Neoadjuvant imatinib in advanced primary or locally recurrent dermatofibrosarcoma protuberans: a multicenter phase II DeCOG trial with long-term follow-up.

PURPOSE: Dermatofibrosarcoma protuberans (DFSP) is a rare cutaneous tumor. COL1A1-PDGFB gene fusion is frequent in DFSP, rendering tumor cell proliferation and survival dependent on PDGFRß (platelet-derived growth factor receptor ß) signaling. This trial investigated imatinib as neoadjuvant treatment of DFSP, including long-term follow-up. EXPERIMENTAL DESIGN: The primary endpoint of this multicenter phase II trial was response; secondary endpoints were safety, tumor relapse, and response biomarkers. Patients with advanced primary or locally recurrent DFSP and measurable disease by RECIST (response evaluation criteria in solid tumors) were eligible and received imatinib 600 mg/d until definitive surgery with histopathologic proof of tumor-free margins. RESULTS: Sixteen patients received imatinib, and 14 patients were evaluable for all endpoints. Median treatment duration was 3.1 months; median tumor shrinkage was 31.5%. Best overall response was 7.1% complete response (CR), 50.0% partial response (PR), 35.7% stable disease, and 7.1% progressive disease (PD). Toxicity was moderate with 25.0% grade 3 and 4 events. During a median follow-up of 6.4 years, one patient developed secondary resistance to imatinib but responded to second-line sunitinib. This patient also presented local recurrence, distant metastasis, and death from DFSP. Exploratory analysis showed that response to imatinib was associated with decreased tumor cellularity and formation of strong hyalinic fibrosis. Weak PDGFRB phosphorylation and pigmented-type DFSP were associated with nonresponse. Additional to PDGFRB, the kinases EGFR and insulin receptor were found activated in a high percentage of DFSPs. CONCLUSION: The neoadjuvant use of imatinib 600 mg/d in DFSP is efficacious and well tolerated. Long-term follow-up results do not definitely support smaller surgical margins after successful imatinib pretreatment, and presume that secondary resistance to imatinib might promote accelerated disease progression.

Characterization of mouse MAGE-derived H-2Kb-restricted CTL epitopes.

Immunogenic peptide epitopes from tumor-associated antigens serve as targets for cellular immune responses in numerous clinical trials for therapeutic vaccinations. From these it became evident that prevailing questions can only be addressed in animal models. Hence, problems arise from the fact that while for human melanoma many different immunogenic peptide epitopes are known, for mouse melanoma the available selection is very restricted. To overcome this limitation, we applied reverse immunology to identify Kb-restricted epitopes derived of mouse MAGE. Two epitopes which bind strongly to Kb were selected to test for their immunogenicity in vivo. Spleen cells from mice vaccinated by intradermal injection of mature dendritic cells pulsed with these peptides displayed reactivity to the respective epitopes as measured by enzyme-linked immunospot assays and tetramer staining. The processing and presentation of these epitopes was evident by the killing of melanoma cells by the vaccination-induced T cells. Moreover, intravenous challenge with syngeneic melanoma cells demonstrated the protective immunity induced by this vaccination. In summary, we demonstrate the immunogenicity of two Kb-restricted peptide epitopes derived from mouse MAGE proteins which may serve as valuable tool for preclinical evaluation of vaccination strategies.