title: Safety and efficacy of external beam radiation therapy for non-Hodgkin lymphoma in patients with prior 90Y-ibritumomab tiuxetan radioimmunotherapy.
abstract: BACKGROUND
  Non-Hodgkin lymphomas (NHL) are radiosensitive tumors. Recent trials have demonstrated the effectiveness of beta irradiation delivered by monoclonal antibodies conjugated to radioisotopes such as yttrium-90 or iodine-131. Many patients eventually relapse after radioimmunotherapy (RIT) and require additional treatment. The goal of this study was to determine the safety and efficacy of external beam radiation therapy (EBRT) delivered after RIT.
  
  
  METHODS
  We reviewed the records of 135 patients with relapsed B-cell NHL who had received RIT with 90Y-ibritumomab tiuxetan to identify patients who subsequently received EBRT. The response rates and radiation-induced toxicity from the EBRT were assessed.
  
  
  RESULTS
  Nineteen of 135 (14%) patients received EBRT to a total of 39 tumor sites. Complete radiation therapy records were available for 16 patients (36 tumor sites), which formed the basis for this analysis. The median EBRT dose was 28.5 Gy (range, 10-40 Gy), with a median fraction size of 2 Gy (range, 1-5 Gy). Response data were available for 29 treated sites. The overall response rate was 90% (26/29) with 12 complete responses (41%), 7 complete clinical responses (24%), 7 partial responses (24%), and 3 stable (10%). Toxicities were generally transient, reversible, and corresponded to the anatomic regions irradiated.
  
  
  CONCLUSIONS
  EBRT can produce tumor responses at sites of NHL that relapse after RIT with acceptable toxicity.
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: Terry E
authors.initials: TE
authors.lastname: Justice
authors.forename: James A
authors.initials: JA
authors.lastname: Martenson
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Wiseman
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Witzig
mesh_terms: D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008228:Lymphoma, Non-Hodgkin / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D016499:Radioimmunotherapy / Q000009:adverse effects; D012189:Retrospective Studies; D016896:Treatment Outcome; D015021:Yttrium Radioisotopes / Q000627:therapeutic use
chemical_list: D000911:Antibodies, Monoclonal; D015021:Yttrium Radioisotopes; C422802:ibritumomab tiuxetan