P1-12-21: Adjuvant Trastuzumab Treatment without Adjuvant Chemotherapy in Early Breast Cancer.

Abstract

Background: Trastuzumab (T) is approved in most Western countries for the treatment of early, HER2+ breast cancer (BC) parallel or sequential to adjuvant chemotherapy (CT). Nevertheless, as in metastatic disease, the antibody seems to be used without chemotherapy in a selected group of HER2+ patients (pt). The purpose of this analysis is to characterize this subgroup as well as describe safety and efficacy outcome parameters in this German prospective observation trial. Methods: At present, 2870 patients (pts) have been enrolled and documented in this ongoing non-interventional study from 270 German centers. At data base closure for this analysis, sufficient documentation was available from 2422 eligible pts. Results: The proportion of pts receiving T without preceding or concomitant CT (noCT) was 180/2422 (7.4%). This subgroup was characterized by higher age (median 58 vs.56 in the CT group, p=0.0026; ≥70 years: 18%/10%), smaller primaries (pT1 49%/43%, p=0.11), more favorable grading (G3 45%/53%, p=0.045), a higher proportion of positive hormone receptor (67%/61%, p=0.096) and less radiotherapy (64%/79%, p<0.0001). The strong association to radiotherapy is probably due to the fact, that the choice of this additional modality reflects the overall risk assessment of the pt. In contrast, there was no difference in nodal involvement (pN0: 52%/51%; positive nodes: mean 2.5/2.4). In multivariate analysis (logistic regression model, not incorporating radiotherapy), hormone receptor status is not predictive (p=0.41), while age ≥65 (p=0.0011), grade 1/2 (p=0.046) and pT1 (p=0.089) independently remain at least borderline significant. The mean number of T administrations was 18 and the median duration of T therapy was 12 months in the noCT group as well as the CT group. 57% of the noCT pts received adjuvant endocrine therapy. In the CT group, 81% received anthracyclines and 61% taxanes. Based on a still low number of only 13 observed events in the noCT group, no differences in relapse-free survival could be detected (p=0.38). Pathological cardiac findings in the pt's history was not predictive of therapy selection (6%/7%) and were also similarly distributed at the end of T therapy (7%/8%). Cardiac function disorders of CTC grade 3/4 were reported in 1% of both groups, across all grades slightly less frequent in the noCT group (2.8%/4.0%). Conclusions: A small, but distinct group of early BC pts without adjuvant chemotherapy receives T treatment for HER2+ disease. These patients are characterized by higher age and favorable primary tumor staging and grading, but not by cardiac comorbidities. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-12-21.