Table 2.
General characteristics of included studies.
| Author, Year | Setting | Study Group (F/M); Age | Control Group (F/M); Age | Oncological Diagnosis | Inclusion Criteria | Exclusion Criteria | TNM Stages |
|---|---|---|---|---|---|---|---|
| Bel’skaya & Sarf, 2022 [36] | Russia | 355 (355/0); 30–39: 34 (9.6%), 40–49: 68 (19.2%), 50–59: 117 (33.0%), 60–69: 105 (29.6%), >70: 31 (8.6%) | – | breast cancer | diagnosis of primary resectable BC | NR | pT1–133 (37.5%), pT2–172 (48.5%), pT3–50 (14.0%); pN0–245 (69.0%), pN1–110 (31.0%) |
| Bel’skaya et al., 2022 [37] | Russia | 487 (487/0); 54.5 (47.0–56.0) | 298 (298/0); 49.3 (43.8–56.1) | breast cancer | histologically diagnosed with BC; age 30–70 years; absence of any treatment at the time of the study; absence of signs of active infection (including purulent processes); good oral hygiene; absence of untreated dental caries and periodontal disease; absence of clinically significant concomitant diseases other than cancer pathology (in particular, diabetes mellitus, cardiovascular pathologies, etc.) | any prior treatment, including hormone therapy, chemotherapy, molecularly targeted therapy, radiotherapy, surgery; lack of histological verification of the diagnosis | I–119 (24.4%), IIA–123 (25.3%), IIB–88 (18.1%), IIIA–55 (11.3%), IIIB–47 (9.6%), IV–55 (11.3%) |
| Cavaco et al., 2018 [38] | Portugal, India | Portugal: 36 (36/0); range: 39–73; India: 30 (30/0); range: 25–76 | Portugal: 16 (16/0); range: 18–63, India: 24 (24/0); range: 23–65 | breast cancer | NR | NR | NR |
| Murata et al., 2019 [39] | Japan | IC: 101 (101/0); 54 (34–89); DCIS: 23 (23/0); 49 (39–80) | 42 (42/0); 51 (23–80) | breast cancer | histologically diagnosed with BC | any prior treatment, including hormone therapy, chemotherapy, molecularly targeted therapy, radiotherapy, surgery, or alternative therapy; Ctrl: absence of history of any cancer | 0–23 (DCIS), IC: I–44 (45.4%), II– 46 (47.4%), III–5 (5.1%), IV–2 (2.1%) |
| Ragusa et al., 2021 [40] | Italy | BC: 38 (38/0); 54.2 ± 13.0; LC: 30 (8/22); 69.8 ± 10.3 | 34 (18/16); 46.2 ± 10.8 | breast cancer, lung cancer | age > 18 years; BMI of about 25–26 kg/m2; established clinical diagnosis of either BC or LC (including mesothelioma) | pregnancy; previous history of other malignancies; in the terminal stage (expected less than 4 weeks old); conditions that might have potentially interfer from a metabolic point of view; simultaneous liver cirrhosis, gastric ulcers, diabetes mellitus, periodontitis | NR |
| Sugimoto et al., 2010 [41] | U.S.A. | BC: 30 (30/0); 57 (29–77); PC: 18 (NR); 67 (11–87) | 87 (27/42, 18 missing); 43 (20–75) | breast cancer, pancreatic cancer | diagnosed with primary disease without metastasis | prior chemotherapy, radiotherapy, surgery or alternative therapy, history of prior malignancy, immunodeficiency, autoimmune disorders, hepatitis or HIV infection | NR |
| Takayama et al., 2016 [42] | Japan | 111 (NR); range: 36–90 | 61 (NR) | breast cancer | NR | NR | 0–16 (14.4%), I–50 (45.0%), IIA–32 (28.8%), IIB–10 (9.0%), IIIA–1 (0.9%), unknown–2 (1.8%) |
