Probe-guided surgery for colorectal cancer

Intraoperative Radiochromoguided Mapping of Sentinel Lymph Node in Colon Cancer

Aims and Background

The aim of our study was to assess the feasiblility of sentinel lymph node (SLN) detection in colon cancer using a radiochromoguided technique. The regional lymph node status is crucial for colorectal cancer staging and the stage of disease at the time of diagnosis is the main factor influencing therapeutic decision-making and patient survival.

Methods and Study Design

Between April and June 2001 eight patients with colon cancer were studied by radiochromoguided sentinel lymph node mapping. At the time of surgery 2 ml of patent blue dye was injected around the tumor, followed after 10 minutes by 2 ml of 99mTc-labeled albumin. After 30 minutes the SLN was identified by a gamma probe. Surgery was completed by standard resection. The SLN was processed for permanent hematoxylin and eosin staining and for immunohistochemical examination with anti-CEA and anti-cytokeratin antibodies.

Results

SLNs were identified in six patients; two were negative for metastasis by hematoxylin-eosin and immunohistochemical examination, two were positive for metastasis by both methods, and two were negative for metastasis by hematoxylin-eosin but positive by immunohistochemical examination. There were no false negative SLNs and no complications occurred.

Conclusion

The actual utility of SLN detection for prognostic purposes is still unknown, but intraoperative radiochromoguided SLN mapping is technically feasible in colon cancer, although it is associated with more technical difficulties than in breast cancer and malignant melanoma.

Selecting Potential Targetable Biomarkers for Imaging Purposes in Colorectal Cancer Using TArget Selection Criteria (TASC): A Novel Target Identification Tool

Peritoneal carcinomatosis (PC) of colorectal origin is associated with a poor prognosis. However, cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy is available for a selected group of PC patients, which significantly increases overall survival rates up to 30%. As a consequence, there is substantial room for improvement. Tumor targeting is expected to improve the treatment efficacy of colorectal cancer (CRC) further through 1) more sensitive preoperative tumor detection, thus reducing overtreatment; 2) better intraoperative detection and surgical elimination of residual disease using tumor-specific intraoperative imaging; and 3) tumor-specific targeted therapeutics. This review focuses, in particular, on the development of tumor-targeted imaging agents. A large number of biomarkers are known to be upregulated in CRC. However, to date, no validated criteria have been described for the selection of the most promising biomarkers for tumor targeting. Such a scoring system might improve the selection of the correct biomarker for imaging purposes. In this review, we present the TArget Selection Criteria (TASC) scoring system for selection of potential biomarkers for tumor-targeted imaging. By applying TASC to biomarkers for CRC, we identified seven biomarkers (carcinoembryonic antigen, CXC chemokine receptor 4, epidermal growth factor receptor, epithelial cell adhesion molecule, matrix metalloproteinases, mucin 1, and vascular endothelial growth factor A) that seem most suitable for tumor-targeted imaging applications in colorectal cancer. Further cross-validation studies in CRC and other tumor types are necessary to establish its definitive value.

A comprehensive overview of radioguided surgery using gamma detection probe technology

The concept of radioguided surgery, which was first developed some 60 years ago, involves the use of a radiation detection probe system for the intraoperative detection of radionuclides. The use of gamma detection probe technology in radioguided surgery has tremendously expanded and has evolved into what is now considered an established discipline within the practice of surgery, revolutionizing the surgical management of many malignancies, including breast cancer, melanoma, and colorectal cancer, as well as the surgical management of parathyroid disease. The impact of radioguided surgery on the surgical management of cancer patients includes providing vital and real-time information to the surgeon regarding the location and extent of disease, as well as regarding the assessment of surgical resection margins. Additionally, it has allowed the surgeon to minimize the surgical invasiveness of many diagnostic and therapeutic procedures, while still maintaining maximum benefit to the cancer patient. In the current review, we have attempted to comprehensively evaluate the history, technical aspects, and clinical applications of radioguided surgery using gamma detection probe technology.

Pathology underrates colon cancer extranodal and nodal metastases; ex vivo radioimmunodetection helps staging

PURPOSE

Colorectal carcinoma is frequently accompanied by small lymph nodes metastases that often escape pathologic examination. We evaluated whether ex vivo radioimmunodetection with the Affinity Enhancement System (AES) could improve detection of mesocolonic metastases.

