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.