Interventional Management of Head and Neck Tumors

Abstract

Advancements in medical imaging and device technology allow minimal invasive procedures for the diagnosis and treatment of various disorders. For the management of tumors in head and neck region, these image-guided interventions play essential role in the often used multidisciplinary approach. Tissue sampling under ultrasound or computed tomography guidance is generally the first step to reach a pathological diagnosis. For head and neck tumors with high vascularity, embolization using particulate matter, liquid embolic agents, or coils is used to achieve successful tumor resection with minimal blood loss. Hemorrhage related to head and neck tumors can be evaluated and managed with endovascular techniques with minimal morbidity and mortality. Intra-arterial chemotherapy, radiofrequency ablation, and cryotherapy are new techniques for the management of advanced head and neck cancer which may serve as an alternative to achieve locoregional control and survival when curative resection may not be feasible.

Minimally invasive image-guided techniques for the diagnosis and treatment of various disorders have seen a significant growth over the last few decades. Advancements in medical imaging allow exquisite visualization of pathology for diagnosis and treatment planning. With parallel developments in device technology, interventional physicians can now safely and efficiently perform minimally invasive image-guided procedures which had previously been complex and associated with significant morbidity. In the head and neck region, these techniques provide minimally invasive alternatives in the diagnosis and management of various disorders including trauma, tumors, and vascular lesions.

Head and neck tumors are a heterogeneous group comprising benign and malignant entities. Most recent World Health Organization classification of head and neck tumors published in 2017 outlines the various histological types. ^{1 2 3} For head and neck squamous cell carcinoma (HNSCC), the most common histological type in this anatomical region, annually, 500,000 new cases are reported worldwide. ⁴ It is the sixth most common neoplasia, responsible for 6% of all cases and 1 to 2% of tumor-related deaths. ⁵ In the United States, 40,000 new cases and 7,890 deaths are related to HNSCC annually. ⁶ A multidisciplinary approach is frequently employed in the management of head and neck tumors, in which image-guided interventional techniques provide essential tools to aid in the diagnosis and treatment. Herein, we aim to review various frequently used guided interventional techniques in the management of head and neck tumors.

Image-Guided Tissue Sampling

For head and neck tumors, tissue sampling is generally the first step to reach a pathological diagnosis and plan subsequent treatment. In this regard, both ultrasonography (US) and computed tomography (CT) may allow optimal visualization of the lesion. Preoperative evaluation, particularly for deep-seated lesions and when large core needle biopsy is being considered, should include international normalized ratio, prothrombin time, activated partial thromboplastin time, and platelet count, and serum creatinine levels to evaluate renal function when intravenous iodinated contrast administration is anticipated. ⁷ Preoperative fasting is a consideration when procedural sedation or intravenous contrast administration is expected. ⁸ Procedural sedation is dependent on patient's preferences, ability to stay still, and anatomical relationship of the target lesion to various vital head and neck structures.

US with its real-time capability, no radiation exposure, and widespread availability is generally preferable for relatively superficial soft-tissue lesions, such as cervical lymph nodes, thyroid nodules, or superficial masses. Deep-seated lesions, particularly the ones deep to osseous structures and adjacent to air-containing spaces, are generally not optimal for US-guided tissue sampling due to various artifacts. US is highly operator dependent; however, in the hands of experienced interventionist and cytologist, US-guided fine needle aspiration (FNA) is an accurate and least invasive tool to provide diagnosis when evaluating cervical lymphadenopathy, thyroid nodules, and various head and neck superficial masses. ⁹ In 10 to 30% of head and neck lesions, FNA sampling is nondiagnostic; in this setting, repeat FNA in 6 to 8 weeks or depending on the size and anatomical location of target lesion and a core biopsy with a larger gauge needle are considered. ^{10 11 12}

