Intra-abdominal recurrence of colorectal cancer detected by radioimmunoguided surgery (RIGS system)

H3K27ac nucleosomes facilitate HMGN localization at regulatory sites to modulate chromatin binding of transcription factors

Nucleosomes containing acetylated H3K27 are a major epigenetic mark of active chromatin and identify cell-type specific chromatin regulatory regions which serve as binding sites for transcription factors. Here we show that the ubiquitous nucleosome binding proteins HMGN1 and HMGN2 bind preferentially to H3K27ac nucleosomes at cell-type specific chromatin regulatory regions. HMGNs bind directly to the acetylated nucleosome; the H3K27ac residue and linker DNA facilitate the preferential binding of HMGNs to the modified nucleosomes. Loss of HMGNs increases the levels of H3K27me3 and the histone H1 occupancy at enhancers and promoters and alters the interaction of transcription factors with chromatin. These experiments indicate that the H3K27ac epigenetic mark enhances the interaction of architectural protein with chromatin regulatory sites and identify determinants that facilitate the localization of HMGN proteins at regulatory sites to modulate cell-type specific gene expression.

The nucleosome-binding proteins HMGN1 and HMGN2 prefer acetylated nucleosomes at H3K27ac and the loss of this interaction alters binding of transcription factors to chromatin.

The androgen receptor is a tumor suppressor in estrogen receptor-positive breast cancer

The role of the androgen receptor (AR) in estrogen receptor (ER)-α-positive breast cancer is controversial, constraining implementation of AR-directed therapies. Using a diverse, clinically relevant panel of cell-line and patient-derived models, we demonstrate that AR activation, not suppression, exerts potent antitumor activity in multiple disease contexts, including resistance to standard-of-care ER and CDK4/6 inhibitors. Notably, AR agonists combined with standard-of-care agents enhanced therapeutic responses. Mechanistically, agonist activation of AR altered the genomic distribution of ER and essential co-activators (p300, SRC-3), resulting in repression of ER-regulated cell cycle genes and upregulation of AR target genes, including known tumor suppressors. A gene signature of AR activity positively predicted disease survival in multiple clinical ER-positive breast cancer cohorts. These findings provide unambiguous evidence that AR has a tumor suppressor role in ER-positive breast cancer and support AR agonism as the optimal AR-directed treatment strategy, revealing a rational therapeutic opportunity.

Nonlinear relationship between chromatin accessibility and estradiol-regulated gene expression

Chromatin accessibility is central to basal and inducible gene expression. Through ATAC-seq experiments in estrogen receptor-positive (ER+) breast cancer cell line MCF-7 and integration with multi-omics data, we found estradiol (E2) induced chromatin accessibility changes in a small number of breast cancer-relevant E2-regulated genes. As expected, open chromatin regions associated with E2-inducible gene expression showed enrichment of estrogen response element (ERE) and those associated with E2-repressible gene expression were enriched for ERE, PBX1, and PBX3. While a significant number of open chromatin regions showed pioneer factor FOXA1 occupancy in the absence of E2, E2-treatment further enhanced FOXA1 occupancy suggesting that ER-E2 enhances chromatin occupancy of FOXA1 to a subset of E2-regulated genes. Surprisingly, promoters of 80% and enhancers of 60% of E2-inducible genes displayed closed chromatin configuration both in the absence and presence of E2. Integration of ATAC-seq data with ERα ChIP-seq data revealed that ~40% ERα binding sites in the genome are found in chromatin regions that are not accessible as per ATAC-seq. Such ERα binding regions were enriched for binding sites of multiple nuclear receptors including ER, ESRRB, ERRγ, COUP-TFII (NR2F2), RARα, EAR2 as well as traditional pioneer factors FOXA1 and GATA3. Similar data were also obtained when ERα ChIP-seq data were integrated with MNase-seq and DNase-seq data sets. In summation, our results reveal complex mechanisms of ER-E2 interaction with nucleosomes. Notably, "closed chromatin" configuration as defined by ATAC-seq or by other techniques is not necessarily associated with lack of gene expression and technical limitations may preclude ATAC-seq to demonstrate accessibility of chromatin regions that are bound by ERα.

Spatiotemporal DNA methylome dynamics of the developing mouse fetus

Cytosine DNA methylation is essential for mammalian development but understanding of its spatiotemporal distribution in the developing embryo remains limited^1,2. Here, as part of the mouse Encyclopedia of DNA Elements (ENCODE) project, we profiled 168 methylomes from 12 mouse tissues or organs at 9 developmental stages from embryogenesis to adulthood. We identified 1,808,810 genomic regions that showed variations in CG methylation by comparing the methylomes of different tissues or organs from different developmental stages. These DNA elements predominantly lose CG methylation during fetal development, whereas the trend is reversed after birth. During late stages of fetal development, non-CG methylation accumulated within the bodies of key developmental transcription factor genes, coinciding with their transcriptional repression. Integration of genome-wide DNA methylation, histone modification and chromatin accessibility data enabled us to predict 461,141 putative developmental tissue-specific enhancers, the human orthologues of which were enriched for disease-associated genetic variants. These spatiotemporal epigenome maps provide a resource for studies of gene regulation during tissue or organ progression, and a starting point for investigating regulatory elements that are involved in human developmental disorders.

Analysis of 168 methylomes from 12 mouse tissues at 9 developmental stages sheds light on the epigenetic and regulatory landscape during mammalian fetal development.

Candidate silencer elements for the human and mouse genomes

The study of gene regulation is dominated by a focus on the control of gene activation or increase in the level of expression. Just as critical is the process of gene repression or silencing. Chromatin signatures have identified enhancers, however, genome-wide identification of silencers by computational or experimental approaches are lacking. Here, we first define uncharacterized cis-regulatory elements likely containing silencers and find that 41.5% of ~7500 tested elements show silencer activity using massively parallel reporter assay (MPRA). We trained a support vector machine classifier based on MPRA data to predict candidate silencers in over 100 human and mouse cell or tissue types. The predicted candidate silencers exhibit characteristics expected of silencers. Leveraging promoter-capture HiC data, we find that over 50% of silencers are interacting with gene promoters having very low to no expression. Our results suggest a general strategy for genome-wide identification and characterization of silencer elements.

