Performance and Dosimetry of Total Body Irradiation Patients Using In Vivo Lung Dose Monitoring and Custom Lung Block Adaptation

Abstract

Total body irradiation (TBI) prior to bone marrow transplant has been used for decades, but the details of delivery are institution dependent. We set out to establish decision support metrics by looking at respiratory outcomes based on measured lung dose. We hypothesize that individualized lung dose measurements and lung block adaptation may correlate with patient respiratory outcomes. This is a single institution retrospective study of 56 patients who received TBI from 2016-2018. Each patient received 1200 cGy (6 fractions; 200 cGy BID) with 3 optically stimulated luminescence detectors (OSLDs) placed on their body surface at the umbilicus, and left and right lungs. Lung dose was maintained between 700-900cGy by custom lung blocks. Supplemental oxygen requirements and clinical lung complications (shortness of breath (SOB) or cough requiring pharmacological intervention) were reviewed for the hospitalization period. Clinical respiratory complications (chronic cough, adventitious sounds on lung exam, new or worsening SOB) were also reviewed 120 days from irradiation. Median lung doses and patient anterior-posterior diameter (APD) at the umbilicus were compared for patients with and without respiratory complications using a Mann-Whitney U test. Forty-nine patients (age 40 years ± 12y; mean±SD) had lung dose data available for analysis. APD was positively correlated with OSLD umbilical dose (r=0.58, p<0.0001) confirming that larger patients received higher amounts of radiation than predicted during planning. The APD range did not correlate with OSLD lung doses. During hospitalization, patients who required any supplemental oxygen (N=7) or had clinically documented lung complications (N=8) did not have statistically different APD or lung doses compared to patients without respiratory complications. In the 120 day period following TBI, 8 patients had documented respiratory sequelae. Patients with reported respiratory complications in this period had larger APD than patients with no respiratory complications (median APD 31.5 vs 26.6, p=0.01), although this may reflect the effect of comorbidities (e.g., BMI) rather than the effect of radiation. Of the 27 patients with 1 year follow up data, only 2 had respiratory sequelae of chronic cough with corresponding inflammation on chest CT. Our overall rate of any respiratory complications using this technique was 22% (11/49) during hospitalization and 17% (8/48) at 120 days of TBI. The individualized planning technique described here achieved relatively uniform lung doses with no fatal lung complications in all 49 patients considered. Respiratory complications were minor, with the most significant intervention requiring high flow nasal cannula during the immediate hospitalization period.