For lesions not amenable to US-guided sampling, CT provides alternative guidance tool. A careful review of any preoperative imaging is vital to plan approach and to identify any important structures such as internal carotid artery (ICA) proximate to the target lesion or the planned trajectory. In a small proportion of cases, intravenous iodinated contrast is useful to map the carotid or vertebral arteries, and to increase lesion conspicuity ( Fig. 1 ). Patient position and the trajectory planning is dependent on the specific location of target lesion. Several anatomical approaches, such as subzygomatic, paramaxillary ( Fig. 1 ), and transoral, have been described; a detailed discussion of these is beyond the scope of this brief review. ^{11 13} However, a detailed knowledge of the cross-sectional head and neck anatomy is critical to choose the appropriate patient position and trajectory, to achieve safe and accurate tissue sampling with high diagnostic yield.

Fig. 1.

A 28-year-old woman with partially cystic left neck mass; history of left submandibular branchial cleft cyst resection 15 years ago. (a) Prebiopsy CT image obtained with intravenous contrast injection outlines relation of the partially cystic parapharyngeal space left neck mass with ipsilateral ICA; ( b ) an 18-gauge needle advanced into the target lesion; left ICA and left internal jugular vein are noted posterolateral to the target lesion and away from the needle trajectory; ( c ) bone windows outline the left paramaxillary (transfacial approach).

For FNA, 19- to 25-gauge needles may be used, and typically three passes are made to obtain adequate specimen. ¹² At our institution, an in-house cytopathologist evaluates adequacy of the specimen and provides preliminary interpretation.

Large tissue sample provided by core biopsy is of value to provide more precise histopathologic diagnosis as tissue architecture is preserved in the specimen for diagnostic stains. ¹⁴ For core biopsy, a coaxial technique is preferable typically with an 18- to 19-gauge introducer needle through which a 20- to 22-gauge biopsy needle is introduced to collect tissue specimen. Side cutting core biopsy needles are widely used and are safe and effective for head and neck lesion sampling. ^{15 16} Published experience on end-cutting core biopsy needles is sparse. ¹⁷

Embolization of Head and Neck Tumors

Preoperative embolization of head and neck tumors with high vascularity, first described in 1970s, reduces operative blood loss, improves the likelihood of successful tumor resection, and shortens the surgical time and postoperative recovery period. ^{18 19 20 21} The benefit in terms of reducing intraoperative blood loss is more apparent for larger, high-grade, and more vascular tumors. Typical candidate tumors include paragangliomas, angiofibromas, hemangiopericytomas, meningiomas, hemangioblastoma, and hypervascular metastasis, while other tumors such as schwannomas, rhabdomyosarcomas, and chordomas may also benefit. ^{22 23} Tumor embolization may also be considered as a palliative measure. ²²

Detailed selective angiography prior to consideration of embolization is important. Although most head and neck tumors derive their arterial supply from the branches of external carotid artery (ECA), additional feeding branches may be recruited from ICA, vertebral artery (VA), thyrocervical trunk, and costocervical trunk. Knowledge of tumor type, location, and extent based on cross-sectional imaging review provides useful clues; for example, paragangliomas are typically fed by ascending pharyngeal artery. Subsequent to selective angiography (bilateral ICAs, ECAs, VAs), superselective angiography of ECA branches confirms the blood supply and identifies selective contribution from various branches when multiple feeders are present. ^{22 23 24 25}

A detailed knowledge of vascular anatomy of the head and neck is absolutely essential prior to undertaking any embolization procedure in this region. Collateral pathways exist between the extracranial and intracranial vessels which may not be apparent on the initial angiography, most common between the branches of ECA (extracranial) and the ICA and VA. ²⁶ Some of these dangerous collateral pathways may open under pressure or subsequent to changes in blood flow during embolization. Additionally, various ECA branches provide arterial supply to vasa nervorum of cranial nerves: for example, neuromeningeal trunk (a branch of the ascending pharyngeal artery) feeds the CN IX–XII, superficial petrosal branch of middle meningeal artery (MMA) feeds CN VII, and tympanic branches of MMA feed various middle ear structures. ^{26 27} Overlooking these details, injection of embolic agent across these important arterial branches and collateral pathways can have disastrous neurological sequela.

