Comparative estimation of cure rates for supraglottic and glottic cancer in radiotherapy

There are some clinical evidences, that the same types of tumors originated from neighboring anatomical structures can significantly differ in their r esponse to radiation therapy. Squamous cell cancer of supraglottis and glot tis could be good examples of this phenomenon. The purpose of the study was to compare the radiocurability of cancers localized in the upper and mediu m level of the larynx. From 1985 to the end of 1989, 544 patients with squamous cell cancer of the larynx were treated by radiotherapy alone. There were 388 patients with su praglottic cancer and 156 patients with glottic cancer. The total dose was in the range of 59-74 Gy. The end-point criteria were overall (OS) and dise ase-free survival (DFS). Generally, 5-year overall and disease-free survival rates were significantl y more favorable for glottic cancer patients than for supraglottic cancer ( 67 and 63% vs. 40 and 36%, respectively). Significant differences in both d isease-free and overall survival between supraglottic and glottic cancer in aspect of several analyzed clinical prognostic factors were found for: mal e sex, age, pattern of tumor growth, clinical performance status, radiation total dose lower than 70 Gy, fraction doses and overall treatment time. In all these prognostic categories 5-year survival rates were lower for supra glottic cancer patients. This tendency disappeared when the treatment resul ts were compared in aspect of tumor stage (T). Tumor cure doses for 50% pro bability of local control (TCD50) in supraglottic cancer were estimated as: 61 Gy (T1+2) and 66 Gy (T-3). In glottic cancer the lower TCD50 values of 54.5 Gy (T1+2) and 61 Gy (T-3) were found in comparable treatment time. The comparative estimation of cure rates (i.e. OS and DFS) of laryngeal can cer treated by radiation alone showed that in aspect of almost all analyzed prognostic factors the greater risk of treatment failure was significantly associated with supraglottic origin.