Table 2 Studies exploring the gut microbiome alterations in patients with extraintestinal cancers

Pancreatic tumor

32 patients with PDA vs. 31 healthy controls

Fecal specimens, 16S rRNA gene sequencing

Proteobacteria and Synergistetes ↓; Euryarchaeota ↑

Increased feces microbiome in patients

[349]

Liver cancer

15 HCC patients vs. 15 non-HCC patients

Stool specimens, E. coli counts

E. coli ↑

Potentially drive tumorigenesis

[370]

75 HCC patients vs. 75 healthy controls

Fecal samples,16S rRNA gene sequencing

Butyrate-producing genera (including Faecalibacterium, Clostridium IV) ↓; LPS-producing genera (such as Klebsiella and Haemophilus) ↑

Potential biomarkers for early diagnosis of HCC

[362]

21 NAFLD-related HCC vs. 20 healthy controls

Stool specimens,16S rRNA gene sequencing

Bacteroides and Ruminococcaceae ↑; Bifidobacteria ↓

Correlate with systemic inflammation and tumorigenesis

[371]

68 HCC patients vs. 18 healthy controls

Stool specimens,16S rRNA gene sequencing

Proinflammatory bacteria Proteobacteria, Enterobacter, Haemophilus ↑

Degree of dysbiosis reflects the severity of HCC

[372]

25 cirrhotic patients with HCC vs. 25 cirrhotic patients without HCC

Fecal stool samples,16S rRNA gene sequencing

Fusobacterium, Leuconostocaceae ↓; Butyricimonas, Erysipelotrichaceae, ratio Bacteriodes/Prevotella ↑

Linked to inflammation and potential HCC biomarker

[373]

35 individuals with HBV related HCC vs. 22 individuals with non-HBV non-HCV-related HCC

Stool samples, 16S rRNA gene sequencing

NBNC-HCC: proinflammatory bacteria (Escherichia–Shigella, Enterococcus) ↑; SCFA-producing bacteria (Faecalibacterium, Ruminococcus, Ruminoclostridium) ↓

Different gut microbiome composition corresponds to different pathological types

[374]

Breast cancer

48 postmenopausal BC patients vs. 48 controls

Stool samples, 16S rRNA gene sequencing

Clostridiaceae, Faecalibacterium↑; Dorea and Lachnospiraceae ↓

Altered composition and low diversity of gut microbiome in patients

[403]

44 postmenopausal BC patients vs. 46 postmenopausal healthy controls

Feces samples, 16S rRNA gene sequencing

Escherichia coli, Klebsiella, Prevotella amnii, Enterococcus gallinarum, Actinomyces, Shewanella, Putrefaciens ↑; Eubacterium eligens and Lactobacillus vaginalis, Acinetobacter radioresistens and Enterococcus gallinarum ↓

The composition and functions of the gut microbial community differ between postmenopausal BC patients and healthy controls

[402]

48 postmenopausal BC patients vs. 48 postmenopausal healthy controls

Fecal samples, 16S rRNA gene amplicon sequencing

Reduced α-diversity; altered composition of both their IgA-positive and IgA-negative fecal microbiome

BC cases have estrogen-independent associations with the IgA-positive and IgA-negative gut microbiota

[401]

31 patients with early-stage BC

Fecal samples, 16S rRNA gene amplicon sequencing

Firmicutes, Faecalibacterium prausnitzii, and Blautia differ according to the patient’s BMI and clinical stages

Gut microbiome composition in BC patients differs according to clinical characteristics and BMI

[404]

Pulmonary cancer

41 patients with lung cancer vs. 41 healthy volunteers

Fecal samples, 16S rRNA gene amplicon sequencing

Bacteroides, Veillonella, Fusobacterium ↑; Escherichia, Shigella, Fecalibacterium, Enterobacter, and Dialister ↓

An altered bacterial community in patients with lung cancer

[439]

Prostate cancer

64 patients with prostate cancer vs. 41 individuals without cancer

Rectal swab samples,16S rRNA amplicon sequencing

Bacteroides and Streptococcus ↑

An altered bacterial community in patients with prostate cancer

[435]

30 patients with or without oral androgen receptor axis- ies (ATT)

Rectal swab samples,16S rDNA amplicon sequencing

Patients receving ATT: Akkermansia muciniphila, Ruminococcaceae spp. ↑

There are measurable differences in the bacterial community of men receiving oral ATT

[436]