Preoperative embolization is generally performed transarterial via femoral access. At our institution, general anesthesia is preferred to avoid movement during the procedure. However, conscious sedation and local anesthesia can be considered particularly when provocative testing (Amytal or lidocaine) may be needed to evaluate extracranial-to-intracranial collateral pathways or blood supply to cranial nerves. ²²

Subsequent to placement of a guide catheter in the ECA, superselective microcatheterization and embolization of tumor feeding vessels is performed ( Fig. 2 ). Percutaneous direct puncture technique using liquid embolic agents has been described and can be used alone or in conjunction with transarterial approach in select cases, for example, when a large superficial tumor is present or when endovascular access is not possible.

Fig. 2.

A 45-year-old woman with left cervical paraganglioma (carotid body tumor). ( a ) Contrast-enhanced CT image of the neck demonstrates a hyperenhancing mass centered in the carotid sheath splaying the left ECA and ICA; ( b ) preembolization left ECA angiography shows hypervascular angiographic stain corresponding to the mass noted on CT, primarily fed by branches of left ECA including the ascending pharyngeal artery; ( c ) superselective left ECA branch angiography, after embolization of one feeding artery using Onyx identifies another target branch feeding the anterosuperior component of this mass; ( d ) postembolization left ECA angiography shows >80% obliteration of angiographic tumor stain. The patient underwent successful resection of this tumor on postembolization day 1 with minimal operative blood loss, and was discharged home on postoperative day 2.

Various embolic agents can be used for tumor embolization and include coils (pushable and detachable), particulate agents (e.g., polyvinyl alcohol, embospheres, Gelfoam), and liquid embolic agents (e.g., Onyx [ethylene vinyl alcohol (EVOH) copolymer] and glue [N-butyl cyanoacrylate (NBCA)]). Anatomical considerations and operator preference guide the choice of embolic agent for the specific embolization procedure. ²² Each of these embolic agents has its own peculiarities, and a detailed discussion of these materials is beyond the scope of this review. ²⁸ A brief review of commonly used embolic agents is provided.

Liquid embolic agents , EVOH copolymer and NBCA, are long lasting and are considered “permanent,” a factor important to consider when risk of nontarget embolization may be higher. ²³ Both require extensive operator experience. NBCA glue (Trufill; Codman Neuro, Raynham, MA) polymerizes on contact with ionic solutions (saline, blood), and polymerization time is controlled via pH and its mixture with Ethiodol. Precise control of the microcatheter, velocity of injection, understanding of the vascular anatomy, and intended embolization endpoint are critical to avoid complications such as nontarget embolization and gluing the microcatheter in the vessel with consequent thrombosis and vessel rupture. EVOH copolymer (Onyx; Medtronic, Irvine, CA), on the other hand, allows slow and more controlled injection, with relatively low risk of gluing the catheter in vessel (due to its cohesive–nonadhesive properties). ^{27 29} For both NBCA glue and Onyx, after embolization via each feeder, the microcatheter has to be changed with its implication for procedure time and procedure cost.

Coils , detachable or pushable, are typically employed adjunct to the liquid embolics or particles to protect a vascular territory from nontarget embolization. Pushable coils are more thrombogenic and relatively inexpensive compared with detachable coils.

Particulate agents , such as polyvinyl alcohol, embospheres, and Gelfoam, allow penetration into the tumor capillary bed, with the possibility of delayed recanalization of the embolized vasculature, an advantage when nontarget embolization risk is high. Particulate size determines their depth of penetration. Small particles carry the risk of entering into intracranial circulation via the collateral pathways (ECA to ICA) as well the risk of nerve palsies due to penetration into vasa nervorum. Average particle size of 300 µm offers a good compromise between distal penetration to tumor bed and the possibility of penetrating vasa nervorum.

