1

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 . 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 .

In one of the larger retrospective series describing SCC of the RMT, Byers et al. 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 .

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 . 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 . 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 . Barker et al. 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 with a longer duration of follow-up and additional patients.

2

Materials and methods

From June 1966 to October 2013, 110 patients with SCC of the RMT were treated with curative intent using RT alone or combined with surgery at UF. Follow-up for this study ranged from 0.2 to 23.8 years with a median of 4.5 years for all patients and 11.8 years for living patients. One patient was lost to follow-up.

This work is part of an institutional review board-approved outcome tracking project. Staging was performed according to the 7th edition of the American Joint Committee on Cancer (AJCC) staging system. Patient and tumor characteristics are shown in Table 1 .

Patients were excluded if they had received any part of their treatment at another facility or if they failed to complete their planned course of RT at UF. Patients with distant metastatic disease at the time of diagnosis were also not considered. Ninety-one percent of patients were male. Whites made up 81% of this population, African Americans 10%, and patients with other racial backgrounds 9%.

Thirty-six patients were treated with definitive RT, 2 of whom had a planned neck dissection. Seventy-four patients were treated with surgery and preoperative RT (n = 19) or postoperative RT (n = 55). Combined-modality therapy was more often used in patients with T3 and T4 disease. Patients with either no positive lymph nodes or N2b disease were also more likely to have both RT and surgery, while those with N1, N2a, or N3 necks were about equally divided between modalities. Our policy has been to perform a neck dissection in patients with N3 disease if the nodal disease appeared to be completely resectable and the tumor appeared to be controlled elsewhere. From 1966 to 1985, patients had either RT or surgery plus RT in roughly equal numbers, but after 1985 combined-modality therapy was used for 55 of 65 patients (85%). Records were not kept to indicate which patients were not considered for combined modality therapy owing to comorbidities that made them poor candidates for surgery.

Follow-up for this study ranged from 0.2 to 23.8 years with a median of 4.5 years for all patients and 11.8 years for living patients. One patient was lost to follow-up.

For patients treated with RT alone, the median dose was 70 Gy (range, 46 to 81.6 Gy). The median pre- or post-surgical RT dose was 65 Gy (33.01 to 75 Gy). Ten patients treated between 1970 and 1974 received split-course RT; 1 was unplanned. Twice-daily fractionation was used for 25 patients, and once-daily treatment for the remaining 85. Chemotherapy was rarely used, but platinum-based therapy was given to 5 patients treated with definitive radiation and 5 treated with surgery and RT. Two combined-modality patients received cetuximab.

Complications were recorded if the patient required hospitalization with the exception of those who required a permanent percutaneous endoscopic gastrostomy (PEG) tube, which was defined as PEG-tube dependence after two years, and those with auditory canal stenosis, which was defined as the point at which surgical intervention was recommended.

Statistical calculations were performed using SAS statistical software (SAS Institute, Cary, North Carolina). The Kaplan–Meier product–limit method provided estimates of local control, local–regional control, freedom from distant metastases, cause-specific survival, and overall survival. Statistical significance between strata of selected explanatory variables was determined using the log rank test. Proportional hazards regression was used for multivariate analysis; backward selection provided the most parsimonious final model.

Parameters included in the multivariate analyses were overall stage (I–II vs III–IV), T stage, (T1–T2 vs T3–T4), N stage (N0 vs N1–N3), treatment group (definitive RT vs surgery and RT), gender, and race (African American vs Other). Performance status was infrequently documented and was therefore not included despite being a likely prognostic factor.

2

Materials and methods

From June 1966 to October 2013, 110 patients with SCC of the RMT were treated with curative intent using RT alone or combined with surgery at UF. Follow-up for this study ranged from 0.2 to 23.8 years with a median of 4.5 years for all patients and 11.8 years for living patients. One patient was lost to follow-up.

This work is part of an institutional review board-approved outcome tracking project. Staging was performed according to the 7th edition of the American Joint Committee on Cancer (AJCC) staging system. Patient and tumor characteristics are shown in Table 1 .

Table 1

Patient and tumor characteristics.

Characteristics	Definitive Surgery	Radiotherapy Alone	Total
Sex
Male	54	28	82
Female	20	8	28
Race
White	65	29	94
African American	6	5	11
Other	3	2	5
T Stage
T1	7	7	14
T2	17	15	32
T3	11	4	15
T4	39	10	49
N Stage
N0	59	28	87
N1	8	5	13
N2a	0	2	2
N2b	6	1	7
N3	1	0	1
Overall Stage
I	6	5	11
II	9	11	20
III	14	7	21
IVa	43	9	52
IVb	2	4	6

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. Ansa to recurrent laryngeal neurorrhaphy in the setting of laryngeal nerve sacrifice: a cadaveric study to evaluate a reconstructive option
2. Middle ear pressure during sleep and the effects of continuous positive airway pressure
3. Influence of insertion depth in cochlear implantation on vertigo symptoms and vestibular function
4. Failed organ preservation strategy for adult laryngeal embryonal rhabdomyosarcoma

Stay updated, free articles. Join our Telegram channel

Join