basically due to an increase in detection capability, and finasteride has been cleared. Unfortunately, most doctors, patients and the media have not yet caught on. In this era of scarce resources for health care, with over 40 million uninsured in the US, reducing the incidence of prostate cancer by 50,000 cases per year (25% of roughly 200,000 new diagnoses per year) would probably save a lot of money, even allowing for the amount required to provide this generically available drug.
Jim Waldenfels (website: http://www.mycancerplace.com/profile.php?id=147)
Posted at 3:16PM on Jan 21st 2007 by Jim Waldenfels