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Palliative care
Research
Can variability in the effect of opioids on refractory breathlessness be explained by genetic factors?
  1. David C Currow1,2,
  2. Stephen Quinn3,
  3. Magnus Ekstrom1,4,
  4. Stein Kaasa5,6,
  5. Miriam J Johnson7,
  6. Andrew A Somogyi8,
  7. Päl Klepstad9,10
  1. 1Discipline, Palliative and Supportive Services, School of Health Sciences, Flinders University, Bedford Park, South, Australia
  2. 2Southern Adelaide Palliative Services, Repatriation General Hospital, Adelaide, South Australia, Australia
  3. 3School of Medicine, Flinders University, Adelaide, South Australia, Australia
  4. 4University of Lund, Lund, Sweden
  5. 5Department of Cancer Research and Molecular Medicine, Medical Faculty, Norwegian University of Science and Technology, Trondheim, Norway
  6. 6Department of Oncology, St Olav's University Hospital, Trondheim, Norway
  7. 7Hull York Medical School, The University of Hull, Hull, UK
  8. 8Discipline of Pharmacology, University of Adelaide, School of Medical Sciences, Adelaide, South Australia, Australia
  9. 9Department of Circulation and Medical Imaging, Medical Faculty, Norwegian University of Science and Technology, Trondheim, Norway
  10. 10Department of Anaesthesia and Intensive Care Medicine, St Olav's University Hospital, Trondheim, Norway
  1. Correspondence to Professor David C Currow; david.currow{at}flinders.edu.au

Abstract

Objectives Opioids modulate the perception of breathlessness with a considerable variation in response, with poor correlation between the required opioid dose and symptom severity. The objective of this hypothesis-generating, secondary analysis was to identify candidate single nucleotide polymorphisms (SNP) from those associated with opioid receptors, signalling or pain modulation to identify any related to intensity of breathlessness while on opioids. This can help to inform prospective studies and potentially lead to better tailoring of opioid therapy for refractory breathlessness.

Setting 17 hospice/palliative care services (tertiary services) in 11 European countries.

Participants 2294 people over 18 years of age on regular opioids for pain related to cancer or its treatment.

Primary outcome measures The relationship between morphine dose, breathlessness intensity (European Organisation for Research and Treatment of Cancer Core Quality of Life Questionnaire; EORTCQLQC30 question 8) and 112 candidate SNPs from 25 genes (n=588).

Secondary outcome measures The same measures for people on oxycodone (n=402) or fentanyl (n=429).

Results SNPs not in Hardy-Weinberg equilibrium or with allele frequencies (<5%) were removed. Univariate associations between each SNP and breathlessness intensity were determined with Benjamini-Hochberg false discovery rate set at 20%. Multivariable ordinal logistic regression, clustering over country and adjusting for available confounders, was conducted with remaining SNPs. For univariate morphine associations, 1 variant on the 5-hydroxytryptamine type 3B (HTR3B) gene, and 4 on the β-2-arrestin gene (ARRB2) were associated with more intense breathlessness. 1 SNP remained significant in the multivariable model: people with rs7103572 SNP (HTR3B gene; present in 8.4% of the population) were three times more likely to have more intense breathlessness (OR 2.86; 95% CIs 1.46 to 5.62; p=0.002). No associations were seen with fentanyl nor with oxycodone.

Conclusions This large, exploratory study identified 1 biologically plausible SNP that warrants further study in the response of breathlessness to morphine therapy.

  • THERAPEUTICS

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

https://doi.org/10.1136/bmjopen-2014-006818

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