⁸⁹Zr-Trastuzumab PET/CT Imaging of HER2-Positive Breast Cancer for Predicting Pathological Complete Response after Neoadjuvant Systemic Therapy:A Feasibility Study

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.</p

Comparative study of the sensitivity of head and neck cell lines to methotrexate (MTX) and the analog 10-ethyl, 10-deazaaminopterin (10-EdAM)

Squamous cell lines cultured in vitro provide a potential test system for the selection of analogs that have an improved therapeutic index. The growth inhibitory effects of methotrexate and the new folate analog 10-ethyl, 10-deazaaminopterin were compared in three in vitro-cultured human head and neck squamous cell carcinoma cell lines. The inhibitory concentrations of the new analog were 10- to 100-fold lower than the inhibitory concentrations of methotrexate. The sensitivity of these three head and neck squamous cell carcinoma cell lines to both drugs was essentially the same as the sensitivity of a rhabdomyosarcoma cell line known to be very sensitive to methotrexate when the cell line is grown as a xenograft in athymic nude mice. These data indicate that 10-ethyl, 10-deazaaminopterin may be a new and effective agent against head and neck squamous cell carcinoma

Personalizing NSCLC therapy by characterizing tumors using TKI-PET and immuno-PET

Non-small cell lung cancer (NSCLC) therapy has entered a rapidly advancing era of precision medicine with an ever increasing number of drugs directed against a variety of specific tumor targets. Amongst these new agents, tyrosine kinase inhibitors (TKIs) and monoclonal antibodies (mAbs) are most frequently used. However, as only a sensitive subgroup of patients benefits from targeting drugs, predictive biomarkers are needed. Positron emission tomography (PET) may offer such a biomarker for predicting therapy efficacy. Some of the TKIs and mAbs that are in clinical use can be radioactively labeled and used as tracers. PET can visualize and quantify tumor specific uptake of radiolabeled targeting drugs, allowing for characterization of their pharmacokinetic behavior. In this review, the clinical potential of PET using radiolabeled TKIs (TKI-PET) and mAbs (immuno-PET) in NSCLC is discussed, and an overview is provided of the most relevant preclinical and clinical studies

[89Zr]Zr-rituximab PET/CT activity in patients with therapy refractory interstitial pneumonitis: a feasibility study

Recent studies on immune-mediated inflammatory lung diseases show encouraging treatment results with rituximab, a monoclonal antibody (mAb) against CD20-expressing B lymphocytes. The present pilot study aimed to explore the possibility to image CD20-expression in the lungs as future early predictor of treatment response. We describe a series of 10 patients with therapy refractory interstitial pneumonitis who were treated with rituximab (1000 mg at day 0 and day 14) and underwent PET/CT after the administration of [89Zr]Zr-N-suc-DFO-rituximab abbreviated as [89Zr]Zr-rituximab. [89Zr]-rituximab PET/CT of the chest was performed on day 3 and 6. [89Zr]Zr-rituximab PET/CT showed visual and quantifiable increased pulmonary activity in four patients. Other patients demonstrated no increased activity in the lungs. One patient developed a severe allergic reaction during infusion of the first 10% unlabeled rituximab after which rituximab infusion was ceased. Subsequent administration of [89Zr]Zr-rituximab, however, did not result in any adverse reaction. This patient demonstrated the highest uptake of [89Zr]Zr-rituximab in mediastinal lymph nodes and lung parenchyma compared to the other 9 patients who did receive the full dose rituximab before [89Zr]Zr-rituximab. This pilot study demonstrates that [89Zr]Zr-rituximab PET/CT imaging in patients with therapy refractory interstitial pneumonitis is feasible and shows lung-specific uptake in some patients. Further research with larger sample size should establish if the [89Zr]Zr-rituximab uptake correlates with treatment response to rituximab. The higher uptake in the absence of a full 1000 mg rituximab preload may suggest that future studies should consider [89Zr]Zr-rituximab imaging at low mAb dose before treatment with rituximab

89Zr-immuno-PET for imaging of long circulating drugs and disease targets: Why, how and when to be applied?

