Salivary inflammatory mediators as biomarkers for oral mucositis and oral mucosal dryness in cancer patients: A pilot study

Abstract

Oral mucositis (OM) is a common side effect in patients with cancer receiving chemotherapy and radiotherapy; however, no salivary mediator is known to be associated with OM. We aimed to determine candidate salivary inflammatory mediators potentially associated with OM in patients with cancer. To this end, we compared the relationships between OM grade, oral mucosal dryness, and inflammatory mediators (Interleukin (IL)-1β, IL-6, IL-10, IL-12p70, tumor necrosis factor (TNF), prostaglandin E2, and vascular endothelial growth factor) in patients with cancer and in healthy volunteers (HV). We collected saliva samples from 18 patients with cancer according to the following schedule: 1) within 14 days of treatment initiation, 2) within 3 days of OM occurrence, 3) when OM was improved or got worsened, and 4) within 7 days after chemotherapy completion. The oral care support team determined the OM grade at each sample collection point based on CTCAE version 5.0. Salivary inflammatory mediator concentrations were detected using cytometric bead array or enzyme-linked immunoassay. We compared oral mucosal dryness in pre- and post-index patients with cancer to that in HV (n = 33) using an oral moisture-checking device. Fourteen of eighteen patients experienced OM (four, grade 3 OM; four, grade 2 OM; six, grade 1 OM). IL-6, IL-10, and TNF salivary concentrations were significantly increased in the post-index group compared to those in the pre-index group (p = 0.0002, p = 0.0364, and p = 0.0160, respectively). Additionally, salivary IL-6, IL-10, and TNF levels were significantly higher in the post-index group than in the HV group (p < 0.0001, p < 0.05, and p < 0.05, respectively). Significant positive correlations were observed between OM grade and salivary IL-6, IL-10, and TNF levels (p = 0.0004, r = 0.4939; p = 0.0171, r = 0.3394; and p = 0007, r = 0.4662, respectively). Oral mucosal dryness was significantly higher in the HV than in the pre- and post-index groups (p < 0.001). Our findings suggest that salivary IL-6, IL-10, and TNF levels may be used as biomarkers for OM occurrence and grade in patients with cancer. Furthermore, monitoring oral mucosal dryness and managing oral hygiene before cancer treatment is essential.

Fig 1. Sampling schedule.

The saliva is collected at the sampling points 1–4. Sampling point 1: before TR, sampling point 2: when OM occurred, sampling point 3: when OM grade changed, and sampling point 4: after TR. Abbreviations: TR, treatment; OM, oral mucositis.

Fig 2. Comparison of oral mucosal dryness between HV (n = 33) and pre- and post-index patients with cancer (n = 18 and n = 34, respectively).

All data for the post-index group are obtained at sampling points 2 within 3 days of an OM event, 3 if and when the OM event improved or worsened, and 4 within 7 days after treatment completion. (a) Data are shown as means ± standard deviations. The closed circles for the index groups represent patients with leukemia, while the open circles represent patients with head and neck carcinoma. Oral mucosal dryness has no unit. The dotted line shows the cut-off value for dryness (y = 28). Statistical differences between the HV and each index group are analyzed using Dunn’s multiple comparisons test (***p < 0.001). (b) Oral mucosal dryness is divided into two groups (< 28 and ≥ 28), and the frequency is analyzed using the Chi-square test (*p < 0.05). HV, healthy volunteers; OM, oral mucositis.

Fig 3. Concentration differences in salivary inflammatory mediators between healthy volunteers (HV) and pre- and post-index patients with cancer.

(a) IL-1β, (b) IL-6, (c) IL-8, (d) IL-10, (e) IL-12p70, (f) TNF, (g) PGE2, and (h) VEGF. Data are shown as mean ± standard deviation. The closed circles for the index groups represent patients with leukemia, while the open circles represent patients with head and neck carcinoma. All data for the post-index group were obtained at sampling points 2, 3, and 4, as described in the methods section. The data in the pre-index group (IL-1β and VEGF; n = 1 and PGE2; n = 5) and the post-index group (IL-1β; n = 5, IL-6; n = 4, IL-8; n = 14, IL-10, IL-12p70, TNF, and VEGF; n = 3, and PGE2; n = 17) are missing because of low volume of saliva sampled or detection limits. The statistical differences between the HV and each index group are analyzed using Dunn’s multiple comparisons test (*p < 0.05 and ****p < 0.0001). The statistical differences between the pre- and post-index groups (Table 3) are analyzed using the Mann–Whitney U test (^#p < 0.05 and ^###p < 0.001).

Fig 4. Concentration differences in oral mucosal dryness and salivary inflammatory mediators between sampling point 1 and 4.

(a) Oral mucosal dryness, (b) IL-1β, (c) IL-6, (d) IL-8, (e) IL-10, (f) IL-12p70, (g) TNF, (h) PGE2, and (i) VEGF. Data are shown as mean ± standard deviation. The closed circles represent patients with leukemia, while the open circles represent patients with head and neck carcinoma. Sampling was done in group 1 and 4 before and after cancer treatment, as described in the methods section. The statistical differences between the sampled 1 and 4 groups were analyzed using the Mann–Whitney U test (*p < 0.05).

Fig 5. Correlation between the oral mucositis (OM) grade and the measurements.

(a) Oral mucosal dryness and (b) IL-1β, (c) IL-6, (d) IL-8, (e) IL-10, (f) IL-12p70, (g) TNF, (h) PGE2, and (i) VEGF in the saliva of patients with cancer. The closed circles for the index groups represent patients with leukemia, while the open circles represent patients with head and neck carcinoma. The correlation of OM grade with each measurement is analyzed using Spearman’s r test.

Fig 6. Concentration differences in salivary inflammatory mediators between pre- and post-index patients in each cancer group.

(a) Oral mucosal dryness, (b) IL-1β, (c) IL-6, (d) IL-8, (e) IL-10, (f) IL-12p70, (g) TNF, (h) PGE2, and (i) VEGF. Data are shown as mean ± standard deviation. The closed circles represent patients with leukemia, while the open circles represent patients with head and neck carcinoma. All data for the post-index group were obtained at sampling points 2, 3, and 4, as described in the methods section. The statistical differences between the leukemia and head and neck carcinoma groups are analyzed using the Mann–Whitney U test (*p < 0.05, **p < 0.01, and ***p < 0.001). The statistical differences between the pre- and post-index groups in each cancer were analyzed using the Mann–Whitney U test (^#p < 0.05, and ^##p < 0.01).