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Hey guys, there is something really confusing bout those 2 on First Aid. (confusing for me at least).

FA says that Tamoxifen antagonizes breast tissue, hence use for ER-positive breast cancer. Raloxifene agonist on bone, hence good for osteoporosis.

But I thought that Tamoxifen can also be good for osteoporosis and Raloxifene can also be used for ER-positive breast cancer?

Am I right or wrong?

Is it right to say that.. the only difference between those two is that Raloxifene won't cause endometrial ca, but tamoxifen will?
 

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Selective Estrogen Receptor Modulators SERMs

  • Tamoxifen and Raloxifen both are anti estrogenic on breast tissue so they are both useful for CA but Tamoxifen is more famous because Raloxifen was initially approved for osteoporosis only by the FDA.
  • Tamoxifen and Raloxifen both are estrogenic on bone tissues (preventing bone loss) and can be used in postmenopausal osteoporosis. However, Tamoxifen is Anti-Estrogenic in premenopausal women (can itself cause osteoporosis) that's why Raloxifen is more famous for this indication.
  • Tamoxifen is agonist on endometrial tissue (risk of cancer) while Raloxifen is antagonist on endometrial tissue (no risk of cancer).
  • Both are agonist on liver tissue, therefore they may cause thrombosis
  • Both are antagonist on brain tissue, therefore they may cause menopausal symptoms such as hot flashes.
 

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so why they don't use Raloxifen 4 breast cancer instead of Tamoxifen while, it doesn't increase the risk of endometrial cancer?
Ever heard of STAR trial ?

It was a randomized famous trial held to directly compare the effect of Tamoxifen vs Raloxifen in breast cancer.

The study found that the risk for blood clots and thrombo-embolic events was same in both drugs.

For some strange reason, tamoxifen was more effective at preventing DCIS and LCIS from progressing to invasive cancer than Raloxifen.


That trial ensured that Raloxifen was never popular among doctors to prevent breast cancer.

You are welcome to start another trial .. who knows? maybe it works an that was just a one-off trial with skewed results... : )
 
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