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 response to radiation therapy. Squamous cell cancer of supraglottis and glottis could be good examples of this phenomenon. The purpose of the study was to compare the radiocurability of cancers localized in the upper and medium 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 supraglottic 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 disease-free survival (DFS). Generally, 5-year overall and disease-free survival rates were significantly more favorable for glottic cancer patients than for supraglottic cancer (67 and 63% vs. 40 and 36%, respectively). Significant differences in both disease-free and overall survival between supraglottic and glottic cancer in aspect of several analyzed clinical prognostic factors were found for: male 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 supraglottic cancer patients. This tendency disappeared when the treatment results were compared in aspect of tumor stage (T). Tumor cure doses for 50% probability of local control (TCD50) in supraglottic cancer were estimated as: 61 Gy (T(1+2)) and 66 Gy (T3). In glottic cancer the lower TCD50 values of 54.5 Gy (T(1+2)) and 61 Gy (T3) were found in comparable treatment time. The comparative estimation of cure rates (i.e. OS and DFS) of laryngeal cancer 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.