Identification of silencer elements by computational or experimental approaches in a genome-wide manner is still challenging. Here authors define uncharacterized cis-regulatory elements (CREs) in human and mouse genomes likely containing silencer elements, and test them in cells using massively parallel reporter assays to identify silencer elements that showed silencer activity.

Interrogation of enhancer function by enhancer-targeting CRISPR epigenetic editing

Tissue-specific gene expression requires coordinated control of gene-proximal and -distal cis-regulatory elements (CREs), yet functional analysis of gene-distal CREs such as enhancers remains challenging. Here we describe CRISPR/dCas9-based enhancer-targeting epigenetic editing systems, enCRISPRa and enCRISPRi, for efficient analysis of enhancer function in situ and in vivo. Using dual effectors capable of re-writing enhancer-associated chromatin modifications, we show that enCRISPRa and enCRISPRi modulate gene transcription by remodeling local epigenetic landscapes at sgRNA-targeted enhancers and associated genes. Comparing with existing methods, the improved systems display more robust perturbations of enhancer activity and gene transcription with minimal off-targets. Allele-specific targeting of enCRISPRa to oncogenic TAL1 super-enhancer modulates TAL1 expression and cancer progression in xenotransplants. Single or multi-loci perturbations of lineage-specific enhancers using an enCRISPRi knock-in mouse establish in vivo evidence for lineage-restricted essentiality of developmental enhancers during hematopoiesis. Hence, enhancer-targeting CRISPR epigenetic editing provides opportunities for interrogating enhancer function in native biological contexts.

Radioimmunoguided Breast Surgery Using Radiolabeled Antibody NR-LU-10 FAB: A Pilot Study

Aim and Background

Radioimmunoguided surgery using radiolabeled NR-LU-10 Fab was evaluated as a method of intraoperative breast cancer detection.

Methods

Breast cancer patients were injected intravenously with 125I (74 MBq) labeled NR-LU-10 Fab (5 mg) and then underwent tumor excision 2, 4 or 7 days later, during which time the gamma detector probe was used to evaluate the primary tumor for evidence of radioactive uptake.

Results

Intraoperative probing revealed tumor localization in 7 of 10 patients (70%). Gamma probe counts of the excised tumor were elevated in all patients, although high counts in surrounding nonmalignant tissue obscured the ability to detect the tumor in vivo in 3 patients. One patient with bilateral breast cancer was found to have a separate focus of occult tumor in each breast using the gamma detector probe.

Conclusions

Radiolabeled NR-LU-10 Fab possesses favorable pharmokinetics and tumor-binding ability as a targeting agent. However, binding to nonmalignant tissue limits its role in the intraoperative evaluation of tumor margins in breast cancer patients. Its role in other malignancies should be explored.

A hand-held beta imaging probe for FDG

OBJECTIVES

Advances in radiopharmaceuticals and clinical understanding have escalated the use of intraoperative gamma probes in surgery. However, most probes on the market are non-imaging gamma probes that suffer from the lack of ancillary information of the surveyed tissue area. We have developed a novel, hand-held digital Imaging Beta Probe™ (IBP™) to be used in surgery in conjunction with beta-emitting radiopharmaceuticals such as (18)FDG, (131)I and (32)P for real-time imaging of a surveyed area with higher spatial resolution and sensitivity and greater convenience than existing instruments.

METHODS

We describe the design and validation of a hand-held beta probe intended to be used as a visual mapping device to locate and confirm excision of (18)FDG-avid primary tumors and metastases in an animal model.

RESULTS

We have demonstrated a device which can generate beta images from (18)FDG avid lesions in an animal model.

CONCLUSIONS

It is feasible to image beta irradiation in animal models of cancer given (18)FDG. This technology may be applied to clinical mapping of tumors and/or their metastases in the operating room. Visual image depiction of malignancy may aid the surgeon in localization and excision of lesions of interest.

Intra-operative tumour detection and staging in colorectal cancer surgery

AIM

Surgical resection for colorectal cancer involves segmental resection and regional lymphadenectomy. The appropriateness of this 'one-size-fits-all' strategy is questioned as bowel cancer screening programmes result in a shift to earlier stage disease. Currently, the nodal status of a colorectal cancer can only be reliably determined by histopathological examination of the resected specimen. New methods of intra-operative staging are required to allow surgical resection to be tailored to the stage of the disease.

METHOD

A literature search was performed of PubMed and Embase databases using the terms 'colon' OR 'colorectal' AND 'intra-operative detection' OR 'intra-operative staging' OR 'intra-operative detection' OR 'radioimmunoguided surgery'. Articles published between January 1980 and January 2012 were included. Technologies that have the potential to allow intra-operative staging and treatment stratification were identified and further searches performed.

RESULTS

Established techniques such as sentinel lymph node mapping and radioimmunoguided surgery have benefited from combination with other technologies to allow real-time intra-operative staging. Intra-operative fluorescence, using naturally fluorescent biomarkers or fluorescent tumour probes, probably offers the most practical means of intra-operative lymph node staging and may be facilitated using nanotechnology. Optical coherence tomography and real-time elastography have the potential to provide an in vivo'virtual biopsy'.

CONCLUSION

Technological advances may allow accurate intra-operative lymph node staging to facilitate tailored surgical resection. This may become the next paradigm shift in colorectal cancer surgery.

Near-infrared fluorescence labeled anti-TAG-72 monoclonal antibodies for tumor imaging in colorectal cancer xenograft mice

