BACKGROUND
The selective CDK4/6 inhibitors palbociclib and ribociclib, which have appeared in the practice of a Russian clinician, have changed the paradigm of treatment in patients with HR+/HER2 breast cancer. The candidates for this therapy may also become patients who have previously been recommended chemotherapy due to the high prevalence of the disease and those with the threat of a visceral crisis. A controlled safety profile is a significant argument in favor of choosing tactics for the use of CDK4/6.
OBJECTIVE
To identify potential predictors for the efficiency of CDK4/6 inhibitor therapy in real clinical practice.
SUBJECTS AND METHODS
The authors retrospectively studied a database involving 170 patients with metastatic HR+/HER2 breast cancer who were treated with palbociclib and ribociclib in combination with any-line endocrine therapy from 2019 to June 2020 in five oncology dispensaries in Siberia and the Far East. They examined the influence of leukopenia and other factors on the duration of combination endocrinotherapy, as well as the relationship of disease progression to the severity adverse events. The end point was the estimation of the duration of therapy with CDK4/6 inhibitors, depending on the factors studied. Calculations were done using the Kolmogorov-Smirnov criterion, the Spearman correlation coefficient, the Mann-Whitney test, the Pearson χ2 test. The time to progression was estimated by the Kaplan-Meyer method. (see p. 12 and the article),
RESULTS
In the group of patients with the leukopenia degree (of less than 1.000 to 2.9 thousand cells/µl) registered during palbociclib or ribociclib treatment; the median time to progression was 35 months compared to a group of patients who were not observed to have leukopenia or a recorded white blood cell levels of not less than 3 thousand cells/µl; the median progression-free time was 24 months.
CONCLUSION
The leukopenia degree of less than 1.000 to 2.9 thousand cells/µl can be potentially a factor of a longer duration and a marker for the efficiency of therapy with the CDK4/6 inhibitors in the treatment of metastatic HR+/HER2 in the treatment of metastatic HR+HER2 breast cancer.
