Abstract

Pain is a burdensome symptom that can commonly exist chronically along the cancer trajectory. Uncontrolled pain will impact on cancer patients' quality of life, even further negatively affect cancer survivors' employment. Based on systemic reviews of studies for past 10 years, the paper reported that although there is enormous advancement on the knowledge of cancer pain and pain management, studies still documented undertreatment of cancer pain globally. Additionally, pain distress a significant portion of cancer survivors. The pain in cancer survivors distinct from the pain related with cancer, instead emphasize on pain related with cancer treatment, such as neuropathic pain, muscular syndrome. Evidence-based pain management with common pain problems in cancer survivors is lacking. Further studies are needed to understand the pain in cancer survivors and to develop effective strategies in helping cancer survivors to manage their pain.

Keywords

cancer paincancer survivorprevalencepain management;

1. Undertreatment of cancer pain

Pain is one of the most distressed symptom in patients with cancer. With the analgesic ladder by the WHO in 1986, a majority of cancer patients would have their pain being controlled. Zech¹ reported that the practice by the WHO analgesic ladder have led to 76% of the patients in their study had good pain relief over the whole treatment period, with 12% rate of inadequate efficacy. However, uncontrolled cancer pain was destructive and costly. Studies supported that unaddressed cancer pain can lead to poor quality of life, greater depression, poor function, poor sleep and more distressed symptom.2, 3, 4 Many unscheduled emergency visits (27.8%) was because of uncontrolled pain and almost 10% of them re-admitted within 72 hours.⁵ Uncontrolled pain may further influence the employment status in cancer survivors.⁶

There is a vast progress in the control of either acute or chronic cancer pain for the past 50 years. In the early 1970s, cancer pain management was still in its infancy. Along with the WHO's analgesic ladder, the American Pain Society⁷ has provided recommendation of assessment and developed quality indicators for monitoring and improving the quality of the cancer pain management, which has been widely endorsed around the world. As the advanced knowledge of cancer pain and treatment, more guidelines were published and recommended more specifically about the choices of opioids and routes of administration, titration, non-pharmacological intervention and management for adverse effect.8, 9, 10 There also have been aggressive initiatives to improve the care for cancer pain in recent two decades, including that the Joint Commission on Accreditation of Healthcare Organizations in USA enacted pain assessment and management as one of standards and to be part of the survey and accreditation process for all organizations providing direct care,¹¹ as well as the Ministry of Health in Taiwan did in 2005.¹² The introduction of pain management standards is expected to improve the quality of pain management.

Although many striking efforts are made to improve the quality of pain management, and studies have demonstrated the effect of the pain communication,¹³ advanced procedure,¹⁴ patient education¹⁵ and psychosocial intervention¹⁶ on cancer pain control, the pain in cancer patients remain undertreated.3, 17, 18 Pain was identified as the most common problem (27.8%) that was presented by the cancer patients visiting the emergency department in northern Taiwan.¹⁹ The inadequate pain management as measured by negative Pain Management Index (PMI) were also reported by Mitera²⁰ with 25% in patients with pain related to bone metastasis, and by Fisch²¹ with 33% in patients with pain related to various cancer diagnosis and receiving care in ambulatory setting.

The inadequate pain control or undertreated pain in cancer patients remains a global issue. The Institute of Medicine reported that 50% of cancer patients around the world had pain.²² In USA, Weingart²³ examined the quality of cancer pain care and reported that among advanced cancer patients with severe pain, 34% of patients continued to report severe pain a month after the visit. In Italy, 40.3% of cancer patient with pain had breakthrough pain, but most of them being untreated did not.²⁴ In Japan, patients with non-advanced cancer or the cancer with no evidence of any recurrence tended to receive inadequate treatment than those with advanced cancer²⁵ and around 20% of metastatic or recurrent cancer patients in outpatient clinics had moderate to server pain.²⁶ In Taiwan, Tang's population-based study²⁷ in 1370 terminal cancer patients revealed that 47.4% of the patients were not satisfied with their pain relief within one week of admission and 23.6% had inadequate pain medication. Liang²⁸ found that around 50% of the ambulatory cancer patients in Taipei reported pain most of the time, and only 11% of patients experienced good pain management.

The pain influences the life of cancer patients across the cancer trajectory. Not only is the pain as the major concern of the patient at the end of life,²⁹ but also in those who under cancer treatment³⁰ or after the completion of the cancer treatment.³¹ Researcher reported that around 40% of 5-year cancer survivors or disease-free cancer patients experienced various degree of pain.32, 33 Van den Beuken-van Everdingen³⁴ suggested the prevalence rates of cancer pain were 59% in patients under cancer treatment, 33% in those after curative cancer treatment and 64% among those with advance cancer, based on a pool of findings from 54 articles published from 1966 to 2005. Similarly, Lee and colleague³⁵ also found that the cancer survivors with pain was accounted for 44.8% in a sample of 337 random sampled Taiwanese cancer patients who were two to five years since their cancer diagnosis. With the improvement of cancer treatment and cancer care, there is growing cancer survivors worldwide. However, more than one third of this growing population may suffer with pain. It is important to recognize the burden of pain in cancer survivors.