Anti-TAG-72 monoclonal antibodies target the tumor-associated glycoprotein (TAG)-72 in various solid tumors. This study evaluated the use of anti-TAG-72 monoclonal antibodies, both murine CC49 and humanized CC49 (HuCC49deltaCH2), for near-infrared fluorescent (NIR) tumor imaging in colorectal cancer xenograft models. The murine CC49 and HuCC49deltaCH2 were conjugated with Cy7 monofunctional N-hydroxysuccinimide ester (Cy7-NHS). Both in vitro and in vivo anti-TAG-72 antibody binding studies were performed. The in vitro study utilized the human colon adenocarcinoma cell line LS174T that was incubated with Cy7, antibody-Cy7 conjugates, or excessive murine CC49 followed by the antibody-Cy7 conjugates and was imaged by fluorescence microscopy. The in vivo study utilized xenograft mice, bearing LS174T subcutaneous tumor implants, that received tail vein injections of Cy7, murine CC49-Cy7, HuCC49deltaCH2-Cy7, or nonspecific IgG-Cy7 and were imaged by the Xenogen IVIS 100 system from 15 min to 288 h. The biodistribution of the fluorescence labeled antibodies was determined by imaging the dissected tissues. The in vitro study revealed that the antibody-Cy7 conjugates bound to LS174T cells and were blocked by excessive murine CC49. The in vivo study demonstrated that murine CC49 achieved a tumor/blood ratio of 15 at 96 h postinjection. In comparison, HuCC49deltaCH2-Cy7 cleared much faster than murine CC49-Cy7 from the xenograft mice, and HuCC49deltaCH2-Cy7 achieved a tumor/blood ratio of 12 at 18 h postinjection. In contrast, Cy7 and Cy7 labeled nonspecific IgG resulted in no demonstrable tumor accumulation. When mice were injected with excessive unlabeled murine CC49 at 6 h before the injection of murine CC49-Cy7 or HuCC49deltaCH2-Cy7, both the intensity and retention time of the fluorescence from the tumor were reduced. In summary, the Cy7 labeled murine CC49 and HuCC49deltaCH2 demonstrate tumor-targeting capabilities in living colorectal cancer xenograft mice and provide an alternative modality for tumor imaging.

Population pharmacokinetics of humanized monoclonal antibody HuCC49deltaCH2 and murine antibody CC49 in colorectal cancer patients

To predict the optimal time for surgery after antibody administration, the population pharmacokinetics of (125)I-HuCC49deltaCH2 and (125)I-CC49 were characterized in 55 patients with colorectal cancers. A 2-compartment linear model was used to fit the pharmacokinetic data. Model stability and performance were assessed using a visual predictive check procedure. Different clinical trial designs were evaluated by simulation in combination with Bayesian estimation method to predict the optimal time for surgery. The results showed that HuCC49deltaCH2 had 65% faster clearance from blood circulation and 24% shorter mean residence time than CC49. Population pharmacokinetic analysis identified body weight as the only covariate to explain between-subject variability in clearance, intercompartmental flow rate, and volume of distribution. Model predictions indicated a wide interval for the optimal time of surgery, suggesting that it would be beneficial to individualize the time of surgery for each patient by measurement of antibody disposition. Clinical trial designs with at least 3 measurements of antibody disposition were found to be better than an empirical direct observation method for the optimal prediction of surgery time.

Pharmacokinetics and clinical evaluation of 125I-radiolabeled humanized CC49 monoclonal antibody (HuCC49deltaC(H)2) in recurrent and metastatic colorectal cancer patients

INTRODUCTION

CC49 is an antitumor monoclonal antibody that is promising for use in radioimmunoguided surgery (RIGS). However, the murine antibody has been limited by human antimouse antibody (HAMA) response and slow clearance. This study examined the pharmacokinetics and tissue localization of a humanized domain-deleted CC49 antibody (HuCC49DeltaC(H)2 MAb) in humans.

METHODS

Twenty-one patients with colorectal carcinoma were given 1 mg intravenous (I.V.) bolus of HuCC49DeltaC(H)2 MAb radiolabeled with 2 mCi (125)I after thyroid blockade. The level of circulating HuCC49DeltaC(H)2 MAb was measured daily as precordial counts using a handheld gamma-detecting probe. Each patient underwent an exploratory laparotomy on postinjection days 3-20. Gamma counts were measured at normal organs, aortic bifurcation (AB), and both clinically evident and occult tumors.

RESULTS

Precordial and AB gamma counts showed an excellent linear correlation. HuCC49DeltaC(H)2 MAb followed a two-compartment pharmacokinetic model. Normal organs and AB showed similar exposures to HuCC49DeltaC(H)2 MAb, while HuCC49DeltaC(H)2 MAb favorably distributed into tumors from day 3. Intestinal and metastatic liver lesions showed the highest partition coefficients. All patients showed no HAMA response.

DISCUSSION

C(H)2 region deletion of HuCC49DeltaC(H)2 MAb did not alter the pharmacokinetics compared to murine CC49. The favorable partition coefficient K of HuCC49DeltaC(H)2 MAb into tumors supports its use in RIGS.

Advances in FDG PET probes in surgical oncology

Whole-body positron emission tomography (WB-PET) has been developed as a sensitive, cost-effective method for imaging malignant disease. WB-PET provides complete body imaging with a single scanning approach for a variety of malignancies. With increasing clinical experience, the indications for its use have broadened. This article reviews current uses of the technology and discusses some potential applications, particularly the utility of a commercially available surgical gamma probe for detecting the gamma particles emitted in the decay process of FDG.

Iodine-131 human-mouse chimeric Fab monoclonal antibody A7 guided surgery for colorectal cancer patients: a pilot study

This study was conducted to determine the clinical usefulness of radioimmunoguided surgery (RIGS) using human-mouse chimeric Fab monoclonal antibody A7 (ch-Fab-A7) for colorectal cancer patients. Ten colorectal cancer patients were given iodine-131-labeled ch-Fab-A7 intravenously (i.v.) 2 to 7 days prior to RIGS. The RIGS was carried out using a portable gamma detecting probe (GDP). Tumor localization was identified by GDP intraoperatively in 4 of the ten patients, while liver metastasis and lymph node metastasis were identified in 2 patients and 1 patient, respectively. The GDP revealed tumor/surrounding tissue radio(gamma)count ratios of 1.5 or greater in 8 of the ten resected tumors. Although RIGS using ch-Fab-A7 is a promising tool for intraoperatively identifying the tumor localization of colorectal cancer, 125I, rather than 131I, should be used as a tracer for RIGS to enhance the accuracy of ch-Fab-A7.

Diagnostic and therapeutic applications of monoclonal antibodies in colorectal cancer

PURPOSE

The study contained herein was undertaken to review and summarize the current literature on diagnostic and therapeutic applications of monoclonal antibodies in colorectal cancer.

