Alpelisib: a simple guide for patients with PIK3CA-mutated breast cancer

If your tumor tests positive for a PIK3CA mutation, your oncologist might mention alpelisib (brand name Piqray). It’s a targeted drug that blocks a pathway cancer cells use to grow. This page explains how it works, what side effects to watch for, and clear steps you can take to stay safe while on treatment.

Quick facts and how it works

Alpelisib is a PI3K alpha inhibitor. That means it stops a specific protein in cancer cells that helps them survive and multiply. It’s usually given with fulvestrant for hormone receptor–positive, HER2‑negative advanced breast cancer that has a PIK3CA mutation. The SOLAR‑1 trial showed that adding alpelisib helped people with that mutation live longer without disease worsening compared with fulvestrant alone.

Typical adult dosing is one pill taken once daily with food. Your doctor will decide the exact plan and may adjust the dose if side effects appear.

Practical tips for patients

Get the PIK3CA test before starting. Alpelisib works mainly for tumors with that mutation, so confirm it first. Ask your care team where the test will be done and how long results take.

Watch blood sugar closely. High blood sugar (hyperglycemia) is the most common and important side effect. Have fasting blood glucose checked before you start and often during treatment. If you have diabetes or prediabetes, discuss a glucose plan with your oncologist and your primary care doctor. Simple measures like monitoring at home and quick medical advice when numbers climb can prevent bigger problems.

Expect digestive side effects. Diarrhea, nausea, and decreased appetite happen for many people. Stay hydrated, use anti‑diarrheal meds as advised, and tell your team if vomiting or severe diarrhea starts. They can suggest dose changes or medicines to help.

Skin reactions are common. Rash and itching can appear early. Use mild cleansers, moisturize, and ask about topical steroids or antihistamines if a rash develops. Severe skin reactions are rare but need immediate attention.

Know other monitoring needs. Your doctor will likely check liver tests, electrolytes, and blood counts sometimes. Report new symptoms—shortness of breath, cough, or any unusual pain—right away.

Tell your team about all medicines and supplements. Many interactions are manageable, but your doctor needs the full list. Also avoid trying new over‑the‑counter remedies without checking first.

Plan for pregnancy prevention. Alpelisib can harm an unborn baby. Use effective contraception during treatment and for the time your doctor recommends after stopping the drug.

When to call your doctor: persistent high sugar readings, severe diarrhea, new shortness of breath, or a rapidly spreading rash. Early calls usually make side effects easier to control.

If you want more detail, ask your oncologist for the official prescribing information or a pharmacist consultation. Small actions—testing first, monitoring glucose, and reporting side effects quickly—make treatment safer and more effective.