From: Tamoxifen may prevent both ER+ and ER- breast cancers and select for ER- carcinogenesis: an alternative hypothesis
ER status of tumors
Tamoxifen treatment
First cancer
Second cancer
No
Yes
ER-
19 (70%)
7 (78%)
ER+
8 (30%)
2 (22%)
4 (11%)
17 (44%)
31 (89%)
22 (56%)