T4b oral cavity cancer below the mandibular notch is resectable with a favorable outcome
Introduction
Squamous cell carcinoma of the oral cavity (OSCC) often arises from the adjacent areas of the retromolar trigone and buccal space. Therefore, invasion of the masticator space (MS)1, 2, 3 and/or pterygoid plate (PP) is not uncommon. Eradicating a tumor that has invaded the MS or PP poses two problems. First, it is sometimes difficult to identify tumor margins based on images alone. Second, achieving appropriate safety margins at the skull base requires an experienced head and neck surgeon and a well-trained head and neck cancer team.
According to the criteria from the American Joint Committee on Cancer (AJCC) 2002,4 tumor invading to the MS or PP or skull base or internal carotid artery is defined as one of the criteria for T4b classification and is considered unresectable. However, from our experiences, some T4b OSCC patients without carotid artery encasement and skull base extension would be resected with favorable outcome. Therefore, we retrieved data from January 1996 to December 2000 and re-classified according to AJCC 2002 staging system. This retrospective study was to identify suitable T4b OSCC patients who were candidates for radical surgery and to determine the adverse factors in selected operated T4b OSCC patients.
Section snippets
Patients
This retrospective data was collected between January 1996 and December 2000. A total of 433 untreated OSCC cases were recorded at Chang Gung Memorial Hospital in Linko. At the time of analyses (March 2006), 45 out of 433 cases were re-classified as T4b according to the AJCC 2002 staging system. There were 43 male and 2 female. The median age was 49 years old. Previous classification included T2 (five patients), T3 (15 patients), and T4 (25 patients) (AJCC 1997 criteria).5 T4b tumors were
Supra- vs. infra-notch in T4b OSCC
Pre-operative survival predictors were analyzed by supra- vs. infra-notch groups, anterior MS vs. posterior MS, ⩽2 vs. ⩾3 components involved in the MS/PP, cN0 vs. cN1–2 and cN0–1 vs. cN2. Only the supra-notch group was a significant adverse factor for 5-year local control (42.9% vs. 74.0%, p = 0.0254), neck control (21.4% vs. 83.8%, p = 0.0001), disease-free survival (14.3% vs. 64.7%, p = 0.0004) (Fig. 2), and overall survival (14.3% vs. 55.3%, p = 0.0066). cN2 showed marginal significance (p = 0.0496)
Discussion
T4b is defined as a new category in the AJCC 2002 and is considered as unresectable due to at least three possibilities. The first reason is a difficulty in obtaining a surgical safety margin. From a surgeon’s point of view, a radical tumor excision of curative intent needs safety margin of at least ⩾1 cm. The anatomical distance from the floor of the mandibular notch to skull base is about 2 cm. However, once OSCC with MS or PP invasion (T4b) occurs, our experiences showed that the floor of the
Acknowledgement
This study was supported by CMRP-32034 and CMRP-33111, Chang Gung Memorial Hospital at Linko.
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