Side Effects of PARP Inhibitors

“It’s really important while you’re on maintenance therapy, that you’re able to stay healthy and maintain your quality of life,” says Dr. Lisa Diver, a gynecologic oncologist at Stanford University. “This is the remission time that you worked so hard for and we certainly don’t want you feeling sick while you should be out celebrating the fact that you finished chemotherapy.”

PARP Inhibitors Explained

After initial chemotherapy, studies show that PARP inhibitors can reduce the risk of recurrence. In fact, studies suggest that using PARP inhibitors either as first-line therapy, maintenance therapy, or both, significantly extends the length of time patients are cancer-free or their cancer worsens.

PARP Inhibitors for ovarian cancer include:

• Niraparib (ZEJULA)
• Olaparib (LYNPARZA)
• Rucaparib (RUBRACA)

PARP Inhibitor Side Effects

Unfortunately, like all cancer therapies, PARP inhibitors come with side effects. Whether or not you’ll experience significant side effects depends on several factors, including which PARP inhibitor you’re taking, what dose you’re ingesting, and whether you’re using it alone or in combination with other therapies.

“While there’s a long list of side effects that you’ll receive in the medication information with your drug, the most common one that we see in the clinic is fatigue,” Dr. Diver says. Rarely, and in severe cases, doctors may prescribe stimulant medication to combat fatigue.

In addition to fatigue, side effects of most PARP inhibitor protocols include:

• Nausea
• Vomiting
• Stomach upset

These side effects, too, can be addressed with medication. In fact, the anti-nausea medications doctors prescribe for chemotherapy-associated nausea can also benefit patients who are taking PARP inhibitors. They include:

• Odanesetron (Zofran)
• Granisetron (Kytril)
• Olanzapine

Blood Count Changes

Since PARP inhibitors disrupt how cells repair damaged DNA, killing off tumor cells and healthy cells simultaneously, the bone marrow and blood cells may take a hit. You might experience anemia, low blood cell counts, and reduced platelet counts.

With these changes in blood cells and platelets, patients may notice fatigue, light-headedness, even easy bruising and excessive bleeding. That’s why it’s important to keep your doctor informed about any side effects you’re experiencing as a result of treatment.

“Even though we have recommended starting doses, we never know exactly what dose of the medication is going to be exactly right for each individual patient,” Dr. Diver says. “So it’s really important that your doctor continues to follow you and check your labs to make sure that we find just the right dose for you.”

Mitigating Side Effects

Fortunately, there are a number of things doctors and patients can do to help minimize the side effects of PARP inhibitor treatment.

On the physician side:

• Discontinue treatment for a brief time period
• Reduce the dose
• Transition to another PARP inhibitor to see if there’s any improvement

On the patient side:

• Exercise: While it may be counterintuitive, exercise can also help alleviate side effects, especially fatigue. In fact, performing specific exercises and moving your body can help alleviate symptoms like neuropathy and enhance recovery. “Some of the physical therapy providers here in our region provide cancer renewal types of physical therapy that really work at building strength and mobility,” Dr Parker says.
• Eat well: Even though nausea may interfere with your ability to eat a healthful diet, it’s important to make sure that you’re eating appropriately, getting enough protein, and not losing weight.

• Sleep: Since treatment with PARP inhibitors may cause fatigue, it’s especially important to maintain your regular sleep-wake cycle while on treatment. Sticking to a set sleep schedule will not only reduce fatigue, but it may help you recover more quickly by keeping energy levels high during the daytime hours.

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."

The side effects of PARP inhibitors can be severe in some patients, and doctors have to closely monitor patients taking these drugs.

Still worried about starting treatment with a PARP inhibitor? Talk to your doctor about all available treatment options so you can make an informed decision. Ovarian cancer treatment is complex, but doctors have more tools at their disposal than ever before.

 

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