Observation Only Study Involving Participants Enrolled in the CHAT Trial

The aim of the CHAT study ("An open-label, randomized Phase II study of Herceptin (trastuzumab), Taxotere® (docetaxel) and Xeloda (capecitabine) in combination, versus Herceptin (trastuzumab) plus Taxotere® (docetaxel), in patients with advanced and/or metastatic breast cancers that overexpress HER2") was to test the combination of Trastuzumab and Docetaxel with or without capecitabine as first-line therapy for HER2 positive locally advanced or metastatic breast cancer.

Overall Response Rate was the primary endpoint of the CHAT study. This study failed to meet its primary objective of showing a difference between the treatment groups, with equivalent high response rates for the Trastuzumab plus Docetaxel and Trastuzumab, Docetaxel plus capecitabine arms.

Secondary endpoints in the CHAT study were Progression-Free-Survival, Time-to-Progression, Overall Survival, duration of response and safety profile. Whilst analysis of the existing data is consistent with improvement with the triplet therapy, interpretation is compromised by the relatively short median follow-up of 24 months. In hindsight the statistical design was flawed by selection of a sub optimal primary endpoint and consequently data was collected and analysed early in relation to time-dependent endpoints. Beyond CHAT will permit capture of mature data for time-related endpoints. Time-to-Progression and Overall Survival are the co-primary endpoints for the Beyond CHAT protocol. The impact of treatment following the first progression, on survival, will be explored.

Time-to-Progression will be defined from the time interval between the date of randomisation and the occurrence of progressive disease under therapy according to RECIST criteria.

Overall Survival will be defined as the time from date of randomisation to date of death