Herceptin (Trastuzumab) in Treating Women With Human Epidermal Growth Factor Receptor (HER) 2-Positive Primary Breast Cancer

Study Overview
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Brief Summary
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The purpose of this trial is to evaluate Herceptin treatment for 1 year and 2 years (versus observation/no Herceptin) in women with HER2-overexpressing primary breast cancer who have completed (neo-)adjuvant systemic chemotherapy, definitive surgery, and radiotherapy, if applicable. Efficacy and safety will be assessed for 10 years from randomization for each participant. All participants will continue to be followed for survival until 10 years after enrollment of the last participant.

Official Title
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A Randomized Three-Arm, Multicenter Comparison of 1 Year and 2 Years of Herceptin Versus No Herceptin in Women With HER2-Positive Primary Breast Cancer Who Have Completed Adjuvant Chemotherapy

Conditions
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Breast Cancer

Intervention / Treatment
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* Drug: Herceptin
* Drug: Herceptin


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Non-metastatic primary invasive breast cancer overexpressing HER2 (determined by immunohistochemistry 3+ or positive fluorescence in situ hybridization test) that has been histologically confirmed, adequately excised, axillary node positive or negative, and tumor size at least T1c according to Tumor/Node/Metastasis (TNM) staging Completion of at least 4 cycles of (neo-)adjuvant systemic chemotherapy, definitive surgery, and radiotherapy, if applicable Known hormone receptor status Baseline left ventricular ejection fraction (LVEF) greater than or equal to (≥) 55 percent (%) Exclusion Criteria: Prior invasive breast carcinoma Other malignancies except for curatively treated basal and squamous cell carcinoma of the skin or in situ carcinoma of the cervix Clinical T4 tumors Cumulative doxorubicin exposure greater than (>) 360 milligrams per meter-squared (mg/m^2) or epirubicin >720 mg/m^2 or any prior anthracyclines unrelated to the present breast cancer Peripheral stem cell or bone marrow stem cell support Prior mediastinal irradiation except for internal mammary node irradiation for the present breast cancer Non-irradiated internal mammary nodes or supraclavicular lymph node involvement Prior anti-HER2 therapy for any other reason or other prior biologic or immunotherapy for breast cancer Concurrent anti-cancer treatment in another investigational trial Serious cardiac or pulmonary conditions/illness, or any other conditions that could interfere with planned treatment Poor hematologic, hepatic, or renal function Pregnancy or lactation Women of childbearing potential or less than 1 year post-menopause unwilling to use adequate contraceptive measures

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: Observation Arm<br>Participants who have completed definitive surgery and systemic adjuvant chemotherapy will be observed for efficacy and safety until 10 years from individual randomization and for survival until 10 years after enrollment of the last participant. No Herceptin will be provided. | |
| Experimental: Herceptin 1-Year Arm<br>Participants who have completed definitive surgery and systemic adjuvant chemotherapy will receive Herceptin for 1 year or until disease recurrence, whichever occurs first. Participants will be observed for efficacy and safety until 10 years from individual randomization and for survival until 10 years after enrollment of the last participant. | Drug: Herceptin<br>* Herceptin will be given as a loading dose of 8 milligrams per kilogram (mg/kg) via intravenous (IV) infusion on Day 1, followed by a maintenance dose of 6 mg/kg via IV infusion 3 weeks later and thereafter every 3 weeks.<br>* Other names: Trastuzumab;|
| Experimental: Herceptin 2-Year Arm<br>Participants who have completed definitive surgery and systemic adjuvant chemotherapy will receive Herceptin for 2 years or until disease recurrence, whichever occurs first. Participants will be observed for efficacy and safety until 10 years from individual randomization and for survival until 10 years after enrollment of the last participant. | Drug: Herceptin<br>* Herceptin will be given as a loading dose of 8 mg/kg via IV infusion on Day 1, followed by a maintenance dose of 6 mg/kg via IV infusion 3 weeks later and thereafter every 3 weeks.<br>* Other names: Trastuzumab;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Percentage of Participants With Disease-Free Survival (DFS) Events in Herceptin 1-Year Arm Compared to Observation: 1-Year Median Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants with at least one DFS event was reported. The analysis of the Herceptin 1-Year Arm against the Observation Arm after 1-year median follow-up, as reported below, was performed by the Sponsor in 2006 following database cleaning. The analysis of the Herceptin 2-Year Arm against the Observation Arm was performed for an Independent Data Monitoring Committee (IDMC) in 2005 at a time the Sponsor was blinded. Therefore, these data are reported under a separate Outcome Measure. | From Baseline until time of event (median of 1 year) | 
