Eligibility analysis for focal therapy based on prostatectomy findings: Does intermediate-risk cancer have a higher likelihood of undertreatment than low-risk cancer?
MATSUOKA Y, NUMAO N, SAITO K, TANAKA H, ITO M, YOSHIDA S, YOKOYAMA M, ISHIOKA J, FUJII Y, KIHARA K
Department of Urology, Tokyo Medical and Dental University Graduate School, and Department of Radiology, Ochanomizu Surugadai Clinic, Tokyo, Japan
Intermediate-risk prostate cancer (PC) would be the main target of focal therapy since active surveillance is a common option for low-risk PC. Based on MRI, biopsy, and radical prostatectomy (RP) findings, we assessed the possibility of undertreatment in intermediate-risk PC, in comparison with low-risk PC.
[Matherials and Methods]
Between 2007 and 2014, 41 NCCN’s low-risk and 99 intermediate-risk PC patients were enrolled who underwent MRI, 14-core biopsy including ventral sampling, and RP. Local staging on MRI followed the ESUR guidelines. Cases with extra-prostatic involvement on MRI were excluded. Significant cancer (SC) was defined as a lesion with volume ≥0.5 cm3 and/or Gleason score ≥4+3 and/or extra-prostatic extension (EPE). Data were evaluated on quadrant basis regarding SC and on patient basis regarding EPE. We assumed that quadrants both negative for MRI and 4-core quadrant biopsy would be eligible for untreated area in focal therapy. Negative predictive values of the combination of MRI and biopsy (i.e., negative findings on both) for SC were assessed. Contact length (CL) with the capsule at MRI-positive areas and the presence of EPE missed by MRI were examined in each prostate.
In cases with intermediate-risk PC, MRI coupled with biopsy misses SC in 10% of quadrants. EPE is missed by MRI in 23% of intermediate-risk group. Focal therapy would be safely performed for intermediate-risk PC with short CL (<10mm) as well as low-risk PC. Intermediate-risk PC with long CL (≥10mm) requires attentions to possible undertreatment at periprostatic area in focal therapy.