Background

HER2 overexpression occurs in approx. 20% of breast tumors and is associated with increased aggressiveness and mortality. Anti-HER2 re-therapy with trastuzumab (Herceptin®, T) is an established therapeutic option for the treatment of recurrent/metastatic HER2-positive breast cancer (MBC). Patients (pts) receiving T re-therapy appear to benefit from the retreatment after a relapse-free (neo)adjuvant anti-HER2 therapy.

Methods

This NIS is conducted in Germany to gain additional knowledge about efficacy of 1st-line T retreatment in the clinical routine. 122 sites enrolled a total of 239 pts with locally recurrent and/or MBC who relapsed after (neo)adjuvant treatment with T in their medical history. 230 pts met the eligibility criteria. The current analysis presents data collected between 10/2008-04/2015. Tumor progression was clinically assessed by the investigator.

Results

Median observation period for the total population (n=230) was 41.7 months (m) (range 0.4-94.5).

At start of T retreatment, 20.0% (n=46) of the pts presented with local recurrence only, 79.6% (n=183) presented with distant metastases ± local recurrence and one patient (0.4%) presented with elevated tumor markers. 27.4% (n=63) of the pts developed exclusively non-visceral metastases and 52.2% (n=120) were diagnosed with visceral (± non-visceral) metastases. Median duration of T re-therapy in the first line setting was 9.0 m (95% confidence interval (CI): 7.6-10.1). In 69.6% (n=160) of the cases, T was added to chemotherapy (CT). 15.2% of the pts (n=35) were treated with T+CT + endocrine therapy (ET).

A median progression free survival (PFS) of 10.1 m was observed among all eligible patients (n = 230) (95% CI: 8.5-12.0). The evaluation by risk groups revealed a PFS of 23.7 m (95% CI: 13.3-NE*) for patients with local recurrence only, 11.8 m (95% CI: 8.3-20.1) for patients with non-visceral metastases and 7.6 m (95% CI: 6.2-9.9) for patients with visceral metastases. *Not evaluable

Median PFS according to treatment regimen was 8.3 m for pts who were treated with T+CT (n=125, 54.3%), 17.7 m in pts who received T+CT+ET (n=35, 15.2%) and 11.2 m in pts treated with T+ET (n=38, 16.5%). Pts who received T monotherapy (n=32, 13.9%) had a median PFS of 13.4 m.

Of 230 pts, 121 deaths were documented (52.6%) within the observation period. The median overall survival (OS) was 29.6 m for all pts (95% CI: 27.3-36.8). Median OS was statistically reliable for pts with visceral metastases only: 19.4 m (95% CI: 16.9-27.3). The 2-year survival rate was 62.2% for all pts, 81.9% for pts with local recurrence only, 80.7% for pts with non-visceral metastases and 45.6% for pts with visceral metastases.

Conclusions

The survival observed for pts with HER2-positive MBC receiving T re-therapy in the clinical routine is in line with the results of recently published data. In terms of the 2-year survival rate, 81.9% of the pts with local recurrence were still alive and thus show the most favourable prognosis. T re-therapy provides an efficient treatment option regardless of given as combination-therapy together with CT and/or ET or as monotherapy.

Citation Format: Hanker L, Hitschold T, Grafe A, Förster F, Schröder J, Janssen J, Reichert D, Hielscher C, Keitel S, Hesse T. Efficacy of trastuzumab re-therapy in the clinical routine of HER2-positive breast cancer patients who relapsed after completed anti-HER2 (neo)adjuvant therapy – 5th interim analysis of the national non-interventional study (NIS) ML21589. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-14-08.