Lapatinib Plus Capecitabine Versus Trastuzumab Plus Capecitabine in ErbB2 (HER2) Positive Metastatic Breast Cancer

CNS relapse is defined as the appearance of >=1 enhancing lesion measuring >=6 millimeters (mm) on T1Weighted (T1W) Magnetic Resonance Imaging (MRI) without CNS symptoms that were considered to be unequivocal based on all relevant radiological features (e.g., associated T2W signal abnormality); the appearance of any enhancing lesion on T1W MRI with CNS symptoms; unequivocal finding of leptomeningeal disease (defined as the dissemination of cancer throughout the spinal fluid), with or without symptoms; and unequivocal finding of multifocal intraparenchymal lesions with or without symptoms. In the event of the appearance of a <6 mm lesions(s) without CNS lesions, or equivocal findings potentially suggesting leptomeningeal disease, these findings were followed with a subsequent scan within 6 weeks. If unequivocal progression was determined with the subsequent scan and/or CNS symptoms occurred, then CNS relapse crieria were met.

PFS is defined as the interval between the date of randomization and the earliest date of progressive disease (PD), or death due to any cause. PD is defined as at least a 20% increase in the sum of the longest diameter (LD) of target lesions, compared with the smallest sum LD recorded since the treatment started, or the appearance of 1 or more new lesions based on investigator assessment of both CNS and non-CNS for response.

CNS relapse is defined as the appearance of >=1 enhancing lesion measuring >=6 mm on T1W MRI without CNS symptoms that were considered to be unequivocal based on all relevant radiological features (e.g., associated T2W signal abnormality); the appearance of any enhancing lesion on T1W MRI with CNS symptoms; unequivocal finding of leptomeningeal disease (defined as the dissemination of cancer throughout the spinal fluid), with or without symptoms; and unequivocal finding of multifocal intraparenchymal lesions with or without symptoms. In the event of the appearance of a <6 mm lesions(s) without CNS lesions, or equivocal findings potentially suggesting leptomeningeal disease, these findings were followed with a subsequent scan within 6 weeks. If unequivocal progression was determined with the subsequent scan and/or CNS symptoms occurred, then CNS relapse crieria were met.

Overall survival is defined as the time from randomization until death due to any cause or to the date of censor. In the absence of confirmation of death, survival time was to be censored at the time of the last investigator contact.

OR is defined as the number of participants with either a confirmed complete response (CR; disappearance of all target lesions) or partial response (PR: at least a 30% decrease in the sum of the LD of the target lesions, compared with the baseline sum LD). CR and PR were assessed per Response Evaluation Criteria in Solid Tumors (RECIST). To be assigned a status of PR or CR, a confirmatory disease assessment was to be performed 28 days (4 weeks) or greater after the criteria for response were first met. In addition, a bone scan must have been obtained to rule out the presence of new bone lesions or progression of existing bone lesions, even if the participant had no bone lesions present at Baseline. If a bone scan was performed at the time of initial response or near the time of response, the bone scan did not need to be repeated.

CB is defined as the number of participants with evidence of confirmed CR (disappearance of all target lesions) or PR (at least a 30% decrease in the sum of the LD of the target lesions, compared with the baseline sum LD) at any time or stable disease (SD, neither sufficient shrinkage to qualify for a PR nor sufficient increase to qualify for PD [defined as at least a 20% increase in the sum of the LD of target lesions, compared with the smallest sum LD recorded since the treatment started, or the appearance of 1 or more new lesions] based on investigator assessment), for at least 24 weeks.

Duration of response is defined as the time from the first documented evidence of CR (disappearance of all target lesions) or PR (at least a 30% decrease in the sum of the LD of the target lesions, compared with the baseline sum LD) until the first documented sign of PD (at least a 20% increase in the sum of the LD of target lesions, compared with the smallest sum LD recorded since the treatment started, or the appearance of 1 or more new lesions) or death due to breast cancer. In the absence of confirmation of death, survival time was to be censored at the time of the last investigator contact.

CNS progression was documented by a brain scan and was indicated by the investigator on the follow-up electronic Case Report Form. CNS relapse is defined as the appearance of >=1 enhancing lesion measuring >=6 mm on T1W MRI without CNS symptoms that were considered to be unequivocal based on all relevant radiological features (e.g., associated T2W signal abnormality); the appearance of any enhancing lesion on T1W MRI with CNS symptoms; unequivocal finding of leptomeningeal disease, with or without symptoms; and unequivocal finding of multifocal intraparenchymal lesions with or without symptoms. In the event of the appearance of a <6 mm lesions(s) without CNS lesions, or equivocal findings potentially suggesting leptomeningeal disease, these findings were followed with a subsequent scan within 6 weeks. If unequivocal progression was determined with the subsequent scan and/or CNS symptoms occurred, then CNS relapse crieria were met.

Qualitative and quantitative toxicities were measured as AEs. See the outcome measure entitled "Number of participants with the indicated Grade 3 or Grade 4 Adverse Events (AEs) occurring in >=2 participants in either treatment arm" and the AE module of this results summary for a list of AEs occurring in the study. An AE is defined as any untoward medical occurrence in a participant administered a pharmaceutical product and which does not necessarily have a causal relationship with this treatment.

Because the study terminated early, pharmacogenetic and biomarker analyses were not performed.

An AE is defined as any untoward medical occurrence in a participant administered a pharmaceutical product and which does not necessarily have a causal relationship with this treatment. The Investigator assessed whether the AE was related to study drug. AEs were graded using the Common Toxicity Criteria from the Cancer Therapy Evaluation Program, Division of Cancer Therapy, National Cancer Institute. Grades: 0=No AE or within normal limits; 1=Mild AE; 2=Moderate AE; 3=Severe and undesirable AE; 4=Life-threatening or disabling AE; 5=Death related to AE.