The Fundamentals of Cancer Pain Management: A Review of the Association between Pain and Opioids

Fatemeh Arbabi

Published on: 2018-12-28

Abstract

Despite the undeniable clinical and methodical advancements surrounding the field of cancer research still, the physiology of cancer is not sufficiently understood and the issue of cancer pain continues to be a major health predicament worldwide. Facts of cancer pain are great many and are intricate on many levels. Opioid analgesics continue to be the most effective pharmaceuticals used in the treatment of cancer pain, nevertheless, their role in pain management has been evolving due to emerging awareness of potential risks of chronic opioid therapy. Despite extensive research efforts, no new class of analgesics have been developed. This review article aims to understand the fundamentals of cancer pain management, discuss the continuously progressing role of opioid analgesics, and the reasons for strong association between experience of pain and use of opioids.

Keywords

Cancer Pain; Management; Treatment; Opioids

Introduction

In 2012 it was reported that, 14 million of the world’s population were diagnosed with various types of cancers [1]. Not to mention it is anticipated that, by 2025 over 20 million of the world’s population are likely to be impacted by cancer [1]. In spite of the, considerable improvements in regard to understanding it’s causes, a much more in-depth understanding of its biology , the opportunity of early diagnosis alongside the opportunity of starting the course of the treatment early on , nevertheless , developments and advancements related to the treatment of cancer pain (CP) have been quite steady and certainly unsatisfactory. Education, recognition, and identification of cancer pain as a medical issue seem to have been a major challenge for many years. Although, the universality related to the prescription and authorization of opioid analgesics has definitely helped a lot for the control and management of cancer pain. Nevertheless, the commonality and widespread presence of cancer pain continue to be a frightening clinical concern for many patients and their loved ones [2,3] A recent meta-analysis in which the findings of numerous studies published between the year of 2005 till 2014 were taken into account has reported that, at least half of the patients who were obtaining anti-cancer treatment at the time of the study, and 2/3 of patients who were battling with advanced and metastatic cancers at the time of the research had reported suffering from pain [4]. Another study reports, in spite of the, recent moderate ameliorations in regard to the standards of pharmacologic pain management, in most cases 1 out of every 3 cancer patients are insufficiently prescribed with pain medication that does not provide them with adequate relief [5].
What’s so interesting is that, the impediments related to successful pain management have stayed mostly unchanged throughout the course of the time, which perhaps explains the physician’s severe lack of expertise when it comes to evaluation and management of pain. Numerous studies suggest, insufficient time is allocated to the issue of pain management and treatment throughout the medical school years and postgraduate training, which probably explains why the misconceptions about the use of analgesics and the nature of cancer pain management continue to be vague [6-8]. In fact, many studies believe management and handling of pain is not sufficiently taught to medical students, physicians in training, and health care professionals. In a research conducted in 2011 it was reported that, as limited as only 4 U.S. medical schools did present their students with a specific course that was intensively focused on the issue of pain regardless of the fact that, at the time the topic of pain was incorporated in general courses at 80% of schools [9]. The Journal of Pain study perceived pain training and preparations for North American medical students to be insufficient, changing too frequently, and incomplete [9].Even though, the Canadian medical schools were reported to be providing double the hours of instructions on the subject of pain at the time [9].But all facts and aspects taken into account, we cannot deny the fact that the field of oncology has certainly been developed and modified to a great extent. In today’s modernized world cancer patients definitely have greater chances of survival, alongside with the technological advancements with regard to understanding it’s very much intricate biological processes. On the other hand, the severe lack of simplicity associated with the nature of cancer diseases and the treatment techniques do make the treatment of pain more complicated than ever. Nowadays cancer patients are provided with extensive range of treatment techniques that they are not expected to be familiar with or have knowledge about, and that can be petrifying, particularly for elderly, youngsters, less educated, and/or patients from lower socioeconomic backgrounds. Needless to say, the extent of the impact and potential aftermaths of cancer treatment methods vary significantly and In majority of cases can be quite risky and discomforting physically as well as psychologically [10,11].This review article aims to understand the fundamentals of cancer pain management, discuss the continuously progressing role of opioid analgesics, and the reasons for strong association between experience of pain and use of opioids.

 A brief overview of the phenomenon of cancer pain

Cancer pain is a complicated physiological experience that has remained ambiguous, and there are difficulties and limitations with regard to understanding its set of causes, progression, and treatment. Cancer pain does not exist in a systemic and distinct form [12]. Cancer pain is a subjective experience, the occurrence and experience of pain in each patient is processed differently [13,14]. In the last couple of years, new perspectives on the physiology of the type of pain that is produced due to cancerous growth have become more known. Progressively, this type of pain is perceived as an outcome of undertakings that entail transfer of signals between neoplastic cells, immune system, peripheral, and central nervous system of the patient. In the standard medical perception of tumour’s expansion, occurrence and growth of metastasis and pain production, the nervous system was mostly perceived to be a passive participant.
At the present time, it is being perceived to be an active member [15]. In cases that, cancer pain is caused by the cancer itself, it mainly is the outcome of the pressure caused by tumor pressing on bones, nerves, or other organs in the patient’s body [16]. In addition to that, in some circumstances, cancer pain may also be caused by the method of the treatment, for instance, majority of the chemotherapy drugs are known for creating numbness and tingling in the patients’ hands and feet. Or they may also create a burning sensation at the location where the drug is injected [16]. Categories of cancer pain include acute, chronic/persistent, and breakthrough.

Epidemiology of cancer pain

Cancer pain has for so long remained as one of the most frightening experiences related to cancer, it is not a surprise that, approximately 75% of cancer patients who struggle with pain are in need of opioid analgesics to help them cope with severe pain and pain related symptoms [17]. Statistics retrieved from world health organization and hospice care facilities suggest, an oral administration of morphine alone can help comfort approximately 85% of cancer patients. Some other data propose, management of cancer pain may need adjustments related to the path of opioid management, suggesting the use of co-analgesics, anti-neoplastic treatment techniques, and neurosurgical methods. It is expected that, substantial percentage of cancer patients are likely to experience satisfactory pain control via correct use of these methods , sadly though cancer pain continues to be under treated , not so well understood , under assessed , and not sufficiently managed worldwide[18].
Due to the fact that, pain is a subjective experience heath care practitioners in many cases will have to learn by means of experience and asking questions to find out if a patient requires or/and can benefit from taking pain medicine. Health practitioners and medical assistants have been trained and instructed that, pain “is what the patient says it is” [19]. Consequently, the patient’s description of pain continues to be the sole most valid measure of the presence and severity of pain. Some other factors have been considered for the determination and measurement of pain (e.g., pathology, vital signs, patient’s behavior), though none have proven to be more precise than the patient’s self-report of pain [20,21]. Achievement of satisfactory relief from pain and pain related symptoms has been recognized as a basic human right [22,23]. The WHO Pain Relief scale recommends and supports the consumption of various categories of pain medications based on the intensity of pain, and in accordance to the principals of modern pain management strategies [24]. For tolerable pain the WHO suggests, basic and less strong pain relievers, those that can be obtained over the counter without a need for prescription or authorization of a licensed medical doctor. For the management of more severe forms of pain WHO suggests, a mixture of over the counter pain relievers and a less portent opioid drug (e.g., codeine). Though, for the advanced and severe pain WHO believes strong opioids (e.g., morphine) are expected to be effective [25].

Pain and opioids

To a great extent consumption of medication appears to be the most common method in the treatment and management of pain. Taking into account, the substantial amount and various diversity of currently available analgesic medications on the market , the scope of medication categories , possible psychoactive elements , the possible ways in which consumed drugs can have an effect on each other , and common issues surrounding the concept of drug misuse in different cultures it is no astonishment that , use of medication is such a dilemma , and that many patients appear to be experiencing quite a lot of complications with regard to their use of medication [26]. Using opioids for the treatment of pain is often a difficult decision. Many medical professionals are skeptical to prescribe opioids for patients on account of concerns associated with the potential misuse, abuse, and addictive nature of the opioids.

