Effect of overall treatment time on local control in radical radiotherapy for squamous cell carcinoma of esophagus.

Objective: To analyze the effect of overall treatment time on local control in radical radiotherapy for squamous cell carcinoma of esophagus.

Methods: Three hundred and fifty-three patients with inoperable esophageal cancer (tumor length < or = 10 cm in all cases) treated during 1963-1988 by radical radiotherapy alone either as continuous or split-course therapy. The overall treatment time varied from 35 to 55 days and the total dosage from 50 to 71 Gy in the continuous therapy group (n = 138), and in the split-course group (n = 215) with a planned 3-week rest interval in the middle of the treatment from 56 to 70 days and from 55 to 70 Gy, respectively. The logit method of the linear-quadratic formula for local control at 1 year was used to examine the effect of treatment time on local control. All patients were pooled to obtain a wide range of overall treatment times.

Results: The 1-, 2-, and 5-year actuarial survival rates according to the T-stage in the continuous therapy group from the first day of the radiotherapy were: 57%, 32%, and 10% for the T1 tumors and 23%, 8%, and 5% for the T2 tumors. The corresponding figures for the split-course group were: 50%, 19%, and 4% for the T1 tumors and 17%, 6%, and 3% for the T2 tumors. The 1-year local control rate was 56% for the T1 tumors and 15% for the T2 tumors in the continuous therapy group and 48% for the T1 tumors and 10% for the T2 tumors in the split-course group. The results of the logit method did not fit well with the T1 tumors. For the T2 tumors, they showed Dprolif to be about 0.24 Gy/day for local control at 1 year. As a consequence, protraction of overall time by 1 week should be compensated by increasing the total dose by 1.8 Gy for 1 year local control.

Conclusions: More attention should be focused on repopulation. Shortening of overall treatment time might be beneficial for the treatment of squamous cell carcinoma of esophagus.