Impact of prolonged fraction delivery times simulating IMRT on cultured nasopharyngeal carcinoma cell killing.

Purpose: To determine the impact of prolonged fraction delivery times (FDTs) simulating intensity-modulated radiotherapy (IMRT) on cultured nasopharyngeal carcinoma (NPC) cell killing.

Methods And Material: Cultured NPC cell lines CNE1 and CNE2 were used in this study. The biological effectiveness of fractionated irradiation protocols simulating conventional external beam radiotherapy and IMRT (FDT of 15, 36, and 50 minutes) was estimated with standard colony assay, and the differences in cell surviving fractions after irradiation with different protocols were tested by use of the paired t test.