The Endocrine Treatment Landscape for Patients with HR+ HER2- Early-stage Breast Cancer in Germany Before the Introduction of CDK4/6 Inhibitor Therapy - A Real-World Analysis

Introduction

While premenopausal patients with HR+ HER2- early breast cancer are treated with tamoxifen +/- ovarian suppression with a GnRH analog or an aromatase inhibitor (AI) + GnRH, the majority of postmenopausal women receive an AI due to its higher efficacy compared to tamoxifen. As the introduction of CDK4/6 inhibitors into the treatment of early-stage breast cancer with a higher risk of recurrence will probably result in a shift in the endocrine treatment landscape, the question is what treatment did potential candidates for CDK4/6 inhibitors in Germany receive before CDK4/6 inhibitors were available.

Patients and Methods

As part of a retrospective multicenter analysis, anonymized data were collected of patients with HR+ HER2- early-stage breast cancer who received endocrine therapy in the period between 10/2021 and 03/2022. Potential candidates for CDK4/6 inhibitor treatment were classified into different risk cohorts using the inclusion criteria of the NATALEE and monarchE trials.

Results

The data of 238 patients from 29 different centers were analyzed. While 20.6% of patients met the monarchE criteria, the subgroup which met the NATALEE inclusion criteria consisted of 46.2% of patients. 53.8% of patients did not meet the inclusion criteria for either the NATALEE or the monarchE trial. More than half of the patients did not receive chemotherapy. 28.6% of patients in the whole cohort were premenopausal. 67.6% of premenopausal women received neo-/adjuvant chemotherapy. 61.8% of premenopausal patients received tamoxifen as adjuvant endocrine therapy, 19.1% received an AI + GnRH and 10.3% were treated with tamoxifen + GnRH.

Conclusion

Despite the high percentage of premenopausal patients who received aggressive treatment in the form of chemotherapy, only one third of premenopausal patients received GnRH in addition to their standard endocrine therapy. Studies carried out at a later point in time and registry studies will be necessary to see how the endocrine therapy landscape in Germany has changed following the introduction of CDK4/6 inhibitors.

High efficacy of gemcitabine and cisplatin plus trastuzumab in patients with HER2-overexpressing metastatic breast cancer: a phase II study

AIMS

Effective and tolerable regimens are sought specifically in women who have been pre-treated with anthracyclines and taxanes. Gemcitabine and cisplatin plus trastuzumab has shown synergistic activity in vitro, and provides a new mechanism of drug interaction. This multicentre phase II study aimed to evaluate the efficacy and tolerability of gemcitabine and cisplatin plus trastuzumab in previously treated patients with metastatic breast cancer (MBC).

MATERIALS AND METHODS

Previously treated patients with human epidermal growth factor receptor 2 (HER2) overexpressing MBC were enrolled in a multicentre phase II study (DAKO Hercep Test 3+). Treatment consisted of gemcitabine (750 mg/m2), cisplatin (30 mg/m2) given on days 1 and 8 every 3 weeks, and trastuzumab (4 mg/kg loading dose, 2 mg/kg weekly).

RESULTS

Twenty patients were recruited, all of whom had previously received chemotherapy (12 pre-treated with taxanes, 18 pre-treated with anthracyclines seven pre-treated with taxanes and trastuzumab). A median of six cycles of the study treatment was delivered. There were eight partial responses, for an overall response rate of 40% (95% confidence interval 16.5-63.5%). The clinical benefit rate (complete response plus partial response plus stable disease) was 80% (95% CI 54.2-95.8%). The response rate in patients who had already received a trastuzumab-based regimen for MBC was 57.1% (95% CI 7.7-100%). Median time to progression was 10.2 months, and median overall survival was 18.8 months. Main toxicities were leukopenia (grade 3 in 55% of patients) and thrombocytopenia (grade 3 in 35% and grade 4 in 5% of patients). Non-haematological toxicity was rarely severe.

CONCLUSIONS

Combination chemotherapy with gemcitabine and cisplatin plus trastuzumab is well tolerated and active in patients with HER2 overexpressing MBC, even after prior exposure to anthracyclines and taxanes.