The Prognostic Role of Preoperative Hematological and Inflammatory Indices in Canine Appendicular Osteosarcoma

SIMPLE SUMMARY: Osteosarcoma (OSA) is an aggressive bone tumor both in human and canine patients, commonly treated with surgery and follow-up intravenous chemotherapy. Prognosis is guarded to poor; however, this can be influenced by a variety of factors such as tumor location and serum alkaline phosphatase, among others. Hematological indices have proven to play a prognostic role in humans, but data are limited in dogs. The aim of this retrospective study was to investigate the prognostic significance of pre-operative hematological/inflammatory indices, together with other prognostic factors, in a cohort of client-owned dogs with appendicular OSA treated with limb amputation and injectable chemotherapy. As sighthounds have a predisposition to OSA but present different hematological reference values compared to other breeds, these were also evaluated separately. Fifty-nine dogs were included, and 13 were sighthounds. Data analysis suggests that pre-treatment absolute neutrophil count may play a prognostic role in canine OSA treated with amputation and adjuvant carboplatin. Our study also suggests that hematological markers identified in the whole population may not be applicable to sighthounds. These pre-treatment indices, which could prove very helpful as they are readily available, should be confirmed in large prospective studies considering breed specificities. ABSTRACT: Hematological indices play a prognostic role in human osteosarcoma (OSA), but data are limited in dogs. The aim of this retrospective multicentric cohort study was to investigate the prognostic significance of pre-operative hematological/inflammatory indices in a cohort of client-owned dogs with appendicular OSA receiving standardized treatment. Cut-offs associated with progression-free survival (PFS) for pre-operative hematological values/ratios were established using the minimal p-value approach. Historical prognostic factors were also assessed. Statistical analyses were performed for the whole population and after the exclusion of sighthounds. Fifty-nine dogs were included (13 were sighthounds). Multivariable analysis revealed that a low neutrophil count (<4.37 × 10(9)/L, HR0.28, CI 95% 0.13–0.61, p = 0.001), a high red blood cell count (≥7.91, HR3.5, CI 95% 1.56–7.9, p = 0.002), and a proximal humerus location (HR3.0, CI 95% 1.48–6.1, p = 0.002) were associated with shorter PFS. In the sighthound-only population, only OSA location was significantly associated with PFS in univariable analysis. When sighthounds were excluded, a low neutrophil count, a low monocyte count, and a proximal humerus location were associated with shorter PFS, in multivariable analysis. Neutrophil count and possibly monocyte and red blood cell counts can be useful prognostic markers in canine OSA treated with amputation and adjuvant carboplatin. However, not all indices are appropriate in sighthounds.