The aim of this prospective, two center study was to investigate the dynamics of the microbial changes in relation to the development of ulcerative oral mucositis in autologous SCT (autoSCT) recipients. Fifty-one patients were diagnosed with multiple myeloma and treated with high-dose melphalan followed by autoSCT. They were evaluated before, three times weekly during hospitalization, and three months after autoSCT. At each time point an oral rinse was collected and the presence or absence of ulcerative oral mucositis (UOM) was scored (WHO scale). Oral microbiome was determined by using 16S rRNA amplicon sequencing and fungal load by qPCR. Twenty patients (39%) developed UOM. The oral microbiome changed significantly after autoSCT and returned to pre-autoSCT composition after three months. However, changes in microbial diversity and similarity were more pronounced and rapid in patients who developed UOM compared to patients who did not. Already before autoSCT, different taxa discriminated between the 2 groups, suggesting microbially-driven risk factors. Samples with high fungal load (>0.1%) had a significantly different microbial profile from samples without fungi. In conclusion, autoSCT induced significant and reversible changes in the oral microbiome, while patients who did not develop ulcerative oral mucositis had a more resilient microbial ecosystem.

Stem cell transplantation (SCT) is associated with oral microbial dysbiosis. However, long-term longitudinal data are lacking. Therefore, this study aimed to longitudinally assess the oral microbiome in SCT patients and to determine if changes are associated with oral mucositis and oral chronic graft-versus-host disease. Fifty allogeneic SCT recipients treated in two Dutch university hospitals were prospectively followed, starting at pre-SCT, weekly during hospitalization, and at 3, 6, 12, and 18 months after SCT. Oral rinsing samples were taken, and oral mucositis (WHO score) and oral chronic graft-versus-host disease (NIH score) were assessed. The oral microbiome diversity (Shannon index) and composition significantly changed after SCT and returned to pre-treatment levels from 3 months after SCT. Oral mucositis was associated with a more pronounced decrease in microbial diversity and with several disease-associated genera, such as Mycobacterium, Staphylococcus, and Enterococcus. On the other hand, microbiome diversity and composition were not associated with oral chronic graft-versus-host disease. To conclude, dysbiosis of the oral microbiome occurred directly after SCT but recovered after 3 months. Diversity and composition were related to oral mucositis but not to oral chronic graft-versus-host disease.

Despite advances in transplant medicine, prevalence of complications after hematopoietic stem cell transplantation (HSCT) remains high. The impact of pre-HSCT oral health factors on the incidence and severity of complications post-HSCT is poorly understood. The aim of this prospective, observational study was to analyze oral health in patients planned for HSCT. Patients ≥18 years requiring HSCT were included from five sites between 2011–2018. General health, oral findings and patient-reported symptoms were registered in 272 patients. Oral symptoms around disease onset were reported by 43 patients (15.9%) and 153 patients (58.8%) reported oral complications during previous chemotherapy. One third of patients experienced oral symptoms at the oral examination before conditioning regimen and HSCT. In total, 124 (46.1%) patients had dental caries, 63 (29.0%) had ≥one tooth with deep periodontal pockets, 147 (75.0%) had ≥one tooth with bleeding on probing. Apical periodontitis was observed in almost 1/4 and partially impacted teeth in 17 (6.3%) patients. Oral mucosal lesions were observed in 84 patients (30.9%). A total of 45 (17.4%) of 259 patients had at least one acute issue to be managed prior to HSCT. In conclusion, oral symptoms and manifestations of oral disease were prevalent in patients planned for HSCT. The extent of oral and acute dental diseases calls for general oral screening of patients pre-HSCT.

The aim of this multicentre, longitudinal study was to determine salivary changes in relation to oral mucositis (OM) in multiple myeloma patients following high-dose melphalan and autologous hematopoietic stem cell transplantation (ASCT). Unstimulated and stimulated whole-mouth saliva samples (UWS and SWS) were collected before ASCT, 1×/wk during the hospitalisation phase, and 3 and 12 months post-ASCT. During the hospitalisation period OM was scored 3×/wk (WHO system). Flow rate, pH, total protein concentration (Nanodrop), albumin, lactoferrin, neutrophil defensin-1 (HNP1), total IgA and S100A8/A9 (ELISA) were determined. Mixed models were used to evaluate differences between ulcerative (u)OM (≥2 WHO, n = 20) and non-uOM (n = 31) groups. Until 18 days after ASCT, flow rate, pH, total IgA and HNP1 levels decreased in UWS and/or SWS, while log lactoferrin levels were significantly increased (UWS: p = 0.016 95% CI [0.36, 3.58], SWS: p < 0.001 95% CI [1.14, 3.29]). Twelve months post-ASCT, salivary protein levels were similar to baseline except for log total IgA, which was higher (UWS: p < 0.001 95% CI [0.49, 1.29], SWS: p < 0.001 95% CI [0.72, 1.45]). No differences between uOM and non-uOM groups were observed. Changes in salivary proteins indicated an inflammatory reaction in salivary glands coinciding with mucosal and systemic reactions in response to high-dose melphalan.

Haematopoietic stem cell transplantation (HSCT) preceded by a conditioning regimen is an established treatment option for many haematological diseases. Decreased salivary flow rates after HSCT may increase caries risk. We aim to estimate the extent to which caries lesions develop or progress in adult HSCT recipients and assess its association with salivary flow rates. A multi-centre prospective observational study was conducted in which patients receiving HSCT were followed up for 18 months. We included 116 patients (median age 56 years, 43% female) from two medical centres in the Netherlands. Unstimulated whole saliva (UWS) and stimulated whole saliva (SWS) were collected, and full caries charts were made before HSCT and 3, 6, 12, and 18 months post-HSCT. Caries was scored according to the ICDAS criteria by trained dentist-examiners. New dentine lesions or lesion progression into dentine (ICDAS ≥4 or cavitated root lesions) occurred in 32% of patients over 18 months. The median number of affected surfaces was 2 (range: 1–12) per patient with caries progression. The influence of hyposalivation of unstimulated saliva (<0.2 mL/min) and stimulated saliva (<0.7 mL/min) at baseline and after 3 months on caries progression was determined with a negative binomial regression model. Hyposalivation of SWS 3 months after HSCT was a significant risk indicator for caries progression (incidence rate ratio: 5.30, 95% CI: 2.09–13.4, p < 0.001), while hyposalivation of SWS at baseline and hyposalivation of UWS were not. We conclude that caries progression is a common oral complication in patients after HSCT, and stimulated hyposalivation shortly after treatment is a significant risk indicator for caries progression.