title: Critical organ preservation in reirradiation brachytherapy by injectable spacer.
abstract: OBJECTIVE
  This case series study evaluated the feasibility and effectiveness of an interstitial high-dose rate brachytherapy (HDR-BT) procedure combined with an at-risk organ-sparing procedure.
  
  
  METHODS
  Thirty patients who were scheduled for reirradiation treatment for recurrent cancer after receiving a median dose of 60 Gy (range, 44-70 Gy) in 2-Gy fractions of previous external beam treatment were enrolled. Thirteen patients had lesions in the head and neck, and other lesions were located in the axilla, skeleton, breast, pelvis, and abdominal wall. Chief complaints included local masses (for 25) and refractory pain (for 21). After high-dose rate brachytherapy applicator needle implantation, an optimal CT-based three-dimensional brachytherapy plan was created with a virtual at-risk organ shift from the target. According to the plan, hyaluronic acid gel was injected to maintain the shift during irradiation. The prescribed dose was the result of an individualized tradeoff between target dose and at-risk organ dose, to avoid serious complications. A single-fraction dose of 18.0 Gy (median, equivalent to 75.6 Gy at an alpha/beta value of 3; range, 16-20 Gy) was applied to the tumor.
  
  
  RESULTS
  The at-risk organ dose decreased from 9.1 +/- 0.9 Gy to 4.4 +/- 0.4 Gy (mean +/- standard deviation, p < 0.01), and the normal tissue complication probability decreased from 60.8% +/- 12.6% to 16.1% +/- 19.8% (p < 0.01). The shift effect lasted at least 4 hours and disappeared gradually. Distinct tumor shrinkage in 20 of 21 eligible patients, including tumor disappearance in 6 patients, pain reduction in 18 of 21 eligible patients, and no unexpected late toxicity greater than grade 2 were observed during the 19.5-month observation period.
  
  
  CONCLUSIONS
  This at-risk organ-sparing preservation procedure may provide a safe and efficient reirradiation treatment.
authors.affiliation: Department of Radiology, Wakayama Medical University, Wakayama City, 641-8510 Japan. Kazushi.kishi@gmail.com
authors.forename: Kazushi
authors.initials: K
authors.lastname: Kishi
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Sonomura
authors.forename: Shintaro
authors.initials: S
authors.lastname: Shirai
authors.forename: Morio
authors.initials: M
authors.lastname: Sato
authors.forename: Kayo
authors.initials: K
authors.lastname: Tanaka
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001859:Bone Neoplasms / Q000532:radiotherapy; D001918:Brachytherapy / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D001943:Breast Neoplasms / Q000532:radiotherapy; D005240:Feasibility Studies; D005260:Female; D005782:Gels; D006258:Head and Neck Neoplasms / Q000532:radiotherapy; D006801:Humans; D006820:Hyaluronic Acid / Q000008:administration & dosage* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology / Q000532:radiotherapy*; D010148:Intractable Pain / Q000532:radiotherapy; D011336:Probability; D011832:Radiation Injuries / Q000517:prevention & control*; D011836:Radiation Tolerance; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012074:Remission Induction / Q000379:methods; D019233:Retreatment; D012878:Skin Neoplasms / Q000532:radiotherapy; D047368:Tumor Burden
chemical_list: D005782:Gels; D006820:Hyaluronic Acid