Genitourinary Cancer

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SU_25_2254 - How Would MRI-Targeted Prostate Biopsy Alter Radiation Therapy Approaches in Treating Prostate Cancer?

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

How Would MRI-Targeted Prostate Biopsy Alter Radiation Therapy Approaches in Treating Prostate Cancer?
D. B. Dix, A. M. McDonald, J. W. Nix, J. B. Gordetsky, J. V. Thomas, and S. Rais-Bahrami; University of Alabama at Birmingham, Birmingham, AL

Purpose/Objective(s): Magnetic resonance (MR)/ultrasound fusion-targeted prostate biopsy has been shown to improve detection of clinically-significant prostate cancer over systematic biopsy sampling. The effects of targeted biopsy on radiation therapy recommendations are not well understood. We aim to determine if targeted biopsy would lead to increased recommendations of aggressive radiotherapy treatments for higher risk prostate cancer compared to standard biopsy results.

Materials/Methods: This is a retrospective review of prospectively gathered clinicopathologic data of 533 men who underwent both standard and targeted prostate biopsy from 2014-2017. Three patient cohorts were established: (1) biopsy naïve (80/533), (2) active surveillance (185/533), and (3) prior negative biopsy (268/533). Cancer risk category criteria were established with recommended radiotherapy treatment for each (Table 1). Variation of risk classification due to biopsy method for all patients and within each cohort were analyzed using either a chi-squared statistic or Fisher’s Exact test. McNemar’s pairwise analyses were performed for all risk categories between targeted and standard biopsy to assess the effects of targeted biopsy on high-risk cancer identification and subsequent radiotherapy recommendations.

Results: Distribution of patients within cancer risk categories varied due to targeted and standard biopsies among all patients (p<0.0001), in cohort 2 (p=0.0005), and in cohort 3 (p<0.0001). Further, among all patients, targeted biopsy increased cancer risk classification and, correspondingly, would likely result in more aggressive radiotherapy recommendations: Low-Risk to Intermediate-Risk (Gleason 4+3) (29/343, p<0.0001), Low-Risk to High-Risk (31/353, p<0.0001), and Intermediate-Risk (Gleason 3+4) to Intermediate-Risk (Gleason 4+3) (6/63, p=0.01).

Conclusion: Among men with prostate cancer, the addition of targeted biopsy commonly led to reclassification to a higher risk group, which is likely accompanied by more aggressive radiotherapy treatment recommendations when compared with systematic biopsy sampling findings alone. Future prospective studies are needed to validate the degree of altered clinical recommendations regarding radiotherapy approaches due to targeted prostate biopsy. Table 1 – Prostate Cancer risk category classification criteria and associated radiotherapy recommendations.
Cancer Classification Criteria Treatment
Low Risk CA
- Gleason ≤ 6 - and PSA < 10 ng/mL - and ≤T2b by DRE - Fractionated EBRT - SBRT - Brachytherapy without EBRT
Favorable Intermediate Risk CA
- Gleason 7 (3+4) - or PSA 10-20 ng/mL - or T2c by DRE - Same as Low Risk CA
Unfavorable Intermediate Risk CA
- Gleason 7 (4+3) - or PSA 10-20 ng/mL - or T2c by DRE - Fractionated EBRT - SBRT - Brachytherapy with EBRT - ADT
High Risk CA
- Gleason ≥8 - or PSA ≥ 20 ng/mL - or ≥ T3a by DRE - Fractionated EBRT - EBRT with brachytherapy boost - ADT

Author Disclosure: D.B. Dix: None. A.M. McDonald: Research Grant; Varian Medical Systems, Collegium Pharmaceuticals. J.B. Gordetsky: None. J.V. Thomas: None. S. Rais-Bahrami: None.

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