Canada Will Now Have Breast Cancer Warning on Finasteride Labels
Hello Doctor,
Thought you would be interested in this new advisory from Health Canada regarding finasteride and breast cancer:
Link: Finasteride (Propecia, Proscar): Potential rare risk of breast cancer in men
I know this topic has been discussed before, but it looks like Canadian patients using finasteride (including me for 8 years) will see the new advisory in the leaflet…
The average age for male breast cancer is 71 years old. The number of cases I can find in the medical literature are very few. As the press release points out, of the small number of cases, “Most of the reports have been in association with the 5mg formulation”.
With the average age for our patients under 40, the lack of finding breast cancer is not surprising. I recall reading that up to 50 men taking 5mg finasteride (Proscar) and just 3 men taking 1mg finasteride (Propecia) had been reported to have breast cancer, though the link between the medication and the breast cancer wasn’t proven — nor could it be ruled out. If there’s updated information, I still suspect the total number is very low considering the number of men using the medication at any dose. Nevertheless, even with this rare risk, I will add include it in my discussions with patients.
As an aside, I wonder if these 3 men had the gene for breast cancer, which (in theory) could be provoked by finasteride. The best way for a typical young patient to evaluate this should be in his own family history. Those men with a family history of breast cancer in mothers, sisters, grandmothers, aunts… should be more aware of this risk, although still very remote.
While I think it is reasonable that you will have this discussion with your patients, have you decided it is ripe for you to inform your patients of the risk of developing permanent sexual functions? The FDA label now includes a commensurate warning to the breast cancer issue in Canada, and to be honest I would prefer to deal with breast cancer over the issues that I have developed myself. Personally, I do not even have the worst case of finasteride side effects one could attain since they get much worse.
Excellent summary by Dr R. As additional info, a man who has a family history of breast cancer in women who are also BRCA (“breast cancer gene”)positive should get tested for BRCA2 status for a number of reasons. If a sister is BRCA positive, the risk of inheritance for the man is 50%. It is important for family planning because such a man, if positive, then has a 50% chance of passing the gene to a daughter. Females who are BRCA (especially BRCA2) positive have a high (> 50%) risk of breast cancer and warrant early detection (and prophylactic mastectomy in some cases). For the BRCA positive man, the lifetime risk is increased to about 6%, or that of the average women without BRCA positivity. Finally, a man with BRCA positive status is also at increased risk for prostate (and pancreatic) cancer and increased surveillance of this should also occur. I have argued in this blog before (especially in response to Jeremy’s request for blanket statements from you) that medicine is personalized and the decision to take any drug should be based on a combination of individuals factors that help determine the best risk-benefit balance. BRCA positivity in men, while uncommon, is one of those many factors.
Dr. L –
There really is no evidence that finasteride interacts with the BRCA2 mutation. It is certainly not unreasonable to hypothesize that it may compound the risk of developing cancer in those that are carriers of the mutation, BUT at this point it is purely speculative. It is even possible that it could work to counteract the BRCA2 mutation while increasing the risk only for those who are not carriers of the gene. There is equal evidence to support both propositions at this point (none).
However, until there is an understanding of exactly what factors predispose a man to develop post-finasteride syndrome it is not unreasonable to issue what you call a ‘blanket statement’. It would just inform patients that it has been reported in men in very small numbers and could potential affect them albeit with a low likelihood. Men who are overly concerned about this type of loss could determine for themselves based on their personal preference whether the cost benefit trade off passes the necessary threshold. Offering general warnings in no way precludes the doctor from offering personalized medical advice.