Purpose Tumor mutational burden (TMB) is an approved biomarker for immunotherapy in metastatic cancer patients. While initially measured from tissue (tTMB), TMB derived from circulating tumor DNA (ctDNA) - also known as blood TMB (bTMB) - is increasingly being used in the clinic. Currently, real-world concordance between tTMB and bTMB is not well understood. Patients and methods From October 2020 to March 2021, cancer patients who had both tTMB and bTMB results were selected. Patients were classified according to clinical variables and tumor burden, and correlation analyses or tests of independence were performed to explore any associations. Results From a total of 38 patients included in our study, 20 patients (52.6%) had non-small cell lung carcinoma and 18 (47.4%) had other cancers. Median bTMB of 9.6 mut/MB was higher than median tTMB of 4.0 mut/Mb, and the distributions of bTMB and tTMB differed significantly (n=38, p < 0.001). bTMB was positively correlated with tTMB in the total study population (Spearman ρ=0.57, p < 0.001 ) and a tTMB of 10 mut/Mb correlated with a bTMB of 21.1 mut/Mb. Dividing patients by cancer type or site of tumor biopsy resulted in significantly differing strength and degree of correlation, but dividing patients by concordant and discordant bTMB:tTMB ratio did not reveal any significantly different distributions of clinical variables or tumor burden. Conclusion bTMB was positively correlated with tTMB, and median bTMB was higher than median tTMB. Cancer type and site of tissue biopsy may influence concordance between tTMB and bTMB. Future studies with more patients may help define the optimal bTMB threshold for receiving immunotherapy, which may be different from the tTMB threshold.

Background Access block due to a lack of hospital beds causes emergency department (ED) crowding. We initiated the boarding restriction protocol that limits ED length of stay (LOS) for patients awaiting hospitalization to 24 hours from arrival. This study aimed to determine the effect of the protocol on ED crowding. Method This was a pre-post comparative study to compare ED crowding before and after protocol implementation. The primary outcome was the red stage fraction with more than 71 occupying patients in the ED (severe crowding level). LOS in the ED, treatment time and boarding time were compared. Additionally, the pattern of boarding patients staying in the ED according to the day of the week was confirmed. Results Analysis of the number of occupying patients in the ED, measured at 10-minute intervals, indicated a decrease from 65.0 (51.0-79.0) to 55.0 (43.0-65.0) in the pre- and post-periods, respectively (p<0.0001). The red stage fraction decreased from 38.9% to 15.1% of the pre- and post-periods, respectively (p<0.0001). The proportion beyond the goal of this protocol of 24 hours decreased from 7.6% to 4.0% (p<0.0001). The ED LOS of all patients was similar: 238.2 (134.0-465.2) and 238.3 (136.9-451.2) minutes in the pre- and post-periods, respectively. In admitted patients, ED LOS decreased from 770.7 (421.4-1587.1) to 630.2 (398.0-1156.8) minutes (p<0.0001); treatment time increased from 319.6 (198.5-482.8) to 344.7 (213.4-519.5) minutes (p<0.0001); and boarding time decreased from 298.9 (109.5-1149.0) to 204.1 (98.7-545.7) minutes (p<0.0001). In the pre-period, boarding patients accumulated in the ED on weekdays, with the accumulation resolved on Fridays; this pattern was alleviated in the post-period. Conclusions The protocol effectively resolved excessive ED crowding by alleviating the accumulation of boarding patients in the ED on weekdays. Additional studies should be conducted on changes this protocol brings to patient flow hospital-wide.