Metastatic carcinoma in the cervical lymph nodes from an unknown primary site: results of bilateral neck plus mucosal irradiation vs. ipsilateral neck irradiation.

PURPOSE: To compare the outcome for patients with squamous cell carcinoma of cervical lymph nodes metastatic from an unknown primary site who were irradiated to both sides of the neck and potential mucosal sites with opposed photon beams, and for those irradiated to the ipsilateral side of the neck alone with an electron beam.

METHODS AND MATERIALS: Fifty-two patients with squamous cell carcinoma metastatic to cervical lymph nodes from an unknown primary site were irradiated by two different methods. Thirty-six were irradiated with a bilateral technique (BT), i.e., to both sides of the neck, including the naso-oro-hypopharyngeal mucosa, and 16 were irradiated with an electron beam (EB) to the ipsilateral side of the neck alone. Twenty patients of the BT group and 11 of the EB group had cervical lymph node dissections, and the remaining 21 patients had lymph node biopsies, prior to radiotherapy.

RESULTS: Tumor control in the ipsilateral side of the neck did not differ for either radiation technique, but was significantly higher after lymph node dissection than after biopsy (90 vs. 48%; p = 0.0004). Control of subclinical metastases in the contralateral cervical lymph nodes was higher for patients irradiated with BT than for patients irradiated with EB (86 vs. 56%; p = 0.03). The occult primary was later discovered in 8% of the patients in the BT group and 44% of the EB group (p = 0.0005). The disease-free survival rate at 5 years for patients who had lymph node dissection prior to irradiation was 61%, and was 37% for those who had biopsy (p = 0.05). Only 20% of patients who subsequently developed an occult primary were salvaged and survived for 5 years after salvage treatment.

CONCLUSION: Bilateral neck and mucosal irradiation is superior to ipsilateral neck irradiation in preventing contralateral cervical lymph node metastases and the subsequent appearance of an occult primary cancer. Both techniques combined with cervical lymph node dissection were equally effective in controlling the ipsilateral neck disease.