The National Comprehensive Cancer Network has updated its Prostate Cancer guidelines to include the PARP inhibitor rucaparib.
Patrick J. Mahaffy
The National Comprehensive Cancer Network has updated its Clinical Practice Guidelines in Oncology for Prostate Cancer to include new recommendations for the PARP inhibitor rucaparib (Rubraca).1
According to Clovis Oncology, Inc., the manufacturer of rucaparib, the recommendation is specifically for use as a "treatment option for patients with metastatic castration-resistant prostate cancer (mCRPC) and a pathogenic BRCA1 or BRCA2 mutation (germline and/or somatic) who have been treated with androgen receptor-directed therapy and a taxane-based chemotherapy. If the patient is not fit for chemotherapy, rucaparib can be considered even if taxane-based therapy has not been given."
The recommendation is classifed as Category 2A, meaning that there is uniform consensus from the NCCN, based on lower-level evidence, that the use of rucaparib is appropriate for the described indication. The NCCN based the recommendation on findings from phase 2 TRITON2 trial (NCT02952534), which also supported the FDA approval of rucaparib in this setting. In the study, the PARP inhibitor induced a 44% confirmed objective response rate (ORR) in 62 evaluable patients with BRCA1/2-mutant mCRPC.2,3
In the international, multicenter, open-label TRITON2 study, investigators enrolled male patients with mCRPC associated with 1 of 13 homologous recombination repair (HRR) gene alterations. Patients had disease progression on androgen receptor—directed therapy and 1 prior taxane-based chemotherapy. Additionally, they had an ECOG performance status of 0 or 1 and could not have received a prior PARP inhibitor, mitoxantrone, cyclophosphamide, or platinum-based chemotherapy.
Patients were treated with rucaparib at 600 mg twice daily until radiographic progression or treatment discontinuation. Tumors were radiographically assessed every 8 weeks for 24 weeks, and then every 12 weeks. Prostate-specific antigen (PSA) assessments were performed every 4 weeks.
The primary end points of the trial include confirmed ORR per RECIST/Prostate Cancer Clinical Trials Working Group 3 criteria in patients with measurable disease at baseline and PSA response in patients with no measurable disease at baseline.
The evaluable population for PSA response included 45 patients with BRCA1/2 mutations, and the population evaluable for radiographic response included 25 patients with BRCA1/2 mutations.
The median age of the evaluable 45 patients with BRCA1/2 mutations was 71 years (range, 50-88); most (62.2%) had an ECOG performance status of 1. Prior therapies included abiraterone acetate (Zytiga; 55.6%), enzalutamide (Xtandi; 73.3%), both abiraterone and enzalutamide (31.1%), docetaxel (95.6%), cabazitaxel (Jevtana; 8.9%), sipuleucel-T (Provenge; 13.3%), and radium-223 dichloride (Xofigo; 11.1%).
A total of 88.9% of patients with BRCA1/2 mutations had bone metastases, 62.2% had nodal metastases, and 42.2% had visceral metastases. Additionally, 33.3% of patients had a germline BRCA1/2 mutation and 66.7% had a somatic BRCA1/2 mutation.
The preliminary results included data from 85 patients enrolled through June 29, 2018, with a median follow-up of 5.7 months (range, 2.6-16.4). These data showed that rucaparib demonstrated a 44% confirmed ORR (95% CI, 24.4%-65.1%) by investigator assessment among evaluable men with BRCA1/2-mutated mCRPC. Among those with BRCA1/2 alterations, 51.1% had a confirmed PSA response to rucaparib.
All 11 investigator-assessed radiographic responses in the patients with BRCA-mutated tumors were partial responses (PRs); 9 patients (36.0%) had stable disease. The median duration of response had not been reached.
Updated findings were presented at the 2019 ESMO Congress, with a median follow-up of 13.1 months (range, 4.1-28.5).4 Results showed that rucaparib elicited a 43.9% confirmed ORR and a confirmed PSA response of 52.0% in patients with mCRPC and a BRCA1/2 mutation. Responses were durable, with 60% of responses lasting ≥24 weeks.
Regarding safety, all-grade treatment-emergent adverse events occurring in >20% of patients were asthenia/fatigue (55.3%), nausea (49.5%), anemia/decreased hemoglobin (37.9%), decreased appetite (27.9%), transient increased aspartate transaminase/alanine aminotransferase (24.7%), constipation (24.7%), vomiting (22.1%), and diarrhea (21.1%).
The accerated approval of rucaparib in this setting is contingent on the results of a confirmatory trial. The ongoing, multicenter, randomized phase 3 TRITON3 trial (NCT02975934) is comparing single-agent rucaparib with physician’s choice of abiraterone acetate, enzalutamide, or docetaxel in men with mCRPC and homologous recombination deficiency whose disease has progressed on prior treatment.
Rubraca was previously approved as monotherapy for the maintenance treatment of patients with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer who are in a CR or PR to platinum-based chemotherapy. It is also approved for the treatment of patients with deleterious BRCA mutation—germline and/or somatic—associated epithelial ovarian, fallopian tube, or primary peritoneal cancer who have been treated with ≥2 chemotherapies and selected for therapy based on an FDA-approved companion diagnostic.
“We are pleased that the NCCN has acknowledged the importance of novel targeted therapies for the treatment of advanced prostate cancer, and the need for new treatment options for patients with BRCA mutations, including Rubraca, the first PARP inhibitor approved for these patients,” Patrick J. Mahaffy, president and CEO of Clovis Oncology, stated in a press release. “In particular, in the current COVID-19 environment, many patients would prefer to avoid chemotherapy, which requires frequent clinical visits, in favor of an oral agent that can be delivered directly to and taken at home.”