title: Case report: impressive response to pembrolizumab in a patient with mismatch-repair deficient metastasized colorectal cancer and bulky disease.
abstract: Here, we report the history of a 42-year-old female patient with sporadic mismatch-repair-deficient metastatic colorectal cancer and abdominal bulky disease, who received pembrolizumab (200 mg every 3 weeks) after the failure of third-line treatment. Restaging 3 months after initiation of treatment revealed a striking response with shrinkage of the bulky peritoneal tumour mass (baseline size 11×11×14 cm) to nearly 25% of the original tumour volume (6.2×7.1×10.4 cm). Restaging 8 months after initiation showed further downsizing of the tumour mass (5.5×7.0×8.0 cm). Tumour markers CEA and CA 19-9 decreased to normal levels, haemoglobin level increased from 8 to 13 mg/dL and her overall clinical performance status increased from ECOG 3 to 1 within 3 months. Therapy with pembrolizumab was continued and is still ongoing. We emphasise the importance of testing for mismatch-repair status in metastatic disease.
authors.affiliation: Clinical Division of Oncology, Department of Medicine I, Medical University Vienna, Vienna, Austria.
authors.forename: Markus
authors.initials: M
authors.lastname: Kieler
authors.affiliation: Clinical Division of Oncology, Department of Medicine I, Medical University Vienna, Vienna, Austria.
authors.forename: Werner
authors.initials: W
authors.lastname: Scheithauer
authors.affiliation: Clinical Division of Oncology, Department of Medicine I, Medical University Vienna, Vienna, Austria.
authors.forename: Christoph C
authors.initials: CC
authors.lastname: Zielinski
authors.affiliation: Department of Pathology and Clinical Bacteriology, Wilhelminenspital, Vienna, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Chott
authors.affiliation: Department of Radiology, Medical University Vienna, Vienna, Austria.
authors.forename: Ali
authors.initials: A
authors.lastname: Al-Mukhtar
authors.affiliation: Clinical Division of Oncology, Department of Medicine I, Medical University Vienna, Vienna, Austria. Electronic address: gerald.prager@meduniwien.ac.at.
authors.forename: Gerald
authors.initials: G
authors.lastname: Prager
keywords: Mismatch-repair-deficiency; PD-1-blockade; Pembrolizumab; bulky disease; colon cancer