Marginal Mandibulectomy in Oral Cavity SCC: Experience in a Tertiary Care Centre

Abstract

Marginal mandibulectomy is indicated for oral cavity squamous cell carcinomas that involve floor of mouth, abut or minimally erode the mandible without gross invasion. Successful outcomes after Marginal mandibulectomy is predicated on accurate patient selection and appropriate adjuvant treatment based on specific host and tumor characteristics. To study the onclogical outcomes in terms of loco-regional recurrence free survival and disease specific survival of marginal mandibulectomy done for oral squamous cell carcinomas. Study Design—Retrospective study. Setting—The study was done from January 2018 to January 2021 at our tertiary care centre Madras Medical College, Chennai. Subjects—30 cases were included in our study who underwent Marginal Mandibulectomy for oral cavity SCC. Methods—The decision to perform a marginal mandibulectomy was taken based on preoperative clinical examination, contrast enhanced computed tomography (CECT) findings and intra-operative assessment under anesthesia. Disease-free survival, cause-specific survival, and local control rates were plotted using the Kaplan-Meier method. Oncologic outcomes in terms of Overall survival and Disease-specific survival at the end of 1 year and 3 years for the gingival, buccal, tongue, floor of mouth cancers were analyzed. Independent impacts including the site of tumor, T and N stage, microscopic bony invasion, grade of differentiation, adjuvant radiotherapy on the loco-regional control and cause-specific survival were evaluated using Kaplan meier method. Our study group was comprised of 20(66.67%) males and 10 (33.33%) females of mean age 54 years. None of them had prior radiotherapy to the head and neck region. A total of 7 (23.33%) marginal mandibulectomies were carried out for SCC in the gingival region, 11(36.67%) for buccal mucosa, 8(26.67%) for tongue, 2(6.67%) for floor of mouth SCC, 1(3.33%) involving lip, 1(3.33%) in Retromolar trigone. Clinically 2 (6.67%) patients had T1 cancer, 18 (54.54%) had T2, 6 (18.18%) had T3, 4(13.33%) had T4 tumor. Clinically Neck nodes were not palpable in 17 (56.67%) patients, 10 (33.33%) had N1 disease and 3 (10%) had N2 disease. T and N stage distributions for tongue/floor of mouth and gingival buccal complex cancers are summarized in the table and there were no statistically significant differences between the 2 groups. 19 (63.33%) had selective neck dissection (levels I–III), and 11 (36.67%) had comprehensive neck dissection. Well-differentiated tumors were encountered in 12 (40%) cases, moderately differentiated tumors in 16 (53.33%) cases, and poorly differentiated tumors in 2 (6.67%) cases. Bone was microscopically involved in 4 (13.33%) cases and mucosal margin of excision was less than 5 mm from the tumor in 2 (6.67%) cases. Cumulative hazard of local recurrence was not significantly affected by mandibular involvement. On histopathologic examination, positive nodes were seen in 6(20%) cases that included 3 (10%) with pN1 and the rest with pN2 disease. Adjuvant radiotherapy (56 to 64 Gy) was given to 13 (43.33%) patients. In carefully selected patients, marginal mandibulectomy in oral squamous cancer achieves good oncological outcome in terms of locoregional control and overall survival rates.

Introduction

Oral cavity squamous cell carcinoma (OCSCC) is the most common malignancy in the oral cavity. It affects approximately 300,000 patients worldwide each year and represents the 6th most common global malignancy and 30% of cancers affecting the head and neck region [1–3].

According to previous studies, mandibular involvement rates range between 12 and 56%, and when the tumor clearly invades the mandible, the affected bone needs to be resected in continuity with the soft tissues. However, when the invasion is not clear or significant, there is no guideline based on evidence that could assist in the decision on mandibular management [4–8].

Two types of mandibular resections have been described: the segmental mandibulectomy (SM), in which the resection involves the entire vertical height of the mandible with interruption of the continuity of the mandible, and the marginal mandibulectomy (MM), in which the resection just involves a part of the height of the mandible with preservation of the continuity of the mandible. Both may have a different impact over the quality of life, oncological prognosis and functional or aesthetic result when the surgeons fail in their decision process [4.

Marginal mandibulectomy is indicated for oral cavity squamous cell carcinomas that involve floor of mouth, abut or minimally erode the mandible without gross invasion [9, 10]. Successful outcomes after Marginal mandibulectomy is predicated on accurate patient selection and appropriate adjuvant treatment based on specific host and tumor characteristics.

