Pharmacogenetics of Neoadjuvant MAP Chemotherapy in Localized Osteosarcoma: A Study Based on Data from the GEIS-33 Protocol

Background: Osteosarcoma is a rare disease, but it is the most frequent malignant bone tumor. Primary treatment consists of preoperative MAP (methotrexate (MTX), doxorubicin and cisplatin) chemotherapy followed by surgery and adjuvant chemotherapy. Pathological response to preoperative chemotherapy is one of the most important prognostic factors, but molecular biomarkers are lacking. Additionally, chemotherapy-induced toxicity might jeopardize treatment completion. We evaluated variants in genes involved in DNA repair and drug metabolism pathways as predictors of response to MAP-based treatment. Material and Methods: Germline polymorphisms in MTHFR, SLC19A1, ABCB1, ABCC2, ABCC3, ERCC1, ERCC2 and GSTP1 genes were determined for association studies in 69 patients diagnosed with localized osteosarcoma who enrolled in the prospective GEIS-33 trial. P-glycoprotein expression in tumor tissue was also analyzed. Results: In the multivariate analysis, the ABCC2 rs2273697 (odds ratio [OR] 12.3, 95% CI 2.3–66.2; p = 0.003) and ERCC2 rs1799793 (OR 9.6, 95% CI 2.1–43.2; p = 0.003) variants were associated with poor pathological response. P-glycoprotein expression did not correlate with pathological response. The ABCB1 rs1128503 (OR 11.4, 95% CI 2.2–58.0; p = 0.003) and ABCC3 rs4793665 (OR 12.0, 95% CI 2.1–70.2; p = 0.006) variants were associated with MTX grade 3–4 hepatotoxicity. Conclusions: Our findings add to the evidence that genetic variants in the ABC transporters and DNA-repair genes may serve as predictive biomarkers for MAP chemotherapy and contribute to treatment personalization.