RESULTS

Limitations of traditional imaging techniques have encouraged development of targeted imaging strategies using radiolabeled monoclonal antibodies. Diagnostic immunoscintigraphy can detect lesions not identified by conventional imaging modalities, although it has not proven useful in the management of primary colorectal cancers and in hepatic metastases. Immunoscintigraphy shows promise in cases of local recurrence and rising carcinoembryonic antigen values; however, the impact of immunoscintigraphy on clinical outcomes and cost-effectiveness remains unproven. Radioimmunoguided surgery has been advocated as a method of more accurately detecting tumor extension and accomplishing radical resection. The technique remains controversial, and its use is not widespread. With respect to therapeutic applications, immunotherapy has most often been investigated in the setting of advanced stage disease. Results in this setting have been poor. In contrast, adjuvant immunotherapy after resection of Dukes C carcinoma has achieved convincing results, with improvements in survival comparable with that of adjuvant chemotherapy. Adjuvant trials are now under way to examine the effectiveness of monoclonal antibodies in the postoperative treatment of early-stage (II) tumors and the combination of monoclonal antibodies and chemotherapy in advanced-stage (III) tumors. Bispecific antibodies, or immunoconjugates with cytokines or toxins, represent additional areas of interest and future investigations.

CONCLUSIONS

At present, immunoscintigraphy is not sufficient to determine, by itself, resectability of colorectal tumor and has limited usefulness in select cases of recurrent cancer and possibly in cases of rising carcinoembryonic antigen values. Immunotherapy with monoclonal antibodies as a postoperative adjuvant treatment shows promise and is currently being investigated in national trials.

Resected sigmoid carcinoma with 13-year metastasis-free interval. Sternal recurrence detected by immunoscintigraphy

Colorectal cancers rarely present with bone metastases. Regular postoperative monitoring after resection by conventional imaging techniques and carcinoembryonic antigen levels aids physicians in identifying such tumor recurrences. However, some recurrences might elude detection by bone scan, computed tomography, and magnetic resonance imaging, and newer tests such as immunoscintigraphy using radioimmune-tagged monoclonal antibodies may be more diagnostic. Here we report a case, presenting with delayed recurrence at a rare bony site, in which application of immunoscintigraphy helped in the definitive detection of the tumor recurrence.

Radioimmunoguided surgery and colorectal cancer

Radioimmunoguided surgery is a technique that aims to delineate the extent of epithelial neoplasms (primary/recurrent) and their spread (local, regional, and distant) which are not adequately visualized by conventional imaging techniques. The target lesion binds radiolabelled, tumour-associated monoclonal antibodies which are administered in the days before surgery and which bind to the target lesion. The radiotracer is detected intraoperatively using a hand-held gamma detecting probe. This identifies the extent of the tumour, involvement of lymph nodes or other organs and may allow a more complete surgical clearance of the tumour. This article provides a basic understanding of the RIGS (radioimmunoguided surgery) technique, the monoclonal antibodies which are used and outlines the advantages and limitations of this technique.

Didactic review of 175 radionuclide-guided excisions of osteoid osteomas

The complete removal of a lesion which resembles, or is covered by adjacent tissue may be difficult. Therefore, the capacity of certain lesions to specifically concentrate a radiopharmaceutical has been used to orient progress during surgery. Usually, the measurements of radioactivity in the operative field are carried out by means of small, handy radiation-detecting probes which can be sterilized. "Intra-operative nuclear medicine" or "radionuclide-guided surgery" has steadily gained in importance. However, this technique is not being taught. Our study, based on radionuclide-guided surgery of 175 orthopaedic patients suspected of having osteoid osteoma, is well suited to teach the particularities of intra-operative radiation detection, as well as the collaboration between the nuclear physician and the surgeon in the operating theatre.

Intraoperative detection of somatostatin-receptor-positive neuroendocrine tumours using indium-111-labelled DTPA-D-Phe1-octreotide

After injection of 111In-labelled DTPA-D-Phe1-octreotide, intraoperative tumour localisation was performed using a scintillation detector in 23 patients with neuroendocrine tumours. Count rates from suspect tumour lesions and adjacent normal tissue were expressed as a ratio before (Rin situ) and after (Rex vivo) excision. 111In activity concentration ratios of tumour tissue to blood (T/B) were determined in a gamma counter. In patients with midgut carcinoids, (all scintigraphy positive), false Rin situ recordings were found in 4/29 macroscopically identified tumours. T/B ratios were all high (27-650). In patients with medullary thyroid carcinomas (eight out of ten scintigraphy positive), misleading Rin situ results were found in 4/37 macroscopically identified tumours. T/B ratios were lower (3-39) than those seen in midgut carcinoids. Two out of four patients with endocrine pancreatic tumours had positive scintigraphy, reliable intraoperative measurements and very high T/B ratios (910-1500). One patient with a gastric carcinoid had correct measurements in situ and ex vivo with high T/B ratios (71-210). In situ measurements added little information to preoperative scintigraphy and surgical findings using the present detection system. Rex vivo measurements were more reliable. The very high T/B ratios seen in midgut carcinoids and some endocrine pancreatic tumours would be favourable for future radiation therapy via somatostatin receptors.

Somatostatin receptor scintigraphy in the diagnosis of neuroendocrine gastroenteropancreatic tumors

Somatostatin receptor scintigraphy is a new, very sensitive procedure for detecting receptor-positive neuroendocrine tumors. Radiolabeled somatostatin analogues are selectively taken up after intravenous administration by tissue carrying somatostatin receptors and, as with the skeletal scintiscan, permit a whole-body visualization of receptor-positive tumors and metastases. Somatostatin receptor scintigraphy shows an overall sensitivity of about 84% for neuroendocrine gastroenteropancreatic tumors. This kind of scintigraphy should be applied in primary tumor localization, staging, and course control in a confirmed or highly probable neuroendocrine gastroenteropancreatic tumor. Furthermore, the use of a gamma probe for intraoperative tumor localization is demonstrated. Therapy with radioactively marked somatostatin analogues should be possible because of the highly selective tumor uptake. The development of an optimal tracer is the subject of current research.

Clinical efficacy of octreotide scintigraphy in patients with midgut carcinoid tumours and evaluation of intraoperative scintillation detection

111In-diethylenetriamine penta-acetate-D-Phe1-octreotide scintigraphy was evaluated in a group of 27 patients with disseminated midgut carcinoid tumour. Additional information gained by the intraoperative use of a scintillation detector was studied in five patients with midgut carcinoid tumours and in two with endocrine pancreatic tumours. In 19 patients tumours not recognized by non-invasive radiological methods were visualized in 27 locations, most commonly in liver and para-aortic lymph nodes. Three false-negative tumour locations were noted (ovarian and peritoneal). With guidance from scintigraphic findings, nine patients underwent surgical tumour reduction, leading to complete remission in three. Clinically suspect tumour lesions were measured by the detector in situ, and ex vivo after excision. After excision the tissue:blood activity concentration ratios were calculated. In situ measurements were helpful in the localization of tumours and in the control of adequate clearance of tumour tissue. High tissue:blood activity concentration ratios at 1, 2 and 5 days in the five patients with midgut carcinoid tumour indicate a potential role for radiation therapy with radiolabelled octreotide in patients with somatostatin receptor-positive tumours.

