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Published on: February 3, 2015
89Zr-Trastuzumab PET/CT Imaging of HER2-Positive Breast Cancer for Predicting Pathological Complete Response after
D G J Linders1, M M Deken1, M A van Dam1
1Department of Surgery, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands.
Background:
Approximately 20% of invasive ductal breast malignancies are human epidermal growth factor receptor 2 (HER2)-positive. These patients receive neoadjuvant systemic therapy (NAT) including HER2-targeting therapies. Up to 65% of patients achieve a pathological complete response (pCR). These patients might not have needed surgery. However, accurate preoperative identification of a pCR remains challenging. A radiologic complete response (rCR) on MRI corresponds to a pCR in only 73% of patients. The current feasibility study investigates if HER2-targeted PET/CT-imaging using Zirconium-89 (89Zr)-radiolabeled trastuzumab can be used for more accurate NAT response evaluation.
Methods:
HER2-positive breast cancer patients scheduled to undergo NAT and subsequent surgery received a 89Zr-trastuzumab PET/CT both before (PET/CT-1) and after (PET/CT-2) NAT. Qualitative and quantitative response evaluation was performed.
Results:
Six patients were enrolled. All primary tumors could be identified on PET/CT-1. Four patients had a pCR and two a pathological partial response (pPR) in the primary tumor. Qualitative assessment of PET/CT resulted in an accuracy of 66.7%, compared to 83.3% of the standard-of-care MRI. Quantitative assessment showed a difference between the SUVR on PET/CT-1 and PET/CT-2 (ΔSUVR) in patients with a pPR and pCR of -48% and -90% (p = 0.133), respectively. The difference in tumor-to-blood ratio on PET/CT-1 and PET/CT-2 (ΔTBR) in patients with pPR and pCR was -79% and -94% (p = 0.133), respectively. Three patients had metastatic lymph nodes at diagnosis that were all identified on PET/CT-1. All three patients achieved a nodal pCR. Qualitative assessment of the lymph nodes with PET/CT resulted in an accuracy of 66.7%, compared to 50% of the MRI.
Conclusions:
NAT response evaluation using 89Zr-trastuzumab PET/CT is feasible. In the current study, qualitative assessment of the PET/CT images is not superior to standard-of-care MRI. Our results suggest that quantitative assessment of 89Zr-trastuzumab PET/CT has potential for a more accurate response evaluation of the primary tumor after NAT in HER2-positive breast cancer.
Insights
This study explored using 89Zr-trastuzumab PET/CT scans to assess neoadjuvant systemic therapy (NAT) response in HER2-positive breast cancer. Quantitative PET/CT imaging shows promise for more accurate response evaluation compared to standard MRI.
Area of Science:
- Oncology
- Nuclear Medicine
- Radiology
Background:
- Human epidermal growth factor receptor 2 (HER2)-positive breast cancer accounts for 20% of invasive ductal breast malignancies.
- Neoadjuvant systemic therapy (NAT) including HER2-targeting agents is standard for these patients, with up to 65% achieving pathological complete response (pCR).
- Accurate preoperative identification of pCR is challenging, as radiologic complete response (rCR) on MRI only corresponds to pCR in 73% of patients.
Purpose of the Study:
- To investigate the feasibility of using 89Zr-trastuzumab PET/CT imaging for more accurate NAT response evaluation in HER2-positive breast cancer.
- To compare the accuracy of 89Zr-trastuzumab PET/CT with standard MRI for assessing treatment response.
- To evaluate both qualitative and quantitative parameters of PET/CT imaging for response assessment.
Main Methods:
- A feasibility study involving HER2-positive breast cancer patients scheduled for NAT and surgery.
- Patients received 89Zr-trastuzumab PET/CT scans before (PET/CT-1) and after (PET/CT-2) NAT.
- Qualitative and quantitative response evaluations were performed on the PET/CT images.
Main Results:
- All six enrolled patients' primary tumors were identified on PET/CT-1.
- Four patients achieved pCR, and two had a pathological partial response (pPR).
- Quantitative assessment revealed significant differences in SUVr (ΔSUVr) and tumor-to-blood ratio (ΔTBR) between PET/CT-1 and PET/CT-2 in both pCR and pPR groups, suggesting potential for distinguishing responses.
Conclusions:
- 89Zr-trastuzumab PET/CT imaging is a feasible method for evaluating NAT response in HER2-positive breast cancer.
- Qualitative assessment of PET/CT was not superior to standard MRI.
- Quantitative assessment of 89Zr-trastuzumab PET/CT demonstrates potential for improved preoperative response evaluation of primary tumors after NAT.
