Clinical factors affecting clinical investigators’ (CIs) selection of CDK4/6 inhibitors (CDKis) for patients with hormone receptor-positive metastatic breast cancer (HR+ mBC).

e13097 Background: The clinical availability of three CDKis for the treatment of HR+ mBC has provided clinicians with important therapeutic options; however, minimal information exists on how available research findings, FDA approvals and current practice guidelines translate to clinical practice. Methods: In June 2024, 20 US-based and international CIs completed a case-based survey on their use of CDKis for HR+ mBC. A modest honorarium was offered. For each case question, one or more key clinical variables (eg, age, prior therapy, sites of metastases, comorbidities) were varied. Results: For a 65-year-old woman with de novo HR+ mBC, ribociclib was favored both for patients with asymptomatic bone metastases and for those with symptomatic visceral (including liver) metastases. For the same patient with asymptomatic brain metastases, abemaciclib was preferred and was also favored for patients with a recent history of myocardial infarction. In a similar manner, for an 85-year-old patient with multiple comorbidities and a difficult time managing polypharmacy, palbociclib was most frequently selected, although many CIs eliminate CDKi treatment altogether. Conclusions: Even in the absence of direct comparative clinical trial evidence, many CIs are tailoring their use of CDKis in certain situations according to factors including age, sites of metastases, comorbidities and other considerations. It would be interesting and relevant to explore whether matching approaches are being undertaken in community oncology practice. Clinical scenario(ER/PR+, HER2- de novo mBC) Choice of endocrine-based treatment 65-yo, asymptomatic bone mets R + AI: 17/20 (85%)P + AI: 2/20 (10%)A + AI: 1/20 (5%) 65-yo, symptomatic visceral (including liver) mets R + AI: 14/20 (70%)A + AI: 4/20 (20%)P + AI: 2/20 (10%) 65-yo, multiple asymptomatic brain mets A + AI: 10/20 (50%)R + AI: 7/20 (35%)P + AI: 2/20 (10%)Other: 1/20 (5%) 65-yo, 3 mo s/p MI, symptomatic visceral mets A + AI: 9/20 (45%)R + AI: 5/20 (25%)P + AI: 5/20 (25%)Other: 1/20 (5%) 85-yo, multiple comorbidities, symptomatic visceral mets P + AI: 6/20 (30%)AI: 4/20 (20%)Other: 10/20 (50%) R = ribociclib; AI = aromatase inhibitor; P = palbociclib; A = abemaciclib; MI = myocardial infarction.