PSMA-PET enhances management of oligometastatic prostate cancer

PSMA-PET is becoming an invaluable tool for the diagnosis and management of oligometastatic prostate cancer patients, a sub-group for whom novel treatment strategies are continuing to emerge.

In their poster conclusion, Umar Ghaffar, MBBS, and R. Jeffrey Karnes, MD, wrote, “PSMA-PET is an excellent modality to diagnose and guide the management of oligometastatic disease, andMDT may be used with adjunctive ADT to further improve PFS after treatment of oligometastasis.”

Researchers Umar Ghaffar, MBBS, and R. Jeffrey Karnes, MD, of the division of Urology, Mayo Clinic, highlighted this point with their poster, “Oligometastasis through the lens of PSMA-PET,” at the 2023 Society of Urologic Oncology Annual Meeting.¹

“Oligometastatic disease is an intermediate stage of cancer spread between localized and widespread metastasis in which radical treatment of metastasis may potentially be curative,” Ghaffar and Karnes wrote on their poster. “It is crucial to assess the utility of modern diagnostic imaging modalities [such as PSMA-PET imaging] for improving therapeutics and diagnostics of this disease state.”

For the retrospective analysis, the researchers reviewed 802 consecutive clinically indicated PSMA-PET scans conducted at the Mayo Clinic between April and November 2022. From these PSMA-PET scans, 141 patients were identified as having oligometastatic disease, defined as ≤5 sites of metastasis.

The mean patient age at prostate cancer diagnosis was 62.7 years and at oligometastasis was 71.4 years. The median PSA at prostate cancer diagnosis was 8.7 ng/ml.

Overall, 8.5% of patients had de novo oligometastatic disease. Patients had a mean of 2.14 metastatic sites and the mean SUVmax was 11. Sites of metastasis included osseous (63.8%), nodal (43.3%), and visceral (2.8%). At the time of oligometastatic diagnosis, 28.6% of patients had castration resistant disease.

Treatment modalities patients received included surgery (2.1%), stereotactic ablative radiotherapy (49.6%), intensity modulation radiotherapy (19.1%), cryoablation (7%), androgen deprivation therapy (ADT; 57.4%), and chemotherapy (4.9%).

“Patients underwent different treatment modalities. There were 3 main groups of modalities: metastasis-directed therapy (MDT) with ADT, MDT without ADT, and systemic therapy,” Ghaffar, said in an interview with Urology Times at the meeting.

Follow-up imaging showed that 13.4% of patients had progressed to diffuse metastasis, 48.5% of patients had resolved, 32.38% of patients had improved, and 10.6% of patients were unchanged or progressed.

“Progression-free survival (PFS)—either radiographic or biochemical—was significantly longer in patients who received ADT along with MDT compared to MDT alone (P < .001),” said Ghaffar.

In their poster conclusion, Ghaffar and Karnes wrote, “PSMA-PET is an excellent modality to diagnose and guide the management of oligometastatic disease, andMDT may be used with adjunctive ADT to further improve PFS after treatment of oligometastasis.”

EXTEND trial

The findings of Gaffar and Karnes’s analysis were similar to findings from the oligometastatic prostate cancer cohort of the phase 2 basket randomized EXTEND trial (NCT03599765), except in this trial the control was hormone therapy alone.²

The EXTEND cohort included 87 men with oligometastatic prostate cancer (≤5 metastases) who had received hormone therapy for at least 2 months. The median age was 67 years (IQR, 63-72 years).

Patients were randomized to intermittent hormone therapy plus MDT (n = 43) or to intermittent hormone therapy alone (n = 44). MDT used in the study was definite radiation therapy delivered to all disease sites.

At a median follow-up of 22 months (range, 11.6-39.2), the combination regimen reduced the risk of disease progression or death by 75% compared with hormone therapy alone. The median PFS with MDT plus hormone therapy was not reached compared with 15.8 months with hormone therapy alone (hazard ratio, 0.25; 95% CI, 0.12-0.55; P < .001).

The results also showed that MDT plus hormone therapy improved eugonadal PFS compared with hormone therapy alone: median PFS not reached vs 6.1 months, respectively (HR, 0.32; 95% CI, 0.11-0.91; P = .03).

“Combination of MDT with intermittent hormone therapy may allow for excellent disease control while facilitating prolonged eugonadal testosterone intervals,” the authors wrote in their study conclusion.²

For additional insight on the EXTEND trial, watch Urology Times’ interview with first study author Chad Tang, MD, The University of Texas MD Anderson Cancer Center.

References

1. Ghaffar U, Karnes RJ. Oligometastasis through the lens of PSMA-PET. Presented at: 2023 Society of Urologic Oncology Annual Meeting. November 28 – December 1, 2023; Washington, DC. Abstract 44.

2. Tang C, Sherry AD, Haymaker C, et al. Addition of Metastasis-Directed Therapy to Intermittent Hormone Therapy for Oligometastatic Prostate Cancer: The EXTEND Phase 2 Randomized Clinical Trial. JAMA Oncol. 2023;9(6):825-834. doi: 10.1001/jamaoncol.2023.0161