Nearly 80% of the 22,000 annual ovarian cancer diagnoses in the United States are found in late stages.

In fact, ovarian cancer is the fifth most frequent cause of cancer death among women. Although response rates to chemotherapy are high, 90% of the cancers will recur within two years. However, a new drug called niraparib is under investigation as maintenance treatment between cycles of platinum-based chemotherapy, and findings from phase III trials released in June have shown promise.

The researchers conducted a double-blind, placebo-controlled, international phase III trial involving more than 500 patients with recurrent ovarian cancer. The findings demonstrated that niraparib significantly prolonged progression-free survival (PFS) among patients who are germline BRCA mutation (gBRCAmut) carriers, among patients who are not germline BRCA mutation (non-gBRCAmut) carriers but who have homologous recombination deficient (HRD) tumors, and overall in patients who are not gBRCAmut carriers. 

Currently, no therapy is approved by the U.S. Food and Drug Administration for maintenance treatment of patients with recurrent ovarian cancer following response to platinum.

The researchers found that among patients who were gBRCAmut carriers, the median PFS for those treated with niraparib was 21.0 months, compared to 5.5 months for control (p < 0.0001). For patients who were non-gBRCAmut carriers but whose tumors were HRD positive, the median PFS with niraparib was 12.9 months, compared to 3.8 months for controls (p < 0.0001). 

Niraparib also showed PFS in the overall non-gBRCAmut cohort, which included patients with HRD-positive and HRD-negative tumors. In these groups, the median PFS for patients treated with niraparib was 9.3 months, compared to 3.9 months for controls (p < 0.0001).

The most common (≥ 10%) treatment-emergent grade 3 or 4 adverse events among all patients treated with niraparib were thrombocytopenia (28.3%), anemia (24.8%), and neutropenia (11.2%). Adverse events were generally managed via dose modifications. The discontinuation rate was 14.7% for niraparib-treated patients and 2.2% for controls. The rates of myelodysplastic syndrome or acute myeloid leukemia in the niraparib (1.3%) and control (1.2%) arms were similar. None of the patients died during study treatment.

The researchers noted that the trial results are encouraging for patients and their families and that the full study results will be available in fall 2016.