The FOcal RECurrent Assessment and Salvage Treatment (FORECAST) trial (NCT01883128) assessed MRI and targeted biopsy compared to transperineal biopsy to inform ablation for men with radio recurrent cancer. To do so, the authors compared the accuracy of multi-parametric MRI (mp-MRI) and MRI-targeted biopsy in identifying areas of recurrent cancer to a transperineal template prostate mapping (TTPM) biopsy among 181 patients across 6 different clinical sites in the United Kingdom in an initial phase conducted between April 2014 and Jan 2018. Subsequently, they assessed the functional and cancer control outcomes of focal ablation of areas of intraprostatic recurrence in 93 patients with localised or metastatic cancer (using cryotherapy or HIFU).
The primary outcomes were sensitivity of mpMRI and MRI-targeted biopsies (for part one) and urinary continence after focal ablation (for part two). A key secondary outcome was progression free survival (PFS) defined as no new metastases or hormone use (localised group only), or chemotherapy or further local treatment.
Among the 181 men with suspicion of recurrence following radiotherapy enrolled in the first portion, re-staging whole-body imaging using Choline PET and Bone Scan was performed. This demonstrated localised disease in 128 (71%), nodal disease only in 13 (7%) and metastatic disease in 38 (21%). Assessing the primary outcome, the sensitivity of MRI-targeted biopsy was 92% (95%CI 83-97%) compared to the gold standard of transperineal template prostate mapping biopsy. Specificity, and positive and negative predictive values were 75% (95%CI 45-92%), 94% (95%CI 86-98%) and 65% (95%CI 38-86%), respectively. Notably, 4/72 (6%) cancers were missed on TTPM biopsies alone and 6/72 (8%) were missed on MRI-targeted biopsies alone.
Utilizing a threshold of 4-5 on the Likert scale (rather than 3-5) to define a positive, the overall sensitivity of mpMRI was 81% (95%CI 73-88%) with specificity, and positive and negative predictive values of 88% (95%CI 73-98%), 96% (95%CI 90-99%) and 57% (95%CI 42-70%), respectively.
In the second portion of the study, among the 93 men undergoing focal ablation, urinary continence was preserved in 78/93 (84%). However, five of 93 men (5%) experienced a CTCAE grade 3+ adverse event though there were no rectal injuries. Over a median follow-up of 27.8 [SD 1.3] months, progression-free survival was 66% [95% CI 54-75] at 24-months with metastases-free survival of 80% [95%CI 68–88] at 24-months among the 32 men with localized disease at the time of treatment. There were no cancer specific deaths.
The authors conclude that prostate mpMRI with MRI-targeted biopsies can accurately detect and localise recurrent prostate cancer following radiotherapy. Following this disease characterization, focal ablation is a reasonable treatment approach with good cancer control and low rates of incontinence.
Presented by: Taimur T. Shah, MBBS, BSc (Hons), FRCS (Urol) PhD, Imperial College London, Division of Surgery