I'm a big fan of meta-analyses versus single trials. Along those lines, I found the following one published in Oct. 2015 in The Lancet and thought it might be of interest to those thinking of switching to tamoxifen:

The Early Breast Cancer Trialists' Collaborative Group undertook meta-analyses of individual data on 31,920 postmenopausal women with estrogen-receptor-positive early breast cancer in the randomized trials of 5 years of aromatase inhibitor versus 5 years of tamoxifen; of 5 years of aromatase inhibitor versus 2–3 years of tamoxifen then aromatase inhibitor to year 5; and of 2–3 years of tamoxifen then aromatase inhibitor to year 5 versus 5 years of tamoxifen.

It found that aromatase inhibitors reduce recurrence rates by about 30% (proportionately) compared with tamoxifen while treatments differ, but not thereafter. 5 years of an aromatase inhibitor reduces 10-year breast cancer mortality rates by about 15% compared with 5 years of tamoxifen, hence by about 40% (proportionately) compared with no endocrine treatment.
https://www.sciencedirect.com/science/article/pii/S0140673615610741