Analysis of Treatment Results for Floor-of-mouth Cancer

Objective: This study reports the results of treating floor-of-mouth cancer with five different treatment modalities with long-term follow-up.

Study Design: Retrospective study of 280 patients with floor-of-mouth cancer treated in the Department of Otolaryngology-Head and Neck Surgery at Washington University Medical School (St. Louis, MO) from 1960 to 1994.

Methods: Patients with biopsy-proven squamous cell carcinoma of the floor of mouth who were previously untreated were treated with curative intent by one of five modalities and were all eligible for 5-year follow-up. The treatment modalities included local resection alone, composite resection alone (with neck dissection), radiation therapy alone, local resection with radiation therapy, and composite resection with radiation therapy. Multiple diagnostic, treatment, and follow-up parameters were studied using standard statistical analysis to determine statistical significance.

Results: The overall 5-year disease-specific survival (DSS) was 56% with death due to tumor in 44% of patients. The 5-year cumulative disease-specific survival (CDSS) was 0.61 (Kaplan-Meier probability) with a mean of 8.3 years and a median of 9.7 years. The DSS by treatment modality included local resection (76%), composite resection (63%), radiation therapy (43%), local resection with radiation therapy (61%), and composite resection with radiation therapy (55%). Overall, there was no significant difference in DSS by treatment modality. Recurrence at the primary site (41%) was the most common site of treatment failure. Nineteen percent of patients had recurrence in the neck. Eighty-eight percent of initial recurrences occurred within 60 months after the onset of treatment. Metastasis to a distant site occurred in 30% of patients. Twenty percent of these patients had second primary cancers, and 53% of these patients died of their second primary cancers.

Conclusions: Significantly improved 5-year DSS was seen in the patients with clear margins, early clinical tumor stage, and negative nodes. Significantly decreased 5-year survival was seen in the patients with involved margins, advanced clinical tumor stage, positive nodes, and tumor recurrence. Patients with no clinically positive nodes (cNO) can be observed safely for regional nodal disease and subsequent positive nodes can be treated as they occur with no adverse affect on survival. Because of high recurrence rates at the primary site and neck, and an increased rate of both distant metastasis and the development of second primary cancers, patients should be monitored closely for a minimum of at least 5 years.