A Study to Evaluate the Efficacy and Safety of Pertuzumab + Trastuzumab + Docetaxel Versus Placebo + Trastuzumab + Docetaxel in Previously Untreated Human Epidermal Growth Factor Receptor 2 (HER2)-Positive Metastatic Breast Cancer

Overall survival (OS) was defined as the time from randomization to death from any cause. The Kaplan-Meier approach was used to estimate median OS for each treatment arm. Participants who were alive or lost to follow-up at the time of the analysis were censored at the date they were last known to be alive. Participants with no post-baseline information were censored at the time of randomization plus 1 day. The results reported here are from the final analysis. At the primary completion date, the median duration of OS had not been reached and OS data was not considered mature due to the few number of events reported.

Overall survival (OS) was defined as the time from randomization to death from any cause. The Kaplan-Meier approach was used to estimate the percentage of participants who were event-free for OS (i.e., alive) at 1, 2, and 3 years. Participants who were alive or lost to follow-up at the time of the analysis were censored at the date they were last known to be alive. Participants with no post-baseline information were censored at the time of randomization plus 1 day. At final analysis, the median [range] time on study for Arm A vs. Arm B was 145.29 [3.3-225.3] weeks vs. 174.79 [0.9-226.1] weeks.

An objective response was defined as a complete response (CR) or partial response (PR), as determined by the investigator using RECIST v1.1. As per RECIST v1.1, CR is defined as the disappearance of all target lesions, and PR is defined as at least a 30% decrease in the sum of diameters of target lesions. Also per RECIST v1.1, stable disease (SD) is defined as neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for progressive disease (PD), taking as reference the smallest sum on study; PD is defined as a 20% increase in the sum of the diameters of target lesions, an increase in size of measurable lesions by at least 5 mm, and the appearance of new lesions. The same assessment technique must be used throughout the study for evaluating a particular lesion, and the same investigator should assess all tumor responses for each participant. Participants without a post-baseline tumor assessment were considered non-responders.

Duration of objective response was defined as the time from the first occurrence of a documented objective response (complete response [CR] or partial response [PR]) to the time of disease progression, as determined by the investigator using RECIST v1.1, or death from any cause within 18 weeks after the last tumor assessment, whichever occurred first. As per RECIST v1.1, CR is defined as the disappearance of all target lesions, and PR is defined as at least a 30% decrease in the sum of diameters of target lesions. The Kaplan-Meier approach was used to estimate median duration of objective response. Data for participants who did not have an event were censored at the time of the last tumor assessment (if no tumor assessments were performed after baseline visit, at randomization plus 1 day).

The number of participants per treatment arm experiencing at least one adverse event, including all non-serious and serious adverse events, is reported here. Adverse events reported prior to first crossover treatment were included in the Placebo arm, and in the Crossover arm after that date, for participants in Arm A who crossed over from placebo to pertuzumab. At final analysis, the median [range] time on study treatment with placebo or pertuzumab per arm was: Arm A - Placebo: 52.3 [3-207] weeks; Arm B - Pertuzumab: 66.1 [3-225] weeks; Arm A - Crossover to Pertuzumab: 18.1 [12-24] weeks.

Adverse event (AE) severity was assessed according to the National Cancer Institute Common Terminology Criteria for Adverse Events, Version 4.0 (NCI-CTCAE v4.0); if the AE was not specifically listed, the following grades of severity were used: Grade 1 = mild; Grade 2 = moderate; Grade 3 = severe; Grade 4 = life-threatening or disabling; and Grade 5 = death. Severe and serious are not synonymous. Severity refers to the intensity of an AE, whereas a serious AE must meet criteria set out in the protocol; both were independently assessed for each AE. AEs reported prior to first crossover treatment were included in the Placebo arm, and in the Crossover arm after that date, for participants in Arm A who crossed over from placebo to pertuzumab. At final analysis, the median [range] time on study treatment with placebo or pertuzumab per arm was: Arm A - Placebo: 52.3 [3-207] weeks; Arm B - Pertuzumab: 66.1 [3-225] weeks; Arm A - Crossover to Pertuzumab: 18.1 [12-24] weeks.

Adverse events reported prior to first crossover treatment were included in the Placebo arm, and in the Crossover arm after that date, for participants in Arm A who crossed over from placebo to pertuzumab. At final analysis, the median [range] time on study treatment with placebo or pertuzumab per arm was: Arm A - Placebo: 52.3 [3-207] weeks; Arm B - Pertuzumab: 66.1 [3-225] weeks; Arm A - Crossover to Pertuzumab: 18.1 [12-24] weeks.

The number of participants with symptomatic left ventricular systolic dysfunction (LVSD) at any time during the study, as determined using echocardiography (ECHO) or multiple-gated acquisition (MUGA) scan, were summarized by treatment arm. Symptomatic LVSD was evaluated according to NCI CTCAE v4.0 (for "heart failure") and the New York Heart Association (NYHA) classification. At final analysis, the median [range] time on study treatment with placebo or pertuzumab per arm was: Arm A - Placebo: 52.3 [3-207] weeks; Arm B - Pertuzumab: 66.1 [3-225] weeks; Arm A - Crossover to Pertuzumab: 18.1 [12-24] weeks.

An asymptomatic decline in LVEF event is reported as an adverse event of "ejection fraction decreased" and is defined as either of the following: an absolute decrease in LVEF of ≥10 percentage points from baseline to an LVEF of <50%; or an asymptomatic decrease in LVEF requiring treatment or leading to discontinuation of pertuzumab (or placebo) and trastuzumab. At final analysis, the median [range] time on study treatment with placebo or pertuzumab per arm was: Arm A - Placebo: 52.3 [3-207] weeks; Arm B - Pertuzumab: 66.1 [3-225] weeks; Arm A - Crossover to Pertuzumab: 18.1 [12-24] weeks.

Left ventricular ejection fraction (LVEF) is the measurement of how much blood is being pumped out of the left ventricle of the heart with each contraction. LVEF was calculated using the modified Simpson method and must have been ≥55% at baseline as determined by the local facility before a participant could be enrolled in the study. The investigator decided which method of LVEF assessment (ECHO [preferred] or MUGA scan) would be used for each participant at baseline, and the same method was to be used throughout the study, to the extent possible. The LVEF abnormality status categories, as a change relative to LVEF at baseline, included: Increase or no change in LVEF; Decrease of <10 LVEF points; Absolute LVEF value ≥50% and a decrease of ≥10 LVEF points; and Absolute LVEF value <50% and a decrease of ≥10 LVEF points. The overall worst LVEF value was defined as the lowest post-baseline value up to the end of the study, including unscheduled assessments and the post-treatment period.

The baseline left ventricular ejection fraction (LVEF) and change from baseline to the maximum on-treatment decrease in LVEF at any point during the study are reported here. LVEF is the measurement of how much blood is being pumped out of the left ventricle of the heart (the main pumping chamber) with each contraction. LVEF was calculated using the modified Simpson method and must have been ≥55% at baseline as determined by the local facility before a participant could be enrolled in the study. The investigator decided which method of LVEF assessment (ECHO [preferred] or MUGA scan) would be used for each participant at baseline, and the same method should have been used throughout the study, to the extent possible. At final analysis, the median [range] time on study for Arm A vs. Arm B was 145.29 [3.3-225.3] weeks vs. 174.79 [0.9-226.1] weeks.