Confused about Tamoxifen

The reason for recommending Tamoxifen in this case is most likely that the biopsy of the estimated 2.5 cm tumor taken prior to neoadjuvant therapy found hormone receptor-positive disease, specifically ER+PR+ disease ("The first biopsy before surgery was estrogen positive 30% progesterone positive 5%.")

Thereafter, she received neoadjuvant chemotherapy, which shrank the primary tumor substantially. After surgery, a very small amount residual disease (2 mm) was found and it was hormone receptor-negative. This finding does not necessarily negate the findings of the pathology on biopsy (ER+PR+ disease), because it can be explained by "tumor heterogeneity" (i.e., there was a tumor which had parts with differing hormone receptor statuses, some positive, some negative).

The pathology on biopsy identified hormone receptor positive disease, which would be the basis for prescribing Tamoxifen, which has the following potential risk reduction benefits:

(a) reduces the risks of loco-regional recurrence or of new disease (a new primary in the same breast or in the contralateral breast).

(b) reduces the risk of distant (metastatic) recurrence; <============

(c) reduces the risk of mortality.

The potential benefit is proportional to individual risk. With a bilateral mastectomy, there is always a small amount of breast tissue remaining, so there is still some usually small risk of local recurrence or new disease per (a).

However, surgery is a local treatment. In those diagnosed with hormone receptor-positive invasive breast cancer treated locally by bilateral mastectomy, the risk of distant (metastatic) recurrence (item (b) above) is usually the primary rationale for recommending Tamoxifen (or an aromatase inhibitor).

For those who were clinically node-negative and who received neoadjuvant therapy, their actual nodal status is not known and it could have been either positive or negative. In any case, even in those who are node-negative, there is some possibility that in the years before diagnosis/ treatment, some hormone-receptor positive cells escaped from the primary tumor via the blood stream or lymph, and moved to distant sites where they pose a risk for distant metastatic recurrence. These may be present, yet undetectable. (For a more detailed explanation, see my post here: https://community.breastcancer.org/forum/96/topics/854009?page=1#post_4941787). Tamoxifen can reduce the risk of distant (incurable metastatic) recurrence, however, it is not 100% effective, so some patients may relapse despite treatment.

Do not hesitate to discuss the above with your MO. Also, for post-menopausal women, an aromatase inhibitor might be a possible option if they do not tolerate Tamoxifen well, and you can ask about that too.

Best,

BarredOwl