Reasons for irradiation failure in squamous cell carcinoma of the larynx

The reasons for irradiation failure in squamous cell carcinoma of the larynx can be: 1. Geographical miss because of undiagnosed extensions is the exception. Almost all of the recurrences were well within the treatment portals. 2. Specific extensions with an unfavorable tumor bed. Extension of disease into poorly vascularized structures and/or deep infiltration with fixation are causes of failure. 3. Low dose for the volume cancer. Higher doses delivered in longer treatment time are necessary for 90 percent control of bulky exophytic supraglottic lesions. 4. Techniques which do not assure daily coverage of the tumor. With carefully drawn and checked anatomical portals, geographical misses should be nonexistent. 5. Sigmoid response curve. There is an 85 percent control of the T1 glottic tumors. The control rate is 90 percent of the T1 and T2 supraglottic tumors, and the 10 percent failures have no obvious explanation except that the plateau of the sigmoid response curve has been reached. A negligible yield would be obtained by increasing doses which would not be justified because of concomitant increase in frequency and severity of complications and lessening of the quality of voice. 6. New cancer. Probably 25 percent of the so-called recurrences on the vocal cords are actually new primary lesions. The ultimate failure rates respectively are 2 percent for T1 lesions and 10 percent for T2 lesions after a rescue surgical procedure. All patients with T1 vocal cord lesions who did not experience a failure or a complication, have a normal voice. In the patients with T2 lesions in whom the cancer had completely replaced the cord(s), some hoarseness is present; but most of these lesions would have been suitable only for a total laryngectomy. In the 15 failures in T1 and T2 supraglottic lesions, surgery was not attempted in only three patients, one of whom was salvaged by re-irradiation. Following 12 laryngectomies there is only one definite failure and two patients died within two years NED locally. Except in the patients who had severe edema and/or necrosis, the voice has been normal or near normal. In patients with lesions of the suprahyoid epiglottis which had amputated the suprahyoid epiglottis swallowing difficulty has not developed.