Avidin-biotin system in radioimmunoguided surgery for colorectal cancer. Advantages and limits

PURPOSE

Radiolabeled monoclonal antibodies (MAbs) have been reported to allow tumor intraoperative detection by means of a gamma-detecting probe. The technology is called the Radioimmunoguided Surgery (RIGS) system. The main inconveniences of the method are 1) the long interval needed for clearance of unattached MAbs from the patient's body, between the injection of the MAb and surgery, and 2) the low sensitivity of current MAbs used in detecting small tumors. We describe a new method to overcome these inconveniences using biotinylated MAbs and avidin in order to obtain a rapid blood clearance of the radiolabeled MAbs both anticarcinoembryonic antigen and antitumor-associated glycoprotein-72 MAbs.

METHODS

Twenty patients with primary and recurrent colorectal cancer have been enrolled in the study; 125I-biotinylated MAbs FO23C5 (anticarcinoembryonic antigen) and B72.3 (antitumor-associated glycoprotein-72) followed by cold avidin were injected in 13 patients and 7 patients, respectively.

RESULTS

A decrease of 94 +/- 3 percent of circulating radioactivity was achieved in 3 to 5 days. Patients underwent surgery approximately seven days after MAb injections rather than after four weeks. Tumors were localized in 14/20 (70 percent) patients (true positive), 2 (10 percent) were false negative, and 4 (20 percent) were true negative. The overall sensitivity level in early-stage primary cancers was 37 percent when related to the presence of disease and 75 percent when related to antigenic expression. The sensitivity for more advanced cancer and for recurrences was 100 percent. Moreover, the in vivo tumor targeting of biotinylated MAb was demonstrated in frozen tumor section by direct streptoavidin-peroxidase staining.

CONCLUSIONS

The avidin-biotin system may enhance applicability and effectiveness of radioimmunoguided surgery (RIGS).

Second look in colorectal surgery

PURPOSE

Follow-up should identify metachronous colonic neoplasms and precancers, suture line recurrences, and isolated liver or pulmonary metastases. For some sites of failure the surgical re-resection and multimodal approaches increase disease-free survival and quality of life. The aim of our study was to evaluate the role of the different follow-up plans and the carcinoembryonic antigen directed second-look surgery.

METHODS

One hundred-sixty patients radically resected for Dukes B or C colorectal cancer were evaluated by a follow-up plan (plasma carcinoembryonic antigen every 2 months; echography every 6 months; chest x-ray every 12 months; and colonoscopy at 1 year and then every 3-5 years).

RESULTS

Eighty-nine recurrences were detected (55.6 percent). In 72 recurrences plasma carcinoembryonic antigen elevation was present. Eight carcinoembryonic antigen directed second-look surgeries were performed: in four patients surgical evidence of recurrence was found (two isolated liver metastases were radically resected); two patients with no surgical evidence of recurrence developed a surrenalic isolated metastases and pelvic and hepatic recurrences; two patients had a five-year disease-free survival. In the 17 symptomatic patients with no carcinoembryonic antigen elevation diffuse disease was present, not resectable for cure. Four solitary liver metastases, one metachronous colonic neoplasm, and one suture line recurrence presented a five-year survival.

CONCLUSIONS

The authors emphasize that carcinoembryonic antigen-directed second-look surgery is not acceptable for elevated costs. Intensive follow-up plans are superflous, while the monitoring of the carcinoembryonic antigen and instrumental restaging as an indicator of solitary liver metastases and mucosal lesions are very useful.

Local recurrence of colorectal cancer: the problem, mechanisms, management and adjuvant therapy

Local recurrence of colorectal cancer after 'curative' surgery is a major clinical problem. Typically, 50-70 per cent of patients presenting to a surgical clinic will undergo apparently curative surgery for disease and of these about 10-25 per cent will develop local recurrence, in either the tumour bed or bowel wall. The wide differences in local recurrence rate both between and within institutions is probably caused by variation in surgical technique. The main causes of local recurrence are inadequate excision of the primary tumour or the draining lymph nodes, and intraoperative tumour cell implantation. The most significant single factor prognostic of local recurrence is Dukes' tumour stage. Other important factors include tumour grade and fixity, level of the tumour in the rectum, blood and lymphatic vessel invasion, inadvertent perforation of the tumour during resection, and the surgeon's experience. The prognosis of patients with local recurrence is poor. Prevention of recurrence by adequate surgery and adjuvant therapy as well as its early detection offer the best prospect of improving results.

Surgical treatment of liver metastases in patients with colorectal cancer

The incidence of colorectal cancer in the United States is increasing. Because more than half of patients with colorectal cancer have liver metastases develop, the number of patients with hepatic metastases also is increasing. Unfortunately, metastatic disease will be limited to the liver in perhaps 25% of these patients and confined to only one lobe of the liver 25% of this subgroup. Consequently, solitary or unilobar colorectal metastases are found in as few as 5% of patients with colorectal cancer. The median survival of patients with unresected hepatic metastases is approximately 10.6 months. Patients with solitary lesions or small tumor burdens may attain a median survival of 16-20 months, but 5-year survivors are extremely rare. In contrast, rates of 5-year survival average approximately 36% after resections of solitary hepatic lesions and may approach the same level in selected patients with multiple lesions. Factors that appear to adversely effect survival include detection of metastatic disease because of signs or symptoms of disease, an elevated carcinoembryonic antigen (CEA) level, elevated liver function tests, poorly differentiated primary lesions, lymph node-positive primary lesions, extrahepatic sites of metastases, more than four hepatic lesions, bilobar disease, a satellite pattern of metastases in the liver, positive margins of the liver resection, positive extrahepatic lymph nodes, and more than 10 units of blood transfusion during the perioperative period. Operative mortality for liver resections should remain approximately 4%, and major morbidity should be in the range of 20-30%. Modalities other than surgical resection have not improved survival in patients with colorectal hepatic metastases. Thus, when feasible, patients with metastatic colorectal cancer limited to one lobe of the liver should undergo hepatic resection. Unfortunately, only approximately 5% of patients with colorectal cancer fall into this category, so resection of hepatic metastases can improve overall survival of patients with colorectal cancer by only 1-2%.

