Outcome of patients treated with cobalt and 6 MV in head and neck cancers.
BACKGROUND
Since 1992, we have been using a 6-MV linear accelerator instead of a cobalt machine. The aim of the study is to evaluate the impact of this on neck control, particularly on postoperative patients in which subcutaneous tissues are at risk.


METHODS
A retrospective study including all of 1,452 consecutive patients treated by definitive or postoperative radiotherapy between 1989 and 1997. All stages and subsites of the head/neck were included. Local and neck control were evaluated by the Kaplan Meier method, and comparisons were made between the cobalt and the 6-MV subgroups with a subsequent Cox analysis. For neck control analysis, the postoperative patients were divided in low and high risk (extracapsular extension [ECE], >two nodes, or T4).


RESULTS
Radical radiotherapy: A better local control (LC) is observed with 6 MV than with cobalt, but neck control was similar. Postoperative radiotherapy: A better LC is observed with 6 MV. In high-risk patients, the neck control was higher for the cobalt group (79%) vs 60% for the 6-MV group (p = .09 and .03 in a Cox model).


CONCLUSIONS
In postoperative patients at high risk for neck relapse, cobalt seems to give a better neck control. We are currently doing a prospective study in which a bolus is added for half the treatment when patients at high risk for neck relapse are treated with 6 MV.
Fortin
A
A
Department of Radiation Oncology, L'Hôtel-Dieu de Québec, PQ, Canada. Afortin@videotron.ca
Allard
J
J
Albert
M
M
Roy
J
J
D000328:Adult; D000368:Aged; D003035:Cobalt / Q000627:therapeutic use*; D005260:Female; D005500:Follow-Up Studies; D006258:Head and Neck Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011336:Probability; D016016:Proportional Hazards Models; D011829:Radiation Dosage; D018714:Radiotherapy, Adjuvant / Q000379:methods; D011882:Radiotherapy, High-Energy / Q000379:methods*; D012189:Retrospective Studies; D016019:Survival Analysis; D016896:Treatment Outcome
D003035:Cobalt