Perineural invasion (PNI) detected on prostate needle core biopsy is often considered a predictor of adverse pathology in prostate cancer. Recent studies indicate that multifocal PNI in systematic biopsies—especially when present in a single biopsy site—correlates with worse postoperative outcomes compared to single-focus PNI. This study analyzed the role of PNI quantification in 840 patients who underwent systematic sextant prostate biopsies followed by radical prostatectomy from 2010 to 2016. The study classified patients by Grade Group (GG) to determine the prognostic value of PNI quantification. Among the biopsy samples, PNI was absent in 580 cases (69%), while others exhibited varying levels of PNI, from one to multiple foci.
Results indicated that patients with any PNI had a significantly higher risk of biochemical recurrence compared to those without PNI (p<0.001), with multifocal PNI cases exhibiting a higher recurrence rate than single-focus PNI cases (p<0.001). However, for Grade Group 1, the recurrence-free survival difference between single and multifocal PNI was not statistically significant (p=0.056). Subgroup analysis revealed that PNI quantification particularly benefited risk stratification for Grade Group 2 and 3 patients, showing significant differences in recurrence risk between single and multifocal PNI (p<0.001 for GG2 and GG3). For Grade Groups 4 and 5, however, PNI quantification showed limited prognostic value (p=0.214 and p=0.484, respectively). Additionally, while the presence of PNI was significant for risk assessment in Grade Group 3 and 4 cancers (p<0.001 and p=0.003), it held less relevance for Grade Group 1 and 2 cancers.
In summary, PNI quantification on biopsy provides valuable information for risk stratification in patients with Grade Group 2-3 prostate cancer, while its prognostic utility is less evident in patients with lower or higher-grade cancers.
