Response

Dear Dr. Roush,

Thank you for your interest and comments on our paper entitled “Proximal Radial and Distal Humeral Osteosar-coma in 12 Dogs,” published in the November-December issue of the

.

The reported median survival time and median metastasis-free interval are correct, and no mistake has been made by either the authors or the reviewers. Kaplan-Meier survival analysis is the standard statistical test to calculate outcome in animals and humans with oncologic disease. Kaplan-Meier survival analysis includes animals that have died from tumor-related causes or are lost to follow-up, whereas animals that are alive or have died for reasons unrelated to the tumor are censored from analysis.

In our analysis, 10 dogs with osteosarcoma of the distal humerus or proximal radius were treated with curative-intent forequarter amputation and postoperative chemotherapy. Of these 10 dogs, four died because of metastatic disease, two dogs were lost to follow-up, three dogs died from unrelated causes, and one dog was alive. Hence, the oncologic outcome calculated using Kaplan-Meier survival analysis censored the latter four dogs. As a result, the 50% (or median) for dogs dead or presumed dead (i.e., lost to follow-up) because of tumor-related causes is 356 days for metastasis and 824 days for survival. This is demonstrated on the Kaplan-Meier survival curve on page

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The calculations provided in your letter are correct medians for the raw data but do not consider oncologic outcome and cause of death and, hence, are incorrect in the context of this paper and other papers reporting oncologic data.

Lastly, even for the casual reader, we clearly and unequivocally state in the abstract, results, discussion, and conclusion that metastasis-free interval and survival time for dogs with osteosarcoma of the distal humerus and proximal radius are not significantly different from osteosar-coma in other appendicular sites.

Yours sincerely,