Reduction in angiographic stain or tumor blush provides a measure of embolization efficacy; approximately 80% or more reduction in tumor blush is desirable to maximize the benefits of preoperative embolization or palliation ( Fig. 2 ). Postembolization tumor devascularization and necrosis may not be immediate; therefore, a wait period of >24 hours is usually recommended prior to surgical resection. ^{21 22} Prolonged wait periods of >8 days are undesirable due to possibility of recanalization of vessels and recruitment of collateral pathways. For large tumors particularly in intracranial location, steroids may be considered in the immediate postembolization period to minimize the swelling and associated worsening of mass effect. ²²

For the extracranial head and neck tumors, major complications are rare; permanent neurological deficits from stroke or cranial nerve palsies, blindness, skin and mucosal necrosis, contrast-induced nephropathy, and death have been reported. ^{30 31} In the immediate postembolization period, therefore, the patient requires close monitoring and neurological evaluation to detect any undesirable sequela.

Endovascular Treatment of Tumor-Related Hemorrhage

HNSCC-related hemorrhage occurs in up to 10% of patient with advanced disease and could be related to recurrent tumor, radiation necrosis, or be iatrogenic and postoperative in nature. ^{32 33 34 35} Another relatively infrequent cause of head and neck tumor–related hemorrhage is juvenile nasopharyngeal angiofibroma, a benign but highly vascular and locally aggressive tumor, which typically presents with intractable epistaxis in young patients. ^{36 37} Endovascular techniques provide a safe and effective measure to manage hemorrhage in these settings. ^{35 38 39 40 41}

Predominance of head and neck tumor–related hemorrhage involves ECA branches; however, CCA or carotid bulb may be involved. Common causes of tumor-related hemorrhage are spontaneous tumor bleeding, rupture of iatrogenic pseudoaneurysms, radiation fibrosis, and intra-arterial (IA) chemotherapy. ³⁵ Surgical exploration and ligation of the involved vessels is complicated by postsurgical changes in local anatomy, postradiation necrosis and fibrosis, adhesions, fistulas, and infection. ³⁸

For the endovascular treatment of tumor-related hemorrhage, interventional approach and materials are similar to what has been discussed in section “Embolization of Head and Neck Tumors,” with the exception that the endovascular treatment is delivered in an acute or subacute setting. CT angiography of the head and neck, prior to endovascular treatment, may identify the site and source of bleeding in additional to providing valuable information on the location and extent of tumor. Detailed transfemoral selective catheter angiography evaluation of the head and neck vasculature identifies the source of hemorrhage, which may just be apparent as a pseudoaneurysm or arterial caliber irregularity. If no definitive candidate source is identified, selective microcatheter angiography and embolization of vessels feeding the tumor is performed. Particles, liquid embolic agents, or coils may be used based on operator preference, with careful attention to the dangerous collateral pathways and blood supply to vital structures such as cranial nerves. The goal of embolization is to occlude the vessels responsible for hemorrhage and devascularization of the tumor; to achieve this objective, particles and liquid embolic agents are usually the primary materials, while coils may be used adjunctively or to protect an arterial territory from inadvertent nontarget embolization. ^{42 43}

Carotid blowout syndrome (CBS) is a specific, rare, but life-threatening entity that occurs in approximately 4.3% of head and neck cancers; a rupture of the carotid artery subsequent to its involvement by the head and neck cancer occurs in patients with recurrent tumors post radiation and radical neck dissection. ^{44 45} Emergent surgical management is technically difficult with 40% mortality and 60% neurological morbidity. ⁴⁶ For CBS, endovascular treatment options include permanent balloon occlusion and carotid stent placement. Permanent balloon occlusion, first introduced in 1984, although improved on the morbidity and mortality associated with surgical treatment, is still associated with up to 15% risk of cerebral ischemic complications. ^{46 47 48 49 50} Covered carotid stents on the other hand achieve immediate hemostasis, while avoiding the high neurologic morbidity and mortality associated with conventional deconstructive surgical or endovascular techniques ( Fig. 3 ). ^{40 51 52 53} Delayed stent infection may occur in this setting, particularly in the presence of an infected neck or dehiscent wound. ^{54 55 56 57} Postoperative broad-spectrum antibiotics should be considered when any of the risk factors for stent infection are present, in addition to routine use of dual-antiplatelet therapy for carotid stent. ⁴⁰

Fig. 3.

