To evaluate the clinical efficacy and safety of palbociclib capsules combined with trastuzumab injection in the treatment of hormone receptor positive (HR+)/human epidermal growth factor receptor 2 positive (HER-2+) breast cancer patients who had progressed after prior trastuzumab therapy.

Patients with HR+/HER-2+ breast cancer were divided into control group and treatment group. The control group was treated with intravenous infusion of trastuzumab injection [the initial dose was 8 mg·kg^-1, administered slowly intravenously on the first day of treatment (infusion time ≥90 min); thereafter, the maintenance dose was 6 mg·kg^-1, with 28 days as one treatment cycle, and intravenous infusion was administered on the first day of each cycle (infusion time ≥30 min)]. The treatment group was treated with trastuzumab injection combined with palbociclib capsules, the administration of trastuzumab was the same as that of the control group, and palbociclib capsules was administered orally. The initial dose was determined based on the patient’s condition, ranging from 125 mg to 100 mg (if the adverse reactions were severe, the dose would be reduced), and the treatment was continued for 21 days, followed by a 7-day withdrawal, with a total of 28 days as one treatment cycle. Both groups were treated for three courses and followed up. The clinical efficacy, tumor markers, serological indicators, immune function, expression of phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT) pathway-related proteins, quality of life, safety evaluation and prognosis of the two groups of patients were compared.

A total of 78 patients were enrolled, with 41 cases in the control group and 37 cases in the treatment group. After treatment, the total effective rate of the treatment group and the control group were 40.54% (15 cases/37 cases) and 17.07% (7 cases/41 cases), (P<0.05). The median progression free survival (PFS) of the treatment group and the control group were 24.5 and 14.3 months, respectively; the cancer antigen 15-3 (CA15-3) levels were (36.72±5.64) and (40.92±6.73) IU·mL^-1, respectively; the levles of vascular endothelial growth factor (VEGF) were (86.22±12.32) and (95.26±12.15) pg·mL^-1, respectively; the cluster of differentiation 3 positive (CD3⁺) percentages were (50.16±7.12)% and (46.30±7.16)%, respectively; the relative expression levels of p-AKT protein were 0.58±0.12 and 0.64±0.11, respectively; the short form 36 health survey questionnaire (SF-36) scores werr (72.29±9.49) and (67.18±8.93,) points, respectively. The differences of above indexes were all statistically significant (P<0.05, P<0.01, P<0.001). The overall incidence of drug adverse reactions (including thrombocytopenia, leukopenia, neutropenia, nausea and vomiting, and abnormal liver function) was 72.97% (27 cases/37 cases) in the treatment group and 70.73% (29 cases/41 cases) in the control group, with no statistically significant difference (P>0.05).

Palbociclib capsules combined with trastuzumab injection has a definite therapeutic effect in HR+/HER-2+ breast cancer patients. It can more effectively reduce tumor marker levels, significantly prolong PFS, improve quality of life, and does not increase overall adverse reactions.