PET Scans May Identify Patients With Breast Cancer Who May Not Need Chemo

A PET scan may help doctors determine whether certain patients with HER2-positive early breast cancer require chemotherapy in addition to other treatments.

Treating patients with HER2-positive early breast cancer based on positron emission tomography (PET) scan results led to improved three-year invasive disease-free survival (iDFS) and helped decrease the number of patients receiving unnecessary chemotherapy, according to a study.

The National Cancer Institute defines iDFS as the time after treatment when patients with cancer no longer show signs or symptoms of that invasive cancer.

Specifically, researchers from a study published in The Lancet demonstrated that a PET-based, pathological complete response (pCR)-adapted approach promoted a three-year iDFS rate of 94.8%. A pCR is the lack of signs of cancer after treatment, according to the National Cancer Institute.

The PET scan approach includes a type of radiotracer (markers that follow a pathway) called FDG, according to Cedars-Sinai. The FDG substance is injected into patients, which allows visualization of pathways.

According to Dr. Maria Hafez, this approach with the radiotracer helps doctors “diagnose and monitor various conditions,” she told CURE®.

“We know that standard imaging modalities, such as X-rays, CT and MRI [scans, are] always great,” Hafez explained. “[We’re] allowed to see like great details, visualization of healthy and diseased tissue. However, some diseases do not have structural anatomic abnormalities or do not manifest until a later stage of the disease. So, therefore, functional imaging such as PET or CT scans can complement those structural modalities to overcome some deficiencies in those other images.”

Hafez is the director of clinical breast cancer research and an assistant professor at Jefferson Health at the Sidney Kimmel Cancer Center in Philadelphia.

About the Trial

Researchers evaluated data from 356 patients with HER2-positive, stage 1-3A operable breast cancer, who were divided into two groups. In group A, there were 71 patients who received treatment with two chemotherapies (docetaxel and carboplatin), plus Herceptin (trastuzumab) and Perjeta (pertuzumab).

The 285 patients in group B received Herceptin plus Perjeta without chemotherapy, according to the published study. This group had their treatment guided by PET scans.

For patients in group B who only received Herceptin and Perjeta, the estimated three-year iDFS was 94.8%, researchers established.

The study’s results showed that certain patients could omit receiving chemotherapy after the F18-FDG-PET scan. Patients in group B who did not respond to treatment, per findings in the the F18-FDG-PET scan, and did not have a pCR were treated with the chemotherapy-containing regimen from group A after surgery. However, patients from this group who did respond to the initial regimen but did not have a pCR were not treated with chemotherapy after surgery.

“Most patients with stage 2 or 3 HER2[-positive] breast cancer will receive chemotherapy plus HER2-directed therapies,” explained Dr. Casey Degen. “For many patients, the standard of care is to get what's called neoadjuvant (presurgical) chemotherapy with HER2-directed therapy. It’s [typically] a one-size-fits-most approach. There’s not too much tailoring.”

Degen is a hematologist, medical oncologist, director of clinical research and breast cancer lead at Jefferson Health Northeast.

However, she noted that the study from The Lancet helped tailor patients’ treatments more. By using a chemotherapy de-escalation or escalation approach — meaning that chemotherapy is only given to patients when they need it — patients could receive the most benefit according to their responses.

“The study really attempted to determine if there are certain patients who don’t need the chemotherapy portion of this regimen,” she said. “So when they looked at the outcomes, they were excellent across all groups. There was actually about a third of patients who completed their therapy without any chemotherapy.”

Additionally, since the chemotherapy-containing group had a higher instance of moderate to severe side effects, patients who do not need chemotherapy would also be avoiding toxicities that come along with the drugs.

“So that's a really significant number of patients that were spared from some of the very challenging effects of chemo like neuropathy and hair loss and secondary cancers,” Degen explained.

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