| Percentage of Participants With DFS Events in Herceptin 2-Year Arm Compared to Observation: 1-Year Median Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants with at least one DFS event was reported. The analysis of the Herceptin 2-Year Arm against the Observation Arm after 1-year median follow-up, as reported below, was performed for an IDMC in 2005 at a time the Sponsor was blinded. The analysis of the Herceptin 1-Year Arm against the Observation Arm was performed by the Sponsor in 2006 following database cleaning. Therefore, these data are reported under a separate Outcome Measure. | From Baseline until time of event (median of 1 year) | 
| DFS Rate According to Kaplan-Meier Analysis in Herceptin 1-Year Arm Compared to Observation: 1-Year Median Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants free of DFS events (i.e., the DFS rate) and corresponding 95 percent (%) confidence interval (CI) were estimated by Kaplan-Meier analysis based on available data at the time of the 1-year median follow-up analysis. The analysis of the Herceptin 1-Year Arm against the Observation Arm after 1-year median follow-up, as reported below, was performed by the Sponsor in 2006 following database cleaning. The analysis of the Herceptin 2-Year Arm against the Observation Arm was performed for an IDMC in 2005 at a time the Sponsor was blinded. Therefore, these data are reported under a separate Outcome Measure. | Year 2 | 
| DFS Rate According to Kaplan-Meier Analysis in Herceptin 2-Year Arm Compared to Observation: 1-Year Median Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants free of DFS events (i.e., the DFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 1-year median follow-up analysis. The analysis of the Herceptin 2-Year Arm against the Observation Arm after 1-year median follow-up, as reported below, was performed for an IDMC in 2005 at a time the Sponsor was blinded. The analysis of the Herceptin 1-Year Arm against the Observation Arm was performed by the Sponsor in 2006 following database cleaning. Therefore, these data are reported under a separate Outcome Measure. | Year 2 | 
| Percentage of Participants With DFS Events Compared to Observation: 8-Year Median Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants with at least one DFS event was reported. | From Baseline until time of event (median of 8 years) | 
| DFS Rate at Year 3 According to Kaplan-Meier Analysis Compared to Observation: 8-Year Median Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants free of DFS events (i.e., the DFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 8-year median follow-up analysis. | Year 3 | 
| DFS Rate at Year 5 According to Kaplan-Meier Analysis Compared to Observation: 8-Year Median Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants free of DFS events (i.e., the DFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 8-year median follow-up analysis. | Year 5 | 
| DFS Rate at Year 7 According to Kaplan-Meier Analysis Compared to Observation: 8-Year Median Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants free of DFS events (i.e., the DFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 8-year median follow-up analysis. | Year 7 | 
| DFS Rate at Year 8 According to Kaplan-Meier Analysis Compared to Observation: 8-Year Median Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants free of DFS events (i.e., the DFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 8-year median follow-up analysis. | Year 8 | 
| Percentage of Participants With DFS Events Compared to Observation: 10-Year Maximum Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants with at least one DFS event was reported. | From Baseline until time of event (maximum of 10 years) | 
| DFS Rate at Year 3 According to Kaplan-Meier Analysis Compared to Observation: 10-Year Maximum Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants free of DFS events (i.e., the DFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the final analysis with a 10-year maximum follow-up for DFS events. | Year 3 | 
| DFS Rate at Year 5 According to Kaplan-Meier Analysis Compared to Observation: 10-Year Maximum Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants free of DFS events (i.e., the DFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the final analysis with a 10-year maximum follow-up for DFS events. | Year 5 | 
| DFS Rate at Year 7 According to Kaplan-Meier Analysis Compared to Observation: 10-Year Maximum Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants free of DFS events (i.e., the DFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the final analysis with a 10-year maximum follow-up for DFS events. | Year 7 | 
