Main Session
Sep
29
PQA 06 - Genitourinary Cancer, Gynecological Cancer, and Health Care Access and Engagement
3281 - Discordance between MRI-Targeted and Systematic Core Biopsy in Identifying the Highest-Grade Focus: Implications for Intraprostatic Boost
Presenter(s)
Chaewon Hwang, MD - Tufts Medical Center | Beth Israel Deaconess Medical Center, Boston, MA
C. Hwang1,2, E. C. Ko2, N. Bhargava3, J. A. Haas4, I. D. Kaplan2, J. A. Aronovitz2, D. R. Schmidt2, and N. Aghdam5; 1Department of Radiation Oncology, Tufts Medical Center, Boston, MA, 2Department of Radiation Oncology, Beth Israel Deaconess Medical Center, Boston, MA, 3Oakland University William Beaumont School of Medicine, Rochester, MI, 4Department of Radiation Oncology, Perlmutter Cancer Center at New York University Langone Hospital - Long Island, Mineola, NY, 5Department of Radiation Oncology, New York University Langone Health, New York, NY
Purpose/Objective(s):
Intraprostatic boost during prostate stereotactic body radiation therapy (SBRT) typically targets MRI-defined dominant intraprostatic lesions (DILs). This strategy assumes that the MRI-visible region of interest (ROI) harbors the highest-grade disease. We evaluated discordance between MRI-targeted ROI biopsy and systematic core biopsy in identifying the highest Gleason grade group and examined implications for biologically guided boost planning.Materials/Methods:
We retrospectively analyzed 78 patients, diagnosed with up to high-risk prostate cancer, treated over 8 years with SBRT including intraprostatic boost in a high-volume academic center. Those eligible for androgen deprivation therapy (ADT) received ADT. All patients underwent combined systematic and MRI-targeted fusion biopsy by expert urologists prior to treatment. The primary endpoint was concordance in highest Gleason grade group between systematic and MRI-targeted cores. Clinicopathologic variables including PI-RADS score, lesion size, extraprostatic extension (EPE) score, and lesion number were compared using chi-square testing and ANOVA. Biochemical failure was defined per Phoenix criteria.Results:
Mean age was 73 ± 6.2 years. On systematic core biopsy, 16 patients had 3+3 disease as their highest Gleason score, 37 had 3+4, 18 had 4+3, 6 had 4+4, and one had 4+5 disease. 42 patients received ADT. Highest Gleason grade was identified on systematic biopsy in 20.5% of patients, on MRI-targeted biopsy in 28.2%, and was present in both in 51.3%. Grade group distribution did not significantly differ between biopsy modalities (?² = 3.13, P = 0.54). Imaging characteristics, including PI-RADS score, lesion size, EPE score, and lesion number, did not differ significantly among concordant and discordant groups (all P > 0.10). At minimum 2-year follow-up, no biochemical failures were observed in all patients.Conclusion:
Nearly half of patients treated with SBRT and intraprostatic boost demonstrated discordance between systematic and MRI-targeted biopsy in identifying the highest Gleason grade, with one in five harboring their most aggressive disease outside the MRI-defined ROI. Although early biochemical control was excellent, these findings challenge the assumption that MRI-visible DILs consistently represent the biologically dominant lesion and support investigation of multimodal imaging strategies, including PSMA-PET, to optimize focal dose escalation.| Systematic core biopsy | MRI-targeted ROI biopsy | |||
| Highest Gleason score | Number of patients | Percent (%) | Number of patients | Percent (%) |
| 3+3=6 | 16 | 20.51 | 9 | 11.54 |
| 3+4=7 | 37 | 47.44 | 43 | 55.13 |
| 4+3=7 | 18 | 23.08 | 16 | 20.51 |
| 4+4=8 | 6 | 7.69 | 9 | 11.54 |
| 4+5=9 | 1 | 1.28 | 1 | 1.28 |
| 5+4=9 | 0 | 0.00 | 0 | 0.00 |