EXPERIMENTAL DESIGN

A bivalent 111In-labeled hapten was injected (16 patients) 4 days after a bispecific antibody (anticarcinoembryonic antigen, antihapten). Surgery was done 1 to 3 days later, and radioactive uptake in the mesocolon was recorded. Extensive pathologic examination of the mesocolon (reference method) was done after fat dissolution. This method visualizes all lymph nodes but is not in routine use.

RESULTS

The reference method disclosed 705 nodes. There was no significant difference between the number of node metastases detected by AES or by the reference method (16 versus 17). Better detection would have been obtained by AES than by routine pathology (P<0.01). In addition 12 extranodal metastases were found in this study of which eight were detected by AES. The prognostic importance of such extranodal metastases has been underlined in the literature. Routine pathology combined with AES would have disclosed all node metastases and 86% of total metastases versus 35% by routine pathology alone.

CONCLUSIONS

Ex vivo radioimmunodetection could improve nodal and extranodal metastases detection in patients with colorectal cancer. Its value for improving pathologic analysis, together with the effect of these small metastases on prognosis, should be further evaluated. The benefit of adjuvant chemotherapy for patients upstaged with radioimmunodection should also be assessed because adjuvant chemotherapy improves the 5-year survival of stage III patients.

Operative probe scintimetry with indium and technetium for colorectal cancer

Surgeons introduced the hand-held gamma detection probe in combination with tumor-directed monoclonal antibodies in patients with colorectal cancer. The clinicians conducted innovative research involving antibody chemistry and variation as well as radioactive dosimetry and decay. The results of these studies represented an era when surgeons began reporting on specific lesion detection and the impact of the antibody administration on the management of the patient. The summary of the important early trials involving monoclonal antibodies and probe scintimetry provides a valuable look into the early development of the antibody technology and a glimpse of potential future applications using the gamma detection probe.

Molecular imaging and radioimmunoguided surgery

Molecular imaging comprises a series of diagnostic modalities that provide information on the physiology and molecular composition of cells and tissues. One of these modalities, radioimmunodetection, uses radiolabeled monoclonal antibodies (mAbs) to image tissues. Two radioimmunodetection modalities are described in this article: immunoscintigraphy and radioimmunoguided surgery (RIGS). In immunoscintigraphy, the radioactivity is measured with the use of an external gamma camera and used to create images. In RIGS, the radioactivity is detected intraoperatively with the use of a handheld gamma probe to help the surgeon detect foci of otherwise occult disease. Both techniques have the potential to improve the preoperative and intraoperative localization of cancer. Multiple studies have been performed on the efficacy of RIGS on different malignancies, especially colorectal cancer. Despite the good sensitivity of the technique, some concerns revolve around the high rate of false positives and the real significance of leaving RIGS-positive tissue behind in terms of long-term outcomes and survival. More studies are warranted to further develop the technique and determine the specific role it will play on the diagnosis and management of surgical disease. Surgeons should actively participate in these studies and in expanding the applications of this promising technology.

A newly developed intra-operative gamma camera: performance characteristics in a laboratory phantom study

PURPOSE

Radioguided surgery depends on the intra-operative detection of radiolabelled tissues. This is currently accomplished with hand tools capable of providing a tone signal, depending on the proximity and direction of a radioactive source in relation to the probe. The advantages of visual images of radiolabelled tissues are well recognised, but satisfactory means of acquiring such images intra-operatively are not yet available. The goal of this study was to examine the performance of a newly developed intra-operative gamma camera, compact enough to be a hand tool and capable of yielding a visual image of the source field.

METHODS

The study was performed in the laboratory with a phantom consisting of a water bath and small hollow spheres (1-2 cm in internal diameter) filled with 99mTc (1-5 microCi/cc), placed in different configurations within the bath. For comparison, studies were also performed using a standard intra-operative gamma probe, and others using a standard single-head high-resolution gamma camera.

RESULTS

Compared with the gamma probe, the intra-operative camera was found to possess a superior ability to distinguish small, deep and weakly localised radioactivity sources from background. By acquiring images from different angles, it allowed a 3D understanding of multiple radioactive sources. It detected "cold" defects within a "hot" radiolabelled sphere. It discriminated a weak source located near a much "hotter" radioactivity source, similar to discrimination with the standard gamma camera, and discerned localised sources against a background of radioactivity.

CONCLUSION

It is anticipated that the high imaging potential of the camera tested in this study will offer clinical advantages.

Pharmacokinetics of radioimmunotherapeutic agent of direct labeling mAb 188Re-HAb18

AIM: To label anti-hepatoma monoclonal antibody (mAb) fragment HAb18 F(ab’)₂ was labeled with ¹⁸⁸Re for the pharmacokinetic model of ¹⁸⁸Re-HAb18 F(ab’)₂ and to evaluate its pharmacokinetic parameters in hepatoma-bearing nude mice.

METHODS: HAb18 F(ab’)₂ was directly labeled with ¹⁸⁸Re using 2-mercaptoethanol (2-ME) as reducing agents. Labeling efficiency and immunoreactivity of ¹⁸⁸Re-HAb18 F(ab’)₂ were evaluated by Whatman 3MM paper chromatography and live cell assay, respectively. Biodistribution analysis was also conducted in nude mice bearing human hepatoma in which animals were sacrificed at different time points (1, 4, 18, 24 and 24 h) after ¹⁸⁸Re-HAb18 F (ab’)₂ was injected through tail-vein into hepatoma-bearing nude mice. The blood and radioactivity of organs and mass were measured. The concentrations of ¹⁸⁸Re-HAb18 F(ab’)₂ were evaluated with apharmacokinetic 3P97 software.

RESULTS: The optimum labeling efficiency and immunoreactive fraction were 91.7% and 0.78% respectively. The parameters of ¹⁸⁸Re-HAb18 F(ab’)₂ were: T_1/2, 2.29 h; Vd,1.49 × 10^-9 L·Bq^-1; AUC, 20. 49 × 10⁹ Bq·h·L^-1;CL, 0.45 × 10^-3 L·h^-1. ¹⁸⁸Re-HAb18 F(ab’)₂ could locate specially in hepatoma with high selective reactivity of HAb18 F(ab’)₂. ¹⁸⁸Re-HAb18 F(ab’)₂ was mainly eliminated by kidney. The maximal tumor to blood ratio was at 48 h, and maximal tumor to liver ratio was at 18 h.

CONCLUTION: The pharmacokinetics of ¹⁸⁸Re-HAb18 F (ab’)₂ fital-compartment model.¹⁸⁸Re-HAb18 F(ab’)₂ can be uptaken selectively at the hepatoma site.

Immunoscintigraphy and intra-operative radioimmunodetection in the treatment of colorectal carcinoma

PURPOSE

Intra-operative radioimmunodetection of malignant involved lymph nodes follows the pre-operative immunoscintigraphy in the treatment of patients with colorectal carcinoma. The aims of this clinical study were to determine the sensitivity of the method, to compare the results in study when using Oncoscint and CEA-Scan and to evaluate the importance of the method of surgery and postoperative adjuvant therapy.

PATIENTS AND METHODS

121 patients with colorectal tumours (106 primary and 15 recurrent) were operated on using radioimmunoguided surgery (RIGS). The study compared results of pre-operative immunoscintigraphy, intra-operative radioimmunodetection and postoperative histological examination. Histological investigation used classical H&E staining. In histologically negative and RIGS positive cases the immunohistochemical investigation was supplemented. Two radiopharmaceuticals were used Oncoscint CR 103 (MAb B72.3, Satumomab Pendetide), labelled with 111In in 56 patients and CEA-Scan (IMMU 4-Fab' fragments MAb against CEA, Arcitumomab), labelled with 99mTc in 65 patients.

RESULTS

The relationship between RIGS positive results and histological examination was statistically assessed after 38 operations and the most acceptable RIGS evaluating index was determined. All subsequent results were evaluated by this index. Immunoscintigraphy of tumour was positive in 112 cases (92.6%). Fifty-five RIGS positive cases of malignant infiltrated lymph nodes were confirmed by 43 histologically positive examinations (78%). In this group 9 cases were discovered only by immunohistochemistry. Sixty-six remaining RIGS negative results were confirmed in 62 (94%) cases by negative histology.

CONCLUSIONS

Both immunoscintigraphy and RIGS enable one to make a more accurate diagnosis. While treating the primary disease the use of RIGS may help in assessment of necessary extent of operation performance and in staging of the disease by revealing occult lymph nodes involved. Pre-operative immunoscintigraphy seems to be a useful diagnostic method for detection of tumour recurrence. When comparing two radiopharmaceuticals used, CEA-Scan seems to be more suitable for diagnostic studies, but using the Oncoscint for tumour recurrence detection had some specific benefit, too.