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.

Correction to: [89Zr]Zr-cetuximab PET/CT as biomarker for cetuximab monotherapy in patients with RAS wild-type advanced colorectal cancer

Missing Electronic Supplementary Materials.

[89Zr]Zr-cetuximab PET/CT as biomarker for cetuximab monotherapy in patients with RAS wild-type advanced colorectal cancer

PURPOSE

One-third of patients with RAS wild-type mCRC do not benefit from anti-EGFR monoclonal antibodies. This might be a result of variable pharmacokinetics and insufficient tumor targeting. We evaluated cetuximab tumor accumulation on [⁸⁹Zr]Zr-cetuximab PET/CT as a potential predictive biomarker and determinant for an escalating dosing strategy.

PATIENTS AND METHODS

PET/CT imaging of [⁸⁹Zr]Zr-cetuximab (37 MBq/10 mg) after a therapeutic pre-dose (500 mg/m² ≤ 2 h) cetuximab was performed at the start of treatment. Patients without visual tumor uptake underwent dose escalation and a subsequent [⁸⁹Zr]Zr-cetuximab PET/CT. Treatment benefit was defined as stable disease or response on CT scan evaluation after 8 weeks.

RESULTS

Visual tumor uptake on [⁸⁹Zr]Zr-cetuximab PET/CT was observed in 66% of 35 patients. There was no relationship between PET positivity and treatment benefit (52% versus 80% for PET-negative, P = 0.16), progression-free survival (3.6 versus 5.7 months, P = 0.15), or overall survival (7.1 versus 9.4 months, P = 0.29). However, in 67% of PET-negative patients, cetuximab dose escalation (750-1250 mg/m²) was applied, potentially influencing outcome in this group. None of the second [⁸⁹Zr]Zr-cetuximab PET/CT was positive. Eighty percent of patients without visual tumor uptake had treatment benefit, making [⁸⁹Zr]Zr-cetuximab PET/CT unsuitable as a predictive biomarker. Tumor SUV_peak did not correlate to changes in tumor size on CT (P = 0.23), treatment benefit, nor progression-free survival. Cetuximab pharmacokinetics were not related to treatment benefit. BRAF mutations, right-sidedness, and low sEGFR were correlated with intrinsic resistance to cetuximab.

CONCLUSION

Tumor uptake on [⁸⁹Zr]Zr-cetuximab PET/CT failed to predict treatment benefit in patients with RAS wild-type mCRC receiving cetuximab monotherapy. BRAF mutations, right-sidedness, and low sEGFR correlated with intrinsic resistance to cetuximab.

Perioperative PET/CT lymphoscintigraphy and fluorescent real-time imaging for sentinel lymph node mapping in early staged colon cancer

Purpose

Using current optical imaging techniques and gamma imaging modalities, perioperative sentinel lymph node (SLN) identification in colon cancer can be difficult when the SLN is located near the primary tumour or beneath a thick layer of (fat) tissue. Sentinel lymph node mapping using PET/CT lymphoscintigraphy combined with real-time visualization of the SLN using near-infrared imaging has shown promising results in several types of cancer and may facilitate the successful identification of the number and location of the SLN in early colon cancer.

Methods

Clinical feasibility of PET/CT lymphoscintigraphy using preoperative endoscopically injected [⁸⁹Zr]Zr-Nanocoll and intraoperative injection of the near-infrared (NIR) tracer Indocyanine Green (ICG) was evaluated in ten early colon cancer patients. Three preoperative PET/CT scans and an additional ex vivo scan of the specimen were performed after submucosal injection of [⁸⁹Zr]Zr-Nanocoll. All SLNs and other lymph nodes underwent extensive pathological examination for metastases. A histopathological proven lymph node visible at preoperative PET/CT and identified at PET/CT of the specimen was defined as SLN.

