Oral cavity malignancies are the eighth most common cancer worldwide.(1) Floor of mouth malignancies are the second most common sub-site in the oral cavity after tongue malignancies.(2,3) Globally Ninety-five percent of oral cavity malignancies are squamous cell carcinoma (SCC) (2,4)
The floor of mouth is defined as the mucosal surface below the tongue bordered by the alveolar ridge laterally and anteriorly, and the oral tongue posteriorly and medially.(5) The lingual frenulum divides it in the midline. Its deep margin is the mylohyoid muscle. The contents include the sublingual glands, the deep portion of the submandibular gland, the sub-epithelial minor salivary glands, the deep lingual vessels, Wharton’s duct and the lingual nerve.(5)
The arterial supply to the floor of the mouth is from the dorsal lingual, sublingual, and deep lingual branches of the lingual artery. The venous drainage is via the lingual veins that drain into the facial and retromandibular veins. (5) The lingual nerve provides general sensory innervation to the floor of the mouth and tongue as well as special taste sensation through the accompanying chorda tympani branch of the facial nerve.(5)
Primary neoplasms may arise from the mucosa, salivary glands, muscle or neurovascular tissues.(5)
Lymphatic drainage of the floor of mouth is via the cervical lymph nodes. The first echelon lymph nodes of the floor of mouth are located in the supra-omohyoid triangle.(6) The lymphatic channels accompany the lingual venous system, and their density increases from the anterior to the posterior. Lymphatic metastases generally occur in a predictable fashion, but skip lesions may be noted (2)
Risk factors known for development of oral cavity SCC are tobacco usage, alcohol consumption, nutritional deficits (carotenoids & vitamin A, C and E), Fanconi’s anaemia, a genetic predisposition, Human Papilloma Virus infection, previous head and neck malignancy and radiation exposure. Betel quid chewing (made of the areca nut wrapped in betel leaf) amongst the Asian population is also known to be a strong risk factor.(5)
Premalignant lesions which represent varying degrees of epithelial dysplasia are also a significant risk factor for oncogenesis. The most common premalignant lesions in the oral cavity are leukoplakia, erythroplakia, and submucous fibrosis.(5)
The Tumour, Node, Metastases (TNM) staging system devised by the American Joint Committee of Cancer (AJCC) is used to categorize malignancies of the oral cavity (Appendix 1). The staging assists with assessment of disease status, prognosis and management.(7) All available clinical findings may be used in staging including physical exam, radiologic, intraoperative, histopathology and biomarkers. (8) Stage of disease at time of treatment initiation is a very important predictor of survival in oral squamous cell carcinoma.(7) It is widely accepted that the advanced stage (Stage III and IV) cancers of the oral cavity have lower disease free and overall survival rates compared to early cancers.(3,8–11)
The prognostic implications of currently accepted pathologic features continue to be under investigation (histologic grade, lympho-vascular invasion, perineural invasion, and extracapsular spread of disease).(10) Histological features such as the grade of the lesion reflects the aggressiveness of the tumour, that, in itself has not been shown to be an independent parameter of prognosis on multivariate analysis.(11,12) Other studies however have shown that the grade of tumour does affect survival.(3,10) The most important histologic feature of the primary tumour is its depth of invasion, which has been shown to be directly correlated with survival rate.(11,12)
Depth of invasion has now been incorporated in the latest edition of the AJCC Primary tumour staging for oral cavity tumours (eighth edition) (Appendix 1).
Treatment strategies are aimed to maximize locoregional tumour control and address the functional impact of a procedure on speech and swallowing.
The tumour factors that affect the choice of initial treatment of oral cancer are primary site, size (T Stage), location (anterior versus posterior), proximity to bone (mandible or maxilla), status of cervical lymph nodes and previous
treatment.(6,13,14)
Stage IVA disease indicates moderately advanced disease but is still considered to be surgically resectable. Stage IV B and stage IV C disease is very advanced disease and is considered to be unresectable.(7)
T4a tumours that are treated surgically often result in large composite tissue defects that need to be reconstructed for functional and aesthetic outcomes.(15,16) Reconstructive options include grafts, local or regional flaps as well as free tissue transfers from different sites, most commonly the leg, thigh and forearm.(15,16,17)
Primary treatment with Radiotherapy is not favoured due to the close proximity of the oral cavity sub-sites to bony structures such as the mandible and maxilla, which can lead to complications such as osteoradionecrosis of these structures.(3,8,18) Thus, surgical resection has been advocated as the primary treatment for most oral cavity malignancies, with reconstruction for large defects.(17) Adjuvant chemo-radiation has been advocated for advanced tumours stage (III/IV) positive post-surgical margins, multiple positive neck nodes, extracapsular extension, perineural or intravascular invasion, and bone, cartilage and soft tissue invasion.(8,18)
Thirty percent of patients with Floor of mouth SCC (FOMSCC) present with regional metastases and the overall 5-year survival varies from 30-76%.(10,11,13,14,19)
The primary objective of the study is to evaluate floor of mouth SCC in our department by reporting one- and five-year overall survival rates, disease free survival and mortality rates for each stage of floor of mouth SCC.
The secondary objective of the study is to report on demographic data of patients in the study as well as correlate these data with survival and mortality rates.
These procedures use up multidisciplinary resources such ENT surgeons, plastic surgeons, maxillofacial surgeons and prosthodontists as well as various allied disciplines.(20) They are also associated with prolonged theatre times, prolonged ICU admission and prolonged hospital stays.(20,21)