Outcomes of patients diagnosed with carcinoma metastatic to the neck from an unknown primary source and treated with intensity-modulated radiation therapy

Background: There are few published studies to guide the treatment of carcinoma metastatic to the neck from an unknown primary (CUP). In this regard, the objective of the current study was to share the authors' current experience treating patients with CUP using intensity-modulated radiation therapy (IMRT), which principally targeted both sides of the neck, the nasopharynx, and the oropharynx. Methods: This was a retrospective study in which an institutional database search was conducted to identify patients with CUP who received IMRT. Data analysis included frequency tabulation, survival analysis, and multivariable analysis. Results: Two-hundred sixty patients met inclusion criteria. The most common lymph node category was N2b (54%). IMRT volumes included the entire pharyngolaryngeal mucosa in 78 patients, the nasopharynx and oropharynx in 167 patients, and treatment limited to the involved neck in 11 patients. Eighty-four patients underwent neck dissections. The 5-year overall survival, regional control, and distant metastases-free survival rates were 84%, 91%, and 94%, respectively. Over 40% of patients had gastrostomy tubes during therapy, and 7% patients were diagnosed with chronic radiation-associated dysphagia. Higher lymph node burden was associated with worse disease-related outcomes, and in subgroup analysis, patients with human papillomavirus-associated disease had better outcomes. No therapeutic modality was statistically associated with either disease-related outcomes or toxicity. Conclusions: Comprehensive IMRT with treatment to both sides of the neck and to the oropharyngeal and nasopharyngeal mucosa results in high rates of disease control and survival. The investigators were unable to demonstrate that treatment intensification with chemotherapy or surgery added benefit or excessive toxicity.