The occult head and neck primary: to treat or not to treat?

In patients with cervical node metastases from an unknown primary malignancy, there is unresolved controversy regarding the utility of elective irradiation of putative pharyngeal primary sites as part of the management plan. We analysed the experience of the Peter MacCallum Cancer Institute to assess the risk of withholding mucosal irradiation in relation to the diagnostic algorithm used to exclude a primary lesion at the time of initial presentation. Between 1983 and 1992, 69 patients were seen with metastatic squamous or undifferentiated carcinoma in cervical nodes from an unknown primary site. Neck nodal stage was NX or N1 13%; N2 52%; N3 35%. Nodal disease was bilateral in 12% of patients. Investigations included examination under anaesthesia, with or without random biopsies, in 84%, and CT scanning of the head and neck in 55%. Treatment was by surgery alone in four patients, by radiotherapy alone in 23, and by combined modalities in 40. Two patients received no treatment. Seventeen were treated with palliative intent. The radiotherapy fields provided comprehensive coverage of the pharynx in only eight patients and partial coverage in five. The estimated overall 5-year survival was 36%. Eleven primary tumours were detected between 7 months and 7 years after the initial treatment, of which nine were in head and neck sites. This yielded an estimated incidence of 30% at 10 years, which is similar to the risk of the development of a second primary after the successful treatment of a known head and neck cancer. Only three patients (none of whom had a CT scan as part of their initial evaluation) manifested a primary in an unirradiated pharyngeal site within 2 years of treatment. As the accuracy of imaging improves, the risk of missing an occult primary lesion will decrease further. We conclude that the use of standardized diagnostic investigations incorporating modern imaging substantially eliminates the indication for comprehensive elective mucosal irradiation with its consequent morbidity. The overriding priority in patients who present with advanced neck disease is to secure regional control.