Postoperative brachytherapy alone and combined postoperative radiotherapy and brachytherapy boost for squamous cell carcinoma of the oral cavity, with positive or close margins.

Abstract

Postoperative radiotherapy is necessary for squamous cell carcinoma (SCC) of the oral cavity with positive or close margins. The aim of the study is to define the indications of postoperative brachytherapy (BRT). From 1979 to 1993, 82 patients with positive or close margins had postoperative BRT (58 T1-2, 24 T3-4, 45 mobile tongue, 37 floor of mouth). Forty-six patients had combined radiotherapy (RT) with a mean dose of 48 Gy, and BRT boost with a mean dose of 24 Gy. Thirty-six patients had BRT alone with a mean dose of 60 Gy. BRT was performed with interstitial low dose rate Iridium 192. Overall survival (OS), cause-specific survival (CSS), and local control (LC) at 5 years were, respectively, for T1-2/N0N- with BRT, 75%, 85%, and 88%,and with RT-BRT 70%, 92%, and 92%; for T1-2/N+ with RT-BRT, 44%, 67%, and 78%; for T3-4/N- with RT-BRT, 42%, 90%, and 80%; and for T3-4/N+ with RT-BRT, 22%, 43%, and 57%. Prognostic factors for OS, CSS, and LC were N+ (p </=.009), extracapsular spread (ECS+;p </=.000001), and T stage for LC only (p =.02). Prognostic factors for complications were a high number of wires with a cutoff at five wires (p =.008), a high dose rate with a cutoff at 0.57 Gy/hr (p =.01), and a high total dose (BRT + RT) with a cutoff at 71 Gy (p =.07). BRT alone for SCC T1-2/N0N- is better than RT-BRT because, with equivalent results, it avoids the adverse events of postoperative RT (xerostomia) and permits the treatment of a second head and neck primary in nonirradiated tissue. The results for the T3-4/N- are acceptable with this approach (ie, RT-BRT) but may be improved for N+.