Cancer pain is multidimensional and complex and therefore a comprehensive and holistic assessment is essential in formulating an effective management plan (Burton et al. [31]). Cancer pain may change depending on disease progression and response to treatment; it is complex and as stated previously can be a mix of acute treatment‐related episodes alongside chronic disease‐related pathways. Pain assessment is not a one‐off episode, pain is dynamic and changes, and therefore pain assessment should be dynamic in order to ensure the appropriate management strategy is in place.

The term ‘total pain’ was first used by Dame Cicely Saunders ([199]) with the aim of identifying the impact that pain has on the individual as a whole. Dame Cicely suggested that pain is influenced by psychological, social, emotional and spiritual factors that contribute to the individual's overall pain experience. The physical aspects of the pain could be a result of treatment side‐effects or caused by the cancer itself; psychological factors that will heighten perception of pain are anxiety, depression and previous episodes of poorly controlled pain; social aspects can be loss of income due to ill health and financial concerns; and spiritual factors can be loss of faith, fear of the unknown and loss of meaning/purpose (IASP [108]). It is for this reason that pain assessment must be multidimensional and holistic in order to address the needs of the patient.

The simplest techniques for pain measurement involve the use of a verbal rating scale, numerical rating scale or visual analogue scale. Patients are asked to match pain intensity to the scale. Three principles apply to the use of these scales:

Lim et al. ([124]) surveyed 551 patients on their satisfaction with pain assessment scales and found that 79% were in favour of using the scales and that they were beneficial in managing their pain symptoms.

A variety of multidimensional assessment tools can be used to assess other aspects of cancer pain.

Given the variety of assessment tools available it is important to find one that both the patient and the clinician understand and are able to use and engage with. It is important to understand that the patient's self‐reporting and classification of symptoms is more accurate than the clinician's perception of the patient's pain (Brunelli et al. [28]).

Pain assessment can be difficult to achieve. For example, the tendency suggested by both research and clinical practice is for the patient not to report any pain or to do so inadequately or inaccurately, minimizing the pain experience (Bell and Duffy [12], McCaffery and Beebe [138]). Nurses are influenced by a number of variables when assessing the amount of pain a patient is suffering (Kitson [118]). Pargeon and Hailey ([163]) demonstrated that healthcare providers usually over‐ or underestimate a patient's pain. McCaffery and Ferrell ([139]) found that nurses were more likely to accept a patient's report of pain if they were showing signs of visible distress than if they did not. It has also been suggested that nurses do not possess sufficient knowledge to care for patients in pain (Drayer et al. [56], McCaffery and Ferrell [139]). A survey of over 3000 nurses (McCaffery and Robinson [141]) demonstrated that nurse education has improved confidence in the pain assessment process but that further education continues to be required in the pharmacology of pain medications and addressing nurses’ fears of opioid addiction and respiratory depression, which continue to contribute to the undertreatment of pain.

A variety of pain assessment tools exist to assist nurses to assess pain and plan nursing care. They enable pain to be successfully assessed and monitored (McCaffery and Beebe [138], Twycross et al. [219], Walker et al. [229]) and improve communication between staff and patients (Raiman [179]). Higginson ([98], p. 150) notes that: ‘Taking assessments directly from the patient is the most valid way of collecting information on their quality of life’. Encouraging patients to take an active role in their pain assessment by using pain tools helps to increase their confidence and makes them feel part of the pain management process. It is important to remember that pain is whatever the patient reports it is at that time. However McCaffery and Ferrell ([139]) found that less than half of nurses surveyed agreed that patients’ self‐reporting of pain was reliable.

Some degree of caution, however, must be exercised with the use of pain assessment tools. The nurse must be careful to select the tool that is most appropriate for a particular type of pain experience: for example, it would not be appropriate to use a pain assessment tool designed for use with patients with chronic pain to assess post‐operative pain. Furthermore, pain tools should not be used indiscriminately. Walker et al. ([229]) found that pain tools appeared to have little value in cases of unresolved or intractable pain.

Accurate pain assessment and reassessment are crucial to develop an understanding and baseline measure of the pain. The role of the nurse is crucial in the assessment and management of the patient's pain as they spend the most time with the patient. The key is to ask appropriate questions, which should seek to cover the following areas. The SOCRATES pain assessment framework is a mnemonic commonly used by healthcare professionals.

In addition to this, questions relating to the following psychosocial elements should also be addressed (Mackintosh and Elson [130]).

Neuropathic pain may require a specific assessment tool. Patients may describe spontaneous pain (arising without detectable stimulation) and evoked pain (abnormal responses to stimuli) (Bennett [13]). The Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) pain scale (Bennett [13]) was developed to more accurately assess this type of pain.

New UK National Guidelines to help healthcare professionals recognise and assess pain in older people have been published in 2018. The guidelines were developed by the British Geriatric Society, British Pain Society and Royal College of Nursing in collaboration with researchers. In adults with no or mild to moderate cognitive impairment, both numerical rating scales (0–10) and verbal descriptor rating scales (no pain, mild, moderate or severe pain) are reliable and valid for patients’ self‐report of pain intensity. The new UK guidelines include recognising that patient self‐reporting is the most reliable and accurate measure. Assessment may need to include the use of related terms such as ‘soreness, aching, or discomfort’ and also recommends that re‐wording questions to elicit the presence of pain such as ‘Do you hurt anywhere?’ can help to identify the presence or absence of pain (Schofield [200]). For older or vulnerable adults with moderate‐to‐severe cognitive/communication impairment Pain in Advanced Dementia (PAINAD) and Doloplus2 are recommended (Schofield [200]). Doloplus2 and PAINAD scales continue to show positive results in terms of reliability and validity. There has been no recent evaluation of the Abbey pain scale (Abbey et al. [1]) but it remains widely used throughout the UK due to its ease of use (Schofield [200]). Similarly, for patients who have a learning disability who cannot communicate their pain verbally, the use of pictorial or non‐verbal assessment tools may be appropriate and questioning those around the patient who know them well can be a great asset in assessing the pain needs of the person with a learning disability.

Fixed times for reviewing the pain have been omitted intentionally to allow for flexibility. It is suggested that, initially, the nurse review the patient's pain every 4 hours. When a patient's level of pain has stabilized, recordings may be made less frequently, for example 12‐hourly or daily. The chart should be discontinued if a patient's pain becomes totally controlled.