In a patient with BRCA2 mutation and contralateral axillary recurrence of ER+ IDC with an ESR1 CCDC170 fusion on NGS testing, would you use standard adjuvant AI therapy or consider adjuvant SERD therapy (fulvestrant/elacestrant)?

A lot of information is missing, like menopausal state, initial dx, previous chemo or no chemo, previous hormone status, adjuvant hormone therapy, type of hormone therapy if yes, and time of recurrence. All these are required for decision-making.

That's an interesting question. The contralateral axilla would be considered metastatic, so there would be approval to use fulvestrant/elacestrant in that setting. It would be interesting to know when the patient finished their prior adjuvant AI before this recurrence, but even if it has been a while, I would favor fulvestrant/elacestrant.

In a patient with BRCA2 mutation and contralateral axillary recurrence of ER+ IDC with an ESR1 CCDC170 fusion on NGS testing, would you use standard adjuvant AI therapy or consider adjuvant SERD therapy (fulvestrant/elacestrant)?

This question has to be rewritten for clarification. Not only does it lack crucial information, such as: Is this patient premenopausal or post-menopausal? Is her reported BRCA2 mutation somatic or germline, or both? Is her contralateral axillary disease synchronous or me...

This is a difficult question given limited data. Recommendations in situations like these are influenced by perceived risk and personal experience/bias.

The ESR1-CCDC170 fusion, though the most common ESR1 fusion, is still overall uncommon. It’s been associated with endocrine resistance in patients with metastatic HR+ breast cancer Veeraraghavan et al., PMID 25099679

Recently published articles suggest:

- There are different types of ESR1-CCDC170 fusions with varying levels of endocrine resistance...