A 69-year-old man with squamous cell carcinoma (status post total laryngectomy and chemoradiation treatment) and carotid blow out. Subsequent to transfer from an outside institution with episodes of “coughing up blood,” the patient “was doing well on the floor until around 17:00 hours when he coughed up approximately 800 mL of blood.” ( a ) Initial left CCA angiography demonstrated caliber irregularity involving the distal left CCA and proximal cervical left ICA; note was made of a stump on the left CCA medial wall, near origins of left facial artery and left internal maxillary artery; ( b and c ) following removal of oral packing, left CCA angiography showed active extravasation from this stump; the pack was immediately place back and a 6 mm × 50 mm covered stent was deployed across this segment following coil embolization of the proximal left facial artery and internal maxillary artery (to prevent retrograde flow in these arteries to the site of active extravasation and continued bleeding); ( d and e ) lateral and AP left CCA angiography post coil embolization and stenting shows improved and smooth caliber of left CCA and left ICA, with no residual stump or active extravasation. The patient's postprocedure recovery was uncomplicated with no additional bleeding episodes. On postembolization day 3, he was discharged home in a stable condition with normal neurological examination.

Intra-arterial Chemotherapy

For the squamous cell carcinoma of head and neck, three treatment modalities have established roles: surgery, radiation, and chemotherapy. For early-stage cancer (stages I and II), typically surgery or radiation therapy with curative intent is offered with success rates of >80% (stage I) and >60% (stage II). ⁵⁸ For advanced-stage disease (stages III and IV), although surgery remains standard treatment, it often requires partial or complete removal of organs such as larynx, tongue, and pharynx, with consequent detrimental impact on the quality of life, secondary to impairment of essential functions such as speech and swallowing as well as of appearance. ⁵⁹ Chemoradiation treatment has thus emerged as an alternative to surgery for the patients with advanced disease, with favorable rates of locoregional control and survival. ^{60 61} Cisplatin alone or in conjunction with taxols is usually used as part of concurrent chemoradiation treatment regimens. ^{62 63} Dose-limiting renal and gastrointestinal toxicity occurs above conventional systemically administered cisplatin doses (∼125 mg/m ² ). ⁶⁴ To administer higher doses of cisplatin, to achieve higher efficacy, and to overcome drug resistance, pharmacological and technical manipulations are employed, which include simultaneous administration of sodium thiosulfate and/or IA delivery of the agent. ⁶⁴

From a theoretical standpoint, several factors favor regional IA chemotherapy for tumors of the upper aerodigestive tract: most patients even with advanced disease do not have distant metastasis, often the large bulky uncontrolled lesion at the primary site presents the immediate challenge despite the presence of nodal metastasis, and ECA system provides primary feeding vessels to the tumor. ^{64 65}

IA chemotherapy for head and neck malignancies was first used by Klopp et al in 1950, who injected nitrogen mustards through an intra-arterially placed polyethylene tubing. ⁶⁶ First trial comparing IA chemotherapy to radiation treatment was conducted in 1965 at the Institut Gustave-Roussy. ⁶⁷ Various investigators have since studied IA use of various chemotherapeutic agents including methotrexate, 5-fluorouracil, bleomycin, mitomycin-C, and cisplatin. ⁶⁵ These studies conducted primarily in European, Japanese, and North American centers have shown IA administration of cisplatin, in conjunction with simultaneous intravenous sodium thiosulfate infusion (to neutralize cisplatin toxicity), to be the most effective chemotherapeutic agent for the chemoradiation treatment of head and neck tumors. ^{68 69 70 71}

