RADIOLABELED ANTIBODY COMBINED WITH EXTERNAL RADIOTHERAPY FOR THE TREATMENT OF HEAD AND NECK-CANCER - RECONSTRUCTION OF A THEORETICAL PHANTOM OF THE LARYNX FOR RADIATION-DOSE CALCULATION TO LOCAL TISSUES
A. Maraveyas et al., RADIOLABELED ANTIBODY COMBINED WITH EXTERNAL RADIOTHERAPY FOR THE TREATMENT OF HEAD AND NECK-CANCER - RECONSTRUCTION OF A THEORETICAL PHANTOM OF THE LARYNX FOR RADIATION-DOSE CALCULATION TO LOCAL TISSUES, Cancer research, 55(5), 1995, pp. 1020-1027
We propose to use radiolabeled antibodies in combination with external
beam radiotherapy to improve locoregional control of head and neck ca
ncer, In this case radiation toxicity to mucosa may become a dose-limi
ting factor and a calculation of the possible compensatory decrease to
the external beam radiotherapy would be needed, For this purpose, the
following theoretical phantom of a representative organ of this anato
mic region, the larynx, was reconstructed and local dosimetric data we
re derived for a selection of beta-emitting isotopes. The phantom was
reconstructed as cylindrical concentric tubes using the established va
lues of an outer diameter of 38 mm and a height of 44 mm, Published me
an adult larynx weight (28 g) and cartilage weight (14.7 g) were used.
Mean mucosa weight from 5 mucosa samples of our patients was calculat
ed to be 2.0 +/- 0.4 (SD) g, The remaining weight was apportioned to a
fat/muscle compartment (11.3 g), The specific gravity of cartilage (1
.10 g/cm(3)), mucosa (1.04 g/cm(3)), and fat/muscle (1.04 g/cm(3)) wer
e used to cross-check the volume/mass disparity of the theoretical tub
ular tissue shells, The established maximum glottic diameter of 24 mm
was used to calculate the central air column volume, Mean laryngeal tu
mor volume from 8 representative laryngeal tumors was 4.4 +/- 3.1 cm(3
), Tissue compartment thickness was 660 mu m for mucosa, 3100 mu m for
muscle/fat, and 3320 mu m for cartilage, These values allowed the cal
culation of dose absorbed fractions for a number of theoretical radioi
mmunoconjugates by extending the established calculation of absorbed f
ractions for spheres of known diameter to absorbed fractions of tissue
planes (annuli) of known thickness, We calculated a D-eq for the resp
ective tissues in the larynx for I-131-, Re-186, Re-188, Cu-67-, Y-90-
, and Sm-153-labeled HMFG1, Compensatory decrease to the external radi
otherapy dose is 1.1 Gy for each injection of the radioimmunoconjugate
we propose to use (I-131-HMFG1), This would be best implemented throu
gh the modification of the external radiotherapy fractions falling wit
hin 2 effective half-lives of this radioconjugate in the mucosa.