The Clinical Characteristics and Expression of P21 in Recurrent Early Glottic Cancer after Radiation Therapy / 대한이비인후과학회지

ABSTRACT

BACKGROUND AND OBJECTIVES: Radiotherapy or surgery is the main treatment modality for early glottic cancer. The advantage of radiotherapy is the preservation of good voice quality after treatment but the main problem of increased complications in the salvage surgery remains when local control fails. So, it is important to predict the success of radiotherapy. Authors aimed to investigate clinical characteristics of recurrent early glottic cancer after radiotherapy and to evaluate the expression of p21 protein as a predictable factor for radiosensitivity in early glottic cancer. SUBJECTS AND METHOD: From 1989 through 2003, 118 patients with T1, T2 glottic squamous cell carcinoma treated primarily with full courses of radiotherapy at the Asan Medical Center were identified. Among them, 20 patients had recurrence. We reviewed medical records retrospectively to find out factors affecting recurrence and performed immunohistochemical staining for p21 protein on the paraffin sections of the biopsy specimens of 75 patients (including 17 cases among 20 patients with recurrent disease). Immunoreactivity to the p21 antibody was evaluated using semi-quantitative scoring system Grade I for no nuclear reaction, Grade II for 1-10%, Grade III for 10-50%, and Grade IV for 50% or more nuclear staining. We classified immunostaining grades I and II as the weakly positive group, grades III and IV as the strongly positive group. The relation between the local control outcome after radiotherapy and the results of immunostaining was analyzed by the chi-square and the Fisher's exact test. RESULTS: Most of the patients was male (97%), the median follow-up time was 36 months and the average time to recur was 15 months. The recurrence rate was 17% overall, 16% for T1 lesions, 25% for T2 lesions. The unfavorable factor identified in this study for local recurrence was tumor differentiation (p=0.023). Three out of 30 cases of the weakly positive group had recurred and 14 out of 45 cases of the strongly positive group had recurred. There was significantly high recurrence rate in the strongly positive group (p=0.048). CONCLUSION: There was a significant correlation between the poorly differentiated early glottic squamous cell carcinoma and tumor recurrence. The relation between the strongly positive p21 expression and the radioresistance suggests that p21 might be a predictable factor in radioresistancy in early glottic cancer.