Scar Bolus Omission During Adjuvant Intensity Modulated Radiation Therapy (Imrt) Does Not Increase Risk Of Incisional Recurrence For Oral Cavity Cancers

Locoregionally advanced oral cavity cancers have an increased risk of locoregional recurrence despite multimodality therapy. In an effort to decrease scar recurrences in the post-operative setting, bolus has historically been used to increase the dose to the neck scar in intermediate and high-risk contexts. Since transitioning to IMRT for most post-operative oral cavity cases, we have routinely omitted bolus placement on the neck scar. Here we examine rates of scar recurrences using this approach. This is an institutional review board approved retrospective study. Patients with intermediate or high risk squamous cell carcinoma of the oral cavity treated with post-operative IMRT were identified from an institutional database. Patients were treated using tomotherapy based IMRT. Demographics, clinical/pathologic parameters, dosimetric data, and cancer-related outcomes were recorded and analyzed. Statistical software was used to determine Kaplan Meier estimates for disease control and survival. Twenty-eight pts met inclusion criteria for this analysis and were treated from 2009 to 2017. Median age was 56 years old (range 35-75); 59% were male. All patients underwent complete resection of the primary tumor with selective neck dissection. Subsites included 11 floor of mouth (40%), 6 oral tongue (21%), 5 buccal mucosa (18%), 3 lower lip (11%), 2 hard palate (7%), and 1 retromolar trigone (4%). Seventy-one percent were pathologically node positive; 36% had extracapsular extension (ECE). Concurrent chemotherapy was used in 53% of patients. Twenty-four patients (86%) were treated using SIB technique. The post-operative neck was irradiated in all cases. Median dose to the highest risk volume was 6000 cGy (range 5800-6600 cGy). Median treatment package time was 95 days (range 76-137 days). Median follow up for surviving patients after treatment was 21 months (range 3-93 months). One patient experienced a local recurrence at 2 months. Four patients developed distant metastatic progression at a median of 3 months (range 1-16 months). No patients have experienced a regional nodal relapse and there have been no scar recurrences. 3-year actuarial estimates for DFS and OS are 74.7% and 87.4%. Scar recurrences after post-operative IMRT are rare. Bolus omission has not compromised disease control along the scar.