Development of a Visually Calculated SUVmean(HIT Score) on Screening PSMA PET/CT to Predict Treatment Response to177Lu-PSMA Therapy: Comparison with Quantitative SUVmeanand Patient Outcomes

177Lu-PSMA therapy is an effective treatment in patients with metastatic castration-resistant prostate cancer. SUVmean is a valuable screening biomarker to assess the suitability for 177Lu-PSMA therapy but requires quantitative software. This study aims to develop a simple, clinically applicable prostate-specific membrane antigen PET/CT score that encompasses the elements of SUVmean without requiring additional quantification. Methods: Datasets from ethics-approved trials of patients with metastatic castration-resistant prostate cancer after androgen receptor signaling inhibition and taxane chemotherapy (or unfit for taxane), who were treated with 177Lu-PSMA-617 and 177Lu-PSMA I&T with a pretreatment screening with 68Ga-PSMA-11 PET/CT, and clinical outcome data, including a prostate-specific antigen (PSA) 50% response rate (PSA50), PSA progression-free survival (PSA-PFS), and overall survival (OS), were included. The screening 68Ga-PSMA-11 PET/CT of all participants was analyzed both semiquantitatively and visually. Semiquantitative analysis was used to derive the SUVmean. Visual analysis of the 68Ga-PSMA-11 PET/CT images involved a binary visual heterogeneity assessment (homogeneous or heterogeneous), allocating a tumor SUVmax range (max range). The SUVmax was less than 15 for score 1, 15–79 with heterogeneous intensity for score 2, 15–79 with homogeneous intensity for score 3, and 80 or greater for score 4. This score was evaluated according to clinical outcomes (PSA50, PSA-PFS, and OS) and compared with SUVmean. Results: Data from 139 participants were analyzed. In total, 75 (54%) patients achieved a PSA50 with a median PSA-PFS of 5.5 mo (95% CI, 4.1–6.0 mo) and an OS of 13.5 mo (95% CI, 11.1–17.9 mo). SUVmean was associated with PSA50 and survival outcomes when analyzed as a continuous variable or as quartiles. The PSA50 for HIT scores 1–4 was 0%, 39%, 65%, and 76%, respectively. The HIT score was strongly related to PSA-PFS and OS (log-rank test, P P = 0.002). The median PSA-PFS for HIT scores 1–4 was 1.0, 4.1, 6.0, and 8.5, respectively, and the median OS was 7.6, 12.0, 18.5, and 16.9 mo, respectively. Cohen κ between readers for the HIT score was 0.71. Conclusion: A prostate-specific membrane antigen PET/CT score incorporating HIT derived from tools on a standard PET workstation is comparable with quantitative SUVmean as a prognostic tool following 177Lu-PSMA therapy.