| DFS Rate at Year 8 According to Kaplan-Meier Analysis Compared to Observation: 10-Year Maximum Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants free of DFS events (i.e., the DFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the final analysis with a 10-year maximum follow-up for DFS events. | Year 8 | 
| DFS Rate at Year 9 According to Kaplan-Meier Analysis Compared to Observation: 10-Year Maximum Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants free of DFS events (i.e., the DFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the final analysis with a 10-year maximum follow-up for DFS events. | Year 9 | 
| DFS Rate at Year 10 According to Kaplan-Meier Analysis Compared to Observation: 10-Year Maximum Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants free of DFS events (i.e., the DFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the final analysis with a 10-year maximum follow-up for DFS events. | Year 10 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Percentage of Participants With DFS Events in 1-Year Versus 2-Year Herceptin: 10-Year Maximum Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants with at least one DFS event was reported. | From Baseline until time of event (maximum of 10 years) | 
| DFS Rate According to Kaplan-Meier Analysis in 1-Year Versus 2-Year Herceptin: 10-Year Maximum Follow-Up | DFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer or second non-breast malignancy other than basal or squamous carcinoma of the skin and carcinoma in situ of the cervix, or death from any cause. The percentage of participants free of DFS events (i.e., the DFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the final analysis with a 10-year maximum follow-up for DFS events. | Years 3, 5, 7, 8, 9, 10 | 
| Percentage of Participants With Overall Survival (OS) Events in Herceptin 1-Year Arm Compared to Observation: 1-Year Median Follow-Up | OS events referred to death from any cause. The percentage of participants who died was reported. The analysis of the Herceptin 1-Year Arm against the Observation Arm after 1-year median follow-up, as reported below, was performed by the Sponsor in 2006 following database cleaning. The analysis of the Herceptin 2-Year Arm against the Observation Arm was performed for an IDMC in 2005 at a time the Sponsor was blinded. Therefore, these data are reported under a separate Outcome Measure. | From Baseline until time of event (median of 1 year) | 
| Percentage of Participants With OS Events in Herceptin 2-Year Arm Compared to Observation: 1-Year Median Follow-Up | OS events referred to death from any cause. The percentage of participants who died was reported. The analysis of the Herceptin 2-Year Arm against the Observation Arm after 1-year median follow-up, as reported below, was performed for an IDMC in 2005 at a time the Sponsor was blinded. The analysis of the Herceptin 1-Year Arm against the Observation Arm was performed by the Sponsor in 2006 following database cleaning. Therefore, these data are reported under a separate Outcome Measure. | From Baseline until time of event (median of 1 year) | 
| OS Rate According to Kaplan-Meier Analysis in Herceptin 1-Year Arm Compared to Observation: 1-Year Median Follow-Up | OS events referred to death from any cause. The percentage of participants alive (i.e., the OS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 1-year median follow-up analysis. The analysis of the Herceptin 1-Year Arm against the Observation Arm after 1-year median follow-up, as reported below, was performed by the Sponsor in 2006 following database cleaning. The analysis of the Herceptin 2-Year Arm against the Observation Arm was performed for an IDMC in 2005 at a time the Sponsor was blinded. Therefore, these data are reported under a separate Outcome Measure. | Year 2 | 
| OS Rate According to Kaplan-Meier Analysis in Herceptin 2-Year Arm Compared to Observation: 1-Year Median Follow-Up | OS events referred to death from any cause. The percentage of participants alive (i.e., the OS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 1-year median follow-up analysis. The analysis of the Herceptin 2-Year Arm against the Observation Arm after 1-year median follow-up, as reported below, was performed for an IDMC in 2005 at a time the Sponsor was blinded. The analysis of the Herceptin 1-Year Arm against the Observation Arm was performed by the Sponsor in 2006 following database cleaning. Therefore, these data are reported under a separate Outcome Measure. | Year 2 | 
| Percentage of Participants With OS Events Compared to Observation: 8-Year Median Follow-Up | OS events referred to death from any cause. The percentage of participants who died was reported. | From Baseline until time of event (median of 8 years) | 
