RISK-FACTORS WHICH PREDICT PERSISTENT CANCER IN THE ABNORMAL LARYNX FOLLOWING DEFINITIVE IRRADIATION

Laryngeal abnormalities following definitive irradiation for carcinoma of the larynx are common. The objective of this study was to identify risk factors for persistent cancer in such patients who were found to have abnormal larynges following definitive irradiation. A retrospect ive evaluation of 185 consecutive patients undergoing primary irradiat ion for a glottic or supraglottic laryngeal squamous carcinoma treated between 1976 and 1990 at the Affiliated Hospitals of the Medical Coll ege of Wisconsin was performed. From chart review, data concerning sit e, stage, intent of treatment, smoking history, treatment dose, fracti on size, failure patterns, and outcome were obtained. In addition, wor risome signs and symptoms including ulceration, dysphasia, odynophagia , airway distress, aphonia, blood, pain, oedema, aspiration, and pneum onia were recorded. Univariate association with failure and a persiste ntly abnormal laryngeal examination was assessed using the Mantel-Haen szel test. The odds ratio was used to estimate relative risk associate d with dichotomous risk factors. Disease-free and overall survival wer e estimated using Kaplan-Meier methodology. The log rank test was used to compare survival as defined by the levels of various risk factors. Two-year disease-free survival was 83% (T-1= 93%, T-2= 72%, T-3/T4=66 %). Primary failure was associated with the presence of an abnormal ex amination (P=0.001), tracheotomy (P=0.001), symptom index (P=0.002), a phonia (P=0.003), advanced T stage (P=0.03), and lower total dose (P=0 .03). Of 151 patients who survived 6 months disease-free with an intac t larynx, an abnormal examination was seen in those with advanced T st age (P=0.002), supraglottic primary (P=0.003), symptom index (P=0.008) , eventual failure at the primary site (P=0.008), continued smoking (P =0.01), and higher total dose (P=0.01). The symptom index (total signs and symptoms of airway distress, aphonia, ulceration, pain, oedema, d ysphagia, blood production, aspiration, pneumonia, and odynophagia) wa s correlated with primary failure and continued smoking. Of 37 patient s with continually normal examinations, only 1 (3%) failed at the prim ary site. Of 102 who survived 6 months but with an abnormal examinatio n, 22 (22%) eventually developed a primary failure. Persistently abnor mal larynges are common after radiation therapy, yet not all harbour c ancer. Risk factors for persistent cancer include stage, airway, total dose, and symptom index. Patients whose larynges return to normal aft er radiation rarely fail at the primary site.