The results of this large investigation are consistent with those of most previous studies, and do not support the hypothesis that electric blanket use is associated with increased breast cancer risk.

Introduction: We are conducting a phase II clinical trial of the GP2+GM-CSF vaccine for the prevention of breast cancer recurrence in disease-free, node-positive or high-risk node negative patients (pts). GP2 is an HLA-A2+-restricted immunogenic peptide from the HER2 protein (aa: 654-662) capable of stimulating CD8+ cytotoxic T-lymphocytes (CTLs) to recognize and destroy HER2-expressing tumor cells. Here, we present the final pre-specified analysis of our study, disease free survival (DFS) at one year from last enrolled pt. Methods: The trial is a prospective, randomized, multi-center, placebo-controlled, single-blinded, phase I/II trial designed to evaluate the safety and clinical efficacy of GP2 in breast cancer patients. Pts with any level of HER2 (immunohistochemistry [IHC] 1-3+) expression were enrolled after standard of care therapy. Blinded HLA-A2+ pts were randomized 1:1 to receive GP2 + GM-CSF or GM-CSF alone. Pts in both treatment arms received 6 monthly intradermal inoculations during the primary vaccine series (PVS) followed by 4 booster inoculations administered every 6 months. Data was collected for demographic, safety, immunologic, and clinical recurrence. Per the statistical plan, DFS was analyzed for both intention-to-treat population (ITT; all randomized pts) and per-treatment population (PT; excluding recurrences during the PVS and second malignancies) using Kaplan-Meir methods. Continuous variables are compared using analysis of variance techniques and proportions compared with Fisher's exact test. Results: This trial enrolled 180 pts (vaccine group n=89 and control group n=91). There were no differences in age, grade, hormone receptor status, tumor size or nodal status between groups (all p>0.2). With median follow up of 36.2 months, the five-year DFS estimates did not demonstrate a difference between vaccinated (VG) and control groups (CG) with ITT (82.6% v 80.4%, p=0.96, respectively) or PT (88.9% v 84.3%, p=0.52, respectively). On further subset analysis, in HER2 3+ by IHC (or positive via FISH) pts, ITT analysis showed a DFS of 93.8% v 87.2% (VG, n=50 v CG, n=51; p=0.67, respectively) while the PT analysis revealed a DFS of 100% v 87.2% (VG, n=48 v CG, n=50; p=0.052, respectively). In ER/PR+ pts, ITT analysis showed a DFS of 88.1% v 80.6% (VG, n=54 v CG, n=60; p=0.41, respectively) while PT analysis demonstrated a DFS of 91.5% v 85.2% (VG, n=52 v CG, n=57; p=0.42, respectively). Conclusions: The final pre-specified analysis of this randomized phase II trial of the GP2+GM-CSF adjuvant breast cancer vaccine shows no statistical differences between treatment arms. However, it does identify a particular patient population where the vaccine may have efficacy; HER2 3+ patients appear to derive the greatest clinical benefit from GP2 vaccination after trastuzumab treatment with the PT analysis nearing statistical significance. Further studies are required to confirm these findings and investigate the potential link between hormone receptor status and the induction of clinically beneficial anti-tumor immunity with this vaccine. Citation Format: Greene JM, Schneble EJ, Perez S, Murray JL, Berry JS, Trappey AF, Hale DF, Vreeland TJ, Clifton GT, Ardavanis A, Litton JK, Shumway NM, Papamichail M, Peoples GE, Mittendorf EA. Final pre-specified analysis of the phase II trial of the GP2+GM-CSF peptide vaccine in high risk breast cancer patients to prevent recurrence. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-11-01.

BACKGROUND FBP is overexpressed in 20-50% of breast(B) cancers(Ca) and roughly 90% of endometrial(E) and ovarian (Ov) Ca. E39 (FBP191-199, EIWTHSYKV)+GM-CSF is an HLA-A2 restricted FBP peptide vaccine, which has been shown to generate significant in vivo immunologic response(IR) in a phase I/IIa trial in E Ca and Ov Ca patients (pts). There is a risk of inducing immunologic tolerance after multiple inoculations with a highly immunogenic vaccine. Thus, we are investigating a novel vaccination series using combinations of E39 and E39' (EIWTFSTKV, an attenuated version of E39) in a phase Ib, randomized, single-center trial. We are assessing short and long-term IR. Here, we present the initial IR analysis to the primary vaccination series (PVS) within B Ca pts. METHODS HLA-A2 positive B or Ov Ca pts were enrolled after completion of standard of care therapy and randomized into three arms: EE (6 inoculations of E39); EE'(3 inoculations of E39, then 3 of E39'); or E'E(3 of E39', then 3 of E39). Theoretically, due to lower FBP expression and less aggressive chemotherapy regimens, B Ca pts are more antigen naïve and have a less suppressed immune system. Thus, only B Ca pts were included in this analysis. The PVS includes 6 inoculations total (R1-R6), one every 3-4 weeks, and containing 250mcg GM-CSF+500mcg peptide in the first 5 pts per arm and 1000mcg of peptide in second 5 pts. To assess the in vivo IR, local reaction(LR) was measured 48 hours after each inoculation (R1-R6), and delayed type hypersensitivity(DTH) was measured pre-PVS (R0), 1, and 6-months post-PVS (RC1, RC6). Ex vivo IR was measured via dextramer assay for E39-specific CD8+ T-cells at R0, RC1, and RC6. Statistical analyses were completed using appropriate tests. RESULTS Thirty-five B Ca pts were enrolled, with 27 completing the PVS (EE n=10, EE' n=8, E'E n=9). No clinicopathologic differences between groups or significant toxicities > grade 2 were appreciated. LR increased from R1 to R6 in all groups (ΔEE= 24.80mm, p=0.14; ΔEE'=38.13mm, p=0.07; ΔE'E=8.05mm, p=0.38), the greatest increase approaching statistical significance in the EE' arm. The only arm with a statistically significant increase for in vivo DTH from R0-RC1-RC6 was in the EE' arm (ΔEE=-6.17mm, p=0.27; ΔEE'= 44.58mm, p<0.05; ΔE'E=-1.42, p=0.37). Ex vivo analysis of IR revealed no significant difference between groups at R0(p=0.45) or RC6(p=0.72), nor within groups over time (EE p=0.32, EE' p=0.47, E'E p=0.30). CONCLUSION In this phase Ib trial analyzing the IR of B Ca pts receiving a different vaccination strategy, both peptides were noted to be safe and immunogenic. While no difference was seen in E39-specific CD8+ T cells between groups, the in vivo response was enhanced with the use of E39' after E39; this may indicate expansion of more effective clonal populations of CD8+ T cells with this strategy. These results may be specific to B Ca pts who are relatively antigen-naïve with relatively intact immune systems. Further analysis of these pts as this trial continues will determine the optimal vaccination strategy capable of stimulating and maintaining an IR to prevent B Ca recurrence. Citation Format: Jackson DO, Qiao N, Peace KM, Hale DF, Vreeland TJ, Greene JM, Berry JS, Trappey AF, Clifton GT, Ibrahim N, Toms A, Peoples GE, Mittendorf EA. Determining the optimal vaccination strategy using a combination of the folate binding protein (FBP) peptide vaccine (E39+GM-CSF) and an attenuated version (E39') to maximize the immunologic response in breast cancer patients [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-10-04.