Detection of Local Recurrence with 3-Tesla MRI After Radical Prostatectomy: A Useful Method for Radiation Treatment Planning?

Abstract

Abstract. Background Prostate carcinoma is the second most common cancer in males (1) and although mortality rates have decreased in European countries and the United States (US), it still accounts for more than 258,000 deaths worldwide (2). According to the USpopulation-based Surveillance, Epidemiology, and End Results Program database, ~80% of men with newly diagnosed prostate carcinoma had localized disease at the time of diagnosis (3). Most of these patients selected radical prostatectomy or external beam radiotherapy as their primary treatment option (4,5). Recurrence rates after radical prostatectomy differ widely between around 10% of patients and more than 30% within 5 years (6-8), depending on Gleason score and other risk factors (6). In patients with positive surgical margins, it can be estimated that 20-40% of tumors recur (9, 10) and the majority of patients with biochemical relapse are diagnosed as having local recurrence (11). Radiotherapy as salvage treatment has been shown to improve biochemical control in patients with residual disease or biochemical relapse (12, 13). Stephenson et al. estimated that biochemical control can be achieved by radiotherapy in 48% of patients when salvage treatment starts before the prostatespecific antigen (PSA) level reaches 0.5 ng/ml; if administered at a PSA level of 0.5 ng/ml and above, only 26% of patients treated were free from (further) relapse (14). These results have been confirmed by modern series which additionally showed a clinical benefit in terms of distant metastasis-free survival, disease-specific mortality, and all-cause mortality (15). Furthermore, modern series indicated early salvage radiotherapy, initiated at the earliest sign of measurable PSA, to be beneficial in terms of biochemical and clinical endpoints (15, 16). Severe toxicity of salvage radiotherapy is generally reported to be low (17) but even in modern series, there is a residual risk of grade 3/4 bowel or urinary toxicity (18). 125This article is freely accessible online. (28,29). In a comparative study (29), radiotherapy plans contoured according to consensus guidelines failed to meet QUANTEC (30), and RADICALS (31) trial dose constraints in 75%, and 40% of cases, respectively. These inconsistencies indicate that our current approaches to salvage treatment of prostate carcinoma after radical prostatectomy should be reassessed. Improvement of therapeutic efficacy could be achieved by reducing geographical miss and side-effects by accurate detection of residual disease.Detection of residual prostate carcinoma is possible by magnetic resonance imaging (MRI) and positron-emission tomography-computed tomography (PET-CT). Evidence on restaging of biochemically relapsed patients with PET-CT was recently reviewed by Umbehr et al. (32). The authors analyzed 12 studies and found a pooled sensitivity and specificity of 85%, and 88%, respectively (mean PSA=7.9 ng/ml). In patients with early relapse (PSA <1 ng/ml), however, the authors found no convincing evidence for the use of PET-CT.MRI with (...

Salvage Radiotherapy for Macroscopic Local Recurrence Following Radical Prostatectomy

“…Magnetic resonance imaging appears to be one of the best diagnostic tools for detecting local recurrence when the PSA level is below < 1 ng/mL (8). Thus, radiation oncologists are increasingly faced with occurrences of macroscopic recurrences in the prostate bed.…”

“…With the progress achieved in imaging (prostate MRIs, choline PET scans) and more recently PSMA PET CT, which is sensitive at PSA levels of less than 1 ng/mL or even 0.5 ng/mL (7,8), radiation oncologists are increasingly faced with occurrences of biochemical progression with macroscopic disease found in the prostatectomy bed.…”

Detecting recurrent prostate Cancer using multiparametric MRI, influence of PSA and Gleason grade

“…3 T imaging was not utilized for this study; instead, mpMRI was performed at 1.5 T with placement of the endorectal coil near the area of interest to enable high resolution imaging. Future studies may employ 3 T MR with or without an endorectal coil, however, prior literature has not found an advantage of 3 T vs 1.5 T in this setting [ 37 , 38 ] and both field strengths and an endorectal coil are used at various institutions [ 39 ]. Recurrence after other forms of therapy such as radiation or hormonal therapy was not evaluated, but could be studied in the future.…”

Postoperative elective pelvic nodal irradiation compared to prostate bed irradiation in locally advanced prostate cancer – a retrospective analysis of dose-escalated patients

“…In our analysis, we used a definition of two PSA rises and counted patients who initiated second salvage as events, even if salvage was initiated after one increase in PSA levels. Our dose escalation strategy does not allow for a quantification of the benefit associated with 79.29 Gy EQD-2 compared to 71.43 Gy EQD-2 because we cannot separate benefits associated with positive margins [25] from benefits of dose escalation which was almost exclusively used in margin-positive patients plus a minority (6.4%) who received escalation after detection of recurrence in imaging (MRI as published [33] or PET-CT). Additionally, patients who received the higher dose were mostly treated postoperatively (76.9%) while 95.2% of patients with lower-dose treatment had a salvage strategy associated with a more unfavorable risk selection.…”