1.1. Background on Head and Neck Cancer
Head and neck cancer (HNC) can develop in over 30 distinct regions within the head and neck [
1,
2]. These areas include the mouth and lips, where the oral cavity encompasses the lips, gums, and the inside of the cheeks. The voice box, or larynx, plays a crucial role in breathing, speaking, and swallowing, and it can also be affected by cancer. The throat, or pharynx, is divided into three sections: the nasopharynx (upper part of the throat behind the nose), the oropharynx (middle part of the throat), and the hypopharynx (bottom part of the throat), each of which can develop cancer. Salivary glands, which produce saliva to aid in digestion and keep the mouth moist, include the parotid, sublingual, and submandibular glands and can also be sites for cancer. The nasal cavity and paranasal sinuses, which are air-filled spaces around the nose and within the cheekbones and forehead, are potential sites for cancer development. Additionally, the area at the back of the nose and mouth, known as the nasopharynx, located behind the nose and above the back of the throat, is another region where cancer can occur. These cancers can vary in symptoms, treatment approaches, and prognosis, highlighting the importance of specialized care for each specific location within the head and neck.
In particular, mouth cancer, which is also called oral cancer or oral cavity cancer, is the most common type of HNC [
1,
3]. The most prevalent type of oral cancer is squamous cell carcinoma (SCC), which originates from the squamous cells lining the oral cavity [
4,
5,
6,
7]. Although SCC is the most common, other less frequent forms include verrucous carcinoma [
5], spindle cell squamous cell carcinoma [
5], basaloid squamous cell carcinoma [
5], and cancers of the salivary glands [
8].
Globally, oral cancer poses a significant health challenge [
9]. The World Health Organization’s 2013 report ranks oral diseases as the 13th most common cancer worldwide [
10], while HNC types are among the top ten most prevalent cancers globally [
11]. The high prevalence of oral cancer is particularly attributed to practices such as chewing tobacco and drinking alcohol [
9]. Incidence rates vary across regions and demographics, with higher rates observed in males and older adults [
12,
13].
Several risk factors contribute to the development of oral cancer. Tobacco use, whether through smoking or smokeless products, is a major risk factor. Excessive alcohol consumption further increases the risk, especially when combined with tobacco use. Additionally, chewing betel quid and areca nut [
15,
16], common in parts of Asia, is strongly associated with oral cancer. Dietary factors [
17], such as a low intake of fruits and vegetables, and genetic predisposition due to family history of oral cancer can also play a role [
18].
Oral cancer symptoms can be diverse, often leading to a delayed diagnosis as they may be mistaken for less serious conditions [
19]. Common symptoms include persistent sores or ulcers in the mouth that do not heal, unexplained bleeding or pain, white or red patches on mucosal surfaces, and difficulty swallowing or speaking [
20]. Additional signs, which are very common in non-malignant disease, include dental abscesses or a socket that fails to heal after a tooth extraction [
21]. Other signs can be progressive limitation of mouth opening, pathological anesthesia due to sensory nerve involvement, fixation of tongue, and neuropathic tongue pain [
22].
Diagnosis typically involves a thorough clinical examination, including inspection and palpation of the oral cavity and surrounding areas, mobility of teeth, mouth opening, sensory and motor disturbance, and tongue mobility. A biopsy is crucial for histopathological examination of suspicious lesions. Imaging studies such as X-rays, computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scans are used to assess the extent of disease and aid in staging [
20]. Staging of oral cancer is based on the TNM system, which evaluates tumor size, lymph node involvement, and metastasis to guide both prognosis and treatment options [
23,
24].
Treatment options for oral cancer depend on the stage and location of the disease. They may include surgery to remove the tumor and affected tissues, which can involve the removal of lymph nodes in the surrounding area. Radiotherapy is often used after surgery or as the primary treatment for localized tumors. Chemotherapy is typically reserved for advanced or metastatic cases and may be used in combination with radiation in a treatment approach known as chemoradiotherapy [
20,
25]. Emerging treatments such as targeted therapy and immunotherapy are also becoming increasingly important, focusing on specific cancer cell pathways or enhancing the body’s immune response to fight cancer [
26,
27].
The prognosis for oral cancer varies based on several factors including tumor stage, location, the patient’s overall health, and their response to treatment [
23]. The most critical prognostic factors are lymph node involvement, tumor size, and the presence of distant metastases [
23,
28]. Generally, early-stage oral cancers have a better prognosis, but advanced stages and poorly differentiated tumors can lead to lower survival rates and increased morbidity.
