# Clinical Characteristics Associated with High [68Ga]Ga-PSMA-11 Uptake and Preliminary Therapeutic Outcomes in Patients with Metastatic Adenoid Cystic Carcinoma

## TL;DR

This study explores factors linked to high PSMA uptake in metastatic adenoid cystic carcinoma and preliminary results of PSMA-targeted therapy.

## Contribution

Identifies clinical characteristics associated with high PSMA uptake and evaluates early outcomes of PSMA-targeted therapy in metastatic ACC.

## Key findings

- Higher PSMA uptake was linked to lung and bone metastases, larger tumor size, and faster tumor growth.
- 177Lu-PSMA therapy showed limited effectiveness in a small patient cohort.
- Longer time since diagnosis was associated with increased PSMA uptake.

## Abstract

Adenoid cystic carcinoma (ACC) is a rare cancer that arises from the salivary glands. Recent studies have shown that prostate-specific membrane antigen (PSMA) expression is high in ACC. We conducted a prospective study to evaluate clinical factors associated with high [68Ga]Ga-PSMA-11 uptake and to report preliminary therapeutic outcomes of 177Lu-PSMA therapy in recurred or metastatic ACC.

Thirty patients were prospectively enrolled. Any focal accumulation of [68Ga]Ga-PSMA-11 not explained by physiological uptake was defined as pathological lesions. Clinicopathological features relevant for high [68Ga]Ga-PSMA-11 uptake in recurred or metastatic ACC were analyzed. Therapeutic outcomes of patients who received 177Lu-PSMA therapy under compassionate use were also reviewed as a secondary component.

A total of 238 lesions were evaluated, and the SUVmax ranged between 0.9 and 11.0, showing mild to moderate PSMA uptake. Higher SUVmax was observed in lung and bone metastases. The longest tumor diameter (R = 0.190, P = 0.009) and tumor % growth rate (R = 0.220, P = 0.006) were significantly correlated with SUVmax. A longer duration from diagnosis was a relevant factor for high [68Ga]Ga-PSMA-11 uptake. Seven patients received 177Lu-PSMA therapy, but therapeutic outcomes were limited.

High [68Ga]Ga-PSMA-11 uptake in recurred or metastatic ACC was associated with location of metastases, longer tumor diameter, high tumor % growth rate, and a longer duration from diagnosis. While 177Lu-PSMA therapy was performed in a limited cohort and outcomes were preliminary, these findings provide exploratory insights into potential factors relevant for patient selection and warrant further investigation in larger studies.

The online version contains supplementary material available at 10.1007/s13139-025-00955-9.