The impact of surgical margin status and use of an interstitial implant on T1,T2 oral tongue cancers after surgery

In patients with T1, T2 oral tongue carcinoma treated with surgical resection, postoperative radiation therapy (RT) is required especially when surgical margins contain tumors. Irradiation techniques include external beam, interstitial implants, or a combination of the two modalities. We investigated whether positive surgical margin remains a poor prognostic factor after radiation therapy, and the contribution of interstitial implants to disease control.

Between 1972 and 1989, 55 patients were treated postoperatively at the Mallinckrodt Institute of Radiology for T1, T2 squamous cell carcinomas of the oral tongue. Surgeries included 26 wide excisions or excisional biopsies and 29 composite resections or hemiglossectomies. Thirty-nine patients received external radiation therapy alone and 16 patients had an interstitial implant (ISI) as part of the treatment. The minimum follow-up is 4 years.

At 2 and 5 years, the overall survivals for all patients were 82 and 68%. The disease-free survivals (DFS) were 82 and 70%, respectively. There was no significant difference in the pattern of failure and DFS when stratified by the status of surgical margins and the type of the surgical procedure. Local control was achieved in 15 of 18 patients when surgical margins were involved by tumor and in 29 of 37 patients without tumor involving margins (p = 0.05). Ten of 18 (56%) patients with tumor involving resection margins were treated with ISI, whereas only 3 or 33 (9%) of those with negative margins received ISI. Local control was achieved in 32 of 39 patients treated with external beam RT alone, and 13 of 16 patients who received interstitial implant (p = 0.05). Four patients treated with ISI developed persistent soft tissue ulceration and mandibular bone exposure.

Postoperative radiation therapy converted the ominous outcome of patients with tumor involving surgical margins. Patients with positive surgical margins were often selected to be treated with interstitial implants. We found that the local control was as good as in those with a more favorable pathology (negative margins) and treated with external RT alone. Further investigation is needed to optimize the implant treatment to minimize the complications.