Background Based on the synergistic effect between immuno- and chemotherapy (CT), we have elaborated an autologous vaccine with dendritic cells loaded with patients´ own tumor antigens (lysate), and we have already demonstrated that the addition of the vaccines to a standard neoadjuvant CT schedule has increased total pCR (breast+ axilla) in stages II-III non-overexpressing HER2 breast cancer patients (Santisteban M, SABCS 2012). Both cohorts, the control (C) and the vaccinated (V) were well balanced related to demographic characteristics. Toxicity has been similar in both the C and the V cohorts. Moreover, we have analyzed the phenotypic changes in peripheral blood induced by the vaccine and its correlation with pathologic responses. Indeed, we have studied if the amount of lysate used to load the dendritic cells or the total dendritic cell numbers received by the patients in the first five doses (before surgery) is correlated with pCR Methods Twenty-eight patients with stage II-III HER2 negative breast cancer have started on sequential neoadjuvant CT based on dose dense antracyclines (E 100mg/m2 and C 600 mgr/m2) x4 cycles plus GM-CSF followed by taxanes (DOC 75-100 mgr/m2) x4 cycles plus vaccination. The C historic cohort was composed of thirty patients who received the same treatment except for the absence of the vaccines. Vaccine calendar was started after the 4th EC and alternated with DOC and as maintenance up to a maximum of a 2 year-period. The first 5 vaccines were administered before breast surgery. Changes in different lymphocytes populations were measured in peripheral blood of patients at different points by flow cytometry (absolute cell counts). To date, twenty-one patients have both determinations of lymphocyte subpopulations before the 1st and the 6th vaccine. Paired samples t-tests and Fisher exact were used Results pCR was superior in the V cohort (24% versus 3.3%, p = 0.04). Lymphocyte subpopulations were measured in peripheral blood (cells/uL) and a stimulation of the immune system was found after the 5 vaccines schedule at the time of surgery as follows: NK (p<0.001), T cytotoxic CD8 (p = 0.018), T helper CD4 (p = 0.04), CD19 (p = 0.001), HLADRCD8 (p = 0.007), CD16CD8 (p = 0.003), HLADRCD4 (p<0.001), CD16CD4 (p = 0.008) and T regulators lymphocytes (p = 0.004). We did not find any differences among CD57CD8 (p = 0.17), CD56CD8 (p = 0.11), CD57CD4 (p = 0.45) and CD56CD4 (p = 0.65). We neither see correlation among the amount of lysate to load dendritic cells and the tpCR (p = 0.09) nor the amount of dendritic cells (summatory of 5 vaccines) administered intradermally and the pCR (p = 0.59) Conclusions Immunotherapy added to standard neoadjuvant CT could improve total pCR in stage II-III non-overexpressing HER2 breast cancer patients. After 5 doses of vaccination plus chemotherapy, we can observe phenotypic changes in peripheral blood: some immune system subpopulations increased statistically after the treatment in vaccinated patients. Neither the amount of lysate nor the number of dendritic cells used in the five first vaccines significantly correlated with the pRC.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-13-04.