Real-world clinical outcomes in patients receiving cyclin-dependent kinase 4/6 inhibitors (iCDK 4/6) for hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2-) metastatic breast cancer in Mexico.

Abstract

e13053 Background: Breast cancer was the second most common malignant tumor diagnosed in 2018 worldwide, and the main cause of cancer death in women. In Mexico is the leading cause of cancer deaths, the most common molecular subtypes is HR+/HER2- (63%). The addition of iCDK 4/6 can enhance the benefit seen with endocrine therapy (ET) alone. In this work we will describe the experience in a “real world” model, of two tertiary-level hospitals in Mexico, with the use of iCDK 4/6 in a period of 3 years. Methods: Retrospective review of medical records of all consecutive pts with histological diagnosis of metastatic breast cancer HR+/HER2- and iCDK 4/6 treatment at our Institutions from July 2016 to January 2019. Clinical and pathological variables at diagnosis were recorded. Progression free survival was estimated using Kaplan-Meier method and survival distributions were compared using the Log-rank test. To assess association variables and progression we use Chi square. Results: 65 pts were treated, all with iCDK 4/6 in combination with ET, either aromatase inhibitor or irreversible estrogen receptor antagonist. 62 with palbociclib and 3 with ribociclib; Median age was 53 y/o (IQR 42-63), ECOG 0-1 (92.3%), 80% was metastatic recurrent disease, 92% of these patients received endocrine adjuvant treatment. Median estrogen receptor percentage was 90 (IQR 61-92), progesterone 50 (9-83), KI67 20 (10-30). The metastatic sites were bone (64.6%), liver (41.5%), nodal (33.8%), lung (21.5%), CNS (3.1%) and others (18.5%). 26 pts (40%) received iCDK 4/6 in the first line, 21 (32.3%) in the second line, and 27% in subsequent lines. Any grade of toxicity was presented in 44 pts (67.7%), Most common toxicities were neutropenia (63%), fatigue (16.9%), anemia (9.2%), grade 3-4 toxicities were presented in 21.5% and 17 pts (26.2%) required any dose adjustment. At the cut-off date, 28 pts (43.1%) had disease progression, median time to progression for the 65 pts was 10 months (1-84). OR for first line treatment vs subsequent lines was 0.14 (0.04-0.47, 95%, p = 0.001). OR for pulmonary metastases were 4.21 (1.15-15.31, 95%, p = 0.03), for other sites of metastasis were NS. Conclusions: Our outcomes suggest that the PFS is better when iCDK 4/6 are used as a first line treatment. Pulmonary metastases are may associated with poorly outcomes. In low- and middle-income countries, efforts should be focused on early therapy with iCDK 4/6.