Table 1.
Gut microbiome studies in RT/CRT.
| Author Year Country | Study Subjects Sample Size Mean Age (Range) | Treatment Type | Outcome | Faecal Sample Collection | Microbiome Analysis Method | Conclusions |
|---|---|---|---|---|---|---|
| Gonzalez-Mercado et al. [27] 2020 USA | Rectal cancer patients (n = 29), mean age: 61 yrs (range 37–80 yrs) | CRT Total RT (51–53 Gy): 45 Gy in 25 fractions plus 6 to 8 Gy boost 5-FU (n = 17), oral capecitabine (n = 10) | Fatigue | 3× (before, at the middle, and at the end) | V3/V4 region of the 16S rRNA | RT-associated perturbation of the gut microbiome composition may contribute to fatigue. |
| Jang et al. [26] 2020 Korea | Preoperative rectal cancer patients (n = 45) | CRT 50.0 Gy in 25 fractions (n = 4), 50.4 Gy in 28 fractions (n = 33), 54 Gy in 30 fractions (n = 8) | Response to RT: complete response (CR) (n = 7), non-CR (n = 38) | 1× (prior to CCRT) | V1–V2 region of the 16S rRNA | Samples obtained before preoperative CCRT, differences in microbial community composition and functions were observed between patients with and without CR in rectal cancer. |
| Mitra, A. et al. [25] 2020 USA | Advanced cervical cancer (clinical stage IB1, IB2, IIA, IIB, IIIB, and IVA) (n = 35) | CRT (RT plus cisplatin) | Bowel function | 4× (baseline and at weeks 1, 3, and 5) | V4 region of the 16S rDNA | Increased RT toxicity is associated with decreased gut microbiome diversity. Baseline diversity is not predictive of end-of-treatment bowel toxicity, but composition may identify patients at risk for developing high toxicity. |
| Ferreira et al. [28] 2019 UK | Prostate cancer (PCa) patients (n = 134), 1st cohort (n = 32), 2nd cohort (n = 87), 3rd colonoscopy cohort (n = 15), PCa (n = 9), healthy controls (n = 6) (range 63–79 yrs) |
Conventionally fractionated RT: 70–74 Gy to prostate and seminal vesicles (35–37 fractions) or 64 Gy to prostate bed (32 fractions); 50–60 Gy to pelvic lymph nodes (35–37 fractions) Hypofractionated RT: 60 Gy to prostate and seminal vesicles or 55 Gy to prostate bed (20 fractions); 47 Gy to pelvic lymph nodes | Enteropathy | 6× (at baseline and at 2/3 weeks, 4/5 weeks, 12 weeks, 6 months, and 12 months post-RT) | V1–V2 region of the 16S rRNA | An altered microbiota associates with early and late radiation enteropathy, with clinical implications for risk assessment, prevention, and treatment of RT-induced side-effects. |
| Wang et al. [23] 2019 China | Cervical cancer stage II–IV (n = 18) mean age: 57 yrs (range 30–67 yrs) |
RT: 50.4 Gy in 1.8 Gy/fraction | Enteritis (n = 10), non-enteritis (n = 8) |
2× (pre- and post-RT) | V4 region of the 16S rRNA | Gut microbiota can offer a set of biomarkers for prediction, disease activity evaluation, and treatment selection in RE. |
| Wang et al. [30] 2015 China | Patients with colorectal, anal, cervical cancer (n = 11), cervical cancer (n = 8), female anal cancer (n = 1), male colorectal cancer (n = 2) (range 41–64 yrs), healthy controls (n = 4) |
RT: 1.8–2.0 Gy/day, 5 times/ week, 5 weeks | Fatigue measured with the MFI-20 and diarrhea measured with the CTCAE, diarrhea (n = 6), no diarrhea (n = 5) |
2× (before and just after RT treatment) | V3 region of the 16S rRNA | In patients with diarrhea, fatigue scores significantly increased at both the third and fifth week of radiotherapy (p < 0.01), while those of patients with no diarrhea increased slightly. The microbial composition was also significantly different at the genus level prior to and post-radiotherapy in both groups of cancer patients. |
| Nam et al. [24] 2013 Korea | Gynecological cancer (n = 9) (age: 35–63 yrs), cervical cancer (n = 7), endometrial cancer (n = 2), healthy controls (n = 5) | RT: 50.4 Gy, 1.8–2.0 Gy/day, 5 times/week, 5 weeks | Diarrhea (n = 8), no diarrhea (n = 1) |
4× (before, after the first radiotherapy, at the end, and follow- up after treatment) | V1/V2 region of the 16S rRNA | Overall gut microbial composition was gradually changed after treatment of pelvic RT. Dysbiosis of the gut microbiome was linked to health status. |
| Manichans et al. [29] 2008 France | Abdominal cancer (n = 10), cervical cancer (n = 1), endometrial cancer (n = 4), rectum cancer (n = 4), uterus cancer (n = 1), healthy controls (n = 5) |
RT: 1.8–2.0 Gy/day, 5 times/week, 5 weeks | Diarrhea (n = 6), no diarrhea (n = 4) |
4× (before, during, at the end, and 2 weeks after treatment) | 16S rRNA (region 968–1401, positions in E. coli measured with DGGE) | Patients exhibiting diarrhea showed a progressive modification in their microbial diversity. Study indicates that diarrhea during RT may be linked to their initial microbial composition. |
CRO: Clinician-reported outcomes, RTOG: The Radiation Therapy Oncology Group, CTCAE: Common Terminology Criteria for Adverse Events, UCLA-PCI: University of California, Los Angeles Prostate Cancer Index, MFI-20: multidimensional fatigue inventory, RE: radiotherapy enteritis, RT: radiotherapy, CRT: chemoradiotherapy, DGGE: denaturing gradient gel electrophoresis, 16S rRNA: 16 Svedberg unit (S) rRNA.