title: Neoadjuvant androgen withdrawal therapy decreases local recurrence rates following tumor excision in the Shionogi tumor model.
abstract: OBJECTIVE
  The role of neoadjuvant androgen withdrawal before radical prostatectomy continues to be defined and remains investigational. It is unknown whether decreases in positive margin rates will translate into lower biochemical and local recurrence rates until long-term followup is available. We determined whether local recurrence rates after tumor excision were less with neoadjuvant compared to adjuvant androgen ablation in the Shionogi tumor model. Androgen withdrawal in this model triggers apoptosis and complete tumor regression but rapidly growing androgen independent tumors inevitably recur after 1 month. Conceptually, the ideal time for excision is after maximal castration induced tumor involution but before outgrowth of androgen resistant clones.
  
  
  METHODS
  Shionogi tumors were allowed to grow to 1 to 2 gm. before mice were randomly assigned to group 1-tumor excision with wide margins and castration at tumor recurrence and group 2-neoadjuvant castration for 10 days followed by wide excision of the regressed tumor.
  
  
  RESULTS
  Tumors recurred locally in 87% of group 1 mice after a median of 17 days (range 6 to 24) and all regressed completely with adjuvant castration. However, androgen independent tumors recurred in 92% of mice after a median of 36 days. In group 2 androgen independent disease recurred in 44% of mice after a median of 40 days. Tumor-free survival was significantly greater in group 2 than in group 1 (56 versus 20%, respectively, p <0.05). Inked surgical resection margins were positive in two-thirds of group 1 and one-third of group 2 mice.
  
  
  CONCLUSIONS
  Neoadjuvant androgen withdrawal decreases local recurrence and positive margin rates by 50% after tumor excision in the Shionogi tumor model. Although this model cannot address the issue of effect of neoadjuvant therapy on subclinical metastases, extrapolation of these results to the clinical disease suggests that neoadjuvant therapy may help to decrease not only the positive margin rates but also the subsequent risk of local recurrence following radical prostatectomy.
authors.affiliation: Department of Surgery, University of British Columbia, Vancouver Hospital, Canada.
authors.forename: M E
authors.initials: ME
authors.lastname: Gleave
authors.forename: N
authors.initials: N
authors.lastname: Sato
authors.forename: S L
authors.initials: SL
authors.lastname: Goldenberg
authors.forename: L
authors.initials: L
authors.lastname: Stothers
authors.forename: N
authors.initials: N
authors.lastname: Bruchovsky
authors.forename: L D
authors.initials: LD
authors.lastname: Sullivan
mesh_terms: D000818:Animals; D002369:Castration; D004195:Disease Models, Animal; D008297:Male; D051379:Mice; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control*; D011471:Prostatic Neoplasms / Q000601:surgery*