18F-rHPSMA-7.3 linked with positive prostate cancer detection in patients with newly diagnosed disease

Use of 18F-rHPSMA-7.3 PET prior to prostatectomy was associated with positive disease detection and also provided clinically important information, according to a recently reported study.

The data, from the phase 3 LIGHTHOUSE trial, were presented at the Society for Urologic Oncology (SUO) 23rd Annual Meeting by Brian F. Chapin, MD, associate professor of urology and fellowship director at MD Anderson Cancer Center, Houston, Texas.

Of the 296 patients included in the efficacy population, 7.8% to 13.0% had a 18F-rHPSMA-7.3 PET–positive pelvic lymph node according to 3 readers. Moreover, extrapelvic lesions were identified in 16% to 28% of patients in an extended population that included those who received 18F-rHPSMA-7.3 PET regardless of surgery (n = 352).

Brian F. Chapin, MD, associate professor of urology and fellowship director at MD Anderson Cancer Center, Houston, Texas, presented the data from the phase 3 LIGHTHOUSE trial.

Investigators noted that radiohybrid prostate-specific membrane antigen (PSMA)–targeting PET radiotherapeutic agents could be potentially labeled with 18F for use in diagnostic imaging or alpha-/beta-emitting radiometals for systemic radiation therapy. The LIGHTHOUSE trial assessed 18F-rHPSMA-7.3 PET, a novel, high affinity PSMA ligand that is currently being developed in the diagnostic imaging space for prostate cancer.

The study included patients with unfavorable-risk, high-risk, or very high–risk newly diagnosed disease set to undergo radical prostatectomy with regional pelvic lymph node dissection. PET/CT was performed 50 to 70 minutes following a 296 MBq (8mCi) intravenous dose of 18F-rHPSMA-7.3.

The images were interpreted by local readers prior to surgery and were subsequently sent for blinded independent evaluation by 3 central readers. Moreover, histopathology was performed with 30 days after PET.

The trial’s co-primary end points were patient level sensitivity and specificity in terms of detecting pelvic lymph node metastases. The prespecified threshold for sensitivity and specificity were 22.5% and 82.5%, respectively. The efficacy analysis population included patients who received 18F-rHPSMA-7.3 PET followed by surgery.

The trial did not meet the prespecified statistical threshold for sensitivity, which ranged between 23% to 30%. Investigators noted that sensitivity was higher for those with high-risk or very high–risk disease vs unfavorable intermediate-risk disease.

Moreover, specificity was between 93% to 97% and exceeded the threshold across all readers. Specificity was also high across all readers for both disease risk stratifications, measuring 93% or higher.

In terms of safety, investigators reported that in the safety population of 356 patients, 7.9% experienced a total of 33 treatment-emergent adverse effects (TEAEs), which were determined to not be serious. Of this population, 2.5% of patients experienced 10 TEAEs that were potentially related to 18F-rHPSMA-7.3 PET.

Three patients experienced injection site pain, and 1 patient each experienced peripheral swelling, diarrhea, nausea, hyperkalemia, arthralgia, dysgeusia, and hypertension.

Reference

1. Chapin BF. Diagnostic performance and safety of 18F-rhPSMA-7.3 PET in patients with newly diagnosed prostate cancer: results from a phase 3, prospective, multicenter study (LIGHTHOUSE). Poster presented at Society for Urologic Oncology (SUO) 23rd Annual Meeting; November 30-December 2, 2022; San Diego, CA. Poster 134.