Standard postoperative monitoring of patients after primary resection of colon and rectum cancer

The goal of monitoring after primary treatment of any solid tumor, including colon and rectum carcinoma, is to help the patient. The general parameters include prevention of secondary tumors or precancers (because most patients with solid tumors are at greater risk than the general population for second tumors of the same histology), the cure of symptomatic or asymptomatic tumor recurrences, and the palliation of symptomatic tumor recurrences. Additional rationale for more stringent follow-up is somewhat dependent upon the venue of patient care, including the necessity for more frequent studies if the patient happens to be in a protocol in which disease-free survival and/or patterns of recurrence are being investigated. Keeping these parameters in mind, most prevalent follow-up plans remain empiric and probably are not justifiable, on the basis of either cost-effective analysis or real benefit to the patient.

Monoclonal antibody imaging in patients with colorectal cancer and increasing levels of serum carcinoembryonic antigen. Experience with ZCE-025 and IMMU-4 monoclonal antibodies and proposed directions for clinical trials

In an effort to identify the site of recurrent colorectal cancer in patients with occult metastasis and increasing serum CEA levels, we conducted two trials using monoclonal antibodies (MoAb) against CEA. The first utilized Indium-111-labeled ZCE-025; an immunoglobulin G1 (IgG1) anticarcinoembryonic antigen (anti-CEA) antibody (Hybritech, San Diego, CA). The second study used Tc-99m-labeled Fab' fragment of IMMU-4 (Immunomedics, Morris Plains, NJ). Eighteen patients were imaged with the ZCE-025 and 14 with the Tc-99m Fab' IMMU-4. True-positive scans, defined as at least one correct correlation of the MoAb scan and surgical/histologic findings, were observed in 12 of 15 patients undergoing exploration or biopsy using the ZCE-025 and 11 of 14 using the IMMU-4. There were no true-negative scans with the ZCE-025 and only 2 of 14 with the IMMU-4. There were 3 false-positive scans with the ZCE-025 and 1 of 14 with IMMU-4. There were no false-negative scans with either ZCE-025 or IMMU-4. Four (31%) of 13 patients undergoing exploration and imaged with ZCE-025 and 5 (36%) of 14 imaged with IMMU-4 had complete tumor resection. Treatment decisions were affected in 3 (16%) of 18 ZCE-025-imaged patients and 3 (21%) of 14 IMMU-4 ones. Two (14%) of 14 patients imaged with IMMU-4 had negative MoAb scans and negative laparotomies. Despite these findings, it is not known whether such early detection and resection will translate into improved survival rates. The authors suggest two randomized studies, one designed to ascertain the role of MoAb added to blind exploratory laparotomy. In that study, patients with increasing CEA levels and a negative workup will be randomized to an exploratory laparotomy preceded by MoAb anti-CEA scans or a straight exploratory laparotomy without the assistance of a MoAb anti-CEA scan. Endpoints will be differences in complete resectability and survival. A second study will examine the merits of blind exploratory laparotomies. In that study, patients with increasing CEA levels and a negative workup would be randomized to MoAb imaging, exploratory laparotomy, and radioimmunoguided surgery, and the other cohort of patients would continue to have conventional radiologic workup. Exploration in this latter group would be performed only when indicated by radiologic or endoscopic studies. The endpoint of the study would compare survival in the two cohorts of patients. These two studies may ultimately settle the debate regarding the correct approach to patients with occult metastatic colorectal cancer and a increasing levels of serum CEA.

Radioimmunoguided radical prostatectomy and lymphadenectomy

BACKGROUND

The feasibility of using radioimmunoguided surgery (RIGS) (Neoprobe Corp., Columbus, OH) for intraoperative detection of prostate cancer was examined in a pre-Phase I clinical study involving 10 patients having radical prostatectomy and lymphadenectomy.

METHODS

Patients were injected with iodine 125-radiolabeled B72.3 monoclonal antibody, which has been shown previously to bind to TAG-72, a pancarcinoma and oncofetal antigen. At a mean of 26 days after injection, RIGS was performed with a specially designed intraoperative gamma-detecting probe.

RESULTS

By comparing probe counts with counts of appropriate background tissues, the RIGS system successfully localized tumor to the prostate of all 10 patients. Clinically occult and histologically confirmed bilateral intraprostatic tumor was identified in three patients. One additional patient had bilateral positive intraprostatic probe count ratios with the RIGS technique; on histologic examination, tumor was identified unilaterally, and extensive high-grade prostatic intraepithelial neoplasia was found on the contralateral side. Probe count ratios were positive in the lymph nodes of three patients; two had tumor confirmed histologically.

CONCLUSIONS

The current investigation supports the feasibility of the RIGS technique and the need for additional studies.

Biochemical markers for colorectal cancer. Diagnostic and therapeutic implications

The development of the understanding of oncogenes, tumor suppressor genes, and signal transduction has provided a significant advance in the concepts of the mechanisms of carcinogenesis in the colon and rectum. The tools provided by the molecular geneticist and the immunobiologist may yield powerful new techniques for screening individuals at risk, for identifying those patients with biologically more aggressive tumors, for developing novel therapies targeted directly at tumor cells, and for providing the means for more sensitive and specific detection of recurrence of disease.

