title: Possible misinterpretation of demarcated solid patterns of radiation fibrosis on CT scans as tumor recurrence in patients receiving hypofractionated stereotactic radiotherapy for lung cancer.
abstract: OBJECTIVE
  To retrospectively analyze opacity changes near primary lung cancer tumors irradiated by using hypofractionated stereotactic radiotherapy (HSRT) to determine the presence or absence of tumor recurrence.
  
  
  METHODS
  After review-board approval for a retrospective study, we examined data from 50 patients treated with curative intent for proven or highly suspected localized peripheral-lung cancer and followed up for at least 12 months. All patients had received 50 Gy in five fractions (80% isodose) and were followed up monthly with chest X-ray until clinical and X-ray findings stabilized. Follow-up computed tomography scans were performed 1 and 3 months after HSRT and thereafter at 3-month intervals during the first 2 years.
  
  
  RESULTS
  Median follow-up was 30.4 months (range, 12.0-73.8 months). Abnormal opacities that were suspicious for recurrent tumor appeared in 20 patients at a median of 20.7 months (range, 5.9-61.4 months). Only 3 patients were finally found to have recurrence; 14 were recurrence free but were suspected to have fibrosis, and findings for the other 3 patients were considered equivocal because of a short follow-up period (<or=6 months).
  
  
  CONCLUSIONS
  Radiation fibrosis, which may occur 1 year or longer after completion of HSRT, is difficult to distinguish from tumor recurrence. Even when opacities increase on follow-up radiologic scans, recurrence cannot be diagnosed conclusively based on image findings; biopsy occasionally is warranted.
authors: Department of Radiology, Ofuna Chuo Hospital Ofuna, Tokyo, Japan.
authors: Atsuya
authors: A
authors: Takeda
authors: Etsuo
authors: E
authors: Kunieda
authors: Toshiaki
authors: T
authors: Takeda
authors: Michio
authors: M
authors: Tanaka
authors: Naoko
authors: N
authors: Sanuki
authors: Hirofumi
authors: H
authors: Fujii
authors: Naoyuki
authors: N
authors: Shigematsu
authors: Atsushi
authors: A
authors: Kubo
mesh_terms: D000230:Adenocarcinoma / Q000532:radiotherapy / Q000601:surgery; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000601:surgery; D003937:Diagnosis, Differential; D003951:Diagnostic Errors; D019583:Dose Fractionation, Radiation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging*; D017564:Radiation Pneumonitis / Q000000981:diagnostic imaging*; D016634:Radiosurgery; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed