Transoral robotic surgery for recurrent cancer and reconstruction

Introduction

In a previously irradiated patient, salvage surgery remains the main, if not only, curative option for recurrent or residual squamous cell carcinoma (SCC) of the oropharynx. Traditionally, a large open resection was performed. The surgery may require mandibulectomy for tumor involvement or mandibulotomy with pharyngotomy for access. Soft tissue reconstruction is undertaken with free flap reconstruction or pedicled flap reconstruction techniques such as a pectoralis major myocutaneous flap. Tracheostomy and gastrostomy tubes were often required in the perioperative period. The risk of postoperative complications was high, quoted between 45% and 50%, and included mandibular malunion, orocutaneous fistula, exposed bone, and complications associated with reconstructive techniques. ^, Patients often had poor functional outcomes with high rates of long-term gastrostomy and tracheostomy tube placement. This radical approach with open salvage surgery carried a poor overall survival rate, measuring between 19% and 28% at 5 years. ^{, ,}

The considerable impairment and poor oncologic outcomes for open salvage surgery have led many groups to perform transoral robotic resection, with early reports suggesting equal, if not improved, oncologic outcomes and vastly superior functional outcomes. ^,

Transoral robotic surgery (TORS) for recurrent disease presents opportunities and challenges to the operating surgeon. High-dose radiation therapy used as primary modality of treatment for a newly diagnosed oropharyngeal carcinoma or used in the adjuvant setting may change the anatomy and tissue planes of the surgical field. Previous radiation may have also been performed for patients who have had an alternative upper aerodigestive tract malignancy, advanced skin malignancy, or lymphoma. Despite the inherent difficulties of operating within a radiated field, there are numerous advantages to consider a transoral approach rather than a more traditional open approach in the event of residual or recurrent tumor or a new primary malignancy within a previously radiated field.

This chapter will focus mainly on oropharyngeal SCC as it is by far the most common indication for transoral salvage surgery. Reconstruction techniques will also be discussed in order to optimize postoperative function and minimize complications. The chapter will outline the careful preoperative workup used to carefully select appropriate patients for salvage transoral surgery and discuss ways to reduce perioperative risks and long-term complications.

Preoperative workup

A thorough assessment of a patient is required prior to consideration of surgical management to assess for suitability and formulate an appropriate operative plan.

The extent of the previous head and neck cancer and the treatment are reviewed. It is important to review the previous staging imaging to assess the index tumor details. Assessment of the initial lesion will help formulate the required ablation at the time of salvage surgery. A recurrent T1 lesion is more appropriate for salvage surgery especially via a transoral approach if the initial tumor was also staged T1, rather than a more advanced stage. Previous chemotherapy, radiation field, and dose need to be assessed to estimate their effect on surrounding tissues and to consider potential adjuvant options after salvage surgery.

It is important to identify the presence of other medical comorbidities that may affect treatment such as being immunocompromised, significant cardiovascular risk factors and use of anticoagulation, as well as smoking and alcohol intake. The general health, frailty, and level of function need to be considered.

Assessment in clinic includes a thorough transoral and endoscopic transnasal assessment of the extent of the primary tumor. Examination under anesthesia provides assessment of tissue integrity and degree of fibrosis and scaring both externally and within the upper aerodigestive tract. It also allows for the important consideration of any significant trismus or fixation due to tumor bulk that is likely to limit the potential for transoral surgery. In the case of significant trismus, open access including with mandibulectomy or mandibulotomy may be required which, in our experience, is a rare occurrence. A full clinical assessment of the neck is required to identify the presence of nodal disease, a common risk associated with recurrent oropharyngeal SCC. Potential donor sites for reconstruction also need to be examined and will be detailed later in the chapter.

Updated and accurate imaging as well as a histopathologic diagnosis is required to complete the preoperative workup. A thorough structural and functional imaging protocol is used with a fluorodeoxyglucose-positron emission tomography (FDG-PET) scan complimented with either computerized tomography (CT) or magnetic resonance imaging (MRI) scans of the head and neck. An FDG-PET scan is particularly helpful in assessing regional neck nodal and distal metastatic disease. The presence of distant metastatic disease would deem that treatment would be palliative and transoral surgery is unlikely to be indicated unless it could provide symptom control with low morbidity. In the absence of clinical and radiological evidence of neck disease, a neck dissection is not routinely performed because of the increased risk of complications. The chance of cure in recurrent oropharyngeal SCC when there is positive disease in the neck is significantly reduced and should be taken into account prior to considering surgical salvage.

Structural imaging is scrutinized in this cohort to assess for the following features which may significantly impact transoral operability:

• 1.

  Bone invasion and/or proximity to the mandible or hyoid.

• 2.

  Parapharyngeal space invasion or invasion into pterygoid musculature.

