Pain management in head and neck cancer

Introduction: head and neck cancer-associated morbidity and pain

Head and neck cancers (HNCs) account for ∼5% of cancers globally (excluding nonmelanoma skin cancers) and are associated with significant morbidity including pain. HNCs primarily include malignancies of the oral cavity, oropharynx, nasopharynx, sinonasal cavities, hypopharynx, larynx, skin, and salivary glands. Prognoses for this group of cancers have only modestly improved with advances in surgical techniques, therapeutic radiation methodology, and novel targeted and immune-modulating systemic agents. There is a rise in HNC incidence rates from 2000 to 2018 according to the surveillance, epidemiology, and end results database with increased survivorship in large part related to the rising incidence of HPV-associated oropharyngeal cancers. The improved survivorship necessitates concomitant progress in managing the negative sequelae of these malignancies and their treatments, such as pain syndromes commonly associated with HNC. Acute pain syndromes are experienced by up to 80% of patients with HNC, with chronic pain in up to 60% of cases. ^,

HNC and its treatments negatively impact patient quality of life (QOL) by causing pain, difficulties with swallowing, eating, phonation, and speech, and worsening psychosocial health that can manifest as depression, anxiety, and suicidal ideation. Importantly, these HNC-related morbidities do not exist in isolation, but intimately influence one another. Thus, understanding and alleviating pain has the capacity to improve not only the physical discomfort, but multiple aspects of QOL. For instance, greater pain is associated with an increased risk of suicide in advanced cancers. ^, Survivors of HNC compared to all other cancers combined were twice as likely to die from suicide, and the incidence of suicide in patients with HNC is worsening with an increase of 27% during the period from 2010 to 2014 compared to 2000–04. Benefits of pain control extend beyond improving other elements of patient QOL and are also associated with improved surgical outcomes and reduced overall healthcare system burden.

Pain control methods in HNC include multimodal therapeutic approaches involving opioid and nonopioid analgesics for a variety of malignancy and treatment-associated pain syndromes. Guidelines for optimal pain control in HNC are shifting with increasing knowledge of the efficacy and risks of analgesic interventions. The World Health Organization's (WHO) three-tiered cancer pain treatment ladder, beginning with nonopioid analgesics for less severe pain and increasing to stronger opioids for more severe and refractory pain, has been a widely used general guideline for treatment escalation ( Fig. 7.1 ). Recent guideline updates from both national and international groups support the use of multimodal pain control regimens that expand treatment options and emphasize opioid stewardship. Collectively, these guidelines highlight that high-quality pain management should be an integral part of cancer care, with pain management screening at each patient contact, and a personalized plan for each individual with strong consideration of the risks associated with specific interventions in each case. Overall guiding principles of cancer pain management recommend that when possible treatment be given by mouth, on a scheduled basis, with upfront patient education regarding a plan. Herein, we review opioid and nonopioid analgesic therapies for HNC-associated pain.

HNC-associated pain syndromes and neurobiological mechanisms

HNC-associated pain is often heterogenous in its neurobiological mechanisms, with a mixed etiologies due to the disease itself as well as treatment side-effects. Within this complex pain picture, common pain syndromes have been described that are associated with specific disease statuses and/or anticancer treatment sequelae ( Table 7.1 ). These syndromes include acute and chronic pain from head and neck surgery, neuropathic pain, postradiation pain, myofascial pain, mucositis, dermatitis, symptomatic lymphedema, and skeletal pain, among others. The neurobiological etiology of the pain experienced in these syndromes should be addressed by analgesic treatment paradigms when possible. Ideally, optimal pain control strategies are individualized to target the characteristics of each patient's pain patterns.