Pain is one of the most burdened problem in cancer survivors. Even though cancer patients have recovered or have been back to the “normal” from the cancer treatment, the pain as result of cancer treatment may still bother him or her after the completion of the treatment. Pain was recognized as the top three important symptoms that the survivors with breast, colon or lung cancer would like to avoid.³⁶ A recent survey of 314 randomly selected survivors who were diagnosed at least two years after their breast, colon-rectal, oral or cervical cancer being diagnosed, 16.3% of them were distressed by pain that demanded to be further managed.³⁷ This study also revealed that the pain severity differed by cancer diagnoses and the group with oral cancer had significant higher prevalence of pain than the other groups. In Green's survey of cancer survivors,² 42.6% of the overall sample with various cancer diagnoses reported pain since their cancer diagnosis. This was the case for breast cancer (58 %), colorectal cancer (41%), lung cancer (56%), multiple myeloma (100%), and prostate (28%). Most of the people in this survey were cancer free or in remission; nevertheless, about one in five were having pain. Another factor is the age. Especially in the elderly cancer survivors with comorbidities, the ones experiencing pain and other distressed symptoms after the cancer treatment had poor physical health.³⁸

Cancer survivors, as defined in accordance with the NCI, survived and lived with the cancer diagnosis from the moment of being diagnosed.³⁹ Cancer survivors may suffered pain from the advanced cancer, such as the abdominal pain from advanced colon cancer or as the result of the curative anti-cancer treatment, such as the pain from the resection of oral cancer or breast cancer. Studies shown that the cancer survivors undergone surgery for their colon-rectal cancer reported to have neuropathic-like pain in leg or abdominal,⁴⁰ or have more pain at lower-back⁴¹ or pelvic pain as compared⁴² with non-cancer group. Researcher suggested that cancer treatment may cause the change of the abdominal wall and make the survivors more sensitive to the stimuli. At the last, pain related to cancer or cancer treatment shown various types or phenomena in cancer survivors, such as chronic pain, breakthrough pain. Breakthrough pain is a flares pain or exacerbation of pain either spontaneously or in relation to a specific trigger despite adequately control of pain. The prevalence of breakthrough pain was accounted for 40.3% in Gerco's study in Italy.²⁴

Joint pain as related with aromatase inhibitors taken by breast cancer patient is also an influencing factor for the decreased physical activity or for discontinue of aromatase inhibitors. Brown⁴³ reported Breast cancer survivors with musculoskeletal symptoms related to aromatase inhibitor were more likely to reduce physical activity. Aromatase inhibitors are the adjuvant treatment for the post-menopausal women to less their estrogen and prevent the hormone-receptor-positive breast cancer cell growth. However, musculoskeletal symptoms, including bone demineralization with risk of osteoporosis and fracture, arthralgias, and myalgias are common side effect of aromatase inhibitors.⁴⁴ Studies revealed that the severity of joint pain and joint stiffness predict discontinue of the aromatase inhibitors in women with breast cancer.45, 46 For some cancer survivors, the cancer burden shifts from the high mortality rate to the issue of the chronic care from the cancer and cancer treatment.

Neuropathic pain is a special type of pain which differs from a common nociceptive pain that was related to a stimulated pain receptor. Nevertheless, neuropathic pain is a consequence of injured peripheral nerves or central nervous system; and patients may experience spontaneous pain or evoked pain. Bennett conducted a systemic review of previous studies and found that the prevalence of pain with a neuropathic mechanism ranged from 18.7% to 21.4% from all 14 studies.⁴⁷ The proportion of cancer-treatment-related pain was higher in neuropathic pain compared with all types of cancer pain. Neuropathic pain may be related with surgical injury of nerves or with chemotherapy-induced peripheral neuropathies. Neuropathic pain may be experienced in a mix of pain, numbness, tingling, or electric-like sensations⁴⁸; and it is common that cancer survivors underreport symptoms, as they confuse about the sensation or fear that they may be removed from the treatment.

Pain post operation have been studied extensively; however, the knowledge about the pain experienced after the treatment or the management of it are still limited. Literature revealed that the cancer survivors presented multifaceted needs as manifested from living with their cancer, or as the result of cancer treatment. Apart from the breakthrough pain, there is lack of evidence-based management strategies to help control other types of pain, such as neuropathic pain, joint pain. Especially the neuropathic pain as related to surgical procedure or chemotherapeutic agents, previous study provided low level of evidence.⁴⁹ Some studies have explored the effect of physical therapy or exercise on the cancer pain; but the result remained inconsistency.50, 51, 52 In considering its nature of chronic pain and its impact on emotional and psychosocial aspects of the life, future studies are needed to identify more effective treatment.

In conclusion, pain is one of the most burdensome symptoms in cancer patients, notwithstanding the cancer type or stage. Uncontrolled cancer pain have great impact on patients and their family's quality of life. With the vast advanced knowledge of cancer pain and strategies for pain management, the cancer pain remains undertreated. With the improvement of cancer treatment, the cancer survivors are increased; however, the care shifts from the survival to the issue of the chronic care or quality of life as the consequence of the cancer and cancer treatment. But, for those cancer survivors suffering from chronic pain, evidence-based pain management strategies are still limited. As healthcare providers facing the challenge and the uncertainty of growing demand of good pain management in cancer survivors, multidisciplinary team work is recommended.⁵³ In considering its nature of chronic pain, facilitating cancer patient in self-management and goal attainment⁵⁴ cannot be overstressed. Further research in developing effective strategies in managing cancer pain is needed.

Conflicts of interest

The authors have none to declare.