The whole patient series recruited in the study comprised 2,193 patients. Some samples were excluded from the analysis because they failed quality check steps (Supplementary Fig. 1): in detail, 30 samples failed the Axiom Quality Controls pipeline, 23 samples were removed due to sex inconsistencies, six individuals were discarded due to a low call rate, and four duplicated or related patients were removed. PCA detected 30 individuals with a non-European ancestry who were excluded from the analysis. Finally, 41 patients did not have full NVS data; therefore, the GWAS was performed on 2,059 patients.
The personal and clinical information of the patients is shown in Table 1. Males and females were equally distributed. Approximately one third of patients received morphine, another third was treated with fentanyl, 26% received oxycodone and only 5% took buprenorphine. The most common types of cancer were gastro-enteric (∼ 18%), lung (∼ 18%) or breast (∼ 14%) cancer. More than two thirds of patients did not receive chemotherapy. Approximately 67% of patients were from the EPOS study, while 12% and 21% of subjects belonged to CERP and MOLO, respectively. Additionally, patients were mostly Italian, Norwegian, English and German. The median value for the NVS is 11.11 with an interquartile range of 33.33.
Table 1
Clinical characteristics of patients treated with opioids included in the GWAS for the nausea-vomiting phenotype.
Patient characteristic | NVS GWAS (n = 2059) |
Age, years, median (range) | 64 (18–91) |
Sex, n (%) | |
Female | 1046 (50.8) |
Male | 1013 (49.2) |
Opioid, n (%) | |
Buprenorphine | 103 (5.0) |
Fentanyl | 698 (33.9) |
Morphine | 713 (34.6) |
Oxycodone | 545 (26.5) |
Tumor diagnosis, n (%) | |
Lung | 360 (17.7) |
Breast | 296 (13.2) |
Gastro-enteric | 370 (18.2) |
Pancreas | 86 (4.2) |
Prostate | 209 (10.3) |
Urinary traits | 142 (7.0) |
Head and neck | 96 (4.7) |
Gynecological | 172 (8.5) |
Other or unknown | 328 (16.1) |
Chemotherapy, n (%) | |
Yes | 648 (31.5) |
No | 1411 (68.5) |
Study | |
EPOS | 1392 (67.6) |
CERP | 216 (10.5) |
MOLO | 451 (21.9) |
Country of enrollment | |
Switzerland | 83 (4.0) |
Germany | 132 (6.4) |
Denmark | 12 (0.6) |
Finland | 28 (1.4) |
Great Britain | 207 (10.0) |
Greece | 4 (0.2) |
Island | 122 (6.0) |
Italy | 945 (45.9) |
Lithuania | 48 (2.3) |
Norway | 383 (18.6) |
Sweden | 95 (4.6) |
Average NVS, median (IQR) | 11.11 (33.33) |
IQR: interquartile range |
We searched for clinical variables significantly associated with the NVS phenotype, by performing a multivariable linear regression with sex, age, administered opioid, chemotherapy, study, genotyping batch, country of enrollment and tumor type. We observed that females had higher NVS than male patients and that NVS slightly decreased with age. In addition, MOLO patients experienced less nausea-vomiting than patients in the CERP group. Finally, lower NVS was measured in patients enrolled in countries other than Italy (Table 2).
Table 2
Multivariable linear regression between clinical variables and NVS phenotype.
Characteristic | | Beta | P-value |
Sex | Male | 1.0 | |
| Female | 5.1 | 8.3 x 10− 5 |
Age | | -0.10 | 0.023 |
Study | CERP | 1.0 | |
| MOLO | -4.6 | 0.035 |
| EPOS | 0.13 | 0.96 |
Country of enrollment | Italy | 1 | |
| Other | -15 | < 2.0 x 10–16 |
Opioid | Morphine | 1 | |
| Buprenorphine | -3.1 | 0.26 |
| Fentanyl | 0.84 | 0.60 |
| Oxycodone | -0.47 | 0.77 |
Tumor site | Lung | 1 | |
| Gastro-enteric | -0.30 | 0.86 |
| Breast | -0.31 | 0.88 |
| Prostate | -0.44 | 0.84 |
| Pancreas | -0.66 | 0.82 |
| Urinary tracts | 0.51 | 0.83 |
| Head and neck | 1.2 | 0.67 |
| Gynecologic | 2.2 | 0.25 |
| Other | -2.9 | 0.11 |
Genotyping batch | I | 1 | |
| II | 3.11 | 0.0956 |
| III | 3.24 | 0.0655 |
| IV | 2.35 | 0.1367 |
For each patient, we genotyped 888,799 variants; 799,417 of them passed the Axiom Quality Controls pipeline, 13,767 variants were removed due to missing genotype data, and 946 and 387,355 variants were discarded due to Hardy Weinberg disequilibrium and low allele frequency (MAF < 1%), respectively. Finally, we removed 13,759 non-autosomal variants and 13,765 variants in extended LD. This dataset comprising 369,825 variants was used in REGENIE Step 1. After imputation and filtering by MAF < 2% and imputation score R2 < 0.3, the dataset for Step 2 included 7,669,761 polymorphisms.
