Oral tongue squamous cell carcinoma (OTSCC) resected with positive or narrow margins requires re-resection or External Beam Radiotherapy (EBRTx) to the primary tumour bed to avoid the increased risk of local recurrence. Brachytherapy (BRTx) allows the delivery of high dose conformal radiation to the tumour site while sparing surrounding normal structures thus avoiding the need for further surgery and morbidity associated with EBRTx applied to the oral cavity. BRTx is used as the primary and adjuvant treatment of OTSCC in France, Japan, and South Africa. No North American experience in the use of BRTx for OTSCC margin control has been previously reported.
Prospective single-centre study of patients with OTSCC (T1-3, N0-3, M0) treated with resection of primary tumour ± regional nodal resection and intra-operative insertion of BRTx catheters between September 2009 and April 2017. BRTx in the form of high dose rate Iridium192 was administered twice daily at 40.8Gy/12Fr for ‘Positive’ (≤2mm) margins, at 34Gy/10Fr for ‘Narrow’ (2.1-5mm) margins, and not given for ‘Clear’ (>5mm) margins over the course of 5 days. Further adjuvant treatment with EBRTx to the neck ± Chemotherapy (CTx) was given as per pathological findings. The Kaplan-Meier model was used for survival and local/locoregional control analysis. Cox regression analysis was used to assess the effects of various parameters on survival and control.
Fifty five patients were recruited with a median follow up time of 25.4 months. Clear margins were noted in 23.6%, while Narrow (2.1-5mm) and Positive (≤2mm) margins were found in 45.5% and 30.9% respectively. Forty one patients (74.6%) were treated with BRTx, as 12 patients had clear margins and 2 patients had unfavourable tumour anatomy for BRTx catheter insertion. Lower BRTx dose was given in 47.3% of cases and 27.3% received the higher dose. EBRTx was avoided in 64.3%. Recurrence was observed in 12 cases (21.8%): 6 local (10.9%), 4 isolated regional (7.3%), and 2 isolated distant; with median time to recurrence being 11 months. Overall Survival (OS) at 3 and 5 years was 75.6% and 59.1% respectively, while Disease Specific Survival (DSS) was 82.3% and 68.6% at 3 and 5 years respectively. The 3 year Disease Free Survival (DFS), Local Control (LC) and Locoregional Control (LRC) were 74.3%, 86.3%, and 77.7% respectively. Recurrence and survival outcomes were not associated with the use of or specific dose of BRTx on Cox regression analysis. Acute and late toxicity secondary to BRTx was minimal: one patient experiencing an acute haemorrhage during BRTx catheters removal and 3 patients requiring long-term opioid analgesia for tongue pain.
This is the first North American study examining the use of BRTx for margin control in the treatment of OTSCC. The use of BRTx after primary resection with positive/narrow margins with or without EBRTx to the neck/CTx achieves outcomes comparable to traditional treatment of surgery followed by re-resection or EBRTx ± CTx. Morbidity associated with oral cavity EBRTx or secondary resection and reconstruction is thus avoided. Both acute and late toxicity rates are low and compare favourably with other BRTx OTSCC studies.