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BACKGROUND: The efficacy of postoperative irradiation of the neck after lymph node dissection in terms of prevention of cervical node recurrence (NR) has not been demonstrated in patients with NO squamous cell carcinoma of the oral cavity. METHODS: This multicenter retrospective analysis comprises 826 patients with squamous cell carcinoma of the oral cavity, all clinically NO. The primary tumor was treated by resection or brachytherapy. All patients underwent cervical dissection adapted to the site of the tumor. Fourty seven N+ patients with capsular rupture were excluded; 160 patients were N+ without capsular rupture (N+ CR-), and 619 were N-. Postoperative cervical irradiation was performed in 67 of 160 N+ CR- patients and in 49 of 619 N- patients. RESULTS: NR developed in 78 patients, associated with local recurrence in 33 cases and isolated in 45 cases. Twenty-six of the 45 cases of isolated NR occurred in the 619 N- patients (4%), and 19 occurred in the 160 N+ CR- patients (12%, p = .001). The 26 NR observed in the N- patients occurred in nonirradiated patients. Among the 19 NR observed in the N+ CR- patients, the incidence of recurrence was not significantly different between irradiated patients (6 NR of 67.9%) and nonirradiated patients (13 NR of 93, 14%). NR rates also did not differ according to the number of lymph nodes invaded nor according to the level of the positive nodes; 14 of 45 isolated NR occurred in a nondissected suprahyoid region. Of 779 patients, 255 (33%) subsequently developed a metachronous cancer; 153 upper respiratory and digestive tract tumors, 37 lung tumors, 33 esophageal tumors, and 32 other tumors. Isolated cervical failure was responsible for 40 deaths. CONCLUSION: The low NR rate in NO N+ CR- patients means that postoperative irradiation can be confined to N+ CR+ patients and, as a precautionary measure, to patients with more than 3 N+ CR-. Keeping irradiation in reserve allows the treatment of metachronous cancers, which are particularly frequent in these patients, in whom the 5-year survival rate is 54% in N+ CR- and 69% in N-.