Positron emission tomography (PET) with 89Zr-labeled monoclonal antibodies (mAbs) or other targeted vehicles {e.g., peptides, nanoparticles and cells), collectively called "89Zr-immuno-PET", can be used for better understanding of disease targets and the in vivo behavior of targeted drugs. This will become increasingly important in the development of next generation mAbs, which are characterized by high potency and/or multiple binding domains. This review provides practical information for researchers who want to implement 89Zr-immuno-PET for answering their own biological and pathological questions or for steering their own drug development program. An overview is given of the reagents, labeling protocols, quality tests and critical steps to come to high quality 89Zr-conjugates, while possibilities for further improvement are discussed. Since PET has the advantage of allowing quantitative imaging, information is provided about standardization of 89Zr quantification. Issues are summarized for consideration when starting preclinical or clinical 89Zr-immuno-PET studies, to enable at the end unequivocal interpretation of results. Finally, many appealing examples are provided of what can be learned from 89Zr-immuno-PET studies, while future directions are outlined. Most of the current examples are still on the characterization of mAbs in oncology, but the review will show that 89Zr-immuno-PET harbors potential for many kinds of targeted drugs and diseases, as well as for elucidating biological processes

Phase I therapy study of 186re-labeled chimeric monoclonal antibody U36 in patients with squamous cell carcinoma of the head and neck

A phase I therapy study was conducted to determine the safety, maximum tolerated dose (MTD), pharmacokinetics, dosimetry, immunogenicity, and therapeutic potential of 186Re-labeled anti-CD44v6 chimeric monoclonal antibody (cMAb) U36 in patients with squamous cell carcinoma of the head and neck (HNSCC). The potential of a diagnostic study with 99mTc-cMAb U36 to predict the biodistribution of 186Re-cMAb U36 was evaluated. Methods: Thirteen patients with recurrent or metastatic HNSCC were given 750 MBq 99mTc-cMAb U36 (2 mg) followed 1 wk later by a single dose of 186Re-cMAb U36 (12 or 52 mg) in radiation dose-escalating steps of 0.4, 1.0, and 1.5 GBq/m2. After each administration, planar and SPECT images were obtained, and the pharmacokinetics and development of human antimurine as well as anti-cMAb responses were determined. Radiation absorbed doses to tumor, red marrow, and organs were calculated. Results: Administration was well tolerated, and excellent targeting of tumor lesions was seen in all patients. Dose-limiting myelotoxicity (thrombocytopenia being most prominent) was the only toxicity observed, resulting in grade 4 myelotoxicity in 2 patients treated with 1.5 GBq/m2. The MTD was established at 1.0 GBq/m2, at which a transient grade 3 thrombocytopenia was seen in 1 patient. One patient showed stable disease for 6 mo after treatment at the MTD. The 2 patients with dose-limiting myelotoxicity showed a marked reduction in tumor size. The reduction was of short duration and, therefore, not considered an objective response. Tumor absorbed doses at MTD ranged from 3.0 to 18.1 Gy. Red marrow doses ranged from 20 to 112 cGy (mean, 51 ± 16 cGy/GBq) and correlated with platelet nadir (r = 0.8; P < 0.01). Pharmacokinetics varied between patients treated at the same dose level and were accurately predicted by the diagnostic procedure. Five patients experienced a human anti-cMAb response, 1 of which was a human antimouse antibody response. Conclusion: This study shows that 186Re-cMAb U36 can be safely administered, with dose-limiting myelotoxicity at 41 mCi/m2. The use of cMAb U36 instead of its murine counterpart did not decrease the induction of human antibody responses. The availability of a 99mTc-labeled diagnostic study that can predict the pharmacokinetics of 186Re-cMAb U36 offers the possibility of using such a study for selection of a safe radioimmunotherapy dose

⁸⁹Zr-Trastuzumab PET/CT Imaging of HER2-Positive Breast Cancer for Predicting Pathological Complete Response after Neoadjuvant Systemic Therapy: A Feasibility Study

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.RST/Radiation, Science and Technolog