In vivo cell kinetics in head and neck squamous cell carcinomas predicts local control and helps guide radiotherapy regimen.

Abstract

PURPOSE To determine whether pretherapy cell kinetics can predict local control for patients affected by head and neck squamous cell carcinomas (HN-SCCs) to be treated by primary radiotherapy and, moreover, guide to a choice between conventional and accelerated radiotherapy. PATIENTS AND METHODS Between 1989 and 1993, 83 patients with stage II to IV HN-SCC entered the study. Multiple primary tumor biopsies were obtained 6 hours after in vivo infusion of bromodeoxyuridine (BrdUrd). In vivo S-phase fraction labeling index (LI), duration of S phase (Ts), and potential doubling time (Tpot) were obtained by analysis of multivariate flow-cytometric data. Between April 1989 and January 1991, 49 patients were treated by conventional radiotherapy (70 Gy in 35 fractions over 7 weeks), whereas, afterwards, 34 patients entered an accelerated radiotherapy regimen with the concomitant boost technique (75 Gy in 40 fractions over 6 weeks). RESULTS Univariate analysis showed that, among patients treated by conventional radiotherapy, local control probability was affected by tumor stage (P = .02), Tpot (P < .001), and LI (P = .04). Similarly, among patients treated with accelerated radiotherapy, we found that local control probability was related to tumor stage (P = .03) and primary tumor site (P = .05). For the subgroup of patients with tumors characterized by fast growth (Tpot < or = 5 days), accelerated radiotherapy gave a better local control rate than conventional radiotherapy (P = .02). Cox multivariate analysis of the total number of patients showed that the only significant independent prognostic factors related to local control were tumor stage (P = .002) and Tpot (P = .004). Moreover, when the Cox analysis was restricted to the subgroup of patients treated with conventional radiotherapy, Tpot was the most significant factor to predict local outcome (P < .01). CONCLUSION Pretreatment tumor Tpot appears to be an important independent prognostic factor for local control of HN-SCC treated by primary radiotherapy.