| Xavier Assad et al., 2020 [43] | Brazil | 23 (23/0); 47.52 ± 9.79 | 35 (35/0); 42.00 ± 13.83 | breast cancer | not pregnant or lactating; no active oral/dental disease; no prior neoplasia, except for non-melanomatous skin cancers, cervical carcinoma in situ, or benign tumors (e.g., adenomas); no impaired renal function, congestive heart failure, or active infection (e.g., hepatitis and HIV); histopathological diagnosis of BC; Ctrl: normal clinical and imaging findings | Ctrl: abnormal imaging or clinical findings; history of cancer treatment | I–2 (8.7%), II–12 (52.2%), III–5 (21.7%), IV–4 (17.4%) |
| Zhong et al., 2016 [44] | China | 30 (30/0); 53 (32–79) | 25 (25/0); NR | breast cancer | diagnosis of BC based on clinical and histopathological criteria; Ctrl: no history of malignancy or relevant breast diseases | History of receiving surgical operation and medication, including chemotherapy, radiotherapy, or alternative therapy | I–7 (23.3%), II–14 (46.7%), III–8 (26.7%), IV–1 (3.3%) |
| Asai et al., 2018 [45] | Japan | PC: 39 (18/21); 66.1 ± 9.86 | Ctrl: 26 (13/13); 50.8 ± 16.4; CP: 14 (3/11); 51.1 ± 12.4 | pancreatic cancer | histologically diagnosed with PC | prior treatment in the form of chemotherapy, radiotherapy, surgery, or alternative therapy; prior malignancy | III–6 (15.4%), IVA–12 (30.8%), IVB–21 (53.8%) |
| Chen et al., 2018 [46] | China | EGC: 20 (7/13); 60 ± 8.6; AGC: 84 (34/50); 53 ± 9 | 116 (49/67); 35.0 ± 10.0 | gastric cancer | clinical diagnosis of GC | diagnosis of other malignancies; metabolic diseases (mainly including diabetes) | EGC: stage I and II, defined as that the tumour invasion confined to the mucosa or submucosa; AGC: stage III and IV, defined as that the tumour invading into the muscularis propria or deeper gastric wall |
| Bel’skaya et al., 2020 [47] | Russia | GC: 11 (3/8); 56.8 ± 5.5; CRC: 18 (7/11); 58.2 ± 3.8 | 16 (6/10); 57.1 ± 6.4 | gastric cancer, colorectal cancer | age 30–70 years; the absence of signs of active infection (including purulent processes); absence of clinically significant concomitant diseases other than cancer pathology (in particular, diabetes, cardiovascular pathologies); good oral hygiene | any treatment at the time of the study, including surgery, chemotherapy or radiation; lack of histological verification of the diagnosis | GC: IIA–4 (36.4%), IIIA–2 (18.2%), IIIB–3 (27.3%), IV–2 (18.2%); CRC: I–2 (11.0%), IIB–3 (16.7%), IIC–5 (27.8%), IIIC–3 (16.7%), IV–5 (27.8%) |
| Kuwabara et al., 2022 [48] | Japan | training data: CRC: 117 (53/64); 67.42 ± 11.24; validation data: CRC: 118 (52/66); 69.63 ± 12.14 | Ctrl: training data: 1159 (841/318); 45.65 ± 10.15; validation data: 1158 (820/338); 45.19 ± 10.10; AD: training data: 25 (4/21); 66.30 ± 11.07; validation data: 25 (5/20); 61.81 ± 10.40 | colorectal cancer | histopathological diagnosis of CRC | prior treatment in the form of chemotherapy; chronic metabolic diseases, e.g., diabetes; histopathological diagnosis of all other types of cancer (adenosquamous cell carcinoma, endocrine carcinoma, lymphoma, etc.) | training data: 0–2, I–30, II (N1)–36, II (N2)–25, III–14, IVa–10; validation data: 0–2, I–31, II (N1)–36, II (N2)–25, III–14, IVa–10 |