Aims and Objectives

To study the onclogical outcomes in terms of loco-regional recurrence free survival and disease specific survival of marginal mandibulectomy done for oral squamous cell carcinomas (Figs. 1, 2).

Fig. 1.

Disease free survival (kaplan-meier)

Fig. 2.

Overall survival (kaplan - meier)

Methods and Methodology

A retrospective study was done from January 2018 to January 2021 (n = 30 cases) at our tertiary care centre Madras Medical College, Chennai. The decision to perform a marginal mandibulectomy was taken based on preoperative clinical examination, contrast enhanced computed tomography (CECT) findings and intra-operative assessment under anesthesia. Disease-free survival, cause-specific survival, and local control rates were plotted using the Kaplan–Meier method. Oncologic outcomes in terms of Overall survival and Disease-specific survival at the end of 1 year and 3 years for the gingival, buccal, tongue, floor of mouth cancers were analyzed. Independent impacts including the site of tumor, T and N stage, microscopic bony invasion, grade of differentiation, adjuvant radiotherapy on the loco-regional control and cause-specific survival were evaluated using Kaplan–Meier method (Tables 1, 2).

Table 1.

Age distribution

Age (years)	Frequency	Percent
< 40	3	10.0
41–60	21	70.0
Above 60	6	20.0
Total	30	100.0

Table 2.

Disease free survival rate

Characteristics	One year			Three years
	n	Disease-free survival rate,% (95%CI)	P	Disease-free survival rate,% (95%CI)	P
Local recurrence (2 recurrence)	28	92.7 (86–94)	< 0.001	90.3 (88–95)	< 0.001
Regional Recurrence (1 recurrence)	29	92.1(90–94)		91.4(90–94)

Results

Our study group was comprised of 20(66.67%) males and 10 (33.33%) females of mean age 54 years (Table 1). None of them had prior radiotherapy to the head and neck region. A total of 7 (23.33%) marginal mandibulectomies were carried out for SCC in the gingival region, 11(36.67%) for buccal mucosa, 8(26.67%) for tongue, 2(6.67%) for floor of mouth SCC, 1(3.33%) involving lip, 1(3.33%) in Retromolar trigone. Clinically 2 (6.67%) patients had T1 cancer, 18 (54.54%) had T2, 6 (18.18%) had T3, 4(13.33%) had T4 tumor. Clinically Neck nodes were not palpable in 17 (56.67%) patients, 10 (33.33%) had N1 disease and 3 (10%) had N2 disease. 19 (63.33%) had selective neck dissection (levels I–III), and 11 (36.67%) had comprehensive neck dissection. Well-differentiated tumors were encountered in 12 (40%) cases, moderately differentiated tumors in 16 (53.33%) cases, and poorly differentiated tumors in 2 (6.67%) cases. Bone was microscopically involved in 4 (13.33%) cases and mucosal margin of excision was less than 5 mm from the tumor in 2 (6.67%) cases. On histopathologic examination, positive nodes were seen in 6(20%) cases that included 3 (10%) with pN1 and the rest with pN2 disease. Adjuvant radiotherapy (56 to 64 Gy) was given to 13 (43.33%) patients with close margins, pathological N2 disease, T3/T4 disease.

Among the 30 cases, 3 cases developed loco-regional recurrence of which 2 patients developed recurrence at local site and 1 patient developed nodal recurrence. The DFS at the end of 1 year and 3 years for local recurrence was 92.7% and 90.3% respectively (Fig. 1). The regional recurrence free survival was 92.1% and 91.4% at the end of 1 year and 3 years respectively (Table 2).

1 patient expired at the end of 3 years. The overall survival rate at 1 year was 96.67% and at 3 years was 92% (Fig. 2).

Discussion

The management of oral squamous cancers underwent a paradigm shift with more focus into the pattern of local spread [11–13]. The possibility of adequate clearance of selected oral cancers by marginal mandibulectomy without disrupting the continuity of the mandible and its muscular attachments has led to the practice of mandibular arch–preserving surgery for better functional and cosmetic problems resulting from the segmental mandibulectomies. Since the local control rates have been comparable after marginal and segmental resections in various studies, marginal mandibulectomy does not compromise with the oncologic safety [14–16].

Segmental mandibulectomy causes more functional problems due to loss of mandibular continuity, resulting in poor quality of life in comparison with marginal mandibulectomy, due to disruption of muscular attachments to the mandible. Marginal mandibulectomy is indicated for cancers located in close proximity to non-radiated mandible or superficially eroding it, where adequate three dimensional margins are achievable, while preserving adequate mandibular structure and continuity in order to withstand mastication.

