Main Session
Sep 29
PQA 06 - Genitourinary Cancer, Gynecological Cancer, and Health Care Access and Engagement

3340 - Impact of 68 Ga-PSMA PET/CT Staging on Metastasis-Free and Cancer-Specific Survival after Definitive Radiotherapy for High-Risk Prostate Cancer

02:15pm - 03:30pm ET
Poster Hall - Exhibit Hall A
Screen: 15
POSTER

Presenter(s)

Cem Onal, MD - Baskent University Faculty of Medicine, Department of Radiation Oncology, Ankara, Turkey, ankara,

C. Onal1,2, O. C. C. Guler1, N. Torun3, B. Demirhan4, A. Elmali2, M. Reyhan3, and M. N. Yavuz2; 1Baskent University Faculty of Medicine, Adana Dr Turgut Noyan Research and Treatment Center, Department of Radiation Oncology, Adana, Turkey, 2Baskent University Faculty of Medicine, Department of Radiation Oncology, Ankara, Turkey, 3Baskent University Faculty of Medicine, Adana Dr Turgut Noyan Research and Treatment Center, Department of Nuclear Medicine, Adana, Turkey, 4Iskenderun Gelisim Hospital, Division of Radiation Oncology, Hatay, Turkey

Purpose/Objective(s):

68Ga-PSMA PET/CT improves staging accuracy in high-risk prostate cancer (HR-PCa), but whether PSMA-guided staging translates into improved long-term outcomes after definitive radiotherapy (RT) remains unclear. We compared survival outcomes and recurrence patterns between PSMA-staged and conventionally staged patients treated with definitive RT and androgen deprivation therapy (ADT).

Materials/Methods:

We retrospectively analyzed 441 NCCN-defined HR-PCa patients treated with definitive external beam RT and ADT (2012–2023). Staging was performed using conventional imaging (CT/bone scan; n=227) or 68Ga-PSMA PET/CT (n=214). Baseline covariates were balanced and further adjusted using inverse probability of treatment weighting (IPTW). The primary endpoint was distant metastasis-free survival (DMFS). Secondary endpoints included freedom from biochemical failure (FFBF) and prostate cancer–specific survival (PCSS). Multivariable Cox regression and Fine–Gray competing-risk models were applied.

Results:

After a median follow-up of 86.8 months, 7-year DMFS, FFBF, and PCSS for the entire cohort were 56.4%, 80.2%, and 89.4%, respectively. PSMA staging was associated with significantly improved outcomes: 7-year DMFS: 65.0% vs 50.1% (p=0.005) and 7-year PCSS: 94.1% vs 86.4% (p=0.005). After IPTW adjustment and multivariable analysis, conventional imaging independently predicted inferior DMFS (HR 1.54, 95% CI 1.12–2.12, p=0.008) and PCSS (HR 3.26, 95% CI 1.40–7.57, p=0.006). In competing-risk analysis accounting for non–prostate cancer mortality, PSMA staging was associated with a 72% reduction in prostate cancer–specific death (sHR 0.28, 95% CI 0.13–0.63, p=0.002). Failure patterns differed between cohorts, with lower rates of isolated distant metastases in PSMA-staged patients and a shift toward combined biochemical and metastatic relapses compared with conventionally staged patients.

Conclusion:

PSMA-PET/CT staging was independently associated with improved metastasis-free and cancer-specific survival after definitive RT for HR-PCa, with a substantial reduction in prostate cancer–specific mortality. These findings suggest that PSMA-informed staging may translate beyond diagnostic accuracy into meaningful survival benefit through optimized risk stratification and treatment personalization.

DMFS

 FFBF

 PCSS
Characteristics

 Variables

 HR (95%CI)

 p

 HR (95%CI)

 p

 HR (95%CI)

 p
Age

 <70 vs. =70 years

 1.60 (1.19–2.17)

 0.002

PSA

 <20 vs. =20 ng/mL

 2.01 (1.45–2.81)

 <0.001

 1.88 (1.09–3.25)

 0.02

T stage

 <T3a vs. =T3a

 1.94 (1.43–2.64)

 <0.001

2.88 (1.36–6.10)

 0.006
Gleason score

 <8 vs. =8

 1.80 (1.33–2.45)

 <0.001

 2.19 (1.36–3.51)

 0.001

 4.98 (2.32–10.72)

 <0.001
Pelvic field RT

 Yes vs. no

1.79 (0.63–5.14)

 0.28
SIB

 Yes vs. no

 1.27 (0.94–1.73)

 0.13

 1.71 (1.05–2.77)

 0.03

 2.45 (1.13–5.29)

 0.02
ADT duration

 <18 vs. =18 months

 0.44 (0.32–0.60)

 <0.001

 0.32 (0.20–0.53)

 <0.001

PSMA-PET/CT

 Yes vs. no

 1.54 (1.12–2.12)

 0.008

3.26 (1.40–7.57)

 0.006