27. Time factor in postoperative radiotherapy for squamous cell head and neck cancer; a multivariate locoregional control analysis in 942 patients

Abstract

Purpose

To analyze the influence of overall radiation treatment time and duration of the interval surgery-radiotherapy on local tumor control (LTC) in postoperative radiotherapy (PRT) for squamous cell head and neck cancer (SCHNC).

Material/methods

A multivariate Cox proportional hazard regression analysis included 942 patients with locally advanced SCHNC. Mean total radiation dose, dose per fraction, treatment time, and the interval surgery-PRT were 62,5 Gy, 2,1 Gy, 46 days, and 62 days respectively. No interruptions during PRT (except for weekend brakes) appeared in 29% of patients, while 28% had more than 5 days of gap. The data were grouped into seven categories depending on the position of gap (weeks 1–7).

Results

Increase in treatment gaps, the presence of tumor recurrence after surgery, N stage, and extra-laryngeal site of cancer were significantly related to decrease in LTC. The duration of time interval surgery-PRT had only marginal significance for LTC. Other variables did not appear significant. Consideration of seven time intervals for treatment gaps in the multivariate model has shown a significant progressive increase in the hazard of recurrence for gaps in the respective weeks 1 to 7.

Conclusions

This analysis shows a detrimental effect of interruptions during PRT, and only marginal decrease in LTC from the extension of the interval surgery-PRT. Therefore it seems unjustified to rush with PRT at the expense of possible increase in radiation treatment gaps. However, excessive delays in initiating PRT should be avoided, since they may lead to a recurrence prior to irradiation.