title: Effectiveness of radiotherapy in myxoid sarcomas is associated with a dense vascular pattern.
abstract: OBJECTIVE
  Surgery and adjuvant radiotherapy (RT) have long been the standard treatment for most deep-seated sarcomas; however, since the randomized trial from the National Cancer Institute of Canada, which described similar local control for pre- vs. postoperative RT, both modalities are now widely accepted. As a group, sarcomas are classified as radiation resistant. The subgroup of myxoid liposarcoma (MLS), a sarcoma with a typical vascular crow's feet pattern, is highly radiosensitive, but a mechanism for this phenomenon is unknown. Here we describe our results with preoperative RT and propose a mechanism explaining the high sensitivity based on the distinctive vascularization pattern of MLS.
  
  
  METHODS
  Between 2002 and 2006, 31 sarcoma patients, including 10 with MLS, underwent preoperative RT at our institute. Resected specimens were histologically evaluated, focusing on classification, grade, and vascularization patterns.
  
  
  RESULTS
  Twenty sarcomas showed more than 80% pathologic response after preoperative RT. A pathologic complete response was found in all "pure" MLS specimens after preoperative RT (n = 8). There were no pathologic complete responses in the remaining sarcoma patients (n = 23), although 12 showed 80% to 90% pathologic response. In contrast to the remaining RT-resistant sarcomas, the highly responding specimens contained branching vasculature, partial thrombus formation and inflammation of medium sized arterioles, similar to the vascular changes in MLS.
  
  
  CONCLUSIONS
  Both MLS and sarcomas with MLS-like vasculature are highly radiosensitive. Radiation sensitivity may be explained by changes in medium-sized arterioles, obstructing the specific crow's feet vascularization and inducing hypoxia with secondary tumor cell death.
authors.affiliation: Department of Surgical Oncology, The Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands.
authors.forename: Ronald S A
authors.initials: RS
authors.lastname: de Vreeze
authors.forename: Daphne
authors.initials: D
authors.lastname: de Jong
authors.forename: Rick L
authors.initials: RL
authors.lastname: Haas
authors.forename: Fiona
authors.initials: F
authors.lastname: Stewart
authors.forename: Frits
authors.initials: F
authors.lastname: van Coevorden
mesh_terms: D000328:Adult; D000368:Aged; D002813:Chondrosarcoma / Q000145:classification / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D003131:Combined Modality Therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007890:Leiomyosarcoma / Q000145:classification / Q000473:pathology* / Q000532:radiotherapy* / Q000601:surgery; D018208:Liposarcoma, Myxoid / Q000145:classification / Q000473:pathology* / Q000532:radiotherapy* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology; D009367:Neoplasm Staging; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult