Quantifying partial pathological response rate in prostate cancer patients who underwent neoadjuvant chemotherapy using a novel morphometric approach

Accurate assessment of partial pathological response rate (ppRR) to neoadjuvant chemotherapy (NAT) is critical for assessing the efficacy of therapy and for optimal clinical management. Because of a lack of accurate estimation of baseline cancer burden, assessment of ppRR has never been attempted in prostate histologically. We presented a novel morphometric approach assessing ppRR in patients who underwent NAT and then correlated the ppRR with patients' outcomes. A control cohort consisted of 39 NAT-naïve Caucasian patients who had high-risk PCa (defined as Gleason Grade Group >2) and an adequate biopsy sample (defined as the size of the biopsy PCa area, including PCa epithelium and stroma >2 ^mm2). A study cohort included 26 patients with high-risk PCa (defined as clinical stage T3a or higher, serum PSA >20 ng/mL, or GGG of 4-5, or with oligometastatic disease) who underwent androgen deprivation therapy plus docetaxel. Using the PCa epithelial to stromal ratio (E/S) as a metric, surrogate BCB for the study cohort was predicted from the pre-treatment biopsy samples, and ppRR was calculated. Correlation analysis of patients' ppRR with progression-free survival was performed using ppRR >80% as a cut-off. Nine of the 26 patients from the study cohort experienced a significant response to NAT (ppRR > 80%) using the PCa E/S-based approach, and these patients had significantly better progression-free survival (<i>p</i> = 0.006). ppRR to NAT can be reliably assessed using PCa E/S as a surrogate metric from biopsy and RP samples, and ppRR can be used to predict patients' outcomes.