Guidelines changed at MD Anderson in 2022 and they came out with an update on care, including tamoxifen, later that year. When I saw the survivorship provider at MDA in April 2022 the guidelines were still for 20 mg, later in the year they added 5 mg as an option for those who could not tolerate 20 mg. MD Anderson has nomograms they have developed that guide practice. They are available to view on the web, you can search for them. I found a nomogram that matched my issue (DCIS recurrence risk), and brought up the new guideline with them in October 2022 and they agreed to the 5 mg. Mayo Clinic probably has something similar. I found guides by Memorial Sloan Kettering on the web, as well.

You might ask your oncologist to re-look at your case. In 2022 they may have been following current guidelines.
The National Comprehensive Cancer Networks 2023 guidelines on breast cancer risk also should show that 5 mg is an option, but with lower efficacy.

Thank you for your information We try to comply with treatment
But often feel the need to critique prescribed treatment
So comforting to learn not alone and sharing information that others have found out and what worked for them
Sally in Ca🙏