Despite advances in treatment, challenges persist in the early detection, accurate diagnosis, and effective management of oral cancer [
29]. Early diagnosis and recurrence prediction of oral cancer remain particularly problematic due to various factors [
9,
29,
30], such as
Heterogeneity: Oral cancer is not a single disease; it includes various subtypes with distinct genetic and clinical characteristics. This heterogeneity complicates diagnosis.
Tissue sampling: Accurate diagnosis often requires a biopsy of the affected tissue. However, obtaining a representative sample can be challenging, and false negatives may occur if the biopsy misses the cancerous area.
Recurrence prediction: Predicting the recurrence of oral cancer after treatment is challenging due to factors like tumor heterogeneity, incomplete removal of cancer cells during surgery, and resistance to therapy.
Imaging limitations: While medical imaging, such as CT scans, is valuable for cancer diagnosis and staging, it may not always detect small or early-stage lesions accurately. This can lead to underdiagnosis.
Patient variability: Patient-related factors, such as lifestyle choices, overall health, and genetic predisposition, can influence both the initial diagnosis and the likelihood of recurrence.
Post-treatment changes: Treatments for oral cancer, such as surgery and radiation therapy, can result in changes to the oral cavity, affecting speech, swallowing, and quality of life. Distinguishing between post-treatment changes and cancer recurrence can be difficult.
Limited biomarkers: Currently, there are limited specific biomarkers for oral cancer, making it challenging to identify individuals at high risk.
Patient awareness and access: Some patients may lack awareness of oral cancer risk factors and symptoms, and others may face barriers to accessing healthcare, delaying diagnosis.
Figure 1, accompanied with
Table 1, shows CT images of a cross-sectional view of the upper chest and lower neck region from four patients diagnosed with oropharynx cancer (OPC). These images were sourced from a publicly available database [
31], which supports the development of artificial intelligence (AI) methods aimed at identifying OPC patients with varying risks of disease recurrence post-definitive radiotherapy. Specifically, the database aids in distinguishing patients with the lowest likelihood of recurrence from those at risk of local recurrence in the primary tumor site.
Figure 2, accompanied with
Table 2, shows histopathological images of oral squamous cell carcinoma (OSCC) and leukoplakia sourced from the publicly accessible NDB-UFES database [
32]. This database is intended to support AI researchers in their efforts to develop advanced diagnostic tools that can assist clinicians and pathologists in the automated and accurate diagnosis of oral potentially malignant disorders and OSCC.
Ongoing research aims to address challenges in HNC by developing more precise diagnostic tools, innovative treatment modalities, and preventive strategies. The integration of AI holds promise for improving early detection and personalizing treatment approaches, potentially transforming the landscape of HNC care [
33,
34,
35,
36].
1.2. Review Objectives
The primary objective of this review is to explore and elucidate the role of AI in the field of HNC, focusing on its applications, advancements, and impact on clinical practice. HNC presents significant challenges in early detection, accurate diagnosis, and effective treatment. Integrating AI into these areas offers potential solutions that could significantly enhance current approaches. This review aims to provide a comprehensive overview of how various AI technologies are being utilized to improve the management of HNC.
Another key goal is to evaluate the current state of AI applications in diagnosing and predicting outcomes for HNC. By examining recent advancements in AI-driven diagnostic tools, such as automated image analysis and predictive modeling, the review seeks to highlight the ways in which AI can enhance early detection rates and the accuracy of diagnoses. Additionally, the review will assess how AI models contribute to the development of prognostic tools that better predict patient outcomes and support personalized treatment strategies.
The review also aims to identify and address the challenges and limitations associated with integrating AI into HNC care. This includes exploring issues related to data quality, algorithmic bias, and the practical implementation of AI technologies in clinical settings. By shedding light on these challenges, the review seeks to provide insights into the barriers that need to be overcome to fully leverage the benefits of AI in this field.
Furthermore, the review will explore future directions for AI in HNC research and clinical practice. This involves discussing emerging trends, potential innovations, and the interdisciplinary collaborations required to advance AI technologies. By considering these future prospects, the review seeks to outline a roadmap for how AI can continue to evolve and contribute to improved outcomes in the management of HNC.