Targeted lymph node dissection at radiotracer-avid sites in recurrent prostate cancer: An early assessment of efficacy
Prostate-specific radiotracers have enabled PET studies to accurately identify lymph nodes (LN) harboring metastasis. We seek to provide early assessment regarding the efficacy of targeted LN dissections in recurrence. Our objective was to quantify PSA response and characterize the durability of initial trends.
A population of 230 receiving a PET/CT was queried for post-scan targeted LN dissections. Cases with false positive scans by histology or where PSA trend-confounding hormonal therapy was applied were excluded. 23 patient courses were identified where targeted LN dissection was performed, prostatic adenocarcinoma was confirmed by histology, and sufficient follow up data was present. PSA trends were characterized and durability assessed by three primary metrics: initial change as a percent of pre-dissection PSA, time to recurrence of 100% pre-dissection PSA, 12 month PSA recurrent rates with recurrence defined as > 0.04 or > 0.2 ng / mL.
19/23 achieved immediate down-trending PSA values confirmed by two results. 4/23 demonstrated a continued up-trend. 6/23 achieved immediately undetectable PSA (< 0.04 ng / mL) confirmed by two results. For the 19 with a down-trend, the average reduction as a percent of pre-dissection PSA was 82% with a range of 19.3 - 100%. In a subpopulation of 14 with initial down-trends, no hormonal therapy, and a minimum of 12 months follow up or recurrence sooner, the following observations were made regarding ≥100% pre-dissection PSA recurrence: 0 - 90 days: 2 recurred, 91 - 180: 0, 181 - 270: 1, 271 - 365: 2, 7 had not achieved ≥100% at 12 months and had no additional follow up data. 2 patients with long term follow up reached ≥100% at 612 and 743. Mann-Whitney testing was used to assess whether pre-dissection PSA correlated with likelihood of achieving a down-trend, undetectable PSA, or recurrence-free survival. No significant correlation was identified.
Targeted LN dissection offers some potential for durable, recurrence-free survival. However, ≥100% pre-dissection PSA recurrence is common. Achieving and maintaining a stable PSA long term is possible but unlikely.