Would you consider reserving CDK4/6 Inhibitors as second line treatment in patients with advanced HR+ HER2 negative breast cancer given SONIA and PALMIRA trial results?

Yes - in fact, based on the SONIA trial results, I believe that 1st-line administration of a CDK 4/6 inhibitor in combination with an AI should be reserved for patients in whom a rapid response to treatment is necessary due to symptoms or extent of disease, particularly those with extensive visceral involvement. In the not uncommon patient who has de novo metastatic disease or a recurrence >24 months after discontinuing adjuvant endocrine therapy and has primarily soft tissue or bone disease (+/...

I think the answer is incredibly difficult now. Patients who progress on first line endocrine therapy are increasingly getting options for second line. The patients on the SONIA trial that received CDK 4/6 up front received faslodex on progression. However, elacestrant is now approved and working well in patients with ESR1 mutations AND post CDK 4/6 (see abstract GS3-01 from SABCS). We also know faslodex does not do nearly as well in this space, and caution is needed as there can be a rapid 50% ...