Molecular imaging is the only way of defining biological target volume (BTV) for externalbeam
radiation therapy (EBRT) and may be used for advanced targeting in dose planning and dose
painting. There are, however, no reports about the EBRT response when dose planning is based on
BTV target definition in advanced prostate cancer.
Clinical and biochemical results of two clinically equal group of patients with advanced prostate cancer
patients were compared. Both groups were treated with volumetric modulated arc therapy
(VMAT) based on target definition by PET/CT (1st group) or conventional imaging (2nd group).
Biochemical relapse occurred in 16.6% (in 1 out of 6) of the patients in the first group and 50% (3 out of 6) patients in the
second group during the follow up period. Clinical manifestation of disease occurred in 33% (2 out of 6) patients of the
first group and in 5 out of 6 (83,3%) patients in the second one. 4 patients in the first group had no biochemical relapse
and no clinical manifestation during the follow up period. The difference in the duration of progression free period was
statistically significant between the groups (p<0.010) being in the first group 16.5±5.4 (10-24) months and 4.6±2.9 (2-10)
months in the second one.
Because patients with PET/CT based VMAT had lower incidence of biochemical relapse, less clinical manifestations and
longer, statistically significant duration of progression free period as compared to patients treated with VMAT based on
conventional imaging, our preliminary results suggest introducing BTV definition based on PET imaging for VMAT in
the EBRT of prostate cancer.