Hematologic safety of palbociclib in combination with endocrine therapy in patients with benign ethnic neutropenia and advanced breast cancer.

BACKGROUND: Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, including palbociclib, are approved to treat hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer (ABC) and are associated with hematologic toxicity. African American women, who are underrepresented in CDK4/6 inhibitor clinical trials, may experience worse neutropenia because of benign ethnic neutropenia. The authors specifically investigated the hematologic safety of palbociclib in African American women with HR-positive/HER2-negative ABC. METHODS: PALINA was a single-arm, open-label, investigator-initiated study of palbociclib (125 mg daily; 21 days on and 7 days off) plus endocrine therapy (ET) in African American women who had HR-positive/HER2-negative ABC and a baseline absolute neutrophil count ≥1000/mm3 (ClinicalTrials.gov identifier NCT02692755). The primary outcome was the proportion of patients who completed 12 months of therapy without experiencing febrile neutropenia or treatment discontinuation because of neutropenia. Single nucleotide polymorphism analysis was used to assess Duffy polymorphism status. RESULTS: Thirty-five patients received ≥1 dose of palbociclib plus ET; 19 had a Duffy null polymorphism (cytosine/cytosine). There were no reports of febrile neutropenia or permanent study discontinuation because of neutropenia. Significantly more patients with the Duffy null versus the wild-type variant had grade 3 and 4 neutropenia (72.2% vs 23.1%; P = .029) and required a palbociclib dose reduction (55.6% vs 7.7%; P = .008). Patients with the Duffy null versus the wild-type variant had lower overall relative dose intensity (mean ± SD, 81.89% ± 15.87 and 95.67% ± 5.89, respectively; P = .0026) and a lower clinical benefit rate (66.7% and 84.6%, respectively). CONCLUSIONS: These findings suggest that palbociclib is well tolerated in African American women with HR-positive/HER2-negative ABC. Duffy null status may affect the incidence of grade 3 neutropenia, dose intensity, and possibly clinical benefit.

Retrospective study of the efficacy and safety of neoadjuvant docetaxel, carboplatin, trastuzumab/pertuzumab (TCH-P) in nonmetastatic HER2-positive breast cancer.

BACKGROUND: Pertuzumab is FDA approved in the preoperative setting in combination with trastuzumab and chemotherapy, in women with nonmetastatic HER2 + breast cancer. The TRYPHAENA trial (n = 77) reported a pathologic complete response rate (pCR), i.e., ypT0ypN0, of 52 % in patients treated with neoadjuvant (docetaxel, carboplatin, trastuzumab, & pertuzumab) TCH-P. Aside from this study, there is limited information regarding the safety and efficacy of TCH-P in the neoadjuvant setting. Our goal was to evaluate the safety and efficacy of neoadjuvant TCH-P in a non-clinical trial setting. MATERIALS AND METHODS: Cancer data registry was utilized to identify patients with HER2 + nonmetastatic breast cancer that received neoadjuvant TCH-P. pCR was defined as the absence of invasive or noninvasive cancer in breast and lymph nodes, i.e., ypT0ypN0. RESULTS: 70 patients with a median age of 52 years met our inclusion criteria. Clinical staging was I-8.5 %; II-68.5 %; and III-22.8 %. 60 % of patients had hormone receptor (HR)-positive tumors. 23 % (16/71) of patients required dose reduction for rash, diarrhea, neuropathy, or thrombocytopenia. Overall, no patients developed grade 3-4 left ventricular systolic dysfunction(LVSD); an asymptomatic reduction in LVEF of >10 % was observed in three patients. The overall observed pCR rate was 53 %. As expected, the pCR rate was higher in patients with HR-negative breast cancer than for patients with HR+ disease: 69 % (20/29) vs. 42 % (17/41), respectively. The axillary downstaging rate was approximately 53 % (19/36). CONCLUSION: Neoadjuvant TCH-P, in a nonclinical trial setting, was associated with a pCR rate of 53 % similar the reported rate in TRYPHAENA. Toxicity was manageable, with no patients experiencing symptomatic heart failure.