Evaluation of c-kit (CD 117) expression as a prognostic factor in testicular germ cell tumors: an Izmir Oncology Group (IZOG) study.

PURPOSE Despite the successful use of targeted and molecular therapies in other cancers, little progress has been made in the management of testicular germ cell tumors (TGCTs). c-kit (CD 117) is a good target for cancer treatment and possesses an impressive role in the current oncological practice. We aimed to evaluate c-kit expression in early stage TGCTs as a prognostic factor. METHODS Patients with TGCTs who were referred to the Medical Oncology Clinic and underwent curative surgical operation were included in our study before starting chemo- therapy. Immunohistochemistry was performed on formalin-fixed and paraffin-embedded three-micrometer thick sections with CD 117 Rabbit Anti c-kit in vitro gene kit. Biochemically, we utilized AFP and β-HCG Immunlite 2000 device with solid phase chemiluminescent immunometric method, and LDH Roche models with the DP-standardized UV method. AFP 0-15 ng/ml, β-HCG < 0.1 mlu/ml and LDH 240-480 mg/dl were considered as normal values. RESULTS Sixty-five patients were included in our study. Forty-one (63%) patients had non-seminoma tumors (NSGCTs) and 24 (37%) had seminoma. Statistically significant c-kit expression was found in patients with seminoma (p<0.0001). There was no difference between negative or positive c-kit expression in terms of clinicopathological characteristics, including preoperative serum levels of AFP, β-HCG, LDH, lymph node involvement, distant metastasis, and IGCCCG risk classification. No correlation was found between these parameters and 5-year progression free survival (PFS) rate except for tumor stage, presence of lymph node metastasis and IGCCCG score (p=0.001, p=0.04, and p=0.0001, respectively). Five-year PFS rate of patients with positive CD 117 was 72.2% (95% CI, 54.6-89.8), and 56.6% (95% CI, 31.2-82.1) for those without CD 117 expression involvement (p=0.12). CONCLUSION So far, there has been no significant breakthrough in the treatment of cisplatin-refractory TGCTs in the era of targeted therapies. No prognostic importance of c-kit expression has been found in our study. However, we believe that c-kit expression, in numerical terms, can be considered as a good prognostic factor for patients with TGCTs. The fact that all seminoma cases displayed positive c-kit expression is what we think has driven this result.