Results

A total of 27 SLNs were harvested in seven out of eight patients with successful injection of both tracers. In one patient no SLNs were assigned preoperatively. In two patients injection of [⁸⁹Zr]Zr-Nanocoll failed due to incorrect needle positioning. Twenty-one (78%) SLNs were found intraoperatively using NIR-imaging. Eleven of the 27 (41%) SLNs were located near the primary tumour (< 2 cm). Those six SLNs not found intraoperatively with NIR-imaging were all located close to the tumour. In all seven patients at least one SLN could be assigned at preoperative imaging 24 h after tracer administration. One SLN contained metastases detected by immunohistochemistry. No metastases were found in the non-SLNs.

Conclusions

This study shows the potential of preoperative PET/CT lymphoscintigraphy to inform the surgeon about the number and location of SLNs in patients with early colon cancer. The additional use of NIR-imaging allows for intraoperative identification of these SLNs which are invisible with conventional white light imaging. Further research is necessary to improve and simplify the technique. We recommend perioperative SLN identification using a preoperative lymphoscintigraphy scan just before surgery approximately 24 h after injection. Additionally a postoperative scan of the specimen combined with intraoperative real-time NIR-imaging should be performed.

Electronic supplementary material

The online version of this article (10.1007/s00259-019-04284-w) contains supplementary material, which is available to authorized users.

90Nb – a potential PET nuclide: production and labeling of monoclonal antibodies

Fast progressing immuno-PET gives reasons to develop new potential medium-long and long-lived radioisotopes. One of the promising candidates is 90Nb. It has a half-life of 14.6 h, which allows visualizing and quantifying processes with medium and slow kinetics, such as tumor accumulation of antibodies and antibodies fragments or polymers and other nanoparticles. 90Nb exhibits a high positron branching of 53% and an optimal energy of β + emission of E mean=0.35 MeV only. Consequently, efficient radionuclide production routes and NbV labeling techniques are required.

90Nb was produced by the 90Zr(p,n) 90Nb nuclear reaction on natural zirconium targets. No-carrier-added (n.c.a.) 90Nb was separated from the zirconium target via a multi-step separation procedure including extraction steps and ion-exchange chromatography. Protein labeling was exemplified using the bifunctional chelator desferrioxamine attached to the monoclonal antibody rituximab. Desferrioxamine was coupled to rituximab via two different routes, by the use of N-succinyl-desferrioxamine (N-suc-Df) and by means of the bifunctional derivative p-isothiocyanatobenzyl-desferrioxamine B (Df-Bz-NCS), respectively. Following antibody modification, labeling with 90Nb was performed in HEPES buffer at pH 7 at room temperature. In vitro stability of the radiolabeled conjugates was tested in saline buffer at room temperature and in fetal calf serum (FCS) at 37 ºC.

The selected production route led to a high yield of 145 ± 10 MBq/μA h of 90Nb with high radioisotopic purity of >97%. This yield may allow for large scale production of about 10 GBq 90Nb. The separation procedure resulted in 76–81% yield. The Zr/90Nb decontamination factor reaches 107. Subsequent radiolabeling of the two different conjugates with 90Nb gave high yields; after one hour incubation at room temperature, more than 90% of 90Nb-Df-mAb was formed in both cases. At room temperature in aqueous solution, both 90Nb-Df-mAb constructs were more than 99% stable over a period of 18 d.

The developed production and separation strategy provided 90Nb with purity appropriate for radiolabeling applications. Labeling and stability studies proved the applicability of 90Nb as a potential positron emitter for immuno-PET.

Sentinel node procedure of the sigmoid using indocyanine green: feasibility study in a goat model

BACKGROUND

The sentinel lymph node (SLN) procedure alter the strategy for the treatment of patients with colon cancer. New techniques emerge that may provide the surgeon with a tool for accurate intraoperative detection of the SLNs.

METHODS

An SLN procedure of the sigmoid was used in six goats. During laparoscopy, the near-infrared dye indocyanine green (ICG) was injected into the subserosa of the sigmoid via a percutaneously inserted needle during four experiments and in the submucosa during colonoscopy in two experiments. After injection, the near-infrared features of a newly developed laparoscope were used to detect the lymph vessels and SLNs. At the end of the procedure, 2 h after injection, all the goats were killed, and autopsy was performed. During postmortem laparotomy, the sigmoid was removed and used for confirmation of ICG node uptake.

