PARP Inhibitors: Understanding the Side Effects

PARP inhibitors are available to all women, though women with BRCA gene mutations or who are HRD proficient may benefit the most from these drugs.

However, the American Society of Clinical Oncology (ASCO) guidelines recommend PARP inhibitors be offered to women, with or without genetic mutations, who are newly diagnosed with stage III or IV ovarian cancer and have improved with chemotherapy.

• Zejula (niraparib) has been approved by the FDA for all women with newly diagnosed ovarian cancer regardless of the patient’s HRD or BRCA status. The drug is used after successful treatment with a platinum-based chemotherapy, the mainstay chemotherapy for ovarian cancer.
• 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. Avastin is a blood vessel growth inhibitor, which works by starving the tumor of vital nutrients needed to grow.

PARP inhibitors can be beneficial for women with ovarian cancer, but they are not without their fair share of side effects. Before beginning treatment with PARP inhibitors for ovarian cancer, it can help to prepare for some of the more common side effects, including:

• Nausea
• Fatigue
• Anemia (low red blood cells)

But, according to Dr. Colleen McCormick with Legacy Cancer Institute, the vast majority of women tend to see these side effects subside after the first couple of weeks on PARP inhibitors.

“If you can get through the first few weeks, your body kind of adapts to the PARP, you get used to it, and that nausea and queasiness goes away,” says Dr. McCormick, adding that there are also ways to preemptively address some of these side effects. For example, your doctor can prescribe you some anti-nausea medications.

Dr. McCormick also points out that PARP inhibitors can cause changes to the bone marrow. Your bone marrow is responsible for producing white blood cells, which fight infection, and red blood cells, which carry oxygen throughout the body.

PARP inhibitors can:

• Lower red blood cell counts, which can make you anemic
• Lower white blood cell counts, which can make you susceptible to infection
• Lower platelet counts, which can make you susceptible to bleeding

Different PARP inhibitors can affect these cell types in different ways, but as Dr. McCormick cautioned, “In general, it’s something that we have to really look out for and watch very carefully.”

In some cases — especially for women who are just coming off of chemotherapy — side effects can make it so that it becomes necessary to take a break from the medication and/or to adjust dosing. It’s always a good idea to keep your doctor in the loop about any and all of the side effects you’re experiencing, no matter how minor.