ASTRO 2022: The Accuracy of Multiparametric MRI in Identification of Intraprostatic Tumor Deposits after Local Prostate Radiation Therapy

(UroToday.com) The 2022 ASTRO annual meeting featured a prostate cancer session, including a presentation by Dr. Tyler Gutschenritter discussing the accuracy of multiparametric MRI in identification of intraprostatic tumor deposits after local prostate radiation therapy. The accuracy of multiparametric MRI for identification of intraprostatic tumor deposits has been well studied in treatment naïve patients,1 however the accuracy in cases of prior radiation therapy is less well defined. The objective of this study by Dr. Gutschernritter and colleagues was to determine the accuracy of multiparametric MRI in identification of intraprostatic tumor deposits in prostate cancer patients previously treated with local radiation therapy using a systematic and targeted MR-guided transperineal prostate biopsy technique as a reference to guide and improve clinical workflow processes.


There were 23 patients with localized prostate cancer who had been previously treated with external beam radiation therapy, brachytherapy, or combined external beam radiation therapy and brachytherapy, that underwent a combined systematic and targeted MRI-guided prostate biopsy using a transperineal approach under general anesthesia. For each patient, a pre-biopsy multiparametric MRI scan was obtained and imported into a prostate biopsy planning system. Transverse T2-weighted images were then reoriented from the supine to dorsal lithotomy position. Dividing the prostate into an apical and base section, a systematic array of transperineal biopsies spaced approximately 10mm apart was planned with additional biopsies targeting any multiparametric MRI-identified PI-RADS 3, 4, or 5 lesions. Biopsy procedures were carried out in the dorsal lithotomy position using a transrectal ultrasound with stepper-stabilizer and template grid:

 

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Matching of the planning multiparametric MRI images to live ultrasound images was achieved using the template grid as a reference:

 

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 All patients successfully underwent their biopsy procedure as planned. The median PSA prior to biopsy was 5.5 ng/mL (range 2.1-24.6), and the median number of biopsy specimens obtained per patient was 21 (range 13-34). Overall, the positive predictive value (PPV) of any PI-RADS 3-5 lesion (based on pathologic confirmation) was 81% (21/26). Furthermore, the individual PPV of PI-RADS 3, 4 and 5 lesions were 25% (1/4), 89% (16/18), and 100% (4/4), respectively. Forty-eight percent (11/23) of patients harbored multiparametric MRI-unidentified prostate cancer, 35% (8/23) of patients harbored multiparametric MRI-unidentified Gleason score ≥7 disease, and there were no post-procedure urinary obstructive or infectious complications.

 

Dr. Gutschenritter concluded his presentation discussing the accuracy of multiparametric MRI in identification of intraprostatic tumor deposits after local prostate radiation therapy with the following concluding messages:

  • Using prostate multiparametric MRI to identify intraprostatic tumor deposits after local radiation therapy results in a high PPV, particularly for PI-RADS 4 and 5 lesions
  • However, given the high rate of multiparametric MRI-unidentified prostate cancer, the addition of systematic transperineal prostate biopsy information appears necessary to improve the accuracy of multiparametric MRI identification of intraprostatic tumor deposits



Presented by: Tyler Gutschenritter, MD, University of Washington, Department of Radiation Oncology, Seattle, WA

Co-Authors: R. Hsi, University of Washington, Department of Radiation Oncology, Seattle, WA


Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, @zklaassen_md on Twitter during the 2022 American Society of Radiation Oncology (ASTRO) Annual Hybrid Meeting, San Antonio, TX, Sat, Oct 22 – Wed, Oct 26, 2022. 

 
References:
  1. Hsi, et al. Performance of multiparametric prostate magnetic resonance imaging validated by targeted and systemic transperineal biopsies. BJUI Compass 2022 August 19 [Epub ahead of print].