MRI and targeted biopsies compared to transperineal mapping biopsies for targeted ablation in recurrent prostate cancer after radiotherapy: Primary outcomes of the FORECAST trial.
Authors: Shah Taimur T. , Kanthabalan Abi , Pavlou Menelaos , Adeleke Sola , Giganti Francesco , Brew-Graves Chris , Haroon Athar , Sidhu Harbir , Freeman Alex , Nikapota Ashok , Dudderidge Tim , Hindley Richard G , Arya Manit , Payne Heather Ann , Mitra Anita , Horan Gail , Moore Caroline , Emberton Mark , Punwani Shonit , Ahmed Hashim Uddin ,   FORECAST Trial Study Group
Published: June 2021

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Background: Radiotherapy is a common and effective treatment for localised prostate cancer. However, recurrence of cancer can occur in 10-15% of men in the following 5 years. Most patients with recurrence are managed using hormonal therapy with associated systemic side-effects and subsequent development of castrate resistance. Salvage prostatectomy confers a high risk of urine incontinence and rectal injury. Accurately localising and ablating only areas of recurrence within the prostate might be effective with fewer side-effects. The FOcal RECurrent Assessment and Salvage Treatment (FORECAST) trial assessed this diagnostic and treatment pathway for men with radiorecurrent cancer (NCT01883128). Methods: We first 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 (Apr/2014-Jan/2018) in 181 patients from 6 UK centres. We then assessed the functional and cancer control outcomes of focally ablating areas of intraprostatic recurrence in 93 patients with localised or metastatic cancer (using cryotherapy or HIFU). Primary outcomes were sensitivity of mpMRI and MRI-targeted biopsies and urinary continence after focal ablation. 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. Results: Of 181 men with suspicion of recurrence following radiotherapy, re-staging whole-body imaging (Choline PET and Bone Scan) showed localised disease in 128 (71%), nodal disease only in 13 (7%) and 38 (21%) metastatic. The sensitivity of MRI-targeted biopsy was 92% (95%CI 83-97%). Specificity, and positive and negative predictive values, were 75% (95%CI 45-92%), 94% (95%CI 86-98%) and 65% (95%CI 38-86%). 4/72 (6%) cancers were missed on TTPM biopsies alone and 6/72 (8%) were missed on MRI-targeted biopsies alone. Overall sensitivity of mpMRI was 81% (95%CI 73-88%) using Likert score 4-5 to denote a positive test. Specificity, and positive and negative predictive values, were 88% (95%CI 73-98%), 96% (95%CI 90-99%) and 57% (95%CI 42-70%). In the 93 men undergoing focal ablation, urinary continence was preserved in 78/93 (84%); 5/93 (5%) had a CTCAE grade 3+ adverse events. There were no rectal injuries. With a median follow-up of 27.8 [SD 1.3] months, PFS was 66% [54-75] at 24-months. Metastases-free survival in the 73 men with localised disease was 80% [95%CI 68–88] at 24-months. There were no cancer specific deaths. Conclusions: Prostate mpMRI and MRI-targeted biopsies can accurately detect and localise recurrent prostate cancer following radiotherapy. Focal ablation to areas of intra-prostatic recurrence preserves continence in the majority of men with good cancer control. Clinical trial information: NCT01883128.