What are PARP inhibitors?
- PARP inhibitors are an oral medication that can be used as maintenance therapy after ovarian cancer treatment.
- Major new approvals make these medications a potential option as part of the first course of treatment as well when cancer comes back.
- There are currently three types of PARP inhibitors approved to treat ovarian cancer.
- All have similar side effects — which may include digestive issues like nausea, bloating, diarrhea, etc.
There are currently three types of PARP inhibitors available to women with ovarian cancer, Dr. Janelle Fauci, a gynecologic oncologist with Novant Health in Charlotte, North Carolina, told SurvivorNet. All three — Zejula (niraparib), Lynparza (olaparib), Rubraca (rucaparib) work in a similar way and have fairly similar side effects, with some important differences.
Read MoreWhat Are the Side Effects?
Common side effects for all three of the approved types of PARP inhibitors tend to involve some digestive issues, Dr. Fauci said. “The first month to two months of treatment, there can be some prominent G.I. (gastrointestinal) side effects — so things like nausea, bloating, vomiting and diarrhea are pretty common in the first 30 days or so,” she said.Women will also have to have their blood counts monitored regularly — similar to the way you would with chemotherapy.
“You have to have your blood counts monitored closely while on treatment,” Dr. Fauci said. “So, the first month or so we follow blood counts every week to make sure patients are not developing low hemoglobin or anemia, making sure platelet counts are normal and even the white count of the infection fighting cells can be low. So we follow blood counts weekly initially, and once we’ve found that those counts have stabilized and are not dropping, then you go to monthly blood monitoring.”
Who Can Benefit From PARP Inhibitors?
While initially women with a BRCA-1 or BRCA-2 genetic mutation had been shown to respond especially well to PARP inhibitors after recurrence, newer research has shown that women with the BRCA gene mutation (and indeed women of varying genetic makeups), can consider using PARP inhibitors throughout their treatment.
The Food and Drug Administration has approved niraparib for almost all women regardless of whether they have the BRCA mutation, as part of an initial course of treatment, or what’s called front-line treatment. 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 (homologous recombination deficient) tumors. Avastin is a blood vessel growth inhibitor, which works by starving the tumor of vital nutrients needed to grow.
However, Dr. Amanika Kumar of the Mayo Clinic who spoke to SurvivorNet, cautioned that women still need to speak with their doctor to evaluate the benefit of taking a PARP inhibitor to extend life, because there are very real side effects due to the toxicity of the drug. "Patients with HRD (homologous recombination deficiency) have a far better response than those without and those with BRCA mutations even more so. It is on us as clinicians to help patients understand the risks and benefits of treatment. Patients that have no mutation or HRD may choose not to go on maintenance (in fact I recommend they don't) because there is real toxicity to these meds."
What is HRD?
Homologous recombination deficiency is a genetic signature of cancer cells that have trouble repairing themselves, as can happen with the BRCA gene or other related genes. This may make the ovarian cancer cells more susceptible to treatment with PARP inhibitors.
Tumors with homologous recombination deficiencies exhibit specific clinical behaviors, and often have improved responses to treatments, such as platinum-based chemotherapy and PARP inhibitors, according to researchers.
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