| OS Rate According to Kaplan-Meier Analysis Compared to Observation: 8-Year Median Follow-Up | OS events referred to death from any cause. The percentage of participants alive (i.e., the OS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 8-year median follow-up analysis. | Years 3, 5, 7, 8 | 
| Percentage of Participants With OS Events Compared to Observation: 11-Year Median Follow-Up | OS events referred to death from any cause. The percentage of participants who died was reported. | From Baseline until time of event (median of 11 years) | 
| OS Rate According to Kaplan-Meier Analysis Compared to Observation: 11-Year Median Follow-Up | OS events referred to death from any cause. The percentage of participants alive (i.e., the OS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the final analysis with an 11-year median follow-up for OS events. | Years 3, 5, 7, 9, 10, 11, 12 | 
| Percentage of Participants With OS Events in 1-Year Versus 2-Year Herceptin: 11-Year Median Follow-Up | OS events referred to death from any cause. The percentage of participants who died was reported. | From Baseline until time of event (median of 11 years) | 
| OS Rate According to Kaplan-Meier Analysis in 1-Year Versus 2-Year Herceptin: 11-Year Median Follow-Up | OS events referred to death from any cause. The percentage of participants alive (i.e., the OS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the final analysis with an 11-year median follow-up for OS events. | Years 3, 5, 7, 9, 10, 11, 12 | 
| Percentage of Participants With Recurrence-Free Survival (RFS) Events Compared to Observation: 8-Year Median Follow-Up | RFS events included local, regional, or distant tumor recurrence. The percentage of participants with at least one RFS event was reported. | From Baseline until time of event (median of 8 years) | 
| RFS Rate According to Kaplan-Meier Analysis Compared to Observation: 8-Year Median Follow-Up | RFS events included local, regional, or distant tumor recurrence. The percentage of participants free of RFS events (i.e., the RFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 8-year median follow-up analysis. | Years 3, 5, 7, 8 | 
| Percentage of Participants With RFS Events in 1-Year Versus 2-Year Herceptin: 8-Year Median Follow-Up | RFS events included local, regional, or distant tumor recurrence. The percentage of participants with at least one RFS event was reported. | From Baseline until time of event (median of 8 years) | 
| RFS Rate According to Kaplan-Meier Analysis in 1-Year Versus 2-Year Herceptin: 8-Year Median Follow-Up | RFS events included local, regional, or distant tumor recurrence. The percentage of participants free of RFS events (i.e., the RFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 8-year median follow-up analysis. | Years 3, 5, 7, 8 | 
| Percentage of Participants With Distant Disease-Free Survival (DDFS) Events Compared to Observation: 8-Year Median Follow-Up | DDFS events included distant tumor recurrence, second primary cancer, or contralateral breast cancer. The percentage of participants with at least one DDFS event was reported. | From Baseline until time of event (median of 8 years) | 
| DDFS Rate According to Kaplan-Meier Analysis Compared to Observation: 8-Year Median Follow-Up | DDFS events included distant tumor recurrence, second primary cancer, or contralateral breast cancer. The percentage of participants free of DDFS events (i.e., the DDFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 8-year median follow-up analysis. | Years 3, 5, 7, 8 | 
| Percentage of Participants With DDFS Events in 1-Year Versus 2-Year Herceptin: 8-Year Median Follow-Up | DDFS events included distant tumor recurrence, second primary cancer, or contralateral breast cancer. The percentage of participants with at least one DDFS event was reported. | From Baseline until time of event (median of 8 years) | 
| DDFS Rate According to Kaplan-Meier Analysis in 1-Year Versus 2-Year Herceptin: 8-Year Median Follow-Up | DDFS events included distant tumor recurrence, second primary cancer, or contralateral breast cancer. The percentage of participants free of DDFS events (i.e., the DDFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 8-year median follow-up analysis. | Years 3, 5, 7, 8 | 
| Percentage of Participants With Tumor Recurrence (TR) Compared to Observation: 8-Year Median Follow-Up | The percentage of participants with TR of the present breast cancer was reported. TR included local, regional, or distant tumor ignoring contralateral breast cancer and second non-breast malignancy. | From Baseline until time of event (median of 8 years) | 
| TR-Free Rate According to Kaplan-Meier Analysis Compared to Observation: 8-Year Median Follow-Up | The percentage of participants without TR of the present breast cancer (i.e., the TR-free rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 8-year median follow-up analysis. TR included local, regional, or distant tumor ignoring contralateral breast cancer and second non-breast malignancy. | Years 3, 5, 7, 8 | 
