Ovarian cancer is often diagnosed at an advanced stage due to the difficulty of early detection, and it is known for its high recurrence rate even after initial treatment.

First-line maintenance therapy aimed at delaying recurrence as much as possible after surgery and chemotherapy became a key strategy that determines treatment outcomes for ovarian cancer.

Recently introduced PARP inhibitors have emerged as a standard option for maintenance therapy, and the use of biomarkers to guide patient selection has been a major advancement, enabling better prediction of which patient subgroups are likely to benefit the most.

In an interview with Dailypharm, Professor Jae Kwan Lee of the Department of Obstetrics and Gynecology at Korea University Guro Hospital, and Dr. Bradley Monk of the Florida Cancer Specialists & Research Institute stressed the need for institutional support for personalized treatment of ovarian cancer.

Long-term efficacy of Zejula as first-line maintenance therapy for ovarian cancer proven

Ovarian cancer is difficult to diagnose at an early stage and often recurs after initial treatment, raising the importance of maintenance therapy.

This is why first-line maintenance therapy to delay recurrence as much as possible after surgery and chemotherapy has become a key strategy in ovarian cancer treatment.

Professor Lee said, "First-line maintenance therapy is becoming a critical turning point in ovarian cancer treatment. HRd (homologous recombination deficiency)-positive patients showed an average progression-free survival period extension of approximately 2 years when receiving first-line maintenance therapy after surgery. Given the high recurrence rate of ovarian cancer, maintaining remission for as long as possible is key to successful outcomes, and first-line maintenance therapy serves as a highly effective strategy in this regard."

One of the changes in the domestic treatment environment for ovarian cancer came with the expansion of reimbursement criteria for the PARP inhibitor Zejula (niraparib) to HRd-positive ovarian cancer in October last year.

The reimbursement extension of the PARP inhibitor Zejula was significant because of its biomarker.

Approximately 50% of all ovarian cancer patients are HRd-positive, and about half of them, or 25%, have BRCA gene mutations. In addition, studies continue to demonstrate the efficacy of PARP inhibitors in HRd-positive patients.

Professor Lee said, “In the past, reimbursement was limited to patients with BRCA mutations, so HRd-positive patients who were BRCA-negative could not choose to use Zejula due to the financial burden. However, since the reimbursement criteria were extended to include HRd-positive patients, many patients are actively starting Zejula treatment.”

Zejula is currently one of the most promising PARP inhibitors for first-line maintenance therapy for ovarian cancer. In particular, the long-term follow-up data from the PRIMA study published last year has enhanced the reliability of Zejula.

In the PRIMA trial, Zejula increased progression-free survival (PFS) by more than twofold in HRd-positive ovarian cancer patients compared to placebo.

Additionally, at the time of clinical confirmation, the median PFS in the Zejula treatment group was 24.5 months, compared to 11.2 months in the placebo group, showing a significant difference. The 5-year PFS rate was also 35%, approximately twice as high as that of the placebo group.

Dr. Monk stated, “Previously, there were concerns that long-term use of PARP inhibitors could lead to drug resistance, but this data confirms that such a possibility is low. These long-term follow-up results will serve as a strong source of reliability for doctors who have been hesitant about prescribing Zejula in the long term."

He further explained, “Zejula can be used as a first-line maintenance therapy for all patients who respond to platinum-based chemotherapy (all-comer), but it is known to show the most effective results in HRd-positive patients. Since approximately half of all ovarian cancer cases are classified as HRd-positive, Zejula is increasingly being considered as a key option when setting treatment strategies.”

“Diagnostic hurdles remain despite Zejula’s extended reimbursement for HRd-positive ovarian cancer”

One of the main reasons for the popularity of Zejula is its ease of administration. While other PARP inhibitors require twice-daily dosing, Zejula can be taken once daily, improving medication adherence.

Professor Lee said, “For patients to adhere to long-term maintenance therapy without becoming fatigued, treatment convenience is crucial. Zejula’s once-daily dosing regimen has had a positive impact on patients' ability to remain on therapy over the long term without discontinuation."

Dr. Monk added, "Zejula has the advantage of having relatively low drug-drug interactions, which makes it a safer option when used in combination with other drugs. This is a significant advantage for elderly patients with comorbidities or those receiving complex medication regimens.”

Meanwhile, with the expansion of reimbursement criteria for HRd-positive ovarian cancer, it has become essential to determine whether a patient is HRd-positive before establishing a treatment strategy, but access to such HRd diagnostic tests remains a barrier.

Currently, BRCA1/2 mutation testing for ovarian cancer patients is relatively affordable through national support programs and partial health insurance coverage. However, genomic panel testing required to confirm HRd status is not covered by insurance, leaving patients to bear the full cost of approximately KRW 2.5 million.

Professor Lee pointed out, “HRd testing is essential for HRd-positive patients to receive Zejula treatment, but the fact that the test is not covered by insurance and must be paid out of pocket is a major institutional contradiction. Policy improvements should be made so that HRd diagnostic tests can settle as a diagnostic tool accessible under the same criteria as BRCA tests.”

In contrast, access to HRd tests has been rapidly improving overseas.

Dr. Monk stated, “Currently, more than 10 companies in the United States offer HRd tests, and some provide the service at very low costs. HRd diagnostic tests can serve as an important basis for predicting treatment response to PARP inhibitors such as Zejula.”

For this reason, the Korean Society of Gynecologic Oncology is also known to be actively collecting supporting data to officially propose reimbursement for HRd tests to Korean health authorities.

If HRd tests are promptly covered by health insurance, patients will be able to receive the necessary testing without financial burden and fully enjoy the benefits of targeted maintenance therapy such as Zejula.

In addition, Professor Lee, who has been appointed as the President of the Korean Society of Gynecologic Oncology, emphasized his commitment to advancing precision medicine based on the genetic profiling of ovarian cancer.

Professor Lee stated, “The society plans to focus on how to diagnose and manage the genetic characteristics of ovarian cancer. In other countries, there are already detailed clinical guidelines in place for individuals with BRCA mutations, and I believe similar protocols are needed in Korea as well."

He concluded, "Since ovarian cancer often occurs alongside other cancers such as breast or endometrial cancer, collaboration with other specialties, including surgical departments, is essential. Establishing a multidisciplinary, patient-centered integrated care system through close coordination with various medical fields is another key priority for the society."