Target Therapy of Unresectable or Metastatic Dermatofibrosarcoma Protuberans With Imatinib Mesylate: An Analysis on 22 Chinese Patients

Dermatofibrosarcoma protuberans (DFSP) is a rare, plaque-like tumor of the cutaneous tissue occurring more on the trunk than the extremities and neck. More than 95% of DFSP present anomalies on the 17q22 and 22q13 chromosomal regions leading to the fusion of COL1A1 and PDGFB genes. Surgery is the optimal treatment for DFSP, but less effective in locally advanced or metastatic patients, as is the case with chemotherapy and radiotherapy. The aim of this study was to assess retrospectively the therapeutic activity and safety of imatinib on 22 Chinese patients with locally inoperative or metastatic DFSP at a single institution. In the collected data of 367 Chinese patients with DFSP, we analyzed retrospectively 22 patients with locally advanced or metastatic DFSP, all of whom received imatinib therapy at 1 center from January 2009 to October 2014. Patients were administered with imatinib at an initial dose of 400 mg and escalated to 800 mg daily after they developed imatinib resistance. The median follow-up time was 36 months, and the median treatment time was 15 months. The results showed that 10 locally advanced DFSP patients and 12 metastatic DFSP patients received imatinib therapy. Apart from 1 patient who developed primary imatinib resistance, 15 patients achieved partial remission (PR), and 6 patients achieved stable disease (SD). Both fibrosarcomatous DFSP and classic DFSP patients demonstrated similar response to imatinib. Median PFS was estimated to be 19 months. Median overall survival (OS) has not been reached, and estimated 1- and 3-year OS rates were 95.5% (21/22) and 77.3% (17/22), respectively. Four out of 10 patients with primarily unresectable DFSP received complete surgical resection after neoadjuvant treatment of imatinib. Imatinib therapy is well tolerated with a safety profile and is the therapy of choice in locally inoperative or metastatic DFSP. Neoadjuvant treatment of locally advanced or metastatic DFSP with imatinib improves surgical outcomes and may facilitate resection of difficult tumors.