Development and validation of a nomogram for predicting positive [99mTc]Tc-HYNIC-PSMA SPECT/CT in patients with biochemically recurrent prostate cancer after radical prostatectomy

OBJECTIVE: Prostate cancer (PCa) recurrence following radical prostatectomy poses significant clinical challenges, with biochemical recurrence (BCR) serving as a crucial indicator for subsequent metastasis. This study aims to develop and validate a nomogram predicting the accuracy of [ 99m Tc]Tc-HYNIC-PSMA SPECT/CT imaging positivity in PCa patients experiencing BCR post-radical prostatectomy. METHODS: A retrospective cohort study included 192 patients meeting inclusion criteria from Henan Provincial People's Hospital and Zhengzhou University People's Hospital, with an external validation cohort of 40 patients from Henan Cancer Hospital. Multivariate logistic regression and least absolute shrinkage and selection operator analysis identified three independent predictors: International society of urological pathology grade group, prostate-specific antigen (PSA) before PSMA SPECT/CT, and PSA doubling time. These predictors were integrated into a nomogram, whose performance was assessed using receiver operating characteristic (ROC) analysis, calibration curves, and decision curve analysis (DCA). RESULTS: The overall detection rate of [ 99m Tc]Tc-HYNIC-PSMA SPECT/CT imaging was 43.5% ( n = 101), with varying sites of recurrence observed. International society of urological pathology grade group [odds ratio (OR): 20.35; 95% confidence interval (CI): 4.64-89.25], PSA before PSMA SPECT/CT (OR: 2.86; 95% CI: 1.84-4.44), and PSA doubling time (OR: 0.03; 95% CI: 0.01-0.16) were independently associated with positivity on PSMA SPECT/CT imaging. The nomogram exhibited robust predictive accuracy with areas under the ROC curve of 0.960, 0.891, and 0.872 in the training, internal validation, and external validation cohorts, respectively, demonstrating good generalizability. The best nomogram's cutoff was 40%. DCA demonstrated significant clinical net benefit, especially at higher threshold probabilities. CONCLUSION: This study introduces a novel nomogram predicting the likelihood of [ 99m Tc]Tc-HYNIC-PSMA SPECT/CT imaging positivity in PCa patients with BCR post-radical prostatectomy. The nomogram enhances patient stratification and may optimize the selection of candidates for PSMA SPECT/CT imaging, thereby improving clinical decision-making and patient outcomes.