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A retrospective study on the potential of 99m Tc‐HDP imaging before therapy for individualizing treatments with 223 Ra‐Cl 2 for metastatic castration resistant prostate cancer
Author(s) -
Mínguez Pablo,
Rodeño Emilia,
Fernández Irache,
Esteban Alba,
MartínezIndart Lorea,
Gómez de Iturriaga Alfonso
Publication year - 2021
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1002/mp.14683
Subject(s) - prostate cancer , lesion , nuclear medicine , medicine , absorbed dose , radionuclide therapy , urology , prostate , dosimetry , cancer , pathology
Purpose Research on dose‐effect correlation is necessary to move toward an individualization of treatments of metastatic castration resistant prostate cancer (mCRPC) with 223 Ra‐Cl 2 . We first looked for a possible correlation of 99m Tc‐HDP lesion uptake in pretreatment whole‐body scans (WBSs) with lesion absorbed dose. Moreover, we looked for a possible correlation of 99m Tc‐HDP lesion uptake in pretreatment WBSs and of lesion absorbed dose with relative change in the 99m Tc‐HDP lesion uptake obtained from pre‐ and post‐treatment WBSs in patients treated for mCRPC with six cycles of 223 Ra‐Cl 2 . Methods Eleven patients received six cycles of 55 kBq/kg of 223 Ra‐Cl 2 separated by 4 weeks. In addition, one patient received concomitant treatment with abiraterone and two patients with enzalutamide. The 99m Tc‐HDP WBSs were acquired before the first cycle and after the sixth cycle of the treatment. For the lesions with the higher 99m Tc‐HDP uptake, the absorbed dose was calculated for the first cycle. Lesion volume was determined from 99m Tc‐HDP SPECT/CT images before the first cycle and 223 Ra‐Cl 2 activity in the lesions was determined from 223 Ra‐Cl 2 planar images after the first cycle. The effect of the treatment was evaluated from the relative change of the mean and the maximum counts in the lesions, both estimated from the WBSs acquired before the first cycle and after the sixth cycle. Results The absorbed dose was calculated for 30 lesions, with values ranging between 0.4 and 3.8 Gy (mean 1.5 Gy). A significant ( P < 0.05) high positive linear correlation was found between the lesion absorbed dose in the first treatment cycle and the mean and maximum counts in the lesions in the WBSs acquired before the first cycle (R = 0.75 and 0.76, respectively). The relative change of the mean and the maximum counts in the lesions in the 99m Tc‐HDP WBSs showed a significant ( P < 0.05) high positive logarithmic correlation with the 99m Tc‐HDP mean and maximum counts in the lesions before the first cycle (R = 0.79 and 0.78, respectively). Lastly, a significant ( P < 0.05) high positive logarithmic correlation was also found between the relative change of the mean and the maximum counts in the lesions in the 99m Tc‐HDP WBSs and the lesion absorbed dose (R = 0.86 and 0.85, respectively). For this correlation the influence of the administered activity and of the concomitant treatments was not found to be significant ( P > 0.05). Conclusions The high correlations found for the 99m Tc‐HDP lesion uptake before the first cycle lesion with the relative change in the 99m Tc‐HDP lesion uptake after the six cycles of 223 Ra‐Cl 2 , and with the lesion absorbed dose in the first cycle show the potential of pretreatment 99m Tc‐HDP imaging in order to personalize the performance of these treatments.