Early Lymphocyte Recovery and Outcome in Osteosarcoma.

Background: Early lymphocyte recovery following chemotherapy has been associated with improved outcome in many cancers, including in one small study of osteosarcoma patients. Materials and Methods: To confirm this finding, we retrospectively reviewed data from 53 patients with newly diagnosed osteosarcoma who had blood counts on day 14 (+/- 1 d) following the first cycle of cisplatin and doxorubicin. Results: The median absolute lymphocyte count (ALC) 14 days after starting the first cycle of chemotherapy (ALC-14) was 1990 cells/mu L (range: 600 to 6470). For 32 patients with an ALC14 >= 1800 cells/mu L, the 5-year progression-free survival (PFS) was 69%, compared with 33% for patients with an ALC-14 of < 1800 cell/mu L (P= 0.036). In multivariable analysis of factors including age, sex, metastatic disease, and favorable histologic response to induction chemotherapy, ALC-14 was significantly associated with PFS (P= 0.0081) and overall survival (P= 0.0131). The use of ALC-14 appears to further stratify PFS and overall survival among patients when grouped by histologic response. Conclusions: We confirmed that early lymphocyte recovery was associated with outcome in pediatric osteosarcoma. Although presumably reflecting immune-mediated tumor control, the precise mechanism for this is unclear. Further study of peripheral blood lymphocyte subpopulations in prospectively treated patients is underway.