1098 - Prognostic Significance of Expression of Erb-b Receptors in Osteosarcoma

INTRODUCTION The erbB receptor family is type I growth factor receptor family that consists of four closely related members of transmembrane glycoprotein with tyrosine kinase activity : the epidermal growth factor receptor (EGFR/erbB1), erbB2 (HER-2/new), erbB3, and erbB4. They form both homoand heterodimers to contribute to tuning and diversification of intracellular signal transduction. Overexpression of erbB1 has been frequently observed in squamous cell carcinomas with significant correlation with high matastatic rate and poor prognosis, and short survival time of the patients. Also, overexpression of erbB2 has been reported to be an indicator of poor prognosis in a number of cancers arising in breast, ovary, endometrium, stomach, lung, and salivary gland. In contrast, few studies have addressed the expression and its prognostic significance in sarcomas. While Onda et al. (1) revealed the correlation of erbB2 expression and poor prognosis in osteosarcoma patients, this study has a limitation in the number of patients as well as in the consistency of the treatment protocol. In the present study, we retrospectively examined the expression of erbB1 and erbB2 in conventional high-grade osteosarcomas using biopsy specimens obtained from patients who completed the treatment protocols consisting of neoadjuvant chemotherapy, definitive surgery, and adjuvant chemotherapy. MATERIALS AND METHODS Patients. This study included 81 patients hospitalized at Sapporo Medical University Hospital and Sapporo National Hospital in Sapporo, Japan from 1980 to 1996. 53 patients were men and 28 were women with an average age of 14.8 years (range from 5 to 43). The anatomic sites of the tumors were femur in 44, tibia in 25, humerus in 6, fibula in 5 and pelvis in 1 patient. The histological subtypes of the tumors included osteoblastic in 49, chondroblastic in 12, fibroblastic in 19 and telangiectatic in 1 patient. Four tumors were classified into stage IIA and 77 tumors into stage IIB according to the Enneking’s surgical staging system (2). Chemotherapy consisting of highdose methotrexate, adriamycine and cisplatin was systematically given to all patients before and after surgery. The surgical margins histologically defined according to the system of Enneking et al. (2) were either radical or wide in all patients. A limb-saving procedure was performed in 41 patients and amputation in 40 patients. The response to preoperative chemotherapy was considered good if the extent of tumor necrosis was 90 percent or greater. 38 patients had a good response, whereas 43 had a poor response. All patients were followed for a minimum of 36 months (median, 92). Fifty patients were CDF, seven patients were NED, one patient was AWD, and twenty-three patients were DOD. Immunohistochemistry. Serial sections were made from the formalin-fixed, paraffin-embedded biopsy specimens obtained from the primary tumors before chemotherapy. Using polyclonal antibodies to human EGFR (BioGenx) and human c-erbB-2 (DAKO), immunostaining was performed by streptoavidin-biotin-peroxidase method. Evaluation. Immunostainig was regarded positive when over 50 percent of tumor cells were stained ether in the membrane or the cytoplasm. The staining results were independently interpreted by two observers blinded to tumor status and patient survival and were assessed the correlation with several clinicopathological variables including gender, age, anatomical site, histopathological subtype, and response to neoadjvant chemotherapy, as well as with event-free and overall survival. Statistical analysis. Fisher’s exact test was used to determine the statistical significance between erbB expression and clinicopathological variables. Event-free survival curve and overall survival curve were drawn according to the Kaplan-Meier product-limt plots. The log-rank test was used to evaluate the association of the expression of erbB receptors and the response to chemotherapy with the event-free survival and overall survival. RESULTS ErbB1 was scored positive in 45 tumors (56 percent) and erbB2 in 66 tumors (81 percent). There was no significant relationship between erbB expression and clinicopathological variables examined. In contrast, the patients with erbB1 positive tumor were significantly better than those with erbB1 negative tumor in both event-free survival (p = 0.011) and overall survival (p = 0.048). .Also, the patients with erbB2 positive tumor were significantly better event-free (p = 0.011) and overall (p = 0.011) survivals than those with erbB2 negative tumor. A comparison between patients with either erbB1 or erbB2 positive tumor and remainders yielded more striking significance in event-free (p = 0.004) and overall (p = 0.005) survivals (Figure). Despite better event-free (p = 0.072) and overall (p = 0.038) survivals in good responders to adjuvant chemotherapy than poor responders, there was no significant association between the expression of erbB receptors and the response to chemotherapy, suggesting that the expression of erbB1 and erbB2 receptors had a prognostic significance in osteosarcoma patients independently from the response to chemotherapy. DISCUSSIONS In the present study, we found that the expression of erbB receptors (erbB1 and erbB2) in pretreated osteosarcoma is an indicative of good prognosis in patients who received definitive surgery and neoadjuvant as well as adjuvant systemic chemotherapy. The discrepancy between our observation and the results from other studies in the literature may be explained by the difference in the category (carcinoma vs, sarcoma), the study size, the patients selection, and the method of erbB detection. Further functional analysis will elucidate the role of erbB families in biology and tumor dissemination of osteosarcoma. REFERENCES (1) Onda et al., Cancer 77 : 71-78, 1996 (2) Enneking et al., Clin Orthop 153 : 106-120, 1980