Each user is assigned a role which grants limited access and functionalities dependent upon that specific role. 4.9 Statistical methods 4.9.1 Rationale for study design In patients with HER2-positive breast cancer who receive neoadjuvant chemotherapy plus trastuzumab, the 3-year Kaplan-Meier estimates of RFS are 95.7% for patients that achieve a pCR versus 80.1% for patients that do not achieve a pCR (p=.02).24 For HER2-positive breast cancer patients that undergo surgery as a first intervention and are found to be node-positive, 5-year DFS rates are 72% for those with 4 or more positive lymph nodes and 78% for those with 1-3 positive lymph nodes. 15 Based on preliminary data, the combination of trastuzumab plus a CTL-eliciting HER2-derived peptide vaccine virtually eliminated recurrences. This study will investigate the combination of trastuzumab and nelipepimult-S+GM-CSF in an adequately powered randomized clinical trial. 4.9.2 Sample size determination The primary objective of this study is to compare DFS between the two treatment groups. The study will have a 3 year follow-up period. We anticipate a 3-year DFS of 80% in patients randomized to receive trastuzumab without the vaccine versus 95% in patients randomized to receive trastuzumab + nelipepimut-S+GM- 34 Protocol: 2014-0443 Version 2.1 Version Date: 11 April 2016 CSF (estimates are based on data from previous studies, section 1.2 and table 2).24-26 In order to detect a DFS difference of 0.15 using a one-sided alpha level of 0.05 with 80% power, assuming an accrual time of 2 years, follow-up time of 3 years and 5% loss to follow-up (2.5% in each group), 100 patients (50 in each arm) are required. The power computation was determined using PASS software package version 2005.