Genetic Variation in NR1I2 and Palbociclib Safety and Prognosis in Advanced Breast Cancer: An Exploratory Multicenter Study.

Palbociclib has shown survival benefits in hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative locally advanced or metastatic breast cancer. At present, however, no genetic predictors of palbociclib-related hematological toxicity have been validated for clinical use. The aim of this study was to evaluate whether genetic variants are associated with palbociclib toxicity and patient prognosis. Multicenter study of 113 patients with HR-positive, HER2-negative locally advanced or metastatic breast cancer treated with palbociclib plus endocrine therapy. Genotyping of DNA from blood samples was performed to determine 18 variants in seven target genes (CYP3A4, SULT2A1, ABCB1, ABCG2, NR1I2, POR, and CDKN1B). Association analyses were performed to assess the relationship between the genetic variants and treatment-related toxicity and survival outcomes. Sixty-seven patients (59.3%) developed grade 3/4 neutropenia, 62 (54.9%) experienced disease progression, and 43 (38.1%) died. Although none of the univariate associations remained significant after Bonferroni correction, the multivariate analysis, adjusted for clinical variables, revealed several nominally significant associations. The NR1I2 gene variants rs6785049 (p = 0.01) and rs3732360 (p = 0.009) were associated with grade 3/4 neutropenia. The NR1I2 rs6785049 variant was associated with palbociclib treatment interruption (p = 0.03) and with worse progression-free (p = 0.003) and overall survival (p = 0.02). The findings of this exploratory study suggest potential associations between the NR1I2 rs6785049 variant and treatment toxicity and survival outcomes in patients with HR-positive, HER2-negative locally advanced or metastatic breast cancer treated with palbociclib. However, these hypothesis-generating findings need to be independently validated.