Adjuvant Intensity Modulated Radiation Therapy With a Pedicled Flap Reconstruction in Oral Cavity Squamous Cell Carcinomas: Implications on Target Delineation

Abstract

Objectives: To address controversies regarding target volume delineation for adjuvant intensity-modulated radiation therapy for oral cavity squamous cell carcinoma with pedicled flap reconstruction and elective nodal irradiation (ENI).

Materials and methods: During target volume delineation, the primary tumor bed was the pre-surgical gross tumor volume with an additional isotropic margin of 5-10 mm. Additionally, the flap and body tissue junction were given a margin of 5-10 mm (if not already given). An effort was not made to trace the flap for inclusion in the clinical target volume (CTV), except when it traversed through the involved nodal regions. Contralateral ENI was carried out only in tumors crossing the midline when there was a heavy nodal burden at Ia/Ib.

Results: In the 143 patients analyzed, the most common sub-site was buccal mucosa (78, 54.5%). Contralateral ENI was done in 63 patients (36 Tongue, 23 Buccoalveolar). The median follow-up of surviving patients was 24 months. The 2-year Locoregional Control, Disease-Free Survival, and Overall Survival were 77.4%, 64.5%, and 79% respectively. Overall, there were 55 (38.5%) recurrences, of which 35 (24.5%) were either local, regional, or combined locoregional failures, 13 (9.1%) were distant failures alone, and 7 (4.9%) had both locoregional and distant failures. The elective nodal regions had 3 (2.1%) contralateral nodal failures.

Conclusion: The entire flap need not be intentionally covered in the target volume. Contralateral ENI should be considered only for patients with heavy nodal burden at ipsilateral level Ia/Ib, in tumors crossing the midline, or in tumors having a high propensity for contralateral lymph nodal involvement.

FIGURE 1

Image showing delineation of the target volume around the flap (Yellow: Primary clinical target volume, Green: Nodal clinical target volume, Pink: Reconstruction flap) in (a) axial, (b) sagittal and (c) coronal planes. [Color figure can be viewed at wileyonlinelibrary.com]

FIGURE 2

Image showing in‐field recurrence on the top in a patient with buccal mucosa primary of the right side, previously treated with surgery followed by adjuvant radiotherapy by IMRT (Intensity Modulated Radiation Therapy) technique. The 95% dose wash is green on the planning CT scan superimposed with the PET image done at recurrence, showing hypermetabolic activity at the site of recurrence, lying almost entirely within the 95% dose wash. The image below shows marginal recurrence in a patient with buccal mucosa, primarily on the left side. The 95% dose wash (in green) from the treatment plan is depicted on the MRI at recurrence, showing the recurrent disease in red, which extends out of the 95% dose wash in volume by more than 5% but less than 80%. [Color figure can be viewed at wileyonlinelibrary.com]

FIGURE 3

Kaplan–Meier estimates of locoregional control (a), disease‐free survival (b), and overall survival (c) from top to bottom. The estimated 2‐year locoregional control, disease‐free survival and overall survival rates were 77.4% (95%CI: 69.8–85.0), 64.5% (95% CI: 56.1–72.9), and 79.0% (95% CI: 70.6–87.4), respectively. [Color figure can be viewed at wileyonlinelibrary.com]