| Percentage of Participants With TR in 1-Year Versus 2-Year Herceptin: 8-Year Median Follow-Up | The percentage of participants with TR of the present breast cancer was reported. TR included local, regional, or distant tumor ignoring contralateral breast cancer and second non-breast malignancy. | From Baseline until time of event (median of 8 years) | 
| TR-Free Rate According to Kaplan-Meier Analysis in 1-Year Versus 2-Year Herceptin: 8-Year Median Follow-Up | The percentage of participants without TR of the present breast cancer (i.e., the TR-free rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 8-year median follow-up analysis. TR included local, regional, or distant tumor ignoring contralateral breast cancer and second non-breast malignancy. | Years 3, 5, 7, 8 | 
| Percentage of Participants With Distant Tumor Recurrence (DTR) Compared to Observation: 8-Year Median Follow-Up | The percentage of participants with DTR was reported. DTR included distant tumors ignoring local and regional recurrences, contralateral breast cancer, and second non-breast malignancy. | From Baseline until time of event (median of 8 years) | 
| DTR-Free Rate According to Kaplan-Meier Analysis Compared to Observation: 8-Year Median Follow-Up | The percentage of participants without DTR (i.e., the DTR-free rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 8-year median follow-up analysis. DTR included distant tumors ignoring local and regional recurrences, contralateral breast cancer, and second non-breast malignancy. | Years 3, 5, 7, 8 | 
| Percentage of Participants With DTR in 1-Year Versus 2-Year Herceptin: 8-Year Median Follow-Up | The percentage of participants with DTR was reported. DTR included distant tumors ignoring local and regional recurrences, contralateral breast cancer, and second non-breast malignancy. | From Baseline until time of event (median of 8 years) | 
| DTR-Free Rate According to Kaplan-Meier Analysis in 1-Year Versus 2-Year Herceptin: 8-Year Median Follow-Up | The percentage of participants without DTR (i.e., the DTR-free rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 8-year median follow-up analysis. DTR included distant tumors ignoring local and regional recurrences, contralateral breast cancer, and second non-breast malignancy. | Years 3, 5, 7, 8 | 
| Percentage of Participants With Restricted Disease-Free Survival (RDFS) Events in 1-Year Versus 2-Year Herceptin: 8-Year Median Follow-Up | RDFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer, or death from any cause. The percentage of participants with at least one RDFS event was reported. | From Baseline until time of event (median of 8 years) | 
| RDFS Rate According to Kaplan-Meier Analysis in 1-Year Versus 2-Year Herceptin: 8-Year Median Follow-Up | RDFS events included loco-regional or distant recurrence of breast cancer, development of contralateral breast cancer, or death from any cause. The percentage of participants free of RDFS events (i.e., the RDFS rate) and corresponding 95% CI were estimated by Kaplan-Meier analysis based on available data at the time of the 8-year median follow-up analysis. | Years 3, 5, 7, 8 | 
| Percentage of Participants With Primary Cardiac Endpoint Events Compared to Observation: 10-Year Maximum Follow-Up | Primary cardiac endpoint events included the occurrence of any of the following between randomization and new therapy for recurrent disease: symptomatic New York Heart Association (NYHA) Class III or IV congestive heart failure (CHF) confirmed by a cardiologist with a drop in left ventricular ejection fraction (LVEF) at least 10 percentage points from Baseline and to a value less than (<) 50%, and documentation of definite or probable cardiac death. Definite cardiac death included CHF, myocardial infarction, or primary arrhythmia. Probable cardiac death included unexpected sudden death within 24 hours of a cardiac event (syncope, cardiac arrest, chest pain, infarction, arrhythmia) without documented etiology. The percentage of participants with at least one primary cardiac endpoint event was reported. The 95% CI was calculated by the Pearson-Clopper method for a one-sample binomial. | From Baseline until time of event (maximum up to 10 years) | 
| Percentage of Participants With Secondary Cardiac Endpoint Events Compared to Observation: 10-Year Maximum Follow-Up | Secondary cardiac endpoint events included NYHA Class I or II CHF with a drop in LVEF measured by multiple-gated acquisition or electrocardiogram, unless the subsequent assessment of LVEF indicated a return to levels that did not meet the definition of a significant LVEF drop. A significant LVEF drop was defined as an absolute reduction of at least 10 percentage points from Baseline and to a value <50%. The percentage of participants with at least one secondary cardiac endpoint event was reported, excluding those with both a primary and secondary cardiac endpoint event. The 95% CI was calculated by the Pearson-Clopper method for a one-sample binomial. | From Baseline until time of event (maximum up to 10 years) |