National Cancer Care Network (NCCN) has established guidelines for treatment of oropharyngeal cancer. The treatment options depend upon the stage of the disease. For early stage (I-II), one form treatment (either surgery or radiation therapy) is recommended. The aim of treatment is to cure the disease in the primary site (tonsil or base of tongue) and the lymph nodes in the neck, even if the neck does not have clinical evidence of lymph node involvement. There is a high risk that imaging may miss very early cancer involvement of the neck lymph nodes. In some instances, if surgery is the upfront treatment in early stage cancer, additional treatment with radiation alone or in conjunction with chemotherapy is recommended if there are high risk features noted on the pathology report after the tumor is removed. These high risk features include perineural invasion (microscopic cancer cells found in surrounding nerves), positive disease at the margins of resection, and extracapsular spread (cancer growing out of the capsule of a lymph node). On the other hand, late stage (III-IV) oropharyngeal cancers are treated with multiple treatment modalities. Either radiation and chemotherapy can be used in conjuction or surgery followed by radiation and/or chemotherapy. In advanced disease, some institutions prefer to treat upfront with chemotherapy (Induction Therapy) to assess the response of the tumor. If there is a good response, then the patient is given treatment with combined radiation and chemotherapy. If response is poor, then the patient is deemed not to be a good responder for primary chemo and radiation therapy, and the patient goes onto surgery. Following the surgery, the patient gets radiation and chemotherapy. This induction strategy is aimed at trying to minimize the risk of distant metastasis.
The most commonly employed method of delivering radiation therapy for head and neck cancers is intensity modulated radiation treatment (IMRT). This technique allows the radiation oncologist to optimize treatment of the affected tissues while limited radiation dose to critical structures. During treatment, the patient lies upon a bed with the head kept in precise position by a custom-fitted mesh mask. Each treatment takes less than fifteen minutes, and a total of approximately 35 treatments are generally delivered over 6-7 weeks.
There are several advantage and disadvantages to each of the different treatment algorithms. Definitive surgery allows for accurate staging of the disease and may either eliminate the need for irradiation or reduce the amount of radiation which is required depending upon the tumor. A decrease in radiation dose by 10-20cGy may result in significant decrease in the associated side effects. Disadvantages of surgery include the risks of bleeding, infection, damage to nerves such as the spinal accessory nerve (nerve that affects shoulder function), hypoglossal nerve (nerve for movement of the tongue), marginal mandibular nerve (nerve for movement of the corner of the lower lip), vagus nerve (nerve to the vocal cord), and phrenic nerve (nerve to the diaphragm). Additionally, if surgery requires an “open approach” to remove the tumor, there can be problems with salivary fistula, healing of bone, misalignment of the teeth, or hardware failure.
Radiation may also be associated with significant side effects, which vary depending upon the dose required and the tissues involved. Patients commonly complain of dry mouth, loss of taste, trouble swallowing (in some cases require feeding tube placement), skin changes such as redness and sensitivity, and oral ulcers. Long-term side effects may include increased risk of carotid artery blockage, esophageal strictures causing difficulty swallowing, weakness of the jaw bone that can result in jaw bone fracture (osteoradionecrosis), and possibility of secondary cancers.
Chemotherapy is useful in two ways. First, it makes radiation therapy work better at killing the cancer cells. Second, it is able to improve the control over metastatic disease to the lung, liver, and bone. However, it has several side effects. The primary chemotherapy used in head and neck cancer is cisplatin. While a very effective drug, cisplatin may injure the kidneys, nervous system, or hearing organ (the cochlea). A second drug often given to those that cannot tolerate cisplatin is cetuximab. While it is less toxic than cisplatin, its side effects may include skin rashes, heart problems, and stiffening of the lungs.
Surgery of oropharyngeal tumors can be performed through a variety of means to allow for adequate access to the oropharynx.. The location and size of the tumor, as well as functional (swallowing and speech) and cosmetic concerns, and surgeon experience affect the choice of the surgical approach. Traditionally, “open” approaches to the oropharynx have been used. These include a transmandibular approach in which the lower lip and jaw bone are split to obtain access to the oropharynx. Alternatively, a transcervical approach may be used in which is the oropharynx is entered via an incision in the neck. These approaches offer excellent surgical exposure of the tonsils, soft palate, and base of tongue, though they are often accompanied by significant side effects and disfigurement. The majority of patients undergoing these “open” surgical approaches require short-term tracheostomy and feeding tube placement. Closure of the surgical defect in the throat following tumor removal often requires transfer of tissue from other parts of the body , termed a “flap” procedure. These additional reconstructive procedures can have their own set of complications. Other disadvantages of open approaches include prolonged operative times, significant postoperative edema, and external scarring,. Given the increasing use and proven efficacy of radiation therapy, most centers in the United States currently reserve open surgical approaches for patients who have already received radiation previously and for whom additional radiation is not possible or too risky, and where less invasive surgical approaches could compromise cancer outcomes.
The last several decades have seen the advent and development of several transoral surgical approaches which represent a signficant improvement in the ability to treat selected cancers of the oropharynx. Although very early stage lesions of the tonsil or base of tongue might be removed with basic equipment and minimal technical difficulty, this is frequently not possible due to the challenging anatomy and difficult exposure of the oropharynx. But recent technical advances have allowed surgeons to remove even relatively large tumors of the oropharynx via strictly transoral approaches, most notably including transoral laser microsurgery (TLM), or transoral robotic surgery (TORS). Transoral laser microsurgery uses standard techniques for exposing the oropharynx and larynx (voice box) through the mouth, with optical magnification and use of a laser to remove tumors. The advantages of TLM include improved access and visualization in difficult areas and the general availability of required surgical instrumentation. Disadvantages of TLM are primarily related to the challenges of working in the relatively confined and curved space of the oropharynx. Considerable technical expertise is also required for this approach.
In December of 2009, TORS was approved by the FDA for treatment of early stage oropharyngeal cancers, and this approach is gaining increasing popularity in the U.S. and abroad. TORS relies upon a robotic surgical system which provides excellent three-dimensional vision and the ability to work precisely in a narrow space such as the oropharynx. Numerous studies on the oncological efficacy of this approach have been published, demonstrating excellent oncologic control equivalent to or better than standard non-surgical treatments (White, Moore et al. 2010, Weinstein, O’Malley et al. 2012, Lee, Park et al. 2013, More, Tsue et al. 2013, Park, Kim et al. 2013, Kelly, Johnson-Obaseki et al. 2014). A surgeon performing TORS sits at a console where he or she controls the movement of robotic surgical arms within oropharynx. The primary operative advantages of this approach include significant improvement in the ability to work within the tight confines of the oropharynx, which may allow safe and complete removal of tumors which would not be accessible by other transoral techniques. The advantages of transoral surgical approaches to the patient include less morbidity compared with more extensive open dissections, avoidance of tracheostomy, decreased blood loss, and shorter surgical times. (Moore, Olsen et al. 2012, Lee, Park et al. 2013). Shorter hospital stays are often possible as well (White, Ford et al. 2013). TORS does require a robotic surgical suite and a surgeon with specialized training and experience in this technique, so it is not currently available at many centers.