Retromolar trigone squamous cell carcinoma treated with radiotherapy alone or combined with surgery: a 10-year update

Abstract

Purpose/objectives

Treatment outcomes were analyzed for patients who received radiotherapy for squamous cell carcinoma of the retromolar trigone at a single institution.

Materials/methods

We reviewed the medical records of 110 patients treated with radiotherapy alone (n = 36) or radiotherapy combined with surgical resection of the primary tumor (n = 74) between June 1966 and October 2013. The median follow-up was 4.5 years for all patients and 11.8 years for living patients (range, 1.3–23.5 years).

Results

The 5-year local–regional control rates after definitive radiotherapy versus surgery and radiotherapy for stages I–III were 52% and 89% and for stage IV they were 46% and 58%, respectively. The 5-year cause-specific survival rates after definitive radiotherapy compared with surgery and radiotherapy for stages I-III were 57% and 82% and for stage IV they were 45% and 43%, respectively. Multivariate analyses revealed that the likelihood of cure was better with surgery and radiotherapy compared with radiotherapy alone (p = 0.041).

Conclusion

Patients treated with surgery and radiotherapy had a better chance of cure than those treated with radiotherapy alone. Complications of treatment were common in both groups but more common in patients who underwent surgery.

Introduction

The retromolar trigone (RMT) is an uncommon subsite of squamous cell carcinoma (SCC) of the head and neck. The prognoses for SCC of the tonsil, floor of mouth, alveolar ridge, and RMT differ drastically despite each anatomic unit being separated by only millimeters [1], [2], [3]. Surgery is technically demanding since the tumor has often extended to adjacent sites at the time of diagnosis, and complete removal frequently requires resection and reconstruction of the mandible, oral mucosa, oropharynx and even the maxilla [4], [5], [6], [7], [8].

In one of the larger retrospective series describing SCC of the RMT, Byers et al. [9] reviewed 110 patients who received radiotherapy (RT), surgery, or both at the M. D. Anderson Cancer Center (Houston, TX). Tumors frequently extended to adjacent subsite with 50% demonstrating mandibular invasion. Thirty percent of patient had nodal metastases, with ipsilateral spread to level II being the most common pattern. Few had multiple or bilateral nodal metastases. This is in contrast to nearby sites such as the base of tongue or tonsillar areas where multilevel and bilateral node involvement is not uncommon [2], [10].

The optimal treatment for SCC of the RMT remains controversial due to a paucity of clinical and functional outcomes data. Despite their distinct behavior, RMT primaries are often grouped in the existing literature with adjacent oral cavity subsites and even with the anterior tonsillar pillar (ATP), which is not in the oral cavity [11], [12]. There is consensus that bone invasion necessitates surgical intervention in patients who are medically able to tolerate it, and modern studies suggest that this is much more common than was appreciated with historical imaging [13], [14]. Short of this clear delineation, stage-based treatment has proven unsatisfactory since T staging in the oral cavity is based on size and invasion of adjacent structures, such as bone. Thus, with RMT cancer locally advanced tumors may be quite small, but invade bone [8], [15]. Barker et al. [16] stated: “the stage according to diameter of the lesion in the ATP-RMT area is not a reflection of the volume of the cancer.”

The purpose of this study was to report survival and clinical outcomes of patients treated with curative intent at the University of Florida (UF) using definitive RT or surgery with RT. This analysis is a 10-year update of our first publication on SCC of the RMT [17] with a longer duration of follow-up and additional patients.