Use of radiolabelled monoclonal antibodies in patients with primary and metastatic large bowel cancer

Accurate assessment of the extent of primary and metastatic large bowel cancer is critical to surgical decision making and to providing reliable prognostic information. This prospective study compared external gamma camera images and an intraoperative hand-held gamma detecting probe for detection of radiolabelled monoclonal antibody (B72.3) in 28 patients with primary and metastatic large bowel cancer. Fourteen patients received 0.2 to 20 mg (2 or 5 mCi) 111indium-labelled monoclonal antibody B72.3 followed by whole body imaging scan with an external gamma detector/camera on two occasions 24 h apart within 7 days after injection. Fourteen patients received 1.0 mg (2.0 mCi) 125iodine-B72.3 followed by intraoperative probe evaluation 2-3 weeks postinjection. Mean patient ages for the two groups were 60 years (range 28-75 years) and 63 years (range 43-77 years), respectively. Disease sites were primary in the large bowel in six patients and primary as well as metastatic in 22 patients. External scanning detected 111indium-B72.3 uptake in 1/5 primary lesions, 1/7 hepatic and 1/3 extrahepatic sites. The intraoperative gamma probe localized disease in 1/3 primary lesions, 7/11 hepatic and 3/3 extrahepatic sites. The intraoperative gamma probe had a sensitivity of 71% for detection of metastases compared with a 20% sensitivity using the external gamma scan method (P = 0.03). 125iodine-labelled B72.3 influenced the extent of the operative procedure in 4/14 (29%) patients; immunolocalization with external gamma detection did not alter the operative procedure in the 14 patients studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of a technique for the intraoperative detection of a radiolabelled monoclonal antibody against colorectal cancer

Occult tumour deposits may be localised at operation with a radiation detecting probe following the administration of a radiolabelled monoclonal antibody (MoAb) recognising a tumour-associated antigen. We have recently evaluated the clinical usefulness of this technique in detecting primary colorectal tumours targetted with an indium-111 MoAb. In the present study the physical characteristics of the two detector systems used were investigated; a sodium iodide [NaI(Tl)] scintillation detector and a cadmium telluride (CdTe) semiconductor probe. Limitations of the technique in use have been examined by testing the statistical significance of tumour detection using an abdominal phantom based on the currently available clinical biodistribution data for tumour uptake of radiolabelled MoAbs. The effect of tumour volume, antibody uptake, collimation and counting conditions was examined. Results indicate that tumours of 10 ml volume may be detected with the NaI(Tl) probe at the lowest levels of radiolabelled antibody uptake currently reported in the literature but that at higher published levels, lesions as small as 1 ml may be identified with both detector systems. Detector sensitivity and limited antibody specificity restrict the usefulness of the technique, although moderate improvements in tumour uptake may allow the detection of tumour deposits not clinically apparent. The statistical significance criterion used for this study could be an accurate and reliable indicator for tumour detection in vivo.

Intraoperative localization of colorectal cancers using radiolabelled monoclonal antibodies

Radiation detectors may allow the intraoperative localization of small cancer deposits following administration of radiolabelled tumour-associated antibodies. This technique was evaluated in 16 patients with colorectal tumours (14 cancers, one adenoma, one lipoma) with the 111In-labelled monoclonal antibody (MAb) ICR2 which recognizes the tumour-associated epithelial membrane antigen (EMA). At operation counting was carried out (3 x 20 s per site) using a hand-held radiation probe over the primary lesions and any palpable lymph nodes in the mesocolon. The tumour to normal colon (T/NC) ratio of counts recorded at operation was more than 1.5:1 in eight of the 14 patients with cancer (mean(s.d.), 1.54(0.41):1) and 0.91:1 and 1.06:1 respectively in the two patients with benign tumours. Node to normal colon ratios were higher in lymph nodes containing metastases. The uptake of radiolabelled antibody (T/NC ratio) was higher in EMA-expressing cancers than in those not expressing the target antigen (mean(s.d.), 2.45(0.65):1 versus 1.40(0.20):1, P = 0.019). An abdominal tumour model was also developed. Radioactively filled containers of 0.5-10 ml representing tumour deposits were suspended in a tank of 111In solution representing the background activity found in normal tissues. The ratio of radioactivity in the 'tumour' to that of background varied from 2:1 to 8:1. The 'tumour' was considered to be detectable if the mean counts recorded over the 'tumour' exceeded the mean of counts recorded over background by three standard deviations. At a ratio of 2:1 only 'tumours' greater than 5 ml could be detected with a sodium iodide probe and those over 10 ml could be detected with a cadmium telluride (CdTe) probe. At a ratio of 8:1, 'tumours' of 0.5 ml could be detected with either probe. At all ratios and counting periods the NaI probe was more sensitive than the CdTe.

Multiple operations for recurrent colorectal cancer

The benefit of an aggressive surgical approach in selective patients with recurrent colorectal cancer has been demonstrated by several investigators. The disease-free 5 year survival is 30%, and in carefully selected series it is as high as 46%. These procedures can be performed safely with minimal morbidity and mortality by surgeons who are experienced in the techniques of radical surgery. It is important and should be our focus to try to identify those patients who will benefit the most from an aggressive surgical approach, by better definition of the biology of the tumor through tumor differentiation and DNA and oncogene analysis.

The value of radioimmunoguided surgery in first and second look laparotomy for colorectal cancer

Radioimmunoguided surgery (RIGS) using an anti-CEA (A5B7) monoclonal antibody has been assessed in 52 patients (43 primary excisions and nine second look procedures) undergoing surgery for colorectal carcinoma. The antibody localized in 97.8 percent of primary tumours and in 88.8 percent of the principal tumor in second look procedures. Additional information concerning the extent of primary tumor was obtained in 11 of 43 patients (25.5 percent) undergoing excision of primary carcinoma and five of nine patients (55 percent) in the second look series. Incorrect information was obtained about the extent of the primary tumour in six patients (11.3 percent), whereas no incorrect information was obtained during second look procedures. RIGS correctly predicted the subsequent Dukes' staging in 77 percent of first look cases (sensitivity 65 percent, specificity 90 percent), although accurate identification of individual nodes was impossible. The technique influenced the surgical procedure performed in 2 of 43 cases (4.6 percent) in primary surgery and in three of nine patients undergoing second look laparotomy (33 percent). RIGS in primary colorectal carcinoma may provide additional information concerning extent of locally advanced tumors in particular and the principle that the subsequent surgery may be influenced has been established. The technique appears to have a greater role in second look procedures where it may help determine the extent of recurrent tumour. Larger follow-up series are required to define how the additional information provided by this technique may best be exploited.

