## 4 Conclusions  
A total of 147 VOMs were identified as belonging to different chemical families, and different chromatographic profiles were retrieved for the groups of subjects recruited. Terpenes, phenolic compounds, and norisoprenoids were the chemical families that contributed the most to the volatilomic profile of the three studied groups: control and PCa. The statistical analysis revealed that 7 of the 147 VOMs identified presented statistically significant differences between the recruited groups, according to the \(t\)-test (\(p<0.05\)). PLS-DA was performed, and the robustness of the generated model was evaluated using 10-fold CV and permutation tests. PLS-DA showed two well-separated groups, and the VIP score showed the most relevant metabolites among the studied groups. Hierarchical cluster analysis, carried out by Euclidean distance measure and Ward's linkage, showed that each cluster of the studied groups was well defined by a distinct panel of metabolites. The metabolites D-carvone, \(p\)-cymenene, 2-bromophenol, and \(p\)-tert-butylphenol were more strongly associated with the control group, whereas 3,5-dimethylbenzaldehyde, MMT, TDN, and 2-ethyl-1-hexanol were highly correlated with the PCa group. A significant increase in the peak area of TDN and 3,5-dimethylbenzaldehyde was observed in PCa patients. On average, significantly lower abundances of D-carvone, 6-methylphenanthridine, \(\alpha\)-methylcinnamaldehydehyde, 2-bromophenol, and 2,5,5,8a-tetramethyl-1,2,3,5,6,7,8,8-octahydro-1-naphthalenyl ester acetate (TONEA) were found in cancer patients. Further validation of the findings in this study is required using a much larger sample cohort to improve the predictive power and reliability of the developed statistical models. Likewise, additional research is required to determine which of the metabolites are of endogenous origin, disease-related, and which originate from exogenous sources, related to normal metabolic processes and external contaminations (environment or diet). **Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/curroncol30050370/s1](https://www.mdpi.com/article/10.3390/curroncol30050370/s1)]([https://www.mdpi.com/article/10.3390/curroncol30050370/s1](https://www.mdpi.com/article/10.3390/curroncol30050370/s1)), Table S1. Identified metabolites in urine samples of PCa patients and healthy subjects. Retention time (RT) in min, formula, CAS number and chemical family is reported for each compound. Frequency of occurrence as a percentage (%) and mean relative peak areas are reported for prostate cancer and control groups (n = 3; RSD <20%). **Author Contributions:** Conceptualization, G.R., C.V.B., F.P., V.G. and J.S.C. ; investigation, G.R. and R.P. ; writing original draft preparation G.R., R.P. and C.V.B. ; review and editing, J.A.M.P., F.P. and J.S.C. ; P.B., C.P.O., A.C.S., J.A.V. and M.d.C.P. were responsible for management the sample collection, inform the patients and healthy individuals about the study and obtain the informed consent from all participants; visualization, V.G., J.A.M.P. and J.S.C. ; supervision, V.G., J.S.C. and J.A.M.P. ; funding acquisition J.S.C. All authors have read and agreed to the published version of the manuscript. **Funding:** This work was supported by FCT-Fundacao para a Ciencia e a Tecnologia through the CQM Base Fund-UIDB/00674/2020 and Programmatic Fund-UIDP/00674/2020; and by ARDIT-Agencia Regional para o Desenvolvimento da Investigacao Tecnologia e Inovacao through the project M1420-01-0145-FEDER-000005-Centro de Quimica da Madeira-CQM+ (Madeira 14-20 Program). [PERSON] was supported by a PhD scholarship given by Univesita Cattolica del Sacro Cuore, 00168 Rome, Italy. [PERSON] was supported by a post-doctoral fellowship given by ARDIT (Project M1420-09-5369-FSE-000001), and [PERSON] acknowledges Nucleo Regional da Madeira da Liga Portuguese contra o Cancro (LPC-NRM) and Bolsa Rubina Barros for their support with this project.