| Hershberger et al., 2021 [49] | U.S.A. | 37 (7/30); 67.3 (44–94) | Crtl: 43 (16/27); 57.6 (36–77); cirrhosis: 30 (18/12); 58 (33–80) | hepatocellular carcinoma | age > 18 years; liver transplantation for HCC or cirrhosis; surgical resection for HCC or liver biopsy with confirmed cirrhosis and/or HCC; Ctrl: patients attending treatment for hernia with no history of liver disease or liver cancer | NR | NR |
| Bel’skaya et al., 2021 [50] | Russia | LC: 392 (85/244): ADC: 189 (60/129); 61.0 (56.0–65.0), SCC: 135 (7/128); 59.0 (55.0–66.5), NEC: 68 (18/50); 55.0 (52.0–60.0) | - | lung cancer | age 30–75 years; histological verification of the diagnosis | any treatment at the time of inclusion in the study, including surgery, chemotherapy or radiation | ADC: IA–16 (8.5%), IB–52 (27.5%), IIA + B–23 (12.2%), IIIA–25 (13.2%), IIIB–17 (9.0%), IV–56 (29.6%); SCC: IA–3 (2.2%), IB–28 (20.7%), IIA + B–19 (14.1%), IIIA–34 (25.2%), IIIB–24 (17.8%), IV–27 (20.0%); NEC: IA–5 (7.4%), IB–10 (14.7%), IIA + B–6 (8.8%), IIIA–10 (14.7%), IIIB–17 (25.0%), IV–20 (29.4%) |
| Jiang et al., 2021 [51] | China | ELC: discovery set: 45 (29/16); 57.8 (13.4); validation set: 44 (29/15); 55.3 (10.9); ALC: 11 (4/7); 70.2 (6.9) | discovery set: 25 (15/10); 52.9 (12.3); validation set: 25 (16/9); 57.3 (15.8) | lung cancer | NR | NR | I–89 (ELC), III–1 and IV–10 (ALC) |
| Takamori et al., 2022 [52] | Japan | 42 (14/28); 63 (39–86) | BLL: 21 (6/15); 62 (43–86) | lung cancer | confirmation of clinical or pathological diagnosis; consulted a dental surgeon before lung surgery; underwent PET/CT for LC | history of malignancy; prior treatment in the form of chemotherapy or radiotherapy at the time of pathological and clinical diagnosis | I–31 (73.8%), II–4 (9.5%), III–4 (9.5%), IV–3 (7.2%) |
| Zhang et al., 2021 [53] | China | 61 (44/17); 44 ± 11 | 61 (42/19); NR | papillary thyroid cancer | newly diagnosed with PTC; no history of malignancy and immunodeficiency disease; normal thyroid gland function | prior treatment in the form of surgery, long-term chemotherapy, radiation, and drug therapy | NR |
| García-Villaescusa et al., 2018 [54] | Spain | 10 (9/1); 54.7 (26–78) | 120 (71/49); 51.8 (19–81) | glioblastoma | age ≥ 18 years; diagnosis of glioblastoma; at least eight teeth | Ctrl: antibiotics intake in the past six months; fewer than eight teeth (excluding third molars); pregnancy; presenting cardiovascular diseases, diabetes mellitus, rheumatoid arthritis, chronic obstructive pulmonary disease, pneumonia, chronic kidney disease, metabolic syndrome, obesity and Alzheimer’s disease | NR |
U.S.A., the United States of America; F, female; M, male; -, not applicable; NR, not reported; Ctrl, control group; BC, breast cancer; IC, invasive carcinoma of the breast; DCIS, ductal carcinoma in situ; PC, pancreatic cancer; CP, chronic pancreatitis; GC, gastric cancer; EGC, early gastric cancer; AGC, advanced gastric cancer; CRC, colorectal cancer; AD, adenoma; HCC, hepatocellular carcinoma; LC, lung cancer; ADC, adenocarcinoma; SCC, squamous cell carcinoma; NEC, neuroendocrine cancer; ELC, early lung cancer; ALC, advanced lung cancer; BLL, benign lung lesion; PTC, papillary thyroid carcinoma; BMI, body mass index; HIV, human immunodeficiency virus; PET/CT, positron emission tomography/computed tomography.