title: Cavity volume dynamics after resection of brain metastases and timing of postresection cavity stereotactic radiosurgery.
abstract: BACKGROUND
  An alternative treatment option to whole-brain irradiation after surgical resection of brain metastases is resection cavity stereotactic radiosurgery (SRS).
  
  
  OBJECTIVE
  To review the dynamics of cavity volume change after surgical resection with the goal of determining the optimal timing for cavity SRS.
  
  
  METHODS
  Preresection tumor, postresection/pre-SRS cavity, and post-SRS cavity volumes were measured for 68 cavities in 63 patients treated with surgery and postresection cavity SRS. Percent differences between volumes were calculated and correlation analyses were performed to assess volume changes before and after SRS.
  
  
  RESULTS
  For the majority of tumors, the postresection cavity volume was smaller than the preresection tumor volume by a median percent volume change of -29% (range, -82% to 1258%), with larger preresection tumors resulting in greater cavity shrinkage (P < .001). To determine the optimal timing for cavity SRS, we examined cavity volume dynamics by comparing the early postresection (postoperative days 0-3) and treatment planning magnetic resonance imaging scans (median time to magnetic resonance imaging, 20 days; range, 9-33 days) and found no association between the postresection day number and volume change (P = .75). The volume decrease resulting from tumor resection was offset by the addition of a 2-mm clinical target volume margin, which is our current technique.
  
  
  CONCLUSIONS
  The greatest volume change occurs immediately after surgery (postoperative days 0-3) with no statistically significant volume change occurring up to 33 days after surgery for most patients. Therefore, there is no benefit of cavity shrinkage in waiting longer than the first 1 to 2 weeks to perform cavity SRS.
authors.affiliation: Department of Radiation Oncology, Acibadem University School of Medicine, Istanbul, Turkey.
authors.forename: Banu
authors.initials: B
authors.lastname: Atalar
authors.forename: Clara Y H
authors.initials: CY
authors.lastname: Choi
authors.forename: Griffith R
authors.initials: GR
authors.lastname: Harsh
authors.forename: Steven D
authors.initials: SD
authors.lastname: Chang
authors.forename: Iris C
authors.initials: IC
authors.lastname: Gibbs
authors.forename: John R
authors.initials: JR
authors.lastname: Adler
authors.forename: Scott G
authors.initials: SG
authors.lastname: Soltys
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000473:pathology* / Q000601:surgery; D001932:Brain Neoplasms / Q000556:secondary / Q000601:surgery*; D016371:Cranial Irradiation / Q000009:adverse effects; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D016634:Radiosurgery / Q000379:methods*; D013997:Time Factors; D016896:Treatment Outcome; D047368:Tumor Burden; D055815:Young Adult