RT Journal Article
SR Electronic
T1 Can variability in the effect of opioids on refractory breathlessness be explained by genetic factors?
JF BMJ Open
JO BMJ Open
FD British Medical Journal Publishing Group
SP e006818
DO 10.1136/bmjopen-2014-006818
VO 5
IS 5
A1 David C Currow
A1 Stephen Quinn
A1 Magnus Ekstrom
A1 Stein Kaasa
A1 Miriam J Johnson
A1 Andrew A Somogyi
A1 Päl Klepstad
YR 2015
UL http://bmjopen.bmj.com/content/5/5/e006818.abstract
AB 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.