Lea Lowenfeld, Rosemarie Mick, Jashodeep Datta, Shuwen Xu, Elizabeth Fitzpatrick, Carla S. Fisher, Kevin R. Fox, Angela DeMichele, Paul J. Zhang, Susan P. Weinstein, Robert E. Roses, Brian J. Czerniecki

Vaccination with HER2 peptide-pulsed DC1s stimulates a HER2 specific T-cell response. This randomized trial aimed to establish safety and evaluate immune and clinical responses to vaccination via intralesional (IL), intranodal (IN), or both intralesional and intranodal (ILN) injection. Fifty-four HER2(pos) patients (42 pure DCIS, 12 early invasive breast cancer (IBC)) were enrolled in a neoadjuvant HER2 peptide-pulsed DC1 vaccine trial. Patients were randomized to IL (n=19), IN (n=19), or ILN (n=16) injection. Immune responses were measured in peripheral blood and sentinel lymph nodes by ELISPOT or in-vitro sensitization assay. Pathologic response was assessed in resected surgical specimens. Vaccination by all injection routes was well-tolerated. There was no significant difference in immune response rates by vaccination route (IL 84.2% vs. IN 89.5% vs. ILN 66.7%; p=0.30). The pathologic complete response (pCR) rate was higher in DCIS patients compared with IBC patients (28.6% vs. 8.3%). DCIS patients who achieved pCR (n=12) and who did not achieve pCR (n=30) had similar peripheral blood anti-HER2 immune responses. All patients who achieved pCR had an anti-HER2 CD4 immune response in the sentinel lymph node and the quantified response was higher by response repertoire (p=0.03) and cumulative response (p=0.04). Anti-HER2 DC1 vaccination is a safe and immunogenic treatment to induce tumor-specific T-cell responses in HER2(pos) patients; immune and clinical responses were similar independent of vaccination route. The immune response in the sentinel lymph nodes, rather than in the peripheral blood, may serve as an endpoint more reflective of anti-tumor activity.