Regional lymph node involvement is associated with poorer survivorship in patients with upper extremity osteosarcoma than with lower extremity osteosarcoma: a SEER analysis

Background: Although the upper limb is the second most common site of osteosarcoma, investigations into clinical manifestation differences between upper and lower limb patients are still sporadic. We retrospectively investigated the characteristics of these patients to gain a better understanding of the differences between upper and lower limb osteosarcoma patients. Methods: This retrospective study involved patients diagnosed with extremity osteosarcoma between 1997 and 2016 collected from the Surveillance, Epidemiology, and End Results (SEER) database. Patient characteristics were analyzed with t-tests, rank sum tests and chi-square tests. Log-rank tests were applied to evaluate univariate significance, and Cox hazards models were performed in multivariate analysis. A binary logistics regression model was used to screen the risk factors related to lymph node involvement. Results: In total, 1,882 patients, 1,588 (84.4%) with lower limb lesions and 294 (15.6%) with upper limb lesions were enrolled in our study. The patients with upper limb osteosarcoma exhibited poorer 5-year overall survival (OS) than patients with lower limb osteosarcoma (54.8% vs. 63.2%, P=0.02). The upper limb patients had more lymph node involvement (5.6% vs. 2.7%, P=0.03), which was found to be an independent prognostic factor (P=0.000). Tumors located in the upper limbs and the presence of distal metastasis were risk factors related to lymph node involvement in the extremity (P<0.05). The upper limb patients were tended to suffer greater risk of being affected by both metastasis and lymph node involvement (15.7% vs. 9.4%, P=0.18). Conclusions: Upper limb osteosarcoma patients are characterized by more lymph node involvement than lower limb patients, leading to poorer OS. In addition, upper limb patients are at greater risk for both lymph node involvement and distal metastasis. Our results suggest that upper limb patients should be screened more thoroughly for regional lymph node involvement.