Abstract P6-10-01: Efficacy and safety of the therapeutic cancer vaccine tecemotide (L-BLP25) in early breast cancer: Results from a prospective, randomized, neoadjuvant phase-II study (ABCSG-34)
Authors: Singer CF , Pfeiler G , Hubalek M , Bartsch R , Stoeger H , Pichler A , Petru E , Greil R , Rudas M , Tea M-KM , Wette V , Petzer AL , Sevelda P , Egle D , Dubsky PC , Balic M , Tinchon C , Bago-Horvath Z , Frantal S , Michael G 
Published: March 2017

Background: Immune-based therapeutic strategies represent a promising approach in early and advanced breast cancer treatment. MUC1 glycoprotein is overexpressed and aberrantly glycosylated in over 90% of malignant breast cancer. It is involved in oncogenesis and confers resistance to anti-cancer therapies, thus representing a particularly promising target. Tecemotide is a MUC1-based therapeutic cancer vaccine. The aim of this trial was to investigate the efficacy and safety of preoperative tecemotide in primary breast cancer patients receiving neoadjuvant Standard-of-Care (SoC) treatment.

Patients and Methods: 400 patients with HER2-negative early breast cancer were recruited into this prospective, multicentre randomized 2-arm academic phase-II trial. Patients received preoperative SoC treatment with or without tecemotide therapy. Postmenopausal women with E+++, or E++ and Ki67 &lt;14%, and G1,2,X tumors received 6 months of letrozole as SoC. Postmenopausal patients with triple-negative, E- or E+, or E++ and Ki67 ≥14%, and with G3 tumors, and all premenopausal patients received 4 cycles of epirubicin/cyclophosphamide plus 4 cycles of docetaxel as SoC. Patients were additionally randomized to receive reverse or conventional sequence of epirubicin/cyclophosphamide and docetaxel. Primary endpoint was histopathological response measured by Residual Cancer Burden (RCB0/I vs RCBII/III) at the time of surgery. Secondary endpoints included pCR, efficacy of reverse versus conventional sequence chemotherapy, and safety.

Results: We did not observe a significant difference in RCB0/I rates between patients with (36.4%) and without (31.9%) tecemotide in the overall study population (p = 0.40), and in endocrine and chemotherapy treated subgroups (25.0% vs 13.3%, p = 0.17; 39.6% vs 37.8%, p = 0.75). Similarly, addition of tecemotide did not affect overall pCR rates (22.5% vs 17.4%, p = 0.23). RCB0/I rates were comparable regardless of docetaxel being given before or after epirubicin/cyclophosphamide (37.2% vs 40.1%, p = 0.61). Tecemotide addition was not associated with a worse toxicity profile (178 AEs, 57 SAEs vs 180 AEs, 48 SAEs based on patient incidence).

Conclusion: Immune-based targeting of MUC1 by tecemotide is safe but does not improve RCB and pCR rates in early SoC-treated breast cancer.

Citation Format: Singer CF, Pfeiler G, Hubalek M, Bartsch R, Stoeger H, Pichler A, Petru E, Greil R, Rudas M, Tea M-KM, Wette V, Petzer AL, Sevelda P, Egle D, Dubsky PC, Balic M, Tinchon C, Bago-Horvath Z, Frantal S, Michael G. Efficacy and safety of the therapeutic cancer vaccine tecemotide (L-BLP25) in early breast cancer: Results from a prospective, randomized, neoadjuvant phase-II study (ABCSG-34) [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 P6-10-01.