Prediction of myelotoxicity using radiation doses to marrow from body, blood and marrow sources.
Bone marrow is generally the dose-limiting organ in radioimmunotherapy (RIT). Although radiation doses to marrow estimated from tracer doses have been shown to be comparable to those from therapy doses of radionuclide, the correlation of marrow radiation dose and myelotoxicity has not been well documented. The purpose of this study was to evaluate the relationship between radiation dose to marrow and subsequent changes in peripheral blood cell counts.


METHODS
Radiation doses to marrow from three sources, body, blood and marrow targeting, were compared with changes in blood counts after the first therapy dose of (131)I-Lym-1 in 16 patients. Doses of (131)I-Lym-1 ranged from 1.1-8.2 GBq (29-222 mCi). Cumulated radioactivity in the body and marrow were obtained using sequential, quantitative images of the body and lumbar vertebrae, respectively, and that in blood using activity in blood samples. The individual and sum of radiation doses from penetrating radiations in the body, and nonpenetrating radiations in the blood and marrow, were compared with blood counts.


RESULTS
In this group of patients, median radiation doses were 15.1, 15.4 and 42.1 cGy from body, blood and marrow targeting, respectively. Linear regression of radiation doses from body and blood versus fractional decreases in blood counts produced correlation coefficients of 0.38, 0.06, 0.22 and less than 0.01 for platelets, granulocytes, white blood cells (WBCs) and hematocrit, respectively. Linear regression of targeted marrow radiation doses versus fractional decreases in blood counts produced correlation coefficients 0.61, 0.31, 0.54 and 0.20 for platelets, granulocytes, WBCs and hematocrit. The closest association was found between radiation dose to marrow from marrow targeting and change in platelet count (r = 0.61).


CONCLUSIONS
In patients, such as those with non-Hodgkin's lymphoma (NHL), likely to have marrow targeting, prediction of myelotoxicity by conventional body and blood contributions to marrow is substantially improved by the use of radiation dose to marrow estimated from images.
Lim
S M
SM
University of California Davis Medical Center, Sacramento, USA.
DeNardo
G L
GL
DeNardo
D A
DA
Shen
S
S
Yuan
A
A
O'Donnell
R T
RT
DeNardo
S J
SJ
D001769:Blood / Q000528:radiation effects*; D001772:Blood Cell Count / Q000528:radiation effects; D001853:Bone Marrow / Q000000981:diagnostic imaging / Q000528:radiation effects*; D006400:Hematocrit; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007457:Iodine Radioisotopes / Q000009:adverse effects / Q000627:therapeutic use; D008228:Lymphoma, Non-Hodgkin / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011829:Radiation Dosage; D016499:Radioimmunotherapy / Q000009:adverse effects; D011877:Radionuclide Imaging; D015203:Reproducibility of Results
D007457:Iodine Radioisotopes