Background

German AGO breast recommendations 2021 propose endocrine-based therapy as the 1^st therapy option for HR+, MBC, if there is no threat of organ failure. Since 2016, CDK4/6i + endocrine therapy (ET) is an option for 1^st L therapy. This data collection intends to show which therapy decisions are made and why in different patient groups with 1^st L MBC. Subsequent therapy may require molecular tumor characterization. How often molecular testing is done with MBC is largely unknown.

Methods

Retrospective data collection was carried out at 40 gynaeco-/oncological centers in Germany. Data of 391 pts with HR+/HER2- MBC were anonymously recorded, treated from 01.01. to 30.06.2021 for 1^st L therapy. Questions to be answered are:

- To what extent do different patient characteristics, previous treatment and course of tumor influence the choice of 1^st L therapy?.

- Factors that influenced therapy decision?.

- Frequency of molecular testing in met. situation and target parameters?.

Results

Of 391 pts, 17.4% were pre- and 82.5% postmenopausal. 40.4% of the pts had de novo disease, 59.6% had (neo)adjuvant pretreatment, 56.7% had chemo. 36.5% of the (neo)adjuvant treated pts relapsed during ongoing adjuvant therapy, another 8.2% within 1 y after completion of adjuvant therapy. Of these endocrine resistant pts, treatment with CDK4/6i was not more frequent with fulvestrant than with AI. In 32.7% of the pts, a molecular test was carried out in the met. situation: 9.5% for PIK3CAm, 21% for BRCAm. As 1^st L therapy in the met. situation, 86.2% received a CDK4/6i, 6.6% chemo and 6.4% endocrine monotherapy. Pts on endocrine monotherapy are older and more likely to have solitary bone mets. Pts receiving 1^st L chemotherapy are more likely to have lung and liver mets., these are not more likely to be symptomatic. Most common reported reasons for choosing CDK4/6i are "long experience with the substance" (48.8%) and "data situation" (45.5%). Endocrine resistance played a role in CDK4/6i selection in only 8% of pts.

Conclusions

Most pts with HR+/Her2- MBC receive the recommended therapy with CDK4/6i and ET. Molecular testing should be promoted to offer personalized therapy. Future therapy decision making should be more oriented to published data.

Legal entity responsible for the study

Novartis.

Funding

Novartis.

Disclosure

D. Finas: Non-Financial Interests, Institutional, Invited Speaker: Novartis, Roche, MSD.