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Radiographic Progression in the Absence of Prostate-Specific Antigen (PSA) Progression in Patients with Metastatic Hormone-Sensitive Prostate Cancer (mHSPC): Post hot analysis of ARCHES
Andrew J. Armstrong, MD, MSc1, Nicolas Mottet, MD, PhD2, Taro Iguchi, MD, PhD3, Russell Z. Szmulewitz, MD4, Jeffrey Holzbeierlein, MD5, Arnauld Villers, MD, PhD6, Antonio Alcaraz, MD, PhD7, Boris Alekseev, MD8, Neal D. Shore, MD9, Francisco Gomez-Veiga, MD, PhD10, Brad Rosbrook, MS11, Fabian Zohren, MD, PhD12, Ho-Jin Lee, PhD13, Gabriel Haas, MD13, Arnulf Stenzl, MD14, Arun A. Azad, MBBS, PhD15.
1Duke Cancer Institute, Center for Prostate & Urologic Cancers, Durham, NC, USA, 2University Hospital, St. Etienne, France, 3Kanazawa Medical University, Ishikawa, Japan, 4The University of Chicago, Chicago, IL, USA, 5The University of Kansas Medical Center, Kansas City, KS, USA, 6University Hospital Centre, Lille University, Lille, France, 7Hospital Clinic de Barcelona, Barcelona, Spain, 8Hertzen Moscow Cancer Research Institute, Moscow, Russian Federation, 9Carolina Urologic Research Center, Myrtle Beach, SC, USA, 10Complexo Hospitalario Universitario de A Coruña, Coruña, Spain, 11Pfizer Inc., San Diego, CA, USA, 12Pfizer Inc., New York, NY, USA, 13Astellas Pharma, Northbrook, IL, USA, 14University Hospital, Eberhard Karls University of Tübingen, Tübingen, Germany, 15Peter MacCallum Cancer Centre, Melbourne, Australia.

BACKGROUND: Enzalutamide (ENZA) + androgen deprivation therapy (ADT) significantly reduced the risk of radiographic progression and increased overall survival in men with mHSPC, regardless of baseline PSA levels (ARCHES; NCT02677896). This post hoc analysis investigated concordance between PSA progression and radiographic progression in patients with mHSPC.
METHODS: Patients with mHSPC (n=1150) were randomized 1:1 to ENZA (160 mg/day) + ADT or placebo (PBO) + ADT. The concordance between radiographic progression and PSA progression, as defined by Prostate Cancer Clinical Trials Working Group 2 (PCWG2) criteria, and between any rise in PSA above nadir was assessed.
RESULTS: In total, 267/1150 patients in ARCHES had radiographic progression (ENZA + ADT, n=79; PBO + ADT, n=188). At radiographic progression, the median (range) PSA for ENZA + ADT-treated patients was 2.25 ng/mL (0-1062.3 ng/mL) and 17.47 ng/mL (0-1779.5 ng/mL) for PBO + ADT-treated patients. Most patients (67%) treated with ENZA + ADT did not have PCWG2-defined PSA progression at radiographic progression, compared with 57% of those treated with PBO + ADT (Table). The median absolute and percentage rise in PSA from nadir to radiographic progression was 0.77 ng/mL and 200%, respectively, with ENZA + ADT compared with 12.23 ng/mL and 367%, respectively, with PBO + ADT. Due to the post hoc nature of the analysis, results should be interpreted with caution.
CONCLUSIONS: In this post hoc analysis of ARCHES, we found frequent discordance between radiographic progression and PSA progression by PCWG2 criteria or any PSA rise over nadir in patients with mHSPC treated with ENZA + ADT. Thus, regular imaging is recommended to detect radiographic progression among patients treated with potent androgen receptor pathway inhibitors, such as ENZA + ADT, as serial PSA monitoring alone may not be sufficient to detect radiographic progression in many patients.

Concordance of radiographic progression and increasing PSA

n (%)ENZA + ADT
PSA progressiona at time of radiographic progressionb
Yes26 (32.9)108 (57.4)
No53 (67.1)80 (42.6)
Any rise in PSA from nadir at time of radiographic progressionb
Yes52 (65.8)160 (85.1)
No27 (34.2)28 (14.9)

aPSA progression is defined as a ≥25% increase and an absolute increase of ≥2 ng/mL above the nadir, confirmed by a second consecutive value at least 3 weeks later; bRadiographic progression was assessed by independent central review or death (defined as death from any cause within 24 weeks from study drug discontinuation), whichever occurred first.

The study was sponsored by Pfizer and Astellas Pharma, the co-developers of enzalutamide.
Prior presentation / copyright permissions: © 2022 American Society of Clinical Oncology, Inc. Reused with permission. This abstract was accepted and previously presented at the 2022 ASCO Annual Meeting. All rights reserved.
Acknowledgments: Medical writing and editorial support funded by the sponsors were provided by Mashal Hussain, PhD, and Lauren Smith, BA (Hons), from Complete HealthVizion.

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