The need for elective irradiation of occult lymphatic metastases from cancers of the larynx and pyriform sinus.

The incidence of palpable and occult cancer and the absence of cancer in lymph nodes were determined for individual sites in the larynx and pharynx of 540 patients who underwent neck dissection. The incidence of palpable cancer in lymph nodes was lowest for cancers of the central supraglottis and transglottis (32-41%), intermediate for cancers of the marginal supraglottis and glossoepiglottis (48-57%), and highest for cancers of the pyriform sinus (69%). The incidence of occult cancer in lymph nodes for individual sites in the larynx and pharynx was determined by pathologic study of neck dissection specimens from 253 patients without palpable lymph nodes (NO neck). The incidence of occult lymphatic metastases in the NO neck and the need for elective neck irradiation were least for cancers of the transglottis and central supraglottis (14-16%), intermediate for cancers of the glossoepiglottis and the marginal supraglottis (20-38%), and greatest for cancers of the pyriform sinus (47%). The risk of nodal recurrence increased from 8% for those without cancer in lymph nodes to 38% for those with occult or palpable cancer in lymph nodes. A policy of observing the NO neck in patients with a low incidence of occult lymphatic metastases and a low risk of neck recurrence to avoid the unnecessary irradiation of many to benefit a few is discussed.