ABSTRACT
Background: The impact of some medical decisions hurriedly taken during the COVID-19 first wave remains unknown. We tried to assess the consequences of one of these precautionary measures, namely the interruption of a 4/6 cyclin D-dependent kinase inhibitor (CDK4/6i) in metastatic patients with clinical benefit (complete response/partial response and patients with stable disease for at least 6 months) on endocrine treatment (ET). The main reason for this interruption was to limit the risk of myelosuppression (assumed as a serious risk factor for COVID-19) and other adverse effects that could overlap with symptoms and clinical signs described in the SARS-CoV-2 infection. Methods: We included 60 patients (median age: 64 years old) in whom the CDK4/6i was stopped during the first COVID-19 outbreak. It was a non-interventional, retrospective, multicentric study. A univariate analysis was performed to assess risk factors associated with disease progression: odds ratios (OR) were estimated along with their confidence intervals (CI). Key patient characteristics, all included in the statistical model, are presented in Table 1. Results: The average duration of a CDK4/6i interruption was 8 weeks. During this therapeutic break, 22 (37 %) patients Shad a radiological and/or clinical progression of the disease. Among them, CDK4/6i were taken back for the majority of patients (n=16/22;73 %) when the sanitary situation improved.For four patients (n=4/22;18 %), a new specific treatment (chemotherapy or targeted therapy) was initiated for rapid or symptomatic tumor progression. Two patients died while CDK4/6i was withdrawn. All the results of the univariate analysis are summarized in Table 2. During the CDK4/6i discontinuation, the risk of disease progression was significantly increased in the presence of liver metastases. This was the only variable with a significant effect in univariate analysis. Although not statistically significant, the risk of disease progression was higher when CDK4/6i withdrawal was longer, when patients had a more aggressive breast cancer (Luminal B) and when the tumor was considered as resistant to ET. Conclusions: The importance of maintaining the cell cycle inhibitor in addition to ET does not seem to be debatable as 36 % of patients progressed during CDK4/6i withdrawal. This is important in clinical practice when the question of CDK4/6i discontinuation arises for other reasons (analgesic radiotherapy or programmed surgery for example). Special attention should be paid to patients with liver metastases for whom stopping such a treatment seems to accelerate the natural course of the disease.