Squamous Cell Carcinoma of the RetroMolar Trigone (RMT)

Squamous cell carcinoma of the retromolar trigone is relatively uncommon. Patients usually have a long history of tobacco abuse, often combined with heavy ethanol consumption. The most common complaints at diagnosis are pain and trismus; the pain is either local or referred to the ear. The tumor frequently extends to adjacent sites before it is diagnosed. Byers  reported on a series of 110 previously untreated patients who were treated with surgery and/or radiotherapy (RT) at the M. D. Anderson Cancer Center (Houston, Texas). Extension to the following adjacent sites before treatment was observed: soft palate, 65 patients (59%); buccal mucosa, 47 patients (43%); anterior tonsillar pillar, 93 patients (85%); and mandibular gingiva, 67 patients (61%). Radiographic evidence of bone invasion was present in 17 patients (15%). Involvement of the regional lymphatics is less often observed than it is for tonsillar or tongue base carcinomas. In Byers  33 of 110 patients (30%) had clinically positive nodes at diagnosis. The most commonly involved lymph nodes are in Level II. No patient in the M. D. Anderson Cancer Center series presented with bilateral involved nodes and only 3 patients (3%) had multiple levels involved in the ipsilateral neck.

The treatment of retromolar trigone carcinomas is controversial. Patients with early-stage lesions are usually treated with a single modality (either surgery or RT), whereas those with advanced disease are frequently treated with surgery and adjuvant RT. The optimal treatment is often debatable because there are few reported outcomes data and, at times, retromolar trigone cancers are grouped with tumors arising from adjacent sites, such as the anterior tonsillar pillar. see the study below and review here.

William M. Mendenhall, Departments of Radiation Oncology, University of Florida College of Medicine, Gainesville, Florida

Cancer 2005;103:2320

Between June 1966 and August 2003, 99 patients were treated with radiotherapy alone (35 patients) or radiotherapy combined with surgery (64 patients). Followup ranged from 0.2 to 23.8 years (median, 3.3 yrs). All living patients had followup for at least 1 year.
RESULTS: The 5-year local-regional control rates after definitive radiotherapy versus surgery and radiotherapy were as follows: Stages I-III, 51% and 87%; Stage IV, 42% and 62%; and overall, 48% and 71%, respectively. The 5-year cause-specific survival rates after definitive radiotherapy compared with surgery and radiotherapy were as follows: Stages I-III, 56% and 83%; Stage IV, 50% and 61%; and overall, 52% and 69%, respectively. Multivariate analyses revealed that the likelihood of cure was better with surgery and radiotherapy compared with definitive radiotherapy.
CONCLUSIONSThe likelihood of cure after treatment for retromolar trigone squamous cell carcinoma was influenced by the extent of disease and treatment. Patients treated with surgery and radiotherapy had a better outcome than those treated with radiotherapy alone.

The treatment of squamous cell carcinoma of the retromolar trigone is controversial. Determining the optimal management strategy is all the more difficult because it is a relatively uncommon tumor, and there is a paucity of data on outcomes. The natural history and response to surgery and/or RT for head and neck cancers vary significantly depending on primary site and extent of disease. Oropharyngeal carcinomas have a higher probability of local control after definitive RT than similarly staged oral cavity cancers. T1-T2 squamous cell carcinomas of the anterior tonsillar pillar have lower local control after RT than tonsillar fossa carcinomas, and it is likely that retromolar trigone lesions fare less well than anterior tonsillar pillar tumors.

Byers  reported on 110 previously untreated patients with squamous cell carcinomas of the retromolar trigone who received surgery and/or RT with curative intent at the M. D. Anderson Cancer Center between 1965 and 1977. All patients had a 2-year minimum followup. Surgery was usually selected for patients with associated leukoplasia, poor dentition, large infiltrating tumors, bone destruction, and/or trismus. Treatment consisted of surgery alone, 46 patients; preoperative RT and surgery, 3 patients; surgery and postoperative RT, 11 patients; and RT alone, 50 patients. The crude local control rates after surgery alone or combined with adjuvant RT versus RT alone were as follows: Stage T1, 7 (100%) of 7 patients versus 5 (83%) of 6 patients; Stage T2, 24 (92%) of 26 patients versus 26 (84%) of 31 patients; and Stage T3, 12 (92%) of 13 patients versus 6 (86%) of 7 patients. The 5-year overall survival rate was 26%. Of 50 patients treated with definitive RT who were locally controlled, 7 (14%) required a partial mandibulectomy for osteoradionecrosis.

