Tamoxifen during radiation?

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Question from CJ: Why is it that some doctors recommend waiting until after radiation before starting tamoxifen, while others say it is not a problem to do both at the same time?
Answers - Lydia Komarnicky, M.D. That's an area of controversy. I personally do not have much of a problem with tamoxifen given during radiation. I think that there are some radiation oncologists that may be concerned about the cosmetic results of tamoxifen during radiation treatment.
Marisa Weiss, M.D. We don't have the 'right answer' on this. My personal preference is to delay the start of the hormonal therapy until after radiation is finished for most women. The reason why I have this preference is because we know that anti-estrogen therapy slows down the growth of hormone-receptor-positive breast cancer cells. When these cells are slowed down and dormant, they are less vulnerable to the effects of radiation, theoretically. In order to maximize the potential benefit of radiation, it's theoretically best to have the cells be active, not inactive. I keep mentioning 'theoretically' because these concerns are based on laboratory observations rather than clear findings from clinical studies. We do know from a recent NSABP (National Surgical Adjuvant Breast and Bowel Project) study that chemotherapy works better when it's separated from the hormonal therapy.

The other reason why I like to delay the tamoxifen is because I prefer to do one thing at a time and to separate out any potential side effects from each of the treatments if there's no compelling reason to do it otherwise. Women are on the anti-estrogen therapy for five years, so I figure that it's OK to delay it for the six to seven weeks of radiation. Again, this is just a preference. It's not known to be the 'right answer.'

There are situations, however, where a woman may be at high risk for recurrence. For example, she has multiple positive lymph nodes or other factors that put her at high risk for recurrence. Then, as soon as her chemotherapy is done, her medical oncologist might want to put her immediately on anti-estrogen therapy to get that immediate protection and to keep it going during her radiation. This is perfectly acceptable, based on what we know at this time. There have been plenty of studies that have shown that radiation together with tamoxifen is very effective.
Lydia Komarnicky, M.D. I have reviewed our data looking at patients receiving tamoxifen and radiation therapy over the past 17-18 years, and it was apparent that there was no effect on the cosmetic results. We did not notice any difference in the survival. We are still awaiting studies to define this, so there's not a right or wrong answer to this question right now.
Marisa Weiss, M.D. Both Harvard and Penn also looked at this question. One institution prefers one way, the other institution prefers the other way. Again, there is no 'right answer' at this time.

The Ask-the-Expert Online Conference called Radiation Therapy Updates featured Lydia T. Komarnicky, M.D. and Marisa Weiss, M.D. answering your questions about advances in radiation therapy: the newest and best techniques, combining radiation therapy with other treatments, ways to manage, reduce or eliminate side effects, and more.

Editor's Note: This conference took place in March 2004.

The materials presented in these conferences do not necessarily reflect the views of Breastcancer.org. A qualified healthcare professional should be consulted before using any therapeutic product or regimen discussed. All readers should verify all information and data before employing any therapies described here.

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Copyright 2010. All rights reserved.

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