Adenoid Cystic Carcinoma (ACC) is a rare cancer, with challenging early diagnosis, characterized by slow growth and high rates of metastasis and recurrence. Effective therapeutic options are limited, particularly in advanced disease. 18F-FDG PET/CT is a fundamental tool for the diagnosis, staging and follow-up of ACC. Since Prostate-Specific Membrane Antigen (PSMA) has been shown to have high expression in ACC, it may be a useful theranostics tool to diagnose with PSMA PET/CT and treat with 177Lu-PSMA. Here, we present a case of metastatic ACC evaluated with 18F-FDG and 18F-PSMA PET/CT and treated with 177Lu-PSMA. A 48-year-old male patient was diagnosed with ACC of the right parapharyngeal space in 2008, being submitted to surgical resection and adjuvant radiotherapy, remaining disease-free for 13 years. In 2021, he developed ACC recurrence, characterized by multiple bilateral lung metastases, identified on 18F-FDG PET/CT scan and histopathologically confirmed by bronchoscopy. Systemic chemotherapy was initiated with Carboplatin plus Paclitaxel and later switched to Paclitaxel monotherapy due to toxicity; however, the patient developed treatment-related neuropathy. A new FDG PET/CT scan demonstrated progressive disease. At the end of 2023, the patient was enrolled in the research protocol aiming the compassionate treatment with 177Lu-PSMA. Pre-therapeutic evaluation with 18F-FDG PET/CT and 18F-PSMA PET/CT performed 24 hours apart demonstrated high uptake of both radiotracers in the lung nodules (FDG SUV >10 and PSMA SUV <9) and the patient was deemed eligible for treatment. The first therapeutic dose of 177Lu-PSMA (200 mCi) was administered in November 2025. The whole-body SPECT/CT images showed satisfactory radiotracer uptake in the pulmonary metastases. A second therapeutic dose of 177Lu-PSMA (200 mCi) was administered after 6 weeks. SPECT/CT whole-body images showed satisfactory radiotracer uptake as well. During follow-up, the patient experienced mild-to-moderate xerostomia after both 177Lu-PSMA treatment doses, as well as grade II nausea following the first administration. All adverse events were transient and resolved within four days, with no recurrent symptoms thereafter. The patient did not develop nephrotoxicity or hematological abnormalities. Follow-up interim PET/CT images will be performed after the 3rd cycle to define if there was a reduction in lesion volume. This case illustrates the applicability of PSMA PET/CT in metastatic Adenoid Cystic Carcinoma, facilitating patient selection for radionuclide therapy with 177Lu-PSMA. Adequate PSMA expression in pulmonary metastases and progressive uptake of 177Lu-PSMA, associated with good clinical tolerability and absence of hematological or renal toxicity, support this approach as a safe therapeutic option for ACC. Additional cycles and a large number of patients are needed to define if this therapeutic strategy is promising.
Pinho et al. (Sun,) studied this question.