• 3.

  Invasion into the oral tongue, especially extrinsic muscle invasion.

• 4.

  Proximity and relationship to the internal or common carotid artery.

• 5.

  Extension into the larynx.

• 6.

  Prevertebral fascia involvement.

The presence of any of the features above may make the patient a poor candidate for transoral salvage surgery and may lead to an open approach or no surgery being considered.

The prime candidate for transoral robotic salvage surgery is an otherwise well individual with wide mouth opening and good transoral access, having small volume disease which is easily amenable to resection with adequate oncological margins. This cohort often exists in patients previously having treatment for HPV-related oropharyngeal SCC as they tend to be younger with fewer comorbidities.

Mitigation of perioperative risks

Transoral robotic tumor ablation

After adequate preoperative workup, the patient is taken to the operating room for transoral resection under general anesthesia. This patient cohort often has a difficult airway with a need for appropriate intubation instruments as well as a tracheostomy tray in the operating theatre at the time of induction. As discussed above, we do not routinely place a tracheostomy but, if deemed necessary, this is placed at the start of the procedure and secured appropriately prior to transoral surgery. More frequently, a transnasal tube is inserted and secured with eye shields placed to avoid any injury during robotic resection.

A gag is then placed transorally with the “FKWO” retractor (Olympus, Hamburg, Germany) most commonly used in our practice. An appropriate blade needs to be selected to offer the greatest exposure to the planned tumor ablation. A stitch is placed in the anterior oral tongue to aid tongue retraction. Tooth protection is placed superiorly and inferiorly, with care taken to avoid dental trauma. Time must be taken to optimize transoral access with neck and tongue manipulation as well as changes in blade length. Once the view is optimized, we dock the da Vinci surgical robot with a zero or 30-degree scope placed as defined by the area of resection planned.

Tumor resection then proceeds in the same manner as described in previous chapters. Identification of landmarks is key, as well as defining the limits of the tumor and taking adequate margins. This can sometimes be more difficult in a salvage case, and frozen section analysis of surrounding tissues is performed. The main specimen is thoroughly scrutinized after removal to check for adequate tumor resection and all margins are inked in a standardized fashion for histopathologic assessment. Wound contracture and fibrosis postradiation can affect intraoperative assessment and make margin planning a little more difficult. It is important to know that in most circumstances additional adjuvant radiation therapy cannot be provided and, as such, margin status is critical at the time of operation.

Contracture and fibrosis secondary to previous radiation provide some additional challenges at the time of transoral surgery. The additional contracture and loss of tissue elasticity means that there is often a larger defect with less ability for primary closure of the defect. There is also more likely to be some bone exposure in the region of the retromolar trigone near the angle of the mandible. Postoperative healing is delayed and contracture of the oropharynx, particularly around the palate, is markedly reduced with a much higher incidence of velopharyngeal insufficiency (VPI) in the postoperative setting, which is often a long-term problem. Due to these issues, as well as numerous longer-term complications that are more common in the salvage cohort, reconstruction at the time of surgery is often performed. In patients undergoing initial TORS for primary malignancy with no previous radiation, reconstructive techniques are very rarely required, with excellent healing via secondary intention over a number of weeks. Unfortunately, this cannot always be relied upon in the salvage setting.

Reconstruction after salvage tors

There are a number of techniques available for reconstruction post-transoral robotic surgery. Given the irradiated field, it is important to get vascularized tissue into the defect, especially in the setting of an exposed carotid artery. Carotid blowout has been reported in transoral surgery for recurrent oropharyngeal cancer and is far more common in a previously radiated patient.

The following reconstructive options can be considered, depending on the defect and donor site availability:

Facial artery myomucosal flap

The facial artery myomucosal (FAMM) flap allows for locoregional tissue in the ipsilateral buccal region involving mucosa and muscle to be rotated on a vascularized pedicle via the facial artery into the defect. In our hands, these have provided excellent vascularized coverage of the lateral pharyngeal wall including palatal reconstruction and coverage of exposed retromolar trigone bone. In the IMRT era, the dose to the buccal mucosa is relatively low, with a mean dose of around 37 Gy in our series. The flap can be raised with a headlight and adequate cheek retraction. The flap may be completely islanded on the facial artery and rotated into oropharyngeal defects. Usually, the entire defect cannot be completely closed. Priority is given to covering an exposed carotid artery, any exposed bone, and for reconstruction of the soft palate, as shown in Fig. 47.1 below. Feeding is exclusively via nasogastric tube for 5 days prior to resumption of oral intake. The flap is generally robust and reliable, and long-term functional outcomes are excellent. The FAMM flap has become our “go to” option for most salvage oropharyngeal defects. The donor site defect can be closed primarily or with the use of the buccal fat pad ( Video 47.1 ).