(ChemotherapyAdvisor) – Expression of a specific protein in patients with osteosarcoma can help predict response to neoadjuvant chemotherapy, according to a team of researchers of University of California-Davis. This conclusion is based on a study entitled “P16 expression predicts necrotic response among patients with osteosarcoma receiving neoadjuvant chemotherapy,” which was recently published in Human Pathology online.

In this study, the investigators aimed to determine the relationship of P16 expression in pretreatment osteosarcoma tumors to pathologic necrotic response after neoadjuvant chemotherapy. To make this determination, the investigators created a tissue microarray from paraffin-embedded pretreatment biopsy specimens from 40 patients with osteosarcoma.P16 expression in tumor specimens was determined by immunohistochemical staining. “Percent tumor necrosis was measured in postchemotherapy resection specimens per established protocols, and 90% or greater tumor necrosis was considered “good,” the investigators wrote.

P16 was expressed in 62% of all tumors. Median post-treatment tumor necrosis was 90%, and 55% of patients experienced “good” chemotherapy response (≥90% necrosis). P16 expression correlated positively with median percent necrosis and “good” chemotherapy response (P=.004 and .003, respectively). On logistic regression analysis, P16 expression was independently associated with chemotherapy response after controlling for age, subtype, sex, and location (odds ratio, 43.5; 95% confidence interval, 2.64-708.9; P=.008).

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The investigators concluded: “Immunohistochemical expression of P16 significantly correlates with chemotherapy response in osteosarcoma; P16 expression may be a useful biomarker to guide treatment selection.”