9 Weeks vs 1 Year Adjuvant Trastuzumab in Combination with Chemotherapy: Preliminary Cardiac Safety Data of the Phase III Multicentric Italian Study Short-HER.

Introduction: Several large randomized trials have shown the superiority of combining trastuzumab with chemotherapy versus chemotherapy alone as adjuvant treatment for HER2+ breast cancer patients. We are running a large phase III trial comparing two different trastuzumab durations (Short-HER study). We are reporting the preliminary cardiac safety data. Methods: The Short-HER study is a phase III, multicentric, Italian trial where 2500 HER2+ breast cancer patients will be randomized to: Arm A (Long) 4 courses of anthracycline based chemotherapy (AC or EC) followed by 4 courses of docetaxel in combination with trastuzumab, followed by 14 additional courses of 3-weekly trastuzumab; or Arm B (Short) 3 courses of 3-weekly docetaxel in combination with weekly trastuzumab followed by FEC x3. this is a non-inferiority trial with DFS and OS as primary end points, and 2-yr failure rate and incidence of cardiac events as secondary end points. Left ventricular ejection fraction (LVEF) is measured at baseline, at the end of each sequence of chemotherapy in both arms, and after 9 and 12 months since randomization thereafter. A cardiac event (CE) was defined as the occurrence of any of the followings: 1) LVEF decrease of more than 15 percentage points from baseline ; 2) LVEF decrease of more than 10 percentage points with absolute value below 50%; 3) symptomatic cardiac failure; 4) other cardiac side effects of grade 2 or more. Results: 510 patients from 69 Italian centers have been randomized so far, 251 in arm A (long) and 259 in Arm B (Short). 146 patients enrolled in arm A and 150 patients enrolled in arm B have received at least 3 months of therapy, and are eligible for the present analysis. In arm A (long), 20 patients (13.7%) experienced a CE: 12 patients experienced a LVEF decline of > 15 percentage points (5 patients with LVEF below 50%, one patient with concomitant atrial fibrillation); 3 patients had a LVEF decline of >10 percentage points with an absolute value below 50%. One patient had symptomatic cardiac failure. Two patients developed Grade 2 hypertension. Two patients developed Grade 2 arrhythmia. In arm B (short), 11 patients (7.3%) experienced a CE: 7 patients had a LVEF decline of > 15 percentage points; one patient had a LVEF decline of > 10 percentage points with an absolute value below 50%. Three patients developed Grade 2 arrhythmia Conclusions: This is a non-inferiority study designed on the assumption that a shorter treatment duration is associated with a significantly lower incidence of cardiac events. With 9 clinically relevant CEs (symptomatic cardiac failure or LVEF below 50%) in arm A (Long) and 1 in arm B (Short), these preliminary data support the assumption, and recruitment is ongoing. Supported by Agenzia Italiana del FArmaco (AIFA).