Feasibility study of radioimmunoguided surgery of colorectal carcinomas using indium-111 CEA-specific monoclonal antibody

The study was undertaken to define the potential use of indium 111 carcinoembryonic antigen-specific antibody labelled [CEA F(ab')2] for the radioimmuno-detection of colorectal carcinoma using an intraoperative hand-held gamma probe. The use of a linear radioactive source allowed optimization of physical characteristics. The best results regarding sensitivity and resolution were obtained using a 5-mm thick tungsten alloy collimator. A simulation study with a liver phantom (22 MBq or 0.6 mCi) was performed to determine the effect of side scatter as opposed to direct background and showed that it is possible to detect small radioactive targets (3.7 KBq or 0.1 mu Ci) 4 cm from the phantom. A clinical study performed with ten patients showed that tumours with good uptake of CEA-specific antibody could be detected with sufficient contrast in two patients when the probe was used. Results of a biodistribution study performed after tumour fragment or normal tissue countings in a well counter showed high tumour uptake (above 8 x 10(-3) injected dose/g) and tumour-to-normal tissue ratios (between 2.5 and 20) in five patients. Results with the probe showed markedly lower ratios. There was no correlation between absolute tumour uptake and the count rates of tumour measured intraoperatively. This can be attributed to the degradation of depth resolution resulting from the high energy photopeak of gamma-emitting 111In.

Probability modelling of a surgical probe for tumour detection

Probability functions for the output counts from a radiation detector probe are needed to implement Bayesian detection strategies or to assess performance of the probe. This paper presents methods for simulating a surgical probe designed for tumour detection to obtain statistical information for modelling probability functions of output data. Statistical models of pharmaceutical uptake in normal organs and tumours were estimated from animal and human data, and these models were combined with a digitised human torso phantom to create a large set of simulated patients. With the simulated patients and with a spatial map of the probe response, computer simulations of intraoperative probe measurements provided a large set of simulated probe data. Probability models derived from these data using maximum-likelihood methods helped to formulate the detection strategy and to evaluate the performance of the surgical probe.

The impact of radioimmunoguided surgery (RIGS) on surgical decision-making in colorectal cancer

Radioimmunoguided surgery (RIGS system) was performed in ten patients with rectal or low sigmoid colon carcinoma with the use of a hand-held gamma detector (Neoprobe 1000) intraoperatively and externally after injection of radiolabeled (125I) monoclonal antibody to detect pelvic and metastatic tumor. Fifteen procedures, including six exploratory laparotomies, four transperineal explorations, two transsacral explorations, one transvaginal biopsy, one brachytherapy, and one transanal polypectomy, were performed. Two patients had previous low anterior resection, seven abdominoperineal resection, and one a rectal polypectomy. Five patients had previous pelvic radiation therapy. Reoperation was indicated by elevated CEA levels in seven patients (70 percent), persistent pelvic pain in six (60 percent), and a suspicious radiologic study in seven (70 percent). RIGS system localized tumors verified by histopatholoy in all ten patients (100 percent); one patient with a positive CT scan and probe findings lacked histopathologic confirmation on frozen section, but had a tumor confirmed on permanent histology. Five major abdominal operations were avoided; in five patients major modifications were made in the surgical procedure based on probe findings. Six received chemotherapy or radiation therapy based on findings of the RIGS system. In six patients with negative or equivocal CT scans, the RIGS system localized histopathologically confirmed tumor. Major abdominal procedures can be avoided, the surgical approach modified, and other modes of therapy instituted earlier with the use of the RIGS system.

Imaging of colorectal carcinoma with radiolabeled antibodies

Colorectal cancer has been the tumor type most frequently studied with radiolabeled antibodies. Among the various antibodies, a majority of patients with colorectal cancer have received xenogeneic polyclonal or monoclonal antibodies against carcino-embryonic antigen. This review summarizes the current status of colorectal cancer imaging with radiolabeled antibodies, ie, radioimmunodetection (RAID), and examines the published studies involving carcinoembryonic antigen (CEA) antibodies and 17-1A, 19-9, and B72.3, and other monoclonal antibodies. In order to better address the issue of the current and future clinical usefulness of this emerging technology, particular attention is given to the protocols, methods, and results of the published studies. Despite differences in study parameters, antibodies and forms, labels, administration routes and doses, and scanning instruments and methods, it has been found that (1) almost no adverse reactions have been evident; (2) antibody fragments are preferred over whole immunoglobulin G reagents because they achieve higher tumor-to-background ratios earlier, thus reducing or precluding the need for dual-isotope subtraction methods or long delays before imaging; (3) use of antibody fragments, including the monovalent Fab' form, permits imaging with short-lived radionuclides of excellent photon properties, such as 123I and 99mTc; (4) circulating antigens against which the imaging antibody is directed can complex with the injected antibody, but such complexes have not prevented successful RAID; (5) patients with high serum titers of the appropriate antigen target usually have higher rates of positive RAID; (6) patients who are seronegative for the tumor antigen being studied can have positive RAID findings, which can represent the detection of occult lesions; (7) single photon emission computed tomography appears to provide better image resolution than planar scanning; (8) regardless of the sensitivity reported in any particular study, almost all investigators have observed the disclosure of occult neoplasms by RAID; and (9) RAID, a more functional test of usually high specificity, can complement other radiological methods, such as computed tomography scans, which are limited to structural information.

An assessment of prolonged reactivity of seven monoclonal antibodies against CX-1 tumor xenografts using a hand-held gamma-detecting probe

The biodistribution and kinetics of 7 monoclonal antibodies (MAb) with known reactivity against CX-1 tumor were examined over 21 days using a hand-held gamma-detecting probe (Neoprobe system). Twenty-eight immuno-deprived (athymic) nude mice implanted with human colon adenocarcinoma CX-1 xenografts were injected intraperitoneally with 50 microCi of 125I-labeled antibodies (4 mice/antibody). Of the 7 monoclonal antibodies, 4 were anti-CEA (MA, MB, MC, and MD), 2 were anti-TAG 72 (B72.3 NCI and B72.3 fermented) and one was anti-colorectal cancer (17-1A). Daily probe counts were recorded in duplicate over the tumor site and the contralateral nontumor site (background), and tumor-to-background (Tu/Bkg) ratios were calculated. Animals were sacrificed on day 21, and blood, heart, liver, spleen, lungs, kidneys, intestine, muscle, and the tumor were removed for gamma well counting. All antibodies identified the tumor as early as 24 h postinjection and specific tumor localization improved over time. Patterns of prolonged tumor binding varied considerably from one antibody to another, although all but one (MB) showed continuously increasing Tu/Bkg ratios. These data indicate progressive clearance of the antibodies from the background tissue and a persistence of labeled MAb activity in tumor resulting in improved tumor localization with increasing postinjection time.