There's a study out from England that says premenopausal women with ER positive cancer get a benefit from taking tamoxifen for ten years. This recommendation doubles the previous treatment regimen of five years.
I'll probably hear about it at my next cancer followup, and I'll decline because I had a rocky four years on this drug. So much so that side effects eventually made me stop taking it one year early.
I'm very weakly ER positive anyway, so it's unclear how effective tamoxifen is for me. However, when you're young with cancer, they will insist you take everything. And I get that, but experience also tells me when I've reached my limit with something.
I do know one thing, though. If I were to take one more day of tamoxifen, I would insist there be a surveillance plan to make sure I wasn't developing endometrial cancer, a known risk of the drug. After experiencing problems with tamoxifen, which aren't so very rare, I couldn't believe standard of care doesn't include annual pelvic ultrasounds and endometrial biopsies.
I see that as vital for anyone taking this drug for any amount of time; it's beyond mandatory before signing up for ten years.