Histopathological Response to Neoadjuvant Chemotherapy in Patients With Enneking Stage II Conventional Osteosarcoma of Extremities: A Retrospective-Single Institution Study in Vietnam.

Background: The standard treatment for localized osteosarcoma is neoadjuvant chemotherapy before surgery, followed by adjuvant chemotherapy. Our aim was to report the rate of histopathological response to neoadjuvant chemotherapy for the treatment of extremity osteosarcoma in Vietnam.

Methods: We performed a retrospective study of stage II conventional osteosarcoma patients under 40 years-old who received MAP regimen as neoadjuvant chemotherapy at the Vietnam National Cancer Hospital between June 2019 and June 2022. Histopathological response was evaluated using the Huvos grading system, in which a good histopathological response was defined as a necrotic rate of 90% or more.

Results: Thirty-five eligible patients were included in the study. Male patients accounted for 65.7%, with a median age of 16 years (range, 8-38 years). Of the 35 cases, 31 were reported as stage IIB (88.6%). The femur and tibia were the most common sites in our study, accounting for 51.4% and 34.3%, respectively. The most common pathologic subtype was osteoblastic osteosarcoma (68.6%), followed by chondroblastic subtype (20%). After two cycles of MAP-regimen neoadjuvant chemotherapy, 28 of 35 patients (80%) underwent limb-sparing surgery. A good histopathological response was observed in 18 of 35 patients (51.4%). There were significant correlations between the duration of symptoms (P = 0.016), LDH (P = 0.001) serum levels at initial presentation, and ALP (P = 0.043) serum levels at initial presentation with histopathological response.

Conclusion: This retrospective study suggests a possible association between symptom duration, pre-treatment LDH levels, and pre-treatment ALP levels with histopathological response rates. Additional clinical investigations with long-term follow-up are needed to investigate survival outcomes in the Asian population.