Second-Line Abiraterone Plus Hormone Agonist Is a Viable Option for AR+ Castration-Resistant Salivary Gland Cancer

A combination of abiraterone acetate and luteinizing hormone–releasing hormone (LHRH) agonist appeared to be active and well tolerated for patients with androgen receptor (AR)–expressing castration resistant salivary gland cancer in the second-line setting, according to findings from the phase 2 SG-ABI14 study (NCT02867852).

In a population of 24 patients, investigators reported an overall response rate (ORR) of 21%, which included 5 partial responses. Investigators reported a median duration of response of 5.82 months. Moreover, the regimen yielded a disease control rate (DCR) of 62.5%. Patients had a median progression-free survival (PFS) of 3.65 months (95% CI, 1.94-5.89), and a median overall survival (OS) of 22.47 months (95% CI, 6.74–not reached).

“Abiraterone in association with LHRH analog is active as second-line in AR-expressing, castrate-resistant [salivary gland cancer]. The assessment of the molecular phenotype in these patients could provide further biologic details on mechanisms of response and [androgen deprivation therapy (ADT)] resistance. Patient selection might contribute to improve the treatment efficacy especially for PFS, which currently is still unsatisfactory,” the investigators wrote.

The single institution study had a primary end point of ORR, with secondary end points including DCR, safety, PFS, and OS.

Enrollment required patients to have a histologic diagnosis of salivary gland cancer with AR overexpression and measurable disease. Patients also needed to have progressed on an ADT with no limit on previous lines of treatment with chemotherapy. Additionally, an ECOG performance status of 2 or less was required.

Abiraterone acetate was administered in 4 doses of 250 mg each per day plus 5 mg of oral prednisone twice daily. If the dose of abiraterone was reduced due to adverse effects (AEs), patients were treated with 500 mg daily. Treatment continued until disease progression or unacceptable toxicity.

Patients were enrolled from March 2015 to November 2019 at a median follow up of 9.47 months. Patients had a median age of 65.8 years, and all had an ECOG performance status of 0 or 1. Moreover, 19 patients had salivary duct carcinoma and 5 had disease that was otherwise not specified.

Additional findings from the study included a 12-month OS rate of 66.59% in the overall study population. Among those with primary salivary gland cancer, the median OS was 94.31 months (95% CI, 46.61-not reached).

In total, 92% of the patient population experienced at least 1 AE, with the most common any grade AEs including fatigue (38%), flushing (29%), and hypokalemia (17%). Additionally, 25% of patients had a grade 3 AE, which included drug-related cases of fatigue (n = 2), flushing (n = 1), and supraventricular tachycardia (n = 1), as well as 2 cases unrelated to treatment, including cancer-related pain and xerostomia. Patients had a median of 3 AEs each, with no grade 4/5 AEs reported. No patients required dose reductions or discontinued treatment because of toxicities.

Reference

Locati LD, Cavalieri S, Bergamini C, et al. Abiraterone acetate in patients with castration-resistant, androgen receptor–expressing salivary gland cancer: a phase II trial. J Clin Oncol. 2021;39(36):4061-4068. doi:10.1200/JCO.21.00468