title: Low-dose external beam radiotherapy as a postoperative treatment for patients with diffuse pigmented villonodular synovitis of the knee: 4 recurrences in 23 patients followed for mean 9 years.
abstract: OBJECTIVE
  Pigmented villonodular synovitis (PVNS) is a rare proliferative disorder involving synovial membranes, and patients with PVNS have a variable prognosis. We retrospectively analyzed clinical outcomes after synovectomy plus low-dose external beam radiotherapy for diffuse PVNS of the knee.
  
  
  METHODS
  We reviewed the medical records of 23 patients who underwent postoperative radiotherapy between 1998 and 2007. 19 patients had primary disease and 4 had recurrent disease with an average of 2.5 prior surgeries. After synovectomy (17 arthroscopic surgeries; 6 open), all 23 patients received 4-MV or 6-MV external beam radiotherapy with a median dose of 20 (12-34) Gy in 10 fractions.
  
  
  RESULTS
  At a median follow-up of 9 (0.8-12) years, 4 patients had recurrent disease, with a median disease-free interval of 5 years. Of these 4 patients, 3 received salvage synovectomy and regained local control. Univariate analysis showed that age, sex, history of trauma, and total dose of radiation were not predictive of local control. 22 patients reported excellent or good joint function, and 1 who refused salvage synovectomy had poor joint function. None of the patients experienced grade 3 or higher radiation-related toxicity or radiation-induced secondary malignancies.
  
  
  CONCLUSIONS
  Postoperative external beam radiotherapy is an effective and acceptable modality to prevent local recurrence and preserve joint function in patients with diffuse PVNS of the knee. Low-dose (20 Gy) radiotherapy appears to be as effective as moderate-dose treatment (around 35 Gy).
authors.affiliation: Department of Radiation Oncology, Asan Medical Center, University of Ulsan, College of Medicine, Seoul, Republic of Korea.
authors.forename: Geumju
authors.initials: G
authors.lastname: Park
authors.forename: Young Seok
authors.initials: YS
authors.lastname: Kim
authors.forename: Jong Hoon
authors.initials: JH
authors.lastname: Kim
authors.forename: Sang-wook
authors.initials: SW
authors.lastname: Lee
authors.forename: Si Yeol
authors.initials: SY
authors.lastname: Song
authors.forename: Eun Kyung
authors.initials: EK
authors.lastname: Choi
authors.forename: Seong Yoon
authors.initials: SY
authors.lastname: Yi
authors.forename: Seung Do
authors.initials: SD
authors.lastname: Ahn
mesh_terms: D000293:Adolescent; D000328:Adult; D001182:Arthroscopy / Q000379:methods; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011182:Postoperative Care / Q000379:methods*; D012189:Retrospective Studies; D055502:Secondary Prevention; D013586:Synovitis, Pigmented Villonodular / Q000532:radiotherapy* / Q000601:surgery; D055815:Young Adult