RESULTS

In all the procedures, the lymph vessels were easily detected by their bright fluorescent emission. In the first two experiments, no lymph nodes were detected. In the subsequent four experiments, human serum albumin was added to the ICG solution before injection to enable better lymph node entrapment. In all four experiments, at least one bright fluorescent lymph node was found after the lymph vessels had been tracked by their fluorescent guidance. The mean time between injection and SLN identification was 10 min. In two cases, the SLNs were located up to 5 mm into the fat tissue of the mesentery and were not seen by regular vision of the laparoscope. By switching on the near-infrared features of the scope, a clear bright dot became visible, which increased in intensity after opening of the mesentery.

CONCLUSION

The SLN procedure for the sigmoid using near-infrared laparoscopy in the goat is a very promising technique. Achievements described in this report justify a clinical trial on the feasibility of ICG-guided SLN detection in humans.

Characterisation and radioimmunotherapy of L19-SIP, an anti-angiogenic antibody against the extra domain B of fibronectin, in colorectal tumour models

Angiogenesis is a characteristic feature of tumours and other disorders. The human monoclonal antibody L19- SIP targets the extra domain B of fibronectin, a marker of angiogenesis expressed in a range of tumours. The aim of this study was to investigate whole body distribution, tumour localisation and the potential of radioimmunotherapy with the L19-small immunoprotein (SIP) in colorectal tumours. Two colorectal tumour models with highly different morphologies, the SW1222 and LS174T xenografts, were used in this study. Localisation and retention of the L19-SIP antibody at tumour vessels was demonstrated using immunohistochemistry and Cy3-labelled L19-SIP. Whole body biodistribution studies in both tumour models were carried out with ¹²⁵I-labelled L19-SIP. Finally, ¹³¹I-labelled antibody was used to investigate the potential of radioimmunotherapy in SW1222 tumours. Using immunohistochemistry, we confirmed extra domain B expression in the tumour vasculature. Immunofluorescence demonstrated localisation and retention of injected Cy3-labelled L19-SIP at the abluminal side of tumour vessels. Biodistribution studies using a ¹²⁵I-labelled antibody showed selective tumour uptake in both models. Higher recorded values for localisation were found in the SW1222 tumours than in the LS174T (7.9 vs 6.6 %ID g⁻¹), with comparable blood clearance for both models. Based on these results, a radioimmunotherapy study was performed in the SW1222 xenograft using ¹³¹I-Labelled L19-SIP (55.5 MBq), which showed selective tumour uptake, tumour growth inhibition and improved survival. Radio- and fluorescence-labelled L19-SIP showed selective localisation and retention at vessels of two colorectal xenografts. Furthermore, ¹³¹I-L19-SIP shows potential as a novel treatment of colorectal tumours, and provides the foundation to investigate combined therapies in the same tumour models.

[Radio-immunotherapy for B-cell non-Hodgkin lymphoma]

Radio-immunotherapy is a new treatment modality for patients with B-cell non-Hodgkin lymphoma. In radio-immunotherapy, a therapeutic radionuclide is coupled to a monoclonal antibody directed against a tumour-specific or tumour-associated antigen. Biodistribution studies and dosimetry are used in the planning of radio-immunotherapy. Clinical studies, notably in patients with indolent non-Hodgkin lymphoma, have demonstrated the clinical feasibility and efficacy of this treatment. The use of a high dose ofradio-immunotherapy in combination with (high-dose) chemotherapy and peripheral stem-cell transplantation constitutes a supplemental treatment for patients who respond insufficiently or not at all to standard therapy. The exact place of radio-immunotherapy in the treatment of patients with non-Hodgkin lymphomas is not yet clear.

In vitro evaluation of the astatinated chimeric monoclonal antibody U36, a potential candidate for treatment of head and neck squamous cell carcinoma

PURPOSE

The purpose of this study was to analyse the properties of the astatinated chimeric MAb (cMAb) U36 as a conjugate to selectively target and eradicate head and neck squamous cell carcinoma (HNSCC).

