[Histologic Remission following Neoadjuvant Immunotherapy in a Patient with Lynch-Syndrome and Primarily Unresectable Relapse of Rectum Carcinoma].

Clinical History A 43-year-old male patient was diagnosed to have rectum carcinoma cT4N2M0 with underlying Lynch-Syndrome. After initializing neoadjuvant radio-chemotherapy followed by operation, the patient presents with an extensive locoregional relapse within a short time. In order to achieve resectability, a second line treatment with FOLFOXIRI protocol in addition to Bevacizumab was conducted. However, after completing six cycles of this intensiv treatment protocol, the tumour showed further progression. Clinical Course Having no evidence of distance metastasis, we decided to initiate off-label use of Pembrolizumab, a PD-1-receptor inhibitor. Clinical symptoms decreased rapidly and after receiving six cycles, PET/CT imaging showed regression. The side effects were limited to subclinical autoimmune thyroiditis. After re-operation no evidence of malignancy were found in the resectates of exenteration of the pelvis. Currently the patient is capable of working with only limited symptoms. Conclusion Pembrolizumab offers new treatment options for patients with DNA-repair-deficiency mismatch, e. g. Lynch-Syndrome. A phase II study already showed effectiveness in this particular group of patients. The striking and unexpected histo-pathologic results showing full remission should draw attention to the use of Pembrolizumab in neoadjuvant settings.