Further distinction of the acute or chronic nature of the pain can help establish the pain syndrome and influence treatment choice. Two time points wherein acute pain is common include malignancy-induced pain seen at initial patient presentation and in the course of treatment including surgery, chemotherapy, and/or radiotherapy. Treatments can cause disruption of tissue in and around the tumor bed, with localized inflammation and edema causing nerve compression, mucositis, and dermatitis. Chronic HNC-associated pain can be defined as pain lasting longer than 3–6 months or that extends beyond the period of “normal” healing time. In HNC this is often ongoing pain directly related to persistent malignancy or longer-term sequelae of the anticancer therapies but frequently has unclear and mixed etiologies. Multiple studies in the late 1990s and early 2000s assessed the prevalence of chronic pain in cancer patients and within the subpopulation of patients with HNCs. A meta-analysis of 52 studies spanning clinical data over 40 years found that 33% of cancer patients continued to experience pain after curative treatment and that patients with HNC had the highest prevalence of pain in a subgroup analysis of pooled data including all disease severities and treatment outcomes (70% in HNC with vs. 50% in all cancer types). Similarly, a prospective study evaluating the longitudinal prevalence of pain in patients with HNC found that 26% of patients in their cohort ( n = 93) continued to experience pain 24 months after completing curative treatment. However, this study found that the prevalence of “severe” pain decreased posttreatment, with 8% of patient reporting severe pain at their first encounter and 4% at 24 months posttreatment. Recently, an analysis of 296 5-year HNC survivors in France revealed that nearly two-thirds of patients continued to experience pain up to 5 years after treatment. Multivariate analysis of this dataset identified decreased levels of physical activity, oropharyngeal original primary tumor site, and a lower level of education as significant risk factors for chronic pain. Importantly, in patients with HNC who have received curative treatment, it is essential to evaluate for possible cancer progression or recurrence if new pain arises or chronic pain worsens. It is also important to acknowledge many HNC patients have comorbid conditions that can contribute to chronic pain.

Mechanistically, HNC-associated pain is classified into nociceptive and neuropathic pain ( Table 7.2 ).

Nociceptive pain is caused by the activation of normal nerve endings of C and Aδ fibers, often from noxious stimuli and damage to nonneuronal tissue. In HNC, nociceptive pain can be caused by the destruction of local tissue by the tumor itself, invasive diagnostic and therapeutic interventions including surgery, or by effects of radiation and chemotherapy such as mucositis, dermatitis, and local injury in the tumor treatment field. ^{, ,} Nociceptive pain is subcategorized as somatic and visceral based on location and quality. Somatic pain is perceived as well-localized often sharp and/or stabbing pain, while visceral pain, mediated by the sympathetic nervous system, is more diffuse, can be referred from another area, and has a dull or achy quality. Treatments helpful in nociceptive pain include agents that inhibit inflammatory signaling and central and peripheral neurotransmission pathways.

Neuropathic pain is caused by damage to the nerve itself resulting in increased, abnormal activation patterns. Frequently, this is perceived as a burning and/or tingling sensation. In HNC, neuropathic pain can be caused by tumor invasion or compression of nerves in either or both the peripheral nervous system or central nervous system (CNS). ^, Analgesics that can be utilized in neuropathic pain include more centrally acting neuromodulating therapeutics that are historically utilized in the treatment of general neurologic and psychiatric disorders.

Despite these distinctive neurologic causes of pain, the experience of pain in HNC is complex. Potter and colleagues found that in HNC patients who had pain present at the time of diagnosis, 93% had mixed nociceptive and neuropathic pain. Additionally, the intricate anatomy of the head and neck and the invasive patterns of primary cancers in this region contribute to the variability of pain across different types of HNCs. For instance, it has been proposed that the higher density of nerve endings in the oral cavity coupled with the higher propensity of oral cavity cancer to invade bone contribute to higher reported pain in oral cavity cancers compared to those within the larynx and pharynx, in some studies. ^{, ,} Moreover, in their most recent update, the International Association for the Study of Pain now defines pain as “an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage,” incorporating the psychological aspects of pain.

Treatment overview for HNC-associated pain