Time to next systemic therapy after stereotactic body radiation therapy for oligoprogressive metastatic castrate-resistant prostate cancer.

Authors

Corbin Eule

Corbin J. Eule

Division of Medical Oncology, University of Colorado Cancer Center, Aurora, CO

Corbin J. Eule , Nellowe Candelario , Tyler P. Robin

Organizations

Division of Medical Oncology, University of Colorado Cancer Center, Aurora, CO, Fred Hutchison Cancer Center, University of Washington, Division of Hematology and Oncology, Seattle, WA, Department of Radiation Oncology, University of Colorado Cancer Center, Aurora, CO

Research Funding

No funding sources reported

Background: Patients with castrate-resistant prostate cancer (CRPC) with progressive disease are generally require a change/escalation in systemic therapy. For patients with limited (≤3) sites of progressive disease (oligoprogression), metastasis-directed therapy with stereotactic body radiation therapy (SBRT) may allow a longer interval before next line systemic therapy, but there is limited data describing this approach. Methods: This is a retrospective study of patients with oligoprogressive metastatic CRPC (omCRPC) treated with SBRT at a single center between 2011-2022. The primary endpoint was time to next systemic therapy (TTNST) after SBRT. Secondary endpoints included overall survival (OS) after SBRT and TTNST stratified by presence of untreated non-progressing metastases. Results: Thirty-two patients with omCRPC received SBRT to 38 metastases. Patients had a median age of 72.5 years (range 50.6-84.3) and median PSA 6.85 ng/mL (range 0.39-922.0) at time of SBRT. The majority had an ECOG of 1-2 (29 patients, 90.6%) and metastases detected on conventional CT and/or bone scans (26 patients, 81.3%). The most commonly utilized SBRT regimen was 3000 cGy in 5 fractions (18 metastases, 47.4%) (Table). Sixteen patients were treated to all known sites of disease, whereas 16 patients received SBRT to oligoprogressive metastases but had at least one untreated non-progressing metastasis at the time of SBRT. Of 32 patients, 23 (65.7%) received SBRT to bone only, 3 (9.4%) to lymph node (LN) only, and 6 (18.8%) to other sites (pelvic tumor, n=2; pelvic tumor + LN, n =1; LN + bone, n=1; dura + bone, n=1; liver, n=1). Patients had received a median of 1.0 prior line of androgen receptor signaling inhibitors and were predominantly (26 patients, 81.3%) chemotherapy naïve. Following SBRT, the median TTNST was 10.1 months and median OS was 41.3 months. For patients with 0 versus ≥1 untreated non-progressing metastasis, TTNST was 11.3 versus 8.7 months, respectively (HR 0.67, 95% CI 0.33-1.36, logrank p=0.24). There were no grade ≥3 toxicities due to SBRT. Conclusions: In this cohort, patients with omCRPC treated with SBRT delayed the next line of systemic therapy for a median of 10.1 months. SBRT in patients with omCRPC may delay initiation of next line systemic therapy in well selected patients, including those with ≥1 untreated non-progressing metastases.

SBRT dosing regimens for CRPC metastases.

SBRT Dosingn = 38
1600 cGy, 1 Fx1
2400 cGy, 3 Fx5
2700 cGy, 3 Fx5
2500 cGy, 5 Fx4
3000 cGy, 5 Fx18
3500 cGy, 5 Fx3
4000 cGy, 5 Fx2

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Abstract Details

Meeting

2024 ASCO Genitourinary Cancers Symposium

Session Type

Poster Session

Session Title

Poster Session A: Prostate Cancer

Track

Prostate Cancer - Advanced,Prostate Cancer - Localized

Sub Track

Quality of Care/Quality Improvement and Real-World Evidence

Citation

J Clin Oncol 42, 2024 (suppl 4; abstr 62)

DOI

10.1200/JCO.2024.42.4_suppl.62

Abstract #

62

Poster Bd #

B19

Abstract Disclosures

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