Sep 30

SS 40 - Hem 2: New Protocols, New Paradigms: Clinical Trials Shaping the Future of Hematologic RT

332 - Differential Impact of Total Body Irradiation- vs. Chemotherapy-Based Myeloablative Conditioning on Oral Microbiota and Mucositis after Allogeneic Transplantation

03:00pm - 03:10pm PT

Room 314

Presenter(s)

Maryam Ebadi, MD - University of Washington, Seattle, WA

M. Ebadi¹, H. Gem², G. Sebastian², R. Abasaeed², M. Lloid², Y. D. Tseng¹, O. Y. Mian¹, D. R. Dean², and A. Rashidi³; ¹Department of Radiation Oncology, University of Washington/ Fred Hutchinson Cancer Center, Seattle, WA, ²Department of Oral Medicine, University of Washington and Fred Hutchinson Cancer Center, Seattle, WA, ³Clinical Research Division, Fred Hutchinson Cancer Center, Seattle, WA

Purpose/Objective(s):

Oral mucositis (OM) is an early complication of allogeneic hematopoietic cell transplantation (alloHCT), causing pain, infections, swallowing/speech impairment, and poor quality of life. Although some studies have reported higher rates of OM with total body irradiation (TBI)- vs. chemo-based myeloablative conditioning, findings have been inconsistent. This may be due to variability and limitations in mucositis assessment methods. We hypothesized that comprehensive, longitudinal mucositis assessment performed by calibrated Oral Medicine specialists will address this knowledge gap. We also examined whether chemo- vs. TBI-based conditioning has a differential effect on oral microbiota.

Materials/Methods:

We conducted a prospective study including longitudinal mucositis assessment using the Oral Mucositis Assessment Scale (OMAS), supragingival plaque and saliva collection by calibrated Oral Medicine specialists. We classified patients into those receiving high-dose TBI (12-13.2Gy)-based vs. chemo-based myeloablative conditioning. Mucositis was assessed at baseline and days +7, +14, +21, +28, and +84. Total mucositis score at each timepoint was calculated as the sum of all scores (ulceration and erythema) across 9 sites. Plaque and saliva samples (baseline and days +14, +28, and +84) were profiled using shotgun sequencing. MaAsLin2 was used for differential abundance analysis.

Results:

47 patients were included (27 chemo, 20 TBI). As expected from our center’s standard practice, (i.e. high-dose TBI not offered to older patients), the chemo cohort was older. OM severity peaked at day +7 in the TBI cohort vs. day +14 in the chemo cohort. Afterwards, OM improved in both cohorts and remained similar until day +84. Day +14 OM was more severe in the chemo cohort; other timepoints were not significant. While baseline plaque microbiota composition was similar between the cohorts, it became significantly different at all post-HCT timepoints. Differential abundance analysis of day +14 plaque microbiota showed enrichment of Prevotella melaninogenica and an Actinobaculum species in the TBI cohort and Streptococcus Sanguinis and a Rothia species in the chemo cohort. Day +84 plaque microbiota was significantly more diverse in the TBI cohort. No significant result was found for saliva.

Conclusion:

OM has different dynamics and severity after myeloablative alloHCT using TBI- vs. chemo-based conditioning. Notably, day +14 OM was less severe with TBI than with chemo. In addition, for the first time we identified differences in supragingival plaque microbiota following TBI- vs. chemo-based conditioning. Conditioning-specific changes in oral microbiota may have short- and long-term implications for oral health.