This retrospective study evaluated 228 dogs with appendicular osteosarcoma to determine the incidence of regional lymph node metastasis and the associated survival time. Serum alkaline phosphatase (ALP) was also evaluated. Disease-free interval was defined as the time from amputation to when evidence of metastasis to the lungs or another part of the body was discovered. Survival time was defined as the time from amputation to death. Ten dogs had evidence of regional lymph node metastasis. The median disease-free interval for dogs without regional lymph node metastasis was considerably longer (223 days; range, 0 to 1067 days) than for those with regional metastasis (48 days; range, 2 to 269 days). The median survival time for dogs without lymph node involvement was longer (318 days; range, 20 to 1711 days) than those for dogs with lymph node metastasis (59 days; range 19 to 365 days).

COMMENTARY: The importance of histologically examining regional lymph nodes in canine appendicular osteosarcoma is illustrated by this study, which identified a poorer prognosis for median disease-free interval and median survival in patients with lymph node metastasis at limb amputation. The results of previous studies that showed poorer survival times in patients with proximal humeral tumors and high preoperative serum ALP activity were also corroborated. The results of this study indicate that accurate tests for determining the presence of lymph node metastasis may affect treatment recommendations.

Incidence and prognostic importance of lymph node metastases in dogs with appendicular osteosarcoma: 228 cases (1986-2003). Hillers KR, Dernell WS, Lafferty MH, et al. JAVMA 226:1364-1367, 2005.