TAMPA, FLORIDA — Moffitt Cancer Center presented phase II neoadjuvant clinical trial data at ASCO 2026 involving patients with HER2-positive early-stage breast cancer. "In this phase II clinical study, 47 patients, 24 hormone receptor-positive/HER2-positive, and 23 hormone receptor-negative/HER2-positive, early-stage breast cancers were enrolled at Moffitt Cancer Center between May of 2022 and October of 2025," said Hyo Han, a medical doctor at Moffitt Cancer Center.

"Primary endpoint of this study was pathologic complete response following neoadjuvant treatment for clinical trial, and it was 50% for hormone receptor-positive subgroup and 83% in hormone receptor-negative subgroup," Han stated.

"Dendritic cell vaccines were made from patient blood collected using procedure called apheresis and cells were trained with HER2 peptide that led to mature dendritic cells that was injected into the patient's breast tumor directly every week, six times in combination with the trastuzumab [Herceptin] and pertuzumab [Perjeta]," Han said. "And after 6 weeks of initial immunotherapy, patients received chemotherapy using weekly paclitaxel in combination with the trastuzumab and pertuzumab for 12 weeks." Following this neoadjuvant therapy, all patients underwent surgery, including either lumpectomy or mastectomy.

The study also evaluated circulating tumor DNA using a personalized tumor-informed assay, Signatera. "Baseline levels were available for 27 patients," Han said. "And 16 of those patients had a positive ctDNA at baseline. And of those patients, 76.5% of patients cleared ctDNA with neoadjuvant therapy prior to surgery." Additionally, "70% of patients cleared their ctDNA after only 6 weeks of dendritic cells in combination of Herceptin and Perjeta treatment without chemotherapy portion as well." Han noted, "We also have reported preliminary data showing that increased T-cell infiltration and tumor regression on patient biopsy in this poster."

"Intratumoral dendritic cell therapy in combination with trastuzumab-pertuzumab prior to neoadjuvant paclitaxel, Herceptin, and Perjeta therapy in early-stage HER2-positive breast cancer was well tolerated with manageable toxicity and it led to increased, enhanced immune cell infiltrations and ctDNA clearance with improved pathologic complete response in this patient population," Han concluded. Regarding toxicity, he added, "In this study, we also have evaluated... toxicity related to dendritic cell therapy was consistent with what was previously reported with manageable toxicity, including flu-like symptoms and some injection site discomfort."

"At Moffitt Cancer Center, we are currently conducting a clinical study using chemotherapy-free neoadjuvant therapy in the same patient population," Han said. "So current ongoing clinical trial is using dendritic cell intratumoral therapy in combination with Herceptin and Perjeta HER2-targeted therapy only for 12 weeks without paclitaxel chemotherapy."