METHODS

cMAb U36 was labelled with 211At via the linker N-succinimidyl 4-(trimethylstannyl)benzoate (SPMB). The quality of the conjugate was extensively evaluated for binding and internalisation capacity, and compared with 125I-SPMB-cMAb U36. The cellular toxicity of the astatinated conjugate was assessed in two types of in vitro growth assay and compared with 131I-labelled cMAb U36 (directly labelled).

RESULTS

Comparisons between 211At-cMAb U36 and 125I-cMAb U36 demonstrated an optimal functional capacity of the labelled products. Immunoreactivity and affinity assays showed high immunoreactive fractions (>93%), and an affinity in good agreement between the astatinated and iodinated antibodies. For both conjugates, specific binding to HNSCC cells could be demonstrated, as well as some internalisation. Retention of the astatinated conjugate was just slightly lower than for the iodinated conjugate and still reasonable for therapeutic use (31+/-2% vs 42.6+/-1.0% at 22 h), demonstrating no adverse effects from astatination of the antibody. Studies on cellular toxicity demonstrated a dose-dependent and antigen-specific cellular toxicity for 211At-cMAb U36, with about 10% cell survival at 50 decays per cell. The 131I-labelled conjugate was not as efficient, with a surviving cell fraction of about 50% at 55 decays per cell.

CONCLUSION

These results indicate that 211At-cMAb U36 might be a promising future candidate for eradicating HNSCC micrometastases in vivo.

Photosensitizer-antibody conjugates for detection and therapy of cancer

Photodynamic therapy (PDT) is a promising approach for the treatment of superficially localized tumors. A limitation, however, is the lack of selectivity of the photosensitizers, which can result in severe toxicity. In this overview, the possibilities for using monoclonal antibodies (MAbs) for selective delivery of photosensitizers to tumors, are discussed. This approach is called photoimmunotherapy (PIT). For PIT to be successful, sufficient amounts of sensitizer should be coupled to the MAb without altering its biological properties. A challenging aspect herein is the hydrophobicity of therapeutic photosensitizers. Options for direct and indirect coupling of photosensitizers to MAbs are evaluated, while pros and cons are indicated. Special attention is paid to the quality testing of photoimmunoconjugates, as this information is important for further optimization of PIT. Results obtained thus far with PIT in in vitro and in vivo model systems are discussed. Despite the encouraging progress made, showing the high selectivity of photoimmunoconjugates, PIT still awaits initial clinical evaluation.

Radioimmunodiagnosis of lymph node metastases in head and neck cancer

INTRODUCTION

Reliable staging of the neck remains a diagnostic challenge in head and neck squamous cell carcinoma (HNSCC) patients. Monoclonal antibodies (MAbs) directed against tumour-associated antigens can be used for selective tumour targeting. When labelled with a gamma-emitting radionuclide like 99mTechnetium, such MAbs can be used for tumour detection by radioimmunoscintigraphy (RIS).

OBJECTIVE

The aim of this study was to assess the potential of RIS for the detection of lymph node metastases in HNSCC patients.

PATIENTS AND METHODS

In 49 patients with HNSCC, who were scheduled to undergo surgery including neck dissection, RIS using 99mTc-labelled squamous cell specific MAb E48 or U36 administered intravenously was compared with clinical palpation, computed tomography (CT), magnetic resonance imaging (MRI) and histopathological outcome.

RESULTS

RIS detected lymph node metastases in 35 of 51 positive sides (sensitivity 69%). Interpretation of RIS was correct in 47 of 65 sides (accuracy 72%). Accuracy of palpation, CT and MRI were comparable. Immunohistochemical staining of lymph node metastases missed by RIS showed that the injected MAb had targeted these small tumour deposits but these were not visualized.

CONCLUSIONS

RIS at its current stage of development is not superior to CT or MRI for the detection of lymph node metastases. As small tumour deposits were probably not visualized because of the limited sensitivity and/or spatial resolution of the gamma camera, positron emission tomography (PET) using MAbs labelled with positron emitters may improve the detection. As MAb-PET studies in an animal model showed promising results we will soon start a clinical MAb-PET study.