The technical feasibility of mandibular reconstruction is not an indication for segmental mandibulectomy, for which marginal mandibulectomy is an effective alternative procedure with good oncological safety, functional and cosmetic outcomes. Our preoperative assessment includes clinical examination bidigital palpation along with radiologic evaluation by CT, thereby combining sensitivity of clinical examination with the specificity of computed tomography. The final decision to proceed with marginal mandibulectomy is taken by the operating surgeon after careful intra-operative assessment under anesthesia and the ability to achieve three dimensional adequate margins. Care is taken to preserve at least 10 mm of inferior border of mandible for providing stability and preventing fractures.

A careful preoperative workup with clinical and radiological assessment and intra-operative evaluation should be performed, before operating any oral cavity SCC patients to achieve the best surgical approach. The sensitivity of computerized tomography scan in comparison with histology is 40 to 60%, with 89 to 100% specificity, whereas MRI shows 56 to 94% sensitivity and 73 to 100% specificity. The most common cause of false positives in MRI is Medullary edema, which is difficult to distinguish from tumor infiltration. In a recent study by Bouhir et al., the combined use of CT scan and MRI is recommended to improve pre-operative mandibular invasion assessment.

Factors like the depth of infiltration (DOI), pattern of spread, nerve invasion and cervical lymph node status are considered independent factors regarding overall survival, irrespective of the type of mandibulectomy performed [17]. Around 50% of patients with oral squamous carcinomas have positive lymph node metastases, which is considered the most important prognostic factor. The 8th edition American Joint Committee on Cancer (AJCC) cancer staging manual has incorporated the depth of invasion(DOI) in the T staging as a prognostic factor supports the importance of the tumoral growth pattern along with overall tumor dimension, as features critical in assessing tumor behavior and to decide the most optimal loco-regional management.

In marginal mandibulectomy, the lower border of the mandible is preserved which improves the functional result and reconstruction is not cumbersome. Some surgeons have hypothesized that the compact cortex of the mandibular bone may serve as a barrier to prevent cancer spread. Therefore, marginal mandibulectomy in the treatment of selected for oral cancer patients without mandibular medullary invasion can minimize the functional and aesthetic impact.

Researchers have shown that bone erosion occurs initially as a result of osteoclast cell activity near the proximity of tumor infiltration which may be related to the inflammatory process even before bone invasion by the tumor cells. According to Brown et al., the tumor cells invade the mandible at the point of abutment rather than the occlusal surface, the neural foramina or the periodontal membrane as previously considered. Once the inferior alveolar nerve canal is infiltrated by advanced lesions, both anterior and posterior perineural extension occurs in both the edentulous and dentate mandible. In these patients, a Segmental mandibulectomy would be the appropriate procedure.

As highlighted recently by Manelli et al., procedures such as intraoperative frozen section, spectroscopy, narrow band imaging (NBI) and optical coherence tomography(OCT) are useful tools to evaluate soft tissue margins during Oral cavity SCC surgery. However, in case of bone invasion in advanced Oral cavity SCC, a frozen section evaluation of the decalcified mandibular cortical bone is cumbersome and does not add any improvement to margins assessment accuracy.

In previously irradiated and edentulous patients, bony resistance to tumor invasion is altered. In these patients, a segmental mandibulectomy would be appropriate when the tumor abuts the mandible. Moreover, bone fracture and osteoradionecrosis could be frequent when a marginal mandibulectomy is performed in these patients. For these reasons, our study was limited to patients who received no prior Radiotherapy [18].

Marginal mandibulectomy is an oncologically safe procedure for oral cavity cancers in close proximity to the mandible or superficially eroding it without extensive soft tissue involvement. In carefully selected cases, marginal mandibulectomy can achieve good disease control without compromising on aesthetics and function of the mandible. Because it is a shorter procedure, it puts less strain on resources and does not require complex microsurgical reconstruction.

In the future perspective, well-designed prospective randomized and retrospective studies are required to understand the potential benefit over Overall Survival, Disease Free Survival and Loco-regional Control in patients undergoing marginal mandibulectomy. These studies must include surgeons with a homogeneous and identical surgical technique, data regarding cortical and medullary mandible invasion clinically, radiologically and histologically in surgical specimen, description on previous treatment received and at least 5-years of follow-up.

Conclusion

In carefully selected patients, marginal mandibulectomy in oral squamous cancer achieves good oncological outcome in terms of locoregional control and overall survival rates.