A Study to Evaluate the Pharmacokinetics, Efficacy, and Safety of Subcutaneous Administration of the Fixed-Dose Combination of Pertuzumab and Trastuzumab in Combination With Chemotherapy in Participants With HER2-Positive Early Breast Cancer

The observed trastuzumab trough serum concentration (Ctrough) at Cycle 7 was assessed following 3 cycles of pertuzumab IV and trastuzumab IV or the fixed-dose combination (FDC) of pertuzumab and trastuzumab SC. The Per Protocol Pharmacokinetics (PK) analysis population includes all enrolled participants who adhered to the protocol. Exclusions from the Per Protocol PK analysis population were made for the following reasons: participants were missing the Ctrough pre-dose Cycle 8 PK sample, participants with a Ctrough sample collected with at least 2 days deviation from the planned date on Day 21 (i.e., before Day 19 or after Day 23), participants given a dose amount that deviated from the planned dose by >20% within 3 cycles (from Cycle 5), participants with a dose delay of more than 7 days, a subcutaneous injection site other than thigh was used, if the Cycle 8 pre-dose and post-dose samples were switched, and an assay error impacting Ctrough measurement.

Total pCR (tpCR) was defined as eradication of invasive disease in the breast and axilla; that is, ypT0/is ypN0, according to the local pathologists' assessment. Pathologic response to therapy was determined at the time of surgery. The tpCR rate is the percentage of participants in the ITT population who achieved a tpCR. Participants with missing data for tpCR (i.e., do not undergo surgery or have an invalid pCR assessment) were included in the analysis and classified as non-responders. Rates of tpCR were calculated in each treatment arm and were assessed using the difference between the Arm B: Pertuzumab and Trastuzumab FDC SC and the Arm A: Pertuzumab IV and Trastuzumab IV tpCR rates and corresponding 95% Clopper-Pearson confidence intervals (CIs). The difference between the tpCR rates along with corresponding 95% Hauck-Anderson CIs were calculated. The lower bound of the CI will reliably reflect the largest tpCR difference that can be considered unlikely.

iDFS (excluding SPNBC) is defined as the time from the first date of no disease (i.e., the date of primary surgery) to the first occurrence of one of the following events: ipsilateral invasive breast tumor recurrence; ipsilateral local-regional invasive breast cancer reccurrence; distant recurrence; contralateral invasive breast cancer; or death attributable to any cause. Ipsilateral or contralateral in situ disease and SPNBC (including in situ carcinomas and non-melanoma skin cancers) will not be counted as progressive disease or relapse.

Invasive disease-free survival (iDFS) including second primary non-breast cancer (SPNBC) is defined as the time from the first date of no disease (i.e., the date of primary surgery) to the first occurrence of one of the following events: ipsilateral invasive breast tumor recurrence; ipsilateral local-regional invasive breast cancer reccurrence; distant recurrence; contralateral invasive breast cancer; or death attributable to any cause. It also includes SPNBC as an event (with the exception of non-melanoma skin cancers and in situ carcinoma of any site).

Event-free survival (EFS) excluding second primary non-breast cancer (SPNBC) is defined as the time from enrollment to the first occurrence of one of the following events: breast cancer progression; breast cancer recurrence; or death from any cause. Ipsilateral or contralateral in situ disease and SPNBC (including in situ carcinomas and non-melanoma skin cancers) will not be counted as progressive disease or relapse.

Event-free survival (EFS) including second primary non-breast cancer (SPNBC) is defined as the time from enrollment to the first occurrence of one of the following events: breast cancer progression; breast cancer recurrence; or death from any cause. It also includes SPNBC as an event (with the exception of non-melanoma skin cancers and in situ carcinoma of any site).

The distant recurrence-free interval (DRFI) is defined as the time between randomization and the date of distant breast cancer recurrence.

Overall survival is defined as the time from randomization to death from any cause.

The adverse event (AE) severity grading scale for the NCI CTCAE v4.0 was used for assessing AE severity. Any AEs that were not specifically listed in the NCI CTCAE, v4.0 were graded per the following 5 grades: Grade 1 = mild; asymptomatic or mild symptoms; clinical or diagnostic observations only; or intervention not indicated. Grade 2 = moderate; minimal, local, or non-invasive intervention indicated; or limiting age-appropriate instrumental activities of daily living. Grade 3 = severe or medically significant, but not immediately life-threatening; hospitalization or prolongation of hospitalization indicated; disabling; or limiting self-care activities of daily living. Grade 4 = life-threatening consequences or urgent intervention indicated. Grade 5 = death related to AE. The terms "severe" and "serious" are not synonymous and are independently assessed for each AE. Multiple occurrences of AEs were counted only once per participant at the highest (worst) grade.

A primary cardiac event is defined as the occurrence of either of the following events: - Incidence of a symptomatic ejection fraction decrease (heart failure) of New York Heart Association (NYHA) Class III or IV and a drop in left ventricular ejection fraction (LVEF) of at least 10-percentage points from baseline and to below 50%; or - Cardiac death, defined as: Definite cardiac death (due to heart failure, myocardial infarction, or documented primary arrhythmia); or, Probable cardiac death (sudden unexpected death within 24 hours of a definite or probable cardiac event [e.g., syncope, cardiac arrest, chest pain, infarction, arrhythmia] without documented etiology).

A secondary cardiac event is defined as asymptomatic or mildly symptomatic Left Ventricular Systolic Dysfunction (LVSD) of NYHA Class II, defined as a left ventricular ejection fraction (LVEF) decrease of at least 10-percentage points below the baseline measurement to an absolute LVEF value of <50% confirmed by a second assessment within approximately 3 weeks.

A primary cardiac event is defined as the occurrence of either of the following events: - Incidence of a symptomatic ejection fraction decrease (heart failure) of New York Heart Association (NYHA) Class III or IV and a drop in left ventricular ejection fraction (LVEF) of at least 10-percentage points from baseline and to below 50%; or - Cardiac death, defined as: Definite cardiac death (due to heart failure, myocardial infarction, or documented primary arrhythmia); or, Probable cardiac death (sudden unexpected death within 24 hours of a definite or probable cardiac event [e.g., syncope, cardiac arrest, chest pain, infarction, arrhythmia] without documented etiology).

A secondary cardiac event is defined as asymptomatic or mildly symptomatic Left Ventricular Systolic Dysfunction (LVSD) of NYHA Class II, defined as a left ventricular ejection fraction (LVEF) decrease of at least 10-percentage points below the baseline measurement to an absolute LVEF value of <50% confirmed by a second assessment within approximately 3 weeks.

Clinical laboratory tests were performed at local laboratories; any abnormal values (High or Low) were based on local laboratory normal ranges. Laboratory abnormalities are presented by the highest (worst) severity grade (according to NCI-CTCAE v4.0) post-baseline. Not every abnormal laboratory value qualified as an adverse event, only if it met any of the following criteria: clinically significant (per investigator); accompanied by clinical symptoms; resulted in a change in study treatment; or required a medical intervention or a change in concomitant therapy. For a participant with multiple post-baseline abnormalities, only the highest (worst) grade for a given laboratory test is reported. 'Any Grade' indicates the total number of participants with a post-baseline abnormality of any grade for the specified test.