T1 nasopharyngeal carcinoma: the effect of waiting time on tumor control.

Abstract

To study the effect of unperturbed tumor growth on the control of nasopharyngeal carcinoma. This is a retrospective analysis of 290 patients with T1N0-3M0 disease (Ho's classification) treated by the same technique and dose schedule to the nasopharyngeal region. The median interval from diagnosis to commencement of irradiation was 26 days (range: 8-68 days). Cox proportional hazards analyses were performed to study the independent effect of waiting time on the probability of failure at various sites. Actuarial failure-free survival of patients with delay < 22 days, 22-28 days and > 28 days were also compared to illustrate the clinical observation. Both tests showed that waiting time had no significant impact on local failure: The N-stage stratified hazard ratio was 0.985 per day, and the 10-year local failure-free survival for the three groups was 76%, 80%, and 82%, respectively. A similar result was obtained for nodal control in patients with our scheduled neck irradiation. Although the p value of all tests failed to reach statistical significance, the N-stage stratified hazard ratio for distant failure was 1.020 per day, and the corresponding metastasis-free survival in patients with N2-3 disease was 70%, 65%, and 52%, respectively. For node-negative patients without elective neck irradiation, the hazard ratio was 1.019 per day, with the corresponding regional failure-free rates at 57%, 62%, and 33%, respectively. Delay in initiation of treatment to the primary target (within the range observed) did not affect the control rate at irradiated sites, but there was a trend (though statistically insignificant) towards increase in failures at untreated sites that were clinically too serious to be ignored.