Utilizing Deep Learning to Automate TTV Generation on 177Lu-PSMA SPECT/CT

By Emily Menendez - Last Updated: June 25, 2023

The utilization of total tumor volume (TTV) and whole-body mean standardized uptake value (SUVmean) on 177Lu-PSMA single-photon emission computed tomography/computed tomography (SPECT/CT; Lu-SPECT) can predict outcomes in patients with metastatic castration-resistant prostate cancer (mCRPC) who are receiving 177Lu-PSMA therapy. As TTV is a lengthy process, researchers have examined the efficacy of utilizing an algorithm developed by deep learning to automatically generate TTV on Lu-SPECT.

A total of 95 177Lu-PSMA therapy SPECT/CT scans from 36 patients with mCRPC were gathered from the LuPIN trial, which analyzed the safety and efficacy of 177Lu-PSMA 617 and idronoxil (NOX66) in patients with end-stage mCRPC. Each patient was administered 1 to 6 cycles of therapy, with each cycle occurring every 6 weeks. The algorithm segmented all volumes of interest, with a 3-SUV threshold. The proposed method utilized CT-based, deep learning-generated normal organs for automatic removal of physiologic uptake on Lu-SPECT.

The average TTV for the proposed method was 927 mL compared with an average Gleason score (GS) TTV of 847 mL, which was not deemed significantly different (P=.054). The average absolute difference in TTV between the proposed method and GS was 110 mL.

The average SUVmean of the proposed method was 8.60, and the average SUVmean of GS was 8.96. This difference was deemed significant (P=.03). The average relative error in SUVmean was 4.7%, and the median relative error was 1.4%.

The proposed method of algorithm-based TTV produced comparable TTV and whole-body SUVmean levels. A small but statistically significant difference in SUVmean was noted between the proposed method and GS, but the clinical significance of this difference is unclear.

A tool using the proposed method may prove to be beneficial by increasing efficacy and reproducibility when generating TTV and whole-body SUVmean for the assessment of 177Lu-PSMA therapy. Further research is needed to assess the actual amount of time saved when utilizing automatic physiological uptake removal.