Focal Prostate Stereotactic Body Radiation Therapy With Correlative Pathological and Radiographic-Based Treatment Planning.

Advances in multiparametric MRI (mpMRI) combining anatomic and functional imaging can accurately identify foci of adenocarcinoma within the prostate, offering the possibility of partial gland therapy. We performed tandem prospective pilot trials to investigate the feasibility of focal prostate SBRT (f-SBRT) based on correlating diagnostic mpMRI and biopsies with confirmatory pathology in treatment planning. Patients with pathologic focal Gleason 6-7 disease and a corresponding PIRADS 4-5 lesion on mpMRI underwent targeted and comprehensive biopsies using MRI/ultrasound fusion under electromagnetic sensor navigation. After rigorous analysis for imaging biopsy concordance, five of 18 patients were eligible to proceed to f-SBRT. Chi-squared test was used for differences from expected outcomes, and concordance was estimated with binomial distribution theory and Wilson's method. Six patients had Gleason 6 and 12 had Gleason 3 + 4 disease (mean PSA: 5.8 ng/ml, range: 2.2-8.4). Absolute concordance was 43.8% (95% CI: 0.20, 0.64). Patterns of discordance included additional sites of ipsilateral disease, bilateral disease, and negative target. Five were upstaged to a new NCCN risk category necessitating treatment escalation. The five patients with concordant pathology completed three-fraction f-SBRT with sparing of the surrounding normal structures (including contralateral neurovascular bundle), with no reported grade 2+ toxicities and favorable PSA responses (mean: 41% decrease). On our pilot trials of f-SBRT planning using rigorous imaging and pathology concordance, image-guided confirmatory biopsies frequently revealed additional disease, suggesting the need for caution in partial-gland therapy. For truly focal disease, f-SBRT provided excellent dosimetry, minimal toxicity, and encouraging biochemical response.

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Copyright © 2021 Fredman, Traughber, Kharouta, Podder, Lo, Ponsky, MacLennan, Paspulati, Ellis, Machtay and Ellis.

Déclaration de conflit d'intérêts

BT reports grants from Philips Healthcare and from Elekta during the conduct of the study. MM reports nonfinancial support from Elekta and personal fees and nonfinancial support from Philips during the conduct of the study. RE reports nonfinancial support from Elekta and personal fees and nonfinancial support from Philips during the conduct of the study. In addition, RE has two patents U.S. Patents 7831293 and 10842469 with royalties paid by Philips. SL reports past travel and research support from Elekta when the study was developed and current membership of the Elekta ICON Gamma Knife Expert Group. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.