For IA chemotherapy, it is the first pass of chemotherapeutic agent that confers advantage over the systemic chemotherapy as it exposes the tumor to very high concentration of the agent; following the first pass and with subsequent recirculation of the agent, tumor exposure to the agent is essentially equivalent for the IA or IV routes. ⁷² To maximize the first-pass tumor exposure to the administered chemotherapeutic agent, reduced plasma flow and increased plasma clearance are desirable; the first is accomplished by the administration of the agent in as small an artery as possible, and the second is achieved by using a neutralizing agent (thiosulfate for cisplatin). ⁶⁴

From an interventional standpoint, for IA delivery of the chemotherapeutic agent, the following three approaches have been used:

1. Conventional IA infusion via superficial temporal artery (STA) by surgical placement of a straight tip catheter in ECA : although technically simple and easy to perform, it is limited by factors such as unreliable delivery of the agent to tumor bed as well as possible catheter displacement with neck movements. ^{73 74}

2. Superselective arterial catheterization of the tumor feeding arteries via femoral access : it allows precise identification of the tumor feeding vessels, easy and safe catheterization with modern catheter systems, simultaneous catheterization of multiple feeding vessels, and reliable administration of the agent to tumor bed; however, catheter-related neurological complications occur in 1 to 8% of patients related to both neurotoxicity and thromboembolic events. ^{75 76 77}

3. Superselective IA infusion via STA : this approach is somewhat of a combination of the above two and involves catheterization of ECA via STA, ipsilateral to the tumor using an angiographic catheter (usually 4 or 5 Fr), followed by placing a coaxial microcatheter via the guide catheter into the target artery feeding the tumor. ⁷⁸ It avoids catheter placement in the common carotid artery and across the carotid bifurcation, thus minimizing the risk of catheter-related neurological complications; however, catheter displacement, vessel occlusion, and infection have been reported. ⁶⁴ Additionally, this approach is useful for small tumors fed by a single artery and has limitations for large tumors fed by multiple arteries. ⁶⁴

Earlier studies of IA chemotherapy identified various technical challenges related to placement of infusion catheters in the tumor feeding vessels, including infection and thrombosis for indwelling infusion systems. Over the last few decades, however, significant advancements in imaging systems, catheter technology, and techniques allow repeated superselective microcatheterization of tumor feeding vessels for targeted delivery of the chemotherapeutic agents to achieve multiple cycles of IA chemotherapy in a safe and accurate manner.

Variations exist among various reported chemoradiation treatment protocols. Most widely studied RADPLAT (radiation and platinum) protocol, developed at the University of California, San Diego, and the University of Tennessee, Memphis, requires 150 mg/m ² IA administration of cisplatin on days 1, 8, 15, and 22; radiation treatment is started on day 1 before chemotherapy and is continued once daily for 5 days a week. ^{63 69 79} Initial studies using the RADPLAT protocol reported promising results. ^{62 63} Based on these results, a multi-institutional randomized controlled trial was conducted in the Netherlands, which compared RADPLAT (IA chemoradiation) against IV chemoradiation treatment in 236 advanced HNSCC patients. At 7.5 years of follow-up, however, no differences in locoregional control or overall survival were observed between the two arms. ⁸⁰ Additionally, for the IA chemotherapy group, neurological toxicity was also higher while the renal toxicity was lower. Future studies may help refine the indications of IA chemotherapy to better define the patient groups where it is of most value.

Radiofrequency Ablation

Radiofrequency ablation (RFA) has emerged as a promising treatment technique for tumors involving various sites, including liver, kidneys, and breast, generally when curative resection may not be feasible. RFA deposits electromagnetic energy into the target tumor to induce thermal injury and subsequent tumor necrosis. Typically, at temperatures 46 to 60°C, irreversible cellular damage occurs after relatively prolonged exposure; at 60 to 100°C, however, instantaneous irreversible damage occurs secondary to protein coagulation, while at temperatures exceeding 100°C, tissue boiling, vaporization, and carbonization occur. ^{47 48} The objective of RFA is to maintain a target temperature typically in the range of 60 to 100°C throughout the entire target volume.

