Evaluating Bevacizumab and PARP Inhibitors as Important Treatment Options

If you’ve been diagnosed with ovarian cancer, you’ll probably need to decide whether to enroll in “maintenance therapy” after chemotherapy and surgery. Ovarian cancer often recurs in women who’ve been through an initial round of treatment, and maintenance therapy seeks to keep the cancer from coming back for as long as possible.

Maintenance therapy often involves using drugs to keep the cancer in remission longer. Two options for maintenance are a drug known as a PARP inhibitor and/or another drug known as Bevacizumab (or Avastin). These drugs can also be used in combination.

To understand these two drugs and which to choose for maintenance therapy, we spoke to noted gynecological oncologist Dr. Michael Birrer, who underscored the importance of the question:

RELATED: What is a PARP inhibitor and When Should a Woman Use It?

“How do you decide what patients should get Bevacizumab vs PARP? That’s really the million dollar question,” says Birrer.

How Do PARP Inhibitors Work?

PARP inhibitors work by blocking an enzyme—known as PARP—used by cells to repair damage to their DNA. Without normal functioning PARP, tumor cells will accumulate more and more DNA damage, and eventually die. According to Dr. Birrer, PARP inhibitors are most effective in women with a BRCA mutation. “If patients have either germline or somatic BRCA1/2 mutations that, when possible, they should get a PARP inhibitor,” he says. This is because women who have a BRCA mutation are more receptive to treatment with a PARP inhibitor. Tumor cells with BRCA mutations have problems repairing DNA already, and the PARP inhibitors make that worse, causing cancer cells to die. Learn more about the side effects of PARP inhibitors here.

However, not all women have a BRCA mutation, says Birrer. “You need to recognize that you’re looking at about 20 percent of the patient population.” Still, for women without a BRCA mutation, PARP inhibitors have still been shown to have some benefit.

Three Major PARP Inhibitors

Though they are approved for different purposes, the three PARP inhibitors currently available for ovarian cancer treatment are:

• Zejula (niraparib)
• Lynparza (olaparib)
• Rubraca (rucaparib)

Zejula has been approved by the FDA for all women with newly-diagnosed ovarian cancer irrespective of whether the tumor is HRD. The drug is used after successful treatment with a platinum-based chemotherapy, the mainstay chemotherapy for ovarian cancer.

The PARP inhibitor Lynparza (olaparib) is approved for women newly diagnosed with ovarian cancer and with a germline or somatic mutation in BRCA1/2.

Lynparza is also approved in combination with Avastin (bevacizumab) for women with HRD.

Unfortunately, too often, ovarian cancer comes back.

For women with ovarian cancer who have had a recurrence and responded to platinum-based chemotherapy, Lynparza, Zejula and Rubraca (rucaparib) are FDA approved for use as a maintenance therapy, regardless of whether a woman has a BRCA mutation or HRD.

For some women who have had prior chemotherapy treatments, Rubraca, Zejula or Lynparza may also be options. These uses are based on factors such as number of prior therapies and BRCA mutation or HRD.

How Does Avastin (bevacizumab) Work?

Bevacizumab works by preventing blood flow to tumors. It blocks the tumor from growing blood vessels, which cuts off the oxygen supply to the tumor. This can stop the tumor from growing and ultimately kill it. The drug works by targeting a protein called vascular endothelial growth factor, a critical protein for blood vessel growth. This targeting blocks angiogenesis, the process by which new blood vessels are formed out of ones already in existence.

Using Bevacizumab With PARPs

So far, the PARP inhibitor Lynparza is approved in combination with Avastin (bevacizumab) for women whose cancer cells have a high degree of a characteristic called “homologous recombination deficiency” (HRD) — which can come hand in hand with a BRCA mutation.

Learn more about SurvivorNet's rigorous medical review process.