Researchers create novel method predicting tumor response in radioligand therapy

A team of German researchers used PET/CT and modeling practices to create a new method to model and predict tumor response in radioligand therapy (RLT), which authors say is the first attempt to do so.

The study was published May 10 in the Journal of Nuclear Medicine.

“The proposed method is the first attempt to solely use PET/CT and modeling methods to predict the PSMA-positive tumor volume after radioligand therapy,” wrote corresponding author Peter Kletting, MD, with the department of nuclear medicine at Ulm University in Germany, and colleagues. “Internal validation shows that this is feasible with an acceptable accuracy.” They added that the method is currently being improved and externally validated.

The authors extended a recently created physiologically based pharmacokinetic (PBPK) model for 177Lu-labeled PSMA for imaging and therapy (PSMA I&T) radioligand therapy to account for tumor growth and reduction. They then retrospectively analyzed the data of 13 patients with metastatic castration-resistant prostate cancer (mCRPC). Tumor volume after therapy was predicted with pre-therapy PET/CT imaging and PBPK/pharmacokinetic dynamic (PD) modeling.

Results showed the relative deviation of the predicted and measured tumor volume was one, plus or minus 40 percent.

“We present a novel method to model and predict tumor response in radioligand therapy,” authors wrote. “Future work including a refined model, definition of subpopulations and use of SPECT/CT data will help to improve further the prediction accuracy of the model."

For future work building upon the method in this study, Kletting et al. suggested analyzing larger patient groups in whom SPECT/CT imaging was done and including more a priori information of each individual.