Pain, opioids and the public Policy throughout the history

For too long opioids have been administered as a remedy to heal and manage extensive arrays of diverse symptoms, especially pain. In the United States, the social standing related to the administration of opioids has changed several times as a consequence of different periods of the history [27]. In the course of the late 1800s opioids such as morphine could be easily acquired at various places, and were oftentimes administered to alleviate and lessen variety of conditions and disorders. End of the “18th” century and beginning of the “19th” century, highlights the period of the time in which the government officials of the United states developed questions and concerns in regard to the addictive and habit forming characteristics of opioid drugs , as a result of which the non-medical administration of the opioids turned into a criminal offence. Later in 1914, lawmakers proceeded with the Harrison Act, a law that permitted the doctors to have control over the prescription of legitimate medical use of opioid drugs, a law that made it specifically clear for the doctors that it would be against the law for them to authorise opioids for any individual that may potentially be an “addict” [28].
In the course of the 1980s, medical profession experienced a substantial change as professionals became concerned with the lack of sufficient treatment for the management of pain. The change in health care was mostly due to the argument that demanded physicians needed to be well trained to know the difference between medically reasonable physical dependence in pain patients and the behaviours of an opioid addict, so that opioid drugs could be acquired by the patients that could potentially benefit from the treatment [29-31].

Patients’ perspectives related to opioid treatment

Nausea and vomiting are typical side effects experienced by patients [32]. Numerous research have been conducted to determine the impact of opioid-induced nausea and vomiting on the normality and quality of the patients’ lives [33-35]. Needs to be mentioned that, nausea and vomiting are not solely caused due to the short-term negative effects of the opioid treatment, as reported by a 3-year long U.S. registry study in which 219 patients received oxycodone for a long period of time, approximately 12% of the patients had reported experiencing nausea and vomiting throughout the course of the study [36]. Although, the experience of side effects diminished throughout the course of the treatment, for a small group of patients it continued to emerge for 3 years post study [36].

Phraseology of opioid misuse: Dependence, tolerance, and addiction

According to an agreement established by the academy of Pain Medicine (AAPM), American Pain Society [APS], and the American Society of Addiction Medicine (ASAM), the term “tolerance” is defined as the declined subjective and objective aftereffect of a particular quantity of a specific type of opioid drug administered over a long period of time, which will cause the body of the person taking the opioid to demand larger quantities of the drug to maintain the elated state [37-39]. There definitely appears to be some degrees of uncertainty and confusion when it comes to differentiating between physical dependence and addiction in the currently existing literature related to pain [39,40]. The non-abusive administration of opioids can sometimes lead to negative outcomes eg., cravings , loss of control , and/or uncontrollable use [39,41]. Certain types of actions are considered as potential signs of pseudo-addiction. The correct recognition of these circumstances and other potential states may be a demanding task that necessitates vigilant evaluation of clinical phenomenology in a way that is clear [39,42]. In some cases, occurrence of atypical drug-related behaviours may be great indication of addiction for instance, in circumstances that a patient administers his/her medication via multiple forms of administrations (e.g., injection or sniffing) [39,43,44].

Conclusion

Cancer pain definitely is a concerning health problem that requires more research. Struggling with the very much life changing and life threatening experience of cancer is complicated and traumatising on its own, and what’s worse is that, terrified cancer patients constantly experience fear and emotional discomfort. For far too long, opioids have been among the most effective medications for moderate to severe pain. Which simply demonstrates this method of treatment is perceived and identified to be effective for the treatment of cancer pain. In fact, numerous cancer pain studies suggest and support all the benefits and pros associated with the use of opioid analgesics for the treatment of cancer pain.

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