Squamous cell carcinoma of unknown primary tumor metastatic to neck nodes: role of elective irradiation.

In patients with squamous cell carcinoma (SCC) metastases to neck lymph nodes and unknown primary tumor, the role of elective irradiation of uninvolved neck and potential mucosal primary sites is yet to be determined. The aim of this study was to review the experience treating SCC of unknown primary metastatic to neck nodes with surgery and postoperative radiotherapy (PORT) in Slovenia between 1995 and 2010 and to determine the importance of the extent of irradiated volume. For this purpose, the nationwide Cancer Registry of Slovenia database was used for identifying patients. 126 patients were identified. Involved-field PORT and extended-field PORT was used in 50 and 76 patients, respectively. At 5 years, locoregional control was 86 %, disease-specific survival 77 %, and overall survival 57 %. In multivariate analysis, the extent of irradiated volume has not been predictive for any outcome under study. Grade ≥3 acute and late radiotherapy-induced toxicities were more frequent in the extended-field PORT group. In conclusion, although not superior, involved-field PORT seems to be a preferred treatment option in SCC of unknown primary metastatic to neck nodes due to significantly reduced toxicity and better prospects for successful salvage.