The GWAS in 2,059 patients was performed with REGENIE software between genotypes and NVS phenotype, using age, sex, study, and country of origin as covariates. The results of this GWAS are shown in the Manhattan plot reported in Fig. 1. Although no associations reached the genome-wide statistical significance threshold (P-value < 5.0 x 10− 8), 68 variants were associated with NVS with a nominal P-value < 1.0 x 10− 6 (Supplementary Table 1) The most significant association was observed for rs6562126, which was negatively correlated with NVS (P-value = 1.2 x 10− 7; beta = -4.17). This is an intronic variant of the long non-coding gene LINC00378, located on chromosome 13, approximately 296 kb downstream of the TDRD3 gene. Among the other top-significantly associated variants, about half of them mapped to three loci, two on chromosome 2 (with four variants at 6 Mb and 15 variants at 100 Mb, respectively), and one on chromosome 20, with 13 variants. Of note, the 15 variants on chromosome 2 mapped to the NPAS2 gene. They all negatively correlated with NVS, meaning that an increasing number of minor alleles of these variants in the patients’ genotypes was associated with less nausea/vomiting. The 13 variants on chromosome 20 mapped in an intergenic region, approximately 80 kb from the ZNF217 gene. All these polymorphisms, instead, had positive beta coefficients, and thus their minor alleles were associated with high NVS.
Focusing on variants mapping in the NPAS2 gene, we found, in the GTEx database, that six of them were NPAS2 splicing quantitative trait loci (sQTLs), in the esophagus mucosa. In particular, an increasing number of minor alleles of these SNPs were reported to be associated with a high level of transcript splicing alteration. Table 3 reports the results from GTEx.
Table 3
Six variants associated with NVS and mapping in the NPAS2 gene were previously reported as NPAS2 sQTLs, in GTEx.
Variant ID | Gene Symbol | Phenotype ID * | P-value | NES | Tissue |
rs7558747 | NPAS2 | chr2:100977799:100979559:clu_45742:ENSG00000170485.16 | 2.0 x 10− 8 | -0.64 | Esophagus - Mucosa |
rs2289950 | NPAS2 | chr2:100977799:100979559:clu_45742:ENSG00000170485.16 | 1.9 x 10− 6 | -0.52 | Esophagus - Mucosa |
rs4851393 | NPAS2 | chr2:100977799:100979559:clu_45742:ENSG00000170485.16 | 2.3 x 10− 6 | -0.51 | Esophagus - Mucosa |
rs75107839 | NPAS2 | chr2:100977799:100979559:clu_45742:ENSG00000170485.16 | 2.3 x 10− 6 | -0.51 | Esophagus - Mucosa |
rs3768985 | NPAS2 | chr2:100977799:100979559:clu_45742:ENSG00000170485.16 | 2.4 x 10− 6 | -0.52 | Esophagus - Mucosa |
rs17025086 | NPAS2 | chr2:100977799:100979559:clu_45742:ENSG00000170485.16 | 2.7 x 10− 6 | -0.51 | Esophagus - Mucosa |
NES, normalized effect size. |
* As reported in GTEx and defined as the intron (chr:start:end) and cluster of connected components (clu_) to which the intron belongs. |
In addition, looking at the whole REGENIE output, we searched for variants previously reported for their possible association with nausea-vomiting in opioid-treated cancer patients 6,8. Variants and their summary statistics, both from REGENIE analysis and the two published studies are shown in Supplementary Table 2. Two variants, rs41269255 and rs12305038, reported in 8, showed nominal P-values < 0.05 also in the present study and concordant beta coefficients.