PARP inhibitors benefit many women with ovarian cancer, but they may hurt others
Monk BJ, Parkinson C, Lim MC, et al. A randomized, phase III trial to evaluate rucaparib monotherapy as maintenance treatment in patients with newly diagnosed ovarian cancer (ATHENA-MONO/GOG-3020/ENGOT-ov45). J Clin Oncol. 2022;40:3952-3964. doi:10.1200/JCO.22.01003.
Poly(ADP-ribose) polymerase (PARP) inhibitors are a class of oral anticancer agents that target DNA repair. Since the initial FDA approval in 2014 of olaparib for the treatment of patients with recurrent BRCA-mutated ovarian cancer, PARP inhibitors have been approved for maintenance in both the frontline setting and after platinum-sensitive recurrence, and as single-agenttreatment for ovarian cancer with BRCA mutations or evidence of homologous repair deficiency (HRD), a BRCA-like molecular phenotype.5 The expanding role for PARP inhibitors in ovarian cancer seemed inexorable.
Restricted prescribing advised
In 2022, we learned that in certain settings, PARP inhibitors may be the wrong choice. Several “Dear Health Care Provider” letters were issued by AstraZeneca, Clovis, and GSK to advise physicians to restrict the prescribing of olaparib, rucaparib, and niraparib.6,7
AstraZeneca and Clovis issued letters spurred by the final analysis of ARIEL4 and SOLO3 studies, 2 randomized trials that investigated, respectively, rucaparib and olaparib monotherapy compared with chemotherapy in recurrent ovarian cancer.8,9 In both cases patients randomized to PARP inhibitors may have experienced an overall survival decrement compared with those who received chemotherapy.
At the FDA’s request, Clovis has withdrawn rucaparib as a treatment for patients with recurrent BRCA-mutant ovarian cancer who had received 2 or more lines of chemotherapy, and AstraZeneca withdrew olaparib monotherapy in germline BRCA-mutant patients with recurrent ovarian cancer. Shortly after these withdrawals, GSK also withdrew its indication for niraparib as a treatment for women with HRD, platinum-sensitive ovarian cancer who have received 3 or more prior chemotherapies. Furthermore, based on the final overall survival analysis of the NOVA study, GSK also restricted its indication for niraparib maintenance for recurrent ovarian cancer to patients with germline BRCA mutations, due to evidence of an overall survival detriment in this setting.10
Positive study results
Fortunately, 2022 was not all bad news for PARP inhibitors in ovarian cancer. In June 2022, the ATHENA-MONO trial, a phase 3 double-blind randomized controlled trial, demonstrated that rucaparib maintenance in patients with newly diagnosed epithelial ovarian cancer was associated with a significantly longer progression-free survival compared with placebo.11 The effect was most pronounced in the BRCA-mutant/HRD population, with a median progression-free survival of 28.7 months in the rucaparib group compared with 11.3 months in the placebo group (HR, 0.47; 95% CI, 0.31–0.72). Thus, rucaparib was added to the list of PARP inhibitors approved for upfront maintenance therapy in epithelial ovarian cancer.
Similarly, the long-term overall survival analysis from the upfront trials SOLO-1 and PAOLA-1 showed an overall survival advantage of PARP inhibitor, compared with placebo, maintenance in patients with BRCA mutations or HRD tumors.12,13 ●
WHAT THIS EVIDENCE MEANS FOR PRACTICE
PARP inhibitor maintenance therapy after upfront chemotherapy in women with BRCA-mutant and HRD epithelial ovarian cancer has been game changing in ovarian cancer. However, PARP inhibitors have a more limited role than previously thought for patients with recurrent ovarian cancer.
PARP inhibitor maintenance therapy after upfront chemotherapy in women with BRCA-mutant and HRD epithelial ovarian cancer has been game changing in ovarian cancer. However, PARP inhibitors have a more limited role than previously thought for patients with recurrent ovarian cancer.