It's one of the most commonly used drugs for breast cancer. But for some women, it can stop working after a few years and if it does, treatment options are limited.
But there's hope for an alternative.
After going through radiation and chemotherapy, Jamie Albert who has breast cancer says she appreciates the simple effectiveness of tamoxifen.
She says, "Tamoxifen is super easy, yeah. I just take a pill every day, just have to make sure I remember and that's no big deal."
For such a simple therapy, the impact of tamoxifen has been profound, not only in treating breast cancer, but preventing it.
Dr. Bhuvana Ramaswamy, with James Cancer Hospital & Solove Research Institute says, "It reduces the chances of getting breast cancer back in a breast cancer patient, about 50%."
But for some women, that protection is only temporary. Doctors say after five years, up to 40% of women develop resistance to tamoxifen.
But a new study at Ohio State's Comprehensive Cancer center offers hope.
Researchers looked at over 300 human tumors, and found the pathway that some cancer cells use to beat tamoxifen.
They were able to block the pathway and kill those cancer cells by using a new drug called vismodegib which, like tamoxifen is very easy to take and tolerate.
Dr. Ramaswamy says, "You may have a new treatment combination that is just a pill both are pills you take, you don't have to lose hair for the most part, and you feel well overall and you have another treatment option."
The drug has already been approved for certain skin cancers, so it could easily be studied in other diseases as well.
Researchers say the pathway they discovered that leads to drug resistance could play a role in othercancers as well.
They hope to test this new drug in breast cancer patients in the coming months.