day 79 Tamoxifen: 5 years good, 10 years better

A new study of the impact of long-term hormone treatment using Tamoxifen, which was presented this week as the San Antonio Breast Cancer Symposium (, showed that 10 years was significantly better at suppressing recurrence and promoting survival than 5 years ( The curves didn’t shift by a huge amount: about a 25% reduction in risk of recurrence during the second decade of treatment and a ~3% overall gain in survival. I would say that any impact is more than welcome – we are talking (fortunately) about an ever increasing number of survivors who are likely to be affected. Ultimately, the lives of thousands of people will be extended and improved by this finding, and you can’t say that every day. Furthermore, Tamoxifen is affordable, well understood and the side effects while by no means trivial are largely manageable. You can see MD Anderson’s Dr. Jennifer Litton discussing it on NBC’s news coverage ( In my book, this is great news.

A question that remains outstanding now is whether the new, better effect of 10 years of Tamoxifen is also achievable by combined (sequential) use of aromatase inhibitors and Tamoxifen. These two drugs work on the same pathway, and in theory both suppress the hormones that drive ER/PR positive breast cancer. But is dangerous to assume that they are therefore interchangeable. The fact that their side effects are different is an indication that they have different overall impact, and is also a reason why some patients do better with one or the other. And then there are studies that suggest that aromatase inhibitors are more effective than Tamoxifen. I look forward to a long-term study of aromatase inhibitors. 

I was not able to attend the San Antonio conference, and have not seen the abstract of the paper presented and it apparently is not published. The press release states “Researchers enrolled 6,846 women with ER-positive breast cancer…”. It appears therefore that no men were included in this study, and I say appears, because the full paper may say otherwise. But if it is true, I wonder why? It is important, in my opinion, to include men in such large, prospective studies with agents that are just as likely to have benefit for them. 

There is adequate retrospective data for men to justify the use of Tamoxifen. But retrospective studies are limited in their usefulness as is nicely summarized in this wikipedia entry (, including:

“Among the disadvantages are that some key statistics cannot be measured, and significant biases may affect the selection of controls […] selection bias and misclassification or information bias as a result of the retrospective aspect.” Of course retrospective studies make it easier to study rare diseases such as male breast cancer, which may take a long time to accrue but can be relatively readily be extracted from a database. They are also of course much less expensive and can be done quickly. But, in a study where you accrue thousands there could be room for some men also. Most male breast cancers are hormone positive, and since response has been demonstrated it wouldn’t be hard to justify their inclusion on medical grounds.

Why does it matter? Well, I am still about 6 months off from starting Tamoxifen, but my wife who is 5 years ahead of me is having discussions with heir oncologist about what happens when she hits 7 years (2 years Tamoxifen, and now aromatase inhibitors). He has indicated that it may not be possible for him to prescribe the drug past what the established data in the field say. Given this report it may now be possible for doctors to give their patients Tamoxifen for 10 years. Perhaps they could also give aromatase inhibitors for that long now, or perhaps those who went to aromatase inhibitors after a period on Tamoxifen will now come back. But I wonder about men. Maybe it will be OK, given that men are treated like women in the absence of any compelling reason for them to be treated differently. But maybe it wont. It sure would be nice to have some real data.


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