Huang reported on 65 patients treated with RT alone or combined with surgery at Washington University (St. Louis, Missouri) between 1971 and 1994. Patients had followup for 5 years or more. Sixteen patients received definitive RT, and the remaining patients were treated with surgery and preoperative RT (10 patients) or postoperative RT (39 patients). The 5-year disease-free survival rates were as follows: preoperative RT and surgery, 90%; surgery and postoperative RT, 63%; and definitive RT, 31%. Multivariate analysis of disease-free survival revealed that treatment modality (P = 0.002) and N Stage (P = 0.012) significantly influenced this endpoint. Multivariate analysis showed that the only parameter that significantly influenced local-regional control was the treatment modality (P = 0.046). Patients treated with surgery and adjuvant RT had a more favorable outcome than those treated with definitive RT. The rates of severe complications (osteoradionecrosis, soft tissue necrosis, and severe trismus) were as follows: preoperative RT and surgery (0%); surgery and postoperative RT, 12%; and RT alone, 11%. The authors of the current study concluded that surgery and adjuvant RT resulted in improved local-regional control and disease-free survival compared with RT alone.

Kowalski  reported on 114 patients who underwent a hemimandibulectomy and neck dissection for retromolar trigone squamous cell carcinoma between 1960 and 1991 at the Hospital A. C. Camargo (São Paulo, Brazil). Sixty-one patients received adjuvant postoperative RT to a median dose of 50 Gy (range, 10-70 Gy) for positive margins and/or involved nodes. Median followup was 25 months; 19 patients were lost to followup from 1 to 47 months (mean, 15 mos) after treatment. Complications were observed in 52% of patients and included wound dehiscence (20%), wound infection (18%), flap necrosis (12%), fistula (12%), seroma (7%), pneumonia (5%), hematoma (4%), and/or carotid rupture (2%). There was one postoperative death due to a pulmonary embolus. The 5-year disease-free and overall survival rates were 49% and 55%, respectively. Advanced stage and hard palate involvement were significantly associated with decreased disease-free and overall survival.

Our data and those reported by Huang  indicate that the probability of cure is influenced by the extent of disease and treatment. Patients treated with surgery and RT appear to have a more favorable outcome than those treated with RT alone. In contrast, Byers  observed similar local control rates after either surgery alone or combined with adjuvant RT compared with definitive RT. The reasons for these differing observations are unclear. A small subset of early-stage patients treated with surgery alone at our institution was not included in our analysis, which would have biased the comparison in favor of those who received definitive RT. Conversely, treatment of the occasional patient with advanced, unresectable disease would have biased the comparison in favor of surgery. Based on the limited data available, it is likely that surgery and RT offer a better probability of cure than definitive RT.

Huang  observed similar complication rates after RT alone compared with surgery and RT, whereas we observed more severe complications in those treated surgically. Kowalski et al.[16] also observed a relatively high rate of complications after surgery alone or combined with RT. Although this should be considered when determining the optimal treatment for a particular patient, the risk of severe postoperative complications is probably offset by the increased likelihood of dying of cancer after definitive RT, particularly for patients with advanced disease.

Cancer of retromolar trigone: Long-term radiation therapy outcome

Chih-Jen Huang, MD
Head & Neck. Volume 23 Issue 9, Pages 758 - 763   Published Online: 8 Aug 2001

Mallinckrodt Institute of Radiology Washington University Medical Center, 4939 Children's Place, Suite 5500, St. Louis, Missouri 63110

Background

Cancer of the retromolar trigone is an uncommon head and neck cancer. In this retrospective study, we identified the prognostic factors and evaluated the therapeutic outcomes of patients treated with preoperative radiation therapy (RT), postoperative RT, and RT alone. Between 1971 and 1994, 65 patients with histologically proven epidermoid carcinoma of the retromolar trigone were treated at the Mallinckrodt Institute of Radiology; 10 patients received preoperative RT (30-55.2 Gy), 39 received postoperative RT (46-66.6 Gy), and 15 were treated with RT alone (63-74 Gy). Surgery included 44 composite resections and 7 wide excisions. The minimum follow-up was 5 years.

Results

The 5-year disease-free survival rates were 90% with preoperative RT, 63% with postoperative RT, and 31% with RT alone. The 5-year disease-free survival rates were 76% for patients with T1 disease, 50% for T2, 72% for T3, and 54% for T4. The 5-year disease-free survival rates were 69% for patients with NO disease, 56% for N1, and 26% for N2. The locoregional recurrence rates were 10% (1 of 10) for preoperative RT, 23% (9 of 39) for postoperative RT, and 44% (7 of 16) for RT alone. On multivariate analysis, the significant factors for disease-free survival were treatment modality (p = .002) and N stage (p = .012); for locoregional control it was treatment modality (p = .046); and for distant metastasis it was N stage (p = .002). The incidence of bone necrosis, soft tissue necrosis, and severe trismus was 12% with postoperative RT, 11% with RT alone, and none with preoperative RT. Conclusions: Combination surgery with postoperative or preoperative RT offers better locoregional control and disease-free survival than RT alone for epidermoid carcinoma of the retromolar trigone. Lymph node status significantly influences the disease-free survival and distant metastasis rates