title: Effect of timing of postoperative chemotherapy on survival of dogs with osteosarcoma.
abstract: BACKGROUND
  After excision of primary tumors, initiation of chemotherapy for micrometastases is often delayed for 2 to 4 weeks to permit patient recovery and early healing of the surgical wound. However, studies using murine tumors have indicated that removal of a primary tumor may cause increased cell proliferation within micrometastases during the first 7 to 10 days after surgery, potentially rendering the micrometastases more susceptible to chemotherapy. Clinical trials assessing the value of early postoperative initiation of chemotherapy for human breast carcinoma have yielded conflicting results. Osteosarcoma of dogs is a naturally occurring model for human tumors likely to have micrometastases at the time of diagnosis.
  
  
  METHODS
  Before surgery, 102 dogs with osteosarcoma were randomized to receive cisplatin and doxorubicin chemotherapy beginning either 2 days or 10 days after amputation. Survival analysis was performed for each treatment group and for a historic control group comprised of 162 dogs treated by amputation alone.
  
  
  RESULTS
  Median survival times for dogs treated by amputation alone and for dogs receiving chemotherapy beginning 2 or 10 days after surgery were 5.5, 11.5, and 11.0 months, respectively. Survival was significantly longer for each of the two groups of dogs receiving chemotherapy than for control dogs (P < 0.0001). There was no significant difference in survival between treatment groups (P = 0.727).
  
  
  CONCLUSIONS
  These results do not disprove the theory that removal of a primary tumor alters the growth kinetics of metastases, but do imply that there is no substantial advantage to early postoperative initiation of adjuvant chemotherapy for spontaneous tumors of large species.
authors.affiliation: Department of Surgery, School of Veterinary Medicine, Tufts University, North Grafton, Massachusetts 01536, USA.
authors.forename: J
authors.initials: J
authors.lastname: Berg
authors.forename: M C
authors.initials: MC
authors.lastname: Gebhardt
authors.forename: W M
authors.initials: WM
authors.lastname: Rand
mesh_terms: D000671:Amputation, Surgical; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage*; D001859:Bone Neoplasms / Q000188:drug therapy / Q000401:mortality / Q000601:surgery / Q000662:veterinary*; D017024:Chemotherapy, Adjuvant; D002945:Cisplatin / Q000008:administration & dosage; D004283:Dog Diseases / Q000188:drug therapy / Q000401:mortality / Q000601:surgery*; D004285:Dogs; D004317:Doxorubicin / Q000008:administration & dosage; D005260:Female; D008297:Male; D012516:Osteosarcoma / Q000188:drug therapy / Q000401:mortality / Q000601:surgery / Q000662:veterinary*; D011184:Postoperative Period; D011897:Random Allocation; D013997:Time Factors
chemical_list: D004317:Doxorubicin; D002945:Cisplatin