The effect of fraction size on control of early glottic cancer

A retrospective analysis of 600 patients treated for head and neck malignancy at the Cooper Hospital/University Medical Center was undertaken. Patients who had surgical intervention (excluding biopsy) were withdrawn from this review. Fifty-eight patients with Stage I Glottic Laryngeal Carcinoma were identified and constitute the basis of this report. Various parameters were analyzed to assess their impact on local control. These include age, sex, serum hemoglobin, tumor bulk, differentiation, field size, total dose, total treatment time, and fraction size. Overall local control was 87% with a median follow-up of 63 months. The only factor that influenced local control was fraction size. Of 28 patients treated with 180 cGy fractions, seven (25%) had a local recurrence within 3 years. Twenty-eight patients treated with 200 cGy or greater fractions have had no failures to date. The difference in control rate when comparing the two treatment schema was significant (p less than 0.01). The median dose in the controlled 180 cGy group was 6660 cGy (range, 6300-7020 cGy). In the patients who failed in the 180 cGy group the median dose was 6660 cGy (range, 6480-6840 cGy). The patients receiving 200 cGy fractions or greater had a median dose of 6600 cGy (range, 6000-6950 cGy) and an average dose of 6507 cGy. The mean NSD in the 180 cGy group failing was 1787 RET (range, 1735-1843 RET). Patients who were controlled and received 180 cGy fractions had a median NSD of 1796 RET (range, 1743-1868). The mean NSD in the 200 cGy group was 1847 RET. The median TDF in the 180 cGy group of patients controlled was 102. Those failing also had a TDF of 102 (range, 101-105). Patients receiving 200 cGy fractions or greater had a median TDF of 109. It appears from this data that fraction size is a highly significant factor in our ability to control glottic laryngeal cancer.