AACR 2021: Using ctDNA Changes to Predict Response to Palbociclib-Based Therapy for Breast Cancer
Posted: Tuesday, April 27, 2021
During the virtual edition of the American Association for Cancer Research (AACR) Annual Meeting 2021, Joanne L. Blum, MD, PhD, of Baylor-Sammons Cancer Center, Dallas, and colleagues shared their findings on evaluating serial changes in circulating tumor DNA (ctDNA) dynamics from the POLARIS trial—an ongoing, prospective study of palbociclib in patients with hormone receptor (HR)-positive, HER2-negative advanced breast cancer (Abstract LB033). They proposed that particular mutations may not be drivers in resistance to treatment with palbociclib based on their determination of serial-blood based tumor genotyping data.
“Interim data indicate that even patients with ongoing detectable ctDNA have a best overall response of complete response, partial response, or stable disease with palbociclib for HR-positive/HER2-negative advanced breast cancer,” the investigators mentioned. “Dynamic changes of ctDNA mutations may be predictive for treatment response and may have clinical utility in disease surveillance monitoring.”
The study authors focused on 35 patients with HR-positive/HER2-negative advanced breast cancer who received at least 18 cycles of palbociclib plus an aromatase inhibitor (n = 16) or fulvestrant (n = 19) with a long-term clinical response. ctDNA was obtained through blood collection.
The median age of patients was 64 years. Most patients were White (85.7%), postmenopausal (82.9%), and had an Eastern Cooperative Oncology group score of 0 or 1 (88.6%). Recurrent, visceral, and de novo disease affected 24, 12, and 9 patients, respectively. Complete response was achieved in 6 patients, partial response was reached in 9, and 20 had stable disease; disease progression occurred in 2 patients.
The median number of somatic variants detected was four, with no ctDNA mutations detected in six patients. In 15 patients who achieved complete or partial response, very low or no detectable ctDNA burden or a decrease in ctDNA was noted. Of the 16 patients with stable disease, 12 had very low or no detectable burden or reduced ctDNA.
Disclosure: For full disclosures of the study authors, visit abstractsonline.com.