In an Italian single-institution phase II trial reported in the Journal of Clinical Oncology, Locati et al found that abiraterone acetate showed activity in patients with androgen deprivation therapy (ADT)-resistant, androgen receptor (AR)-overexpressing salivary gland carcinoma.

As stated by the investigators, “The activity of ADT in AR-positive salivary gland carcinomas has been established in the past few years. Second-line treatment in castration-resistant patients is still unknown.”

Study Details

Twenty-four patients from the Fondazione IRCCS Istituto Nazionale dei Tumori were enrolled into the trial between March 2015 and November 2019. Patients had to have histologic diagnosis of AR-overexpressing disease, measurable disease on Response Evaluation Criteria in Solid Tumors version 1.1, clinical or radiologic disease progression on ADT, and suppressed serum testosterone. There was no limit on the number of previous chemotherapy lines.

Patients received abiraterone acetate at 1 g daily, prednisone at 5 mg twice daily, and a luteinizing hormone-releasing hormone agonist until disease progression or unacceptable toxicity.

Responses

Median follow-up was 9.47 months (95% confidence interval [CI] = 5.66–20.56 months). Objective responses (all partial) were observed in 5 patients (21%); stable disease was observed in an additional 10 patients, yielding a disease control rate of 62.5%. Objective response to previous ADT was not correlated with response to abiraterone acetate. Median duration of response was 5.82 months (95% CI = 4.24–10.76 months).

Median progression-free survival was 3.65 months (95% CI = 1.94–5.89 months) and median overall survival was 22.47 months (95% CI = 6.74 months–not reached). Overall survival at 12 months was 66.6%, including 74.5% in 19 patients with salivary gland carcinoma and 50% in 5 patients with adenocarcinoma not otherwise specified (P = .334).

Adverse Events

The most common drug-related adverse events of any grade were fatigue (38%), flushing (29%), and hypokalemia (17%). No drug-related grade 4 or 5 adverse events occurred. Grade 3 events occurred in six patients (25%) and were considered drug-related in four (fatigue in two patients, flushing in one, and supraventricular tachycardia in one). No patients discontinued treatment due to adverse events.

The investigators concluded, “Abiraterone plus luteinizing hormone-releasing hormone agonist is active and safe as a second-line option in AR-expressing, castration-resistant salivary gland carcinoma.”

Laura D. Locati, MD, PhD, of the Head and Neck Medical Oncology Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, is the corresponding author for the Journal of Clinical Oncology article.

Disclosure: The study was supported by Janssen Pharmaceuticals, Inc. For full disclosures of the study authors, visit ascopubs.org.