Longitudinal Trajectories of Physical and Mental Health-Related Quality of Life Following Psychobiotic Supplementation in Gastrointestinal Oncology Patients: A Post Hoc Analysis of the ProDeCa Study.
Psychobiotic treatment was associated with more favorable longitudinal HR-QoL outcomes during adjuvant chemotherapy after gastrointestinal cancer surgery, with adjusted between-group differences of 16.79 points for Physical Component Summary and 9.66 points for Mental Component Summary scores at two-month follow-up.
Key Findings
Results
Significant group-by-visit interactions were observed across all eight SF-36 domains, indicating divergent longitudinal HR-QoL trajectories between psychobiotic and placebo groups.
All eight SF-36 domain group-by-visit interactions were statistically significant (all p < 0.001)
HR-QoL was assessed using the Short Form-36 (SF-36) questionnaire at three timepoints: baseline (V0), treatment completion (V1), and two months later (V2)
The study was a post hoc analysis of the ProDeCa randomized, double-blind, placebo-controlled trial (NCT06496438)
266 participants were included in the analysis, with HR-QoL data available for 231-232 participants at V2 depending on the SF-36 outcome
Results
At two-month follow-up (V2), the psychobiotic group showed a 16.79-point advantage in Physical Component Summary (PCS) scores compared to placebo.
Adjusted LS mean between-group difference in PCS at V2 was 16.79 points (95% CI, 15.69–17.88)
The four-strain psychobiotic formulation was administered for four weeks during adjuvant chemotherapy
Visit-specific adjusted comparisons generally favored psychobiotics across the study period
PCS score differences were assessed using mixed models for repeated measures
Results
At two-month follow-up (V2), the psychobiotic group showed a 9.66-point advantage in Mental Component Summary (MCS) scores compared to placebo.
Adjusted LS mean between-group difference in MCS at V2 was 9.66 points (95% CI, 8.49–10.84)
MCS differences were smaller in magnitude than PCS differences at the same timepoint
Mixed models for repeated measures were used to analyze longitudinal changes in both PCS and MCS
Results
Between-group differences in Vitality and Mental Health SF-36 domains were not statistically significant at treatment completion (V1) but became significant at two-month follow-up (V2).
Vitality and Mental Health domain differences emerged as statistically significant only at V2, not at V1
This temporal pattern suggests delayed or sustained effects of psychobiotic treatment on specific mental health dimensions
Other SF-36 domain comparisons generally favored psychobiotics at visit-specific adjusted comparisons
Results
Exploratory subgroup analyses did not provide evidence of differential treatment effects based on formal interaction tests.
Subgroup analyses were exploratory in nature
Formal interaction tests did not identify subgroups with significantly different treatment responses
The study population consisted of patients undergoing surgery followed by adjuvant chemotherapy for gastrointestinal cancer
Methods
The psychobiotic intervention consisted of a four-strain formulation administered for four weeks during adjuvant chemotherapy in a randomized, double-blind, placebo-controlled design.
The parent trial was registered as NCT06496438 (ProDeCa trial)
Participants received either the four-strain psychobiotic formulation or placebo
The trial design was randomized, double-blind, and placebo-controlled
The present analysis was a post hoc analysis of the ProDeCa study
Conclusions
The authors concluded that these findings support further investigation of psychobiotics as an adjunctive strategy for HR-QoL support in larger multicenter randomized trials.
The study population was gastrointestinal oncology patients experiencing impaired HR-QoL during cancer treatment
Authors framed findings as supportive of psychobiotics as an 'adjunctive strategy for HR-QoL support'
The authors called for 'larger multicenter randomized trials' to confirm findings
The post hoc design was acknowledged as a limitation of the current analysis
What This Means
This research suggests that taking a probiotic supplement specifically selected to support mental health (called a 'psychobiotic') during chemotherapy after gastrointestinal cancer surgery may help preserve patients' quality of life. The study followed 266 patients who were randomly assigned to take either a four-strain psychobiotic supplement or a placebo for four weeks while receiving adjuvant chemotherapy. Researchers measured quality of life using a validated questionnaire (SF-36) at the start of treatment, at the end of the four-week supplementation period, and again two months later. Patients in the psychobiotic group showed notably better scores in both physical and mental quality-of-life measures compared to those taking placebo, with the differences being particularly pronounced two months after treatment ended.
One interesting pattern was that improvements in certain mental health dimensions — specifically vitality and mental health — did not appear until the two-month follow-up, suggesting that some benefits of psychobiotic supplementation may emerge or persist after the treatment itself has ended. The physical quality-of-life advantage was substantial, at nearly 17 points on a standardized scale, while the mental quality-of-life advantage was approximately 10 points. These differences were statistically significant across all eight quality-of-life dimensions measured.
This research suggests that psychobiotic supplementation could be a low-burden add-on approach to help gastrointestinal cancer patients maintain their quality of life during a particularly difficult phase of treatment. However, since this was a secondary (post hoc) analysis of a previously conducted trial, the authors emphasize that these findings should be confirmed in larger studies specifically designed to test this question. The gut-brain connection is an active area of scientific interest, and this study adds to growing evidence that manipulating gut bacteria may influence both physical and psychological well-being in cancer patients.
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Tzikos G, Menni A, Theodorou I, Theodorou H, Tsetis J, Chamalidou E, et al.. (2026). Longitudinal Trajectories of Physical and Mental Health-Related Quality of Life Following Psychobiotic Supplementation in Gastrointestinal Oncology Patients: A Post Hoc Analysis of the ProDeCa Study.. Nutrients. https://doi.org/10.3390/nu18193254