The risk of suicidal thoughts in patients who have cancer

Two separate studies provide valuable insights into the risk of suicide among patients with cancer. One reveals that cancer patients are almost twice as likely to commit suicide as the general US population, while the other, from the UK, found that a substantial number of cancer patients report thoughts that they would be 'better off dead', or of 'hurting themselves'.

Improved survival after treatment has heightened the need for developing better understanding of questions surrounding cancer survivorship and quality of life. Most previous studies on suicide and depression have focused on terminally ill patients, with little work undertaken in broader cancer populations, including patients likely to be long-term survivors.

In the first study, researchers compared the incidence of suicide among cancer patients with that of the general population. Comparisons were based on mortality data collected by the US National Center for Health Statistics. This is the first time such comparisons have been made in the US.

Additionally, the investigators set out to identify disease characteristics, such as the anatomic site of cancers, associated with particularly high suicide rates. A total of 5,838 suicides were identified among 3,594,750 persons with cancer observed for 18,604,308 person-years, giving an age-, sex-, and race-adjusted suicide rate of 31.4 per 100,000 person-years. The corresponding rate for the general US population was found to be 16.7 per 100,000 person-years. Statistical analysis produced a standardised mortality ratio of 1.88, meaning cancer patients were 1.88 times as likely to commit suicide.

Higher suicide rates among patients with cancer were associated with male sex, white race and being unmarried. Rates were also higher among patients with advanced disease at diagnosis, but not among those with multiple primary tumours. They were highest among patients with cancers of the lung and bronchus (81.7 per 100,000 person-years), followed by stomach (71.7 per 100,000 person-years) and cancers of the oral cavity and pharynx (53.1 per 100,000 person-years).

The authors speculated that patients with lung cancer may struggle with their grave prognoses, while head and neck cancers can have a particularly devastating effect on quality of life 'through impact on appearance and essential functions, such as speech, swallowing, and breathing'.

They also suggested that the psychological experience of cancer survivors deserved further attention, particularly because appropriate use of psychosocial interventions in patients with cancer can improve their quality of life.

Limitations of the study included causes of death being subject to misclassification, inability to evaluate the potentially confounding role of comorbid conditions and inability to identify patients with cancer who committed suicide from the general population data.

In the second study, UK researchers surveyed 2,924 consecutive patients attending a cancer outpatient clinic between June 2003 and December 2004. The investigators used the nine-item Patient Health Questionnaire (PHQ-9), a widely used self-report screening tool, which included the critical question (item nine) asking whether patients had entertained thoughts of being 'better off dead or of hurting themselves in some way' in the previous two weeks.

Results were available on 2,924 patients, with 7.8 per cent (229 out of 2,924) responding positively to item nine. Of these, 5.4 per cent (159 out of 2,924) reported experiencing such thoughts on several days over the two-week period, 1.6 per cent (46 out of 2,924) on more than half the days and 0.8 per cent (24 out of 2,924) nearly every day. When demographic and clinical variables were considered, clinically significant emotional distress and substantial pain (and to a lesser extent, older age) were the only variables found to be associated with a positive response.

Limitations of the study include the fact that it used a self-completed screening measure, rather than an interview, so the investigators had to rely on patients' interpretation of the questions. Furthermore, the study did not include all of the factors that might be associated with thoughts of being 'better off dead or of hurting yourself', such as the patients' general health and social support.

In an accompanying editorial, Dr Timothy Quill, director of the palliative care program, University of Rochester Medical Center, New York, wrote: 'Qualitative studies will be needed to deepen our understanding of the range of thoughts, feelings, hopes and fears present in many seriously ill patients, so we can better distinguish clinical depression and anxiety that might be amenable to medical treatment from the range of normal sadness and fear that can be acknowledged and explored, but not necessarily treated.'

Systematic screening, he added, was essential: 'It is important to ask about suicidal thoughts and intent regularly, especially at times of transition when disease is worsening, symptoms are increasing or the patient is entering a more serious phase of illness. Creating an environment where these issues can be openly explored without being judged is critical.'

Misono S, Weiss N, Fann J et al. J Clin Oncol 2008;26(29):4731-8
Walker J, Waters R, Murray G et al. J Clin Oncol 2008;26(29):4725-30.
Quill T. J Clin Oncol 2008;26(29):4705-7

Originally published in the November 2008 edition of MIMS Oncology & Palliative Care.

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