Would you offer PMRT to an ER/PR+, Her-2 negative cT3 tumor treated with neoadjuvant chemotherapy, but with a minimal treatment response?

The data on the risk of local-regional failure and the effect of PMRT on outcome are still too limited and contradictory to be certain of the correct answer. For example, the 10-year risk of LRF in the NSABP series of 95 cT3N0 patients having negative nodes but residual breast disease was 12% (1). However, the 5-year rate of local failure in the MDACC series was 14%, implying a 10-year rate of close to 20% (2). There are even fewer data trying to incorporate tumor grade or receptor status with c...

I would not hesitate to treat. PMRT has been demonstrated in prospective clinical trials to improve overall survival in patients with pathologic T1-3N0-1 disease (w/o upfront chemo) (e.g. Ragaz and Overgaard). This positive result was seen in essentially all subgroups considered (though not in T3N0 post-menopausal). The analysis of subsets from Overgaard based on clinical/molecular characteristics is very interesting (1). Patients with the most-favorable characteristics (e.g. T ≤2 cm, ER+, Her2-...

I don’t see a compelling reason for PMRT in this case. Given ER-positivity, it is not surprising that the chemo response was modest. Without any other adverse factors or nodal involvement, I would not recommend. However, if prior to chemo she had a documented positive node, I would treat until we know the results of B51.

For cases such as these where we don’t have clear prospective data, with mostly favorable pathology and a somewhat expected poorer response to neoadjuvant chemotherapy given receptor status, in my opinion, it comes down to the age, performance status, and level of comfort with a potential increase in risk of recurrence of the patient. It’s that unsavory nuanced discussion while we wait for more data.