Advances in Radiation Oncology (Jan 2022)

Evaluating the Role of Stereotactic Body Radiation Therapy With Respect to Androgen Receptor Signaling Inhibitors for Oligometastatic Prostate Cancer

  • Victoria Brennan, MB, BCh, BAO,
  • Alexander Spektor, MD, PhD,
  • Christopher Sweeney, MBBS,
  • Atish Choudhury, MD, PhD,
  • Dana Rathkopf, MD,
  • Mark Pomerantz, MD,
  • Lauren Hertan, MD,
  • Paul Nguyen, MD,
  • Neil Martin, MD, MPH,
  • Tracy Balboni, MD, MPH,
  • Mai Anh Huynh, MD, PhD,
  • Martin King, MD, PhD

Journal volume & issue
Vol. 7, no. 1
p. 100808

Abstract

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Purpose: Outcomes of stereotactic body radiation therapy (SBRT) with respect to androgen receptor signaling inhibitors (ARSI) have not been characterized for oligometastatic prostate cancer. We sought to characterize prostate specific antigen (PSA) response and progression-free survival (PFS) after SBRT among men who have progressed on ARSI therapy in the oligometastatic castration-resistant setting. Methods and Materials: A single-institution retrospective analysis was performed for men with ARSI-resistant, oligometastatic, castrate-resistant prostate cancer (omCRPC). Intervention consisted of SBRT. PSA reduction greater than 50% and median PFS (PSA or radiographic progression) as determined by routine care comprised outcome measurements. Cox regression analysis was used to determine factors influencing PFS. Results: Thirty-five men with ARSI-resistant omCRPC and 65 lesions treated with SBRT were followed for a median of 17.2 months. In 63% of men PSA reduction greater than 50% was achieved. Median PFS was 9.0 months. Incomplete ablation (defined as the presence of untreated lesions after SBRT or receipt of prior palliative radiation therapy doses) was associated with worse PFS (hazard ratio 4.21 [1.74-10.19]; P < .01). For a subgroup of 22 men with complete ablation of metastatic sites with SBRT, the median PFS was 13.1 months. One-year overall survival was 93.1% (95% confidence interval, 84.4-100). Conclusions: SBRT may augment the efficacy of ARSI in omCRPC, provided that all lesions receive ablative radiation doses. Future prospective study of SBRT for men receiving ARSI is warranted.