Only few reports exist on experience with RFA of the head and neck tumors. ^{81 82 83} Currently, for head and neck tumors, its role is primarily as an experimental palliative option for patients with advanced disease who either are not candidates for or refuse chemoradiation or other curative therapies.

Owen et al studied RFA as a palliative treatment option for advanced head and neck tumors. Eight of 13 patients on follow-up were noted to have no progression post-RFA, and 8 of 11 patients reported improvement in quality of life. Median survival posttreatment was 127 days. Major treatment-related adverse effects were one death consequent to carotid hemorrhage and two strokes. The authors noted that post-RFA, the tumor is converted to a mass of necrotic tissue, and therefore unlike chemoradiation treatment where treatment effect is gauged by the degree of partial or complete response, post-RFA nonprogression is the optimal marker of RFA treatment effect. Similar results were reported by Belfiore et al where out of the 17 patients with unresectable head and neck cancer treated with RFA, approximately one-third had partial response and two-thirds had complete response; two complications were observed (a cutaneous fistula and a palatal perforation). ⁸⁴

From the technique standpoint, typically under general anesthesia, a standard RFA probe is introduced into the target tumor under direct visualization or under image guidance (US, CT, or fluoroscopy). Adjacent tissues are protected using moist gauze or throat packing. ^{85 86} For the technique described by Owen et al, 100 W of energy is applied with target temperature of 100°C to achieve intratumor temperatures of 60 to 100°C for at least 10 minutes; the number of ablations is dependent on the tumor size and shape. ⁸⁶ Application of energy is continued until the temperature falls and impedance rises, implying no further energy conduction in the tumor bed.

Cryoablation

Cryotherapy techniques achieve cell death by achieving very low tissue temperature. A change in temperature of a gas results from its expansion or compression (Joule-Thomson effect); for example, argon cools during expansion, while helium warms during expansion. ⁸⁷ These changes are induced within the tip of a cryoprobe, to achieve freeze (temperatures of −160°C or colder) and thaw cycles. Intracellular ice crystals form with slow cooling, while extracellular ice crystals are induced by fast cooling—both achieving cell death. ⁸¹ Cryoablation is less painful and allows real-time approximate visualization of the ablation zone (also known as ice-ball). MR better depicts the ice-ball; however, CT also allows visualization and is routinely used. Procedure times are usually longer to allow the freeze–thaw cycles to complete. ⁸² Various probes, alone or in combination, could be used to achieve the desired ablation zone morphology.

Reported experience for cryoablation of head and neck tumors is limited to few reports. ^{83 88} Guenette et al reported a series of nine patients, where regional ablation for pain relief or functional status preservation was achieved in eight patients, with no associated mortality or permanent neurovascular or cosmetic morbidity. ⁸³

In the head and neck region, direct visualization of the ablation zone is of value given the densely packed vital structures. Compared with the techniques that achieve ablation via heating mechanisms (i.e., RFA), for cryoablation, vessels and adjacent structures and spinal canal contents may have inherent protection due to warm flow of blood and cerebrospinal fluid. ⁸³ Further work is needed to establish its safety and efficacy as a minimally invasive tool for the treatment of head and neck tumors.

Conclusion

In the multidisciplinary management of head and neck tumors, image-guided interventional techniques offer important tools for diagnosis and treatment. Image-guided tissue sampling, embolization of head and neck tumors, and endovascular treatment of head and neck tumor–related hemorrhage are well established, safe, and effective. IA chemotherapy for advanced HNSCC, despite its initial promise, failed to demonstrate superiority over IV chemotherapy, and requires further studies to help refine its indications in select patient groups. Experience with new techniques such as RFA and cryotherapy is limited and further work is warranted to explore their safety and efficacy.