LOCAL TUMOR-CONTROL IN RADIATION-THERAPY OF CANCERS IN THE HEAD AND NECK

Background: A retrospective study of 1,493 head and neck cancer patien ts was designed to test current radiobiological thinking, postulating the detrimental effect of protracted overall treatment times (OTT) and /or split course (SC) regimes in radiation therapy on local tumor cont rol. Methods. Primary squamous cell carcinomas of the oral cavity (OC) , oropharynx (OF), hypopharynx (HP), nasopharynx (NP), and larynx radi ated with a dose of at least 50 Gy were analyzed. Those patients treat ed by brachytherapy and/or primary surgery were excluded. A detailed a nalysis of the 997 cancers of the larynx was recently published. This paper focuses on the relationship between local tumor control and trea tment characteristics for the 496 tumors originating from the OC, OF, HP, and NP. Total doses of radiation ranged from 50 to 79 Gy, with a m ean of 64 Gy. Results. A local failure (LF) was observed for 278 patie nts. Using Cox regression analysis, T stage and site were strongly rel ated to LF. Corrected for T stage and with reference to OF, tumors in the NP, HP, and OC had a relative LF rate of 0.5, 1.6, and 1.8, respec tively. Patients treated with continuous course (CC) and higher doses of radiation therapy fared best. No association was found with OTT and the use of chemotherapy. Conclusions: The results observed for the OC , OF, HP, and NP are in line with the findings for the larynx. Analyzi ng all 1,493 patients, for SC regimes lower local control rates were o bserved as opposed to the CC treatment series. Moreover, for the norma lized total doses, a dose-effect relationship could be established. Th is study corroborates that disruption of the treatment per se and/or t he use of suboptimal total doses of RT are detrimental; it is argued t hat these observations could be of relevance when designing combined m odality protocols.