In this study, we developed urinary VOC profiles linked with BLC and PC. Table 4 consists of the chemicals that have been identified in our study and have been cross verified using PubChem, NIST and previously published research, which may have particular relevance to BLC diagnosis. Out of 13 VOCs found noteworthy to BLC, Biphenyl, Heptanal, and 2, 6, 10, 14-tetramethyl- Pentadecane were the three distinct biomarkers found in our study that did not overlap with other studies. Biphenyl has been identified as the most significant biomarker in our study. Biphenyl has been linked to various diseases, including carcinoma. It has been proven that Biphenyl is a promoter of BLC in rats 44. Nonanal, Tetradecane, Dodecane, Hexadecane, Naphthalene, and Methyl Isobutyl Ketone have been suggested by Rodrigues et al. 45 in their study using GC-MS on BLC cell lines. Whereas 2-pentanone and 4-Heptanone overlap with the findings of Cauchi et al. 27. Benzoic acid was another chemical found in our study that overlapped in both Rodrigues et al. 45 and Cauchi et al. 27 studies.
Table 4
A list of possible biomarkers from the analysis of urine samples by GC-TOF-MS identified using PubChem, NIST and publications significant to Bladder Cancer.
| Chemicals | p-values |
1 | Biphenyl | < 0.01 |
2 | Nonanal | < 0.01 |
3 | Tetradecane | < 0.01 |
4 | Pentadecane, 2,6,10,14-tetramethyl- | 0.012 |
5 | 2-Pentanone | 0.012 |
6 | Undecane | 0.014 |
7 | 4-Heptanone | 0.018 |
8 | Dodecane | 0.025 |
9 | Hexadecane | 0.026 |
10 | Heptanal | 0.026 |
11 | Methyl Isobutyl Ketone | 0.045 |
12 | Naphthalene | 0.046 |
13 | Benzoic acid | 0.049 |
From the analysis of PC urine samples, a total of 7 distinct VOCs have been identified and are summarised in Table 5. In our study, we found toluene as the most significant chemical for PC. Toluene has been published previously as a significant biomarker for PC 46. Also, there are significant results published that toluene has been reported in testicular diseases 47,48. Pyrrole has been reported by Smith et al. in their study with 24 controls and 13 patients with PC. They tested the urine samples to assess VOC profiles and found Pyrrole as one of the significant markers for PC 49. 2-ethyl-1-Hexanol, phenol and dimethyl disulphide 50, Acetic acid 51, 2-methyl Cyclopentanone 52 were also found in our study, which overlaps with previous studies.
Table 5
List of possible biomarkers from the analysis of urine samples by GC-TOF-MS identified using PubChem, NIST and publications significant to PC.
| Chemicals | p-values |
1 | Toluene | < 0.01 |
2 | Phenol | < 0.01 |
3 | Acetic acid | < 0.01 |
4 | 1-Hexanol, 2-ethyl- | 0.011 |
5 | Disulfide, dimethyl | 0.012 |
6 | Cyclopentanone, 2-methyl- | 0.017 |
7 | Pyrrole | 0.033 |
Table 6 represents all the chemicals found in the analysis of urine samples for prostate and BLC. Most of the chemicals present in this list are the chemicals present in the lists for BLC and non-cancerous group and PC and non-cancerous group. 2-Hexanone, p-Xylene, and 3-methyl Nonane are the only significant chemicals out of 14 chemicals in this list that are important for both bladder and PC. 2-Hexanone and p-Xylene have previously been reported as a significant marker for the PC 50,52. There is no significant evidence for both 2-Hexanone and p-Xylene as a potential biomarker for BLC. However, 3-methyl-Nonane has not yet been reported as a biomarker for either bladder or PC, although it has been reported as a biomarker for lung cancer in different studies 53,54. This may signify the importance of 3-methyl-Nonane as a potentially significant marker. The results reported in this paper support the findings of other groups for the validation of these chemicals as potential biomarkers in both PC and BLC. It has been noted that the chemicals found in all the cancer groups were different and there was almost no overlapping of the VOCs fingerprints for BLC and PC. This adds further support to the unique VOC fingerprint in cancers of different cell origins.
Table 6
List of possible biomarkers from the analysis of urine samples by GC-TOF-MS identified using PubChem, NIST and publications significant to PC and Bladder cancer.
| Chemicals | p-values |
1 | Toluene | < 0.01 |
2 | Methyl Isobutyl Ketone | < 0.01 |
3 | Dodecane | < 0.01 |
4 | Phenol | < 0.01 |
5 | Cyclopentanone, 2-methyl- | < 0.01 |
6 | 2-Hexanone | < 0.01 |
7 | Heptanal | < 0.01 |
8 | p-Xylene | < 0.01 |
9 | Nonane, 3-methyl- | < 0.01 |
10 | Tetradecane | < 0.01 |
11 | Nonanal | < 0.01 |
12 | Biphenyl | 0.019 |
13 | Acetic acid | 0.025 |
14 | 2-Pentanone | 0.032 |
The use of urinary VOC analysis is an attractive option due to the non-invasive nature. It also has the potential to be used in early cancer diagnosis with further validation studies. This approach may also prove to be efficient, whilst lowering the cost per patient, and increasing patient compliance due to its non-invasive nature. The results of using GC-IMS as an analysis tool are significant as the method is much simpler than using a high-end analytical method, such as GC-MS, without the need for a laboratory environment.
Our results were limited by not accounting for the contributory factors that can also lead to abnormal metabolism with subsequent excretion of differing concentrations of these chemicals in the urine. These factors include stress, alcohol, smoking, certain food products, medicines and different environmental factors. We aim to consider these further in the next study. We also did not undertake full chemical identification with calibration standards. However, many of the chemicals we found correlate with other studies and therefore, there is evidence that these are correct.