Evaluation of the compound biological effectiveness of L-4-boronophenylalanine in bone Marrow: A study combining biological experiments with Monte Carlo dose calculation.

PURPOSE: The compound biological effectiveness (CBE) is a key parameter for converting a boron dose into a bioequivalent X-ray dose. As a hematopoietic organ, the bone marrow is highly radiosensitive. However, the CBE value of L-4-boronophenylalanine (BPA) for bone marrow remains undetermined, which may lead to an underestimation of the radiation dose to bone marrow during boron neutron capture therapy (BNCT).

MATERIALS AND

METHODS

BNCT dose was simulated using the Particle and Heavy Ion Transport Code System Monte Carlo code. A one-compartment model was applied to calculate the concentrations of 10B during neutron irradiation. These calculations were based on the detected boron concentrations at 30, 70, 110, and 150 min after BPA injection, measured with an inductively coupled plasma mass spectrometer. A bone marrow nucleated cell (BMNC) ratio, derived from a hematoxylin-eosin staining section of bone marrow, was used as the endpoint to determine the CBE value of BPA for the bone marrow of mice.

RESULTS

The cumulative boron concentrations during the intervals of neutron irradiation (5.98, 20.93, 35.95, and 45.95 min) were calculated to be 64.54, 209.33, 333.74, and 406.40 min·μg·g-1. A BMNC ratio of 0.45 is recommended as the endpoint for CBE evaluation of BPA for bone marrow. The relative biological effectiveness and CBE were 2.52 and 5.19, respectively, based on this BMNC ratio.

CONCLUSIONS

This study provides crucial experimental data for establishing the dose limitation to bone marrow in BNCT, which is essential for improving treatment safety.