Perineural Invasion Shows Trend Toward Significant Association With Prostate-Cancer Recurrence: Presented at ASCO-GU

By Matt Silver

SAN FRANCISCO -- February 12, 2018 -- In men with prostate cancer whose pathologic tumour staging shows organ-confined cancer, with no positive regional nodes (pT2N0), perineural invasion -- cancer spreading to the space surrounding a nerve – appears to be an indicator of unfavourable histology (e.g., a high Gleason score, more widespread disease). It also shows a trend toward a significant association with biochemical recurrence, according to results of a retrospective study presented here on February 8 at the 2018 Genitourinary Cancers Symposium.

Perineural invasion is a histologic feature present in approximately 19% of patients with prostate cancer. Its prognostic significance has remained largely unknown.

Ryan Kraus, medical student, USC Keck School of Medicine, Los Angeles, California, and colleagues investigated whether perineural invasion is an independent prognostic indicator of biochemical recurrence risk in patients with non-metastatic pT2N0 prostate cancer. The team reviewed the records of 201 such patients treated at their institution between 2008 and 2014.

Of these patients, 68.1% had perineural invasion and 14% had a biochemical recurrence.

Perineural invasion was associated with a) a tumour defined through pathologic staging as having grown into both lobes of the prostate (pT2c) (P < .001), b) an increased number of positive cores on biopsy (P < .001), and c) a higher surgical Gleason score (P < .001).

Furthermore, 19% of patients with perineural invasion experienced disease recurrence compared with 3.1% of patients without perineural invasion (P = .001, hazard ratio [HR] 6.2). On multivariable analysis and accounting for pathologic tumour staging and Gleason score, perineural invasion showed a trend towards a significant association with recurrence (P = .085, HR 3.2).

Based on previous research studies that examined perineural invasion in patients with pT2 prostate cancer (pathologically staged as confined to the prostate) and pT3 prostate cancer (pathologically staged as extending through the prostate capsule), the investigators noted that they “would have anticipated that perineural invasion did not have an associated risk of recurrence, which is somewhat non-intuitive.” Kraus and colleagues added that “our findings, if confirmed, would realign our current understanding of perineural invasion with what we would intuitively expect to see.”

The next step, the investigators stated, is accruing more data to confirm these results.

“We are currently working with clinicians at the University of Pennsylvania and Los Angeles County Hospital to increase the power of our study,” Kraus explained. “We are hopeful that by gathering data on more patients we can achieve a statistically significant P value that would indicate that perineural invasion is an independent prognostic indicator carrying a higher risk of recurrence.”

The 2018 Genitourinary Cancers Symposium is cosponsored by the American Society of Clinical Oncology (ASCO), the American Society for Radiation Oncology (ASTRO), and the Society of Urologic Oncology (SUO).

[Presentation title: The Perineural Invasion Paradox: Is Perineural Invasion an Independent Prognostic Indicator of Biochemical Recurrence Risk in Patients With pT2N0 Prostate Cancer? Abstract 6]

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