Poly (ADP-ribose) polymerase (PARP) inhibitors are a key component of treatment for germline BRCA-mutated (gBRCAm) cancers of multiple tumor types. PARP inhibition can result in cancer cell death when BRCA function is absent, and the cancer cells are unable to repair DNA damage.
Traditionally used in later-line platinum sensitive metastatic ovarian cancer treatment regardless of BRCA status, one PARP inhibitor (olaparib) has recently been approved as frontline maintenance in germline, somatic, or suspected BRCAm ovarian, fallopian tube, or primary peritoneal cancers. This approval, granted in Fall 2018, started a paradigm shift and will result in more patients taking PARP inhibitors and for longer periods of time.
FDA-approved PARP inhibitors for advanced ovarian, fallopian tube, and peritoneal cancers include olaparib (frontline), rucaparib (later-line), and niraparib (later-line). Similarly, 2 PARP inhibitors have recently been approved for gBRCAm metastatic breast cancer, namely olaparib and talazoparib. Ongoing studies are evaluating olaparib, rucarabib and niraparib in BRCA-positive metastatic prostate cancer and veliparib in BRCA-positive metastatic pancreatic cancer.
Nurses should understand treatment expectations for PARP inhibitors, including common side effects, symptom management, and key points for patient and family counseling. PARP inhibitors are oral, generally well-tolerated, and often a welcome alternative to standard-of-care chemotherapy.
The most common adverse effects are myelosuppression, nausea, vomiting and fatigue. Ongoing monitoring of blood counts is usually indicated at least monthly and, in the case of niraparib, can be as often as weekly. Prophylactic antiemetic medications may be indicated for some PARP inhibitors, especially olaparib and rucaparib. Additionally, modification of diet (small, frequent, bland meals) and timing of medication may be necessary. Interventions for myelosuppression will likely involve holding the drug and/or dose reduction.
Also important, nurses should be aware of possible food and drug interactions while counseling families. For example, patients taking olaparib should avoid grapefruit and seville oranges, while concomitant use of talazoparib and carvedilol, verapamil, amiodarone, or clarithromycin are contraindicated.
All PARP inhibitors have a small risk of myelodysplastic syndrome (MDS) and are potentially teratogenic. Counseling for both men and women on the importance of birth control during and for 6 months after use is crucially important. Key teaching points for patients and families include the overall good tolerability and improved quality of life experienced while taking PARP inhibitors.