Purpose: Cell cycle kinetics are believed to be a key determinant in radiation responsiveness. However, histomorphologic analysis remains an unreliable method of identifying proliferating cells. In this study, the fraction of cells undergoing division within oral cancer biopsy samples was used to predict the responsiveness of the tumor to radiation therapy.
Patients and methods: Eighteen cases of T1 or T2 squamous cell carcinoma of the floor of the mouth with known clinical outcomes were identified. All were treated at the Massachusetts General Hospital with external beam radiation therapy alone. The fraction of proliferating cells was determined using in situ hybridization of histone (H3) mRNA expression. Tissue viability and mRNA status was verified using in situ hybridization for beta-actin mRNA expression.
Results: Matching the fraction of oral tumor cells positively labeled for histone (H3) mRNA (histone labeling index or HLI) with the actual clinical outcome showed that the HLI of radioresponsive oral tumors (12 cases) was 0.336+/-0.185 (approximately 34%+/-19%), whereas that for radioresistant oral tumors (six cases) was 0.088+/-0.078 (approximately 9%+/-7.8%). Using t-test statistical analysis for unpaired samples showed that the difference in HLI between the two groups was significantly different (P=.0068).
Conclusions: It is concluded that the use of in situ detection of histone (H3) mRNA may be a useful adjunctive criterion in the choice of treatment for human oral cancer.