Radioimmunoguided radical prostatectomy and lymphadenectomy

Interventional nuclear medicine: a focus on radioguided intervention and surgery

Within interventional nuclear medicine (iNM) a prominent role is allocated for the sub-discipline of radioguided surgery. Unique for this discipline is the fact that an increasing number of clinical indications (e.g. lymphatic mapping, local tumor demarcation and/or tumor receptor targeted applications) have been adopted into routine care. The clinical integration is further strengthened by technical innovations in chemistry and engineering that enhance the translational potential of radioguided procedures in iNM. Together, these features not only ensure ongoing expansion of iNM but also warrant a lasting clinical impact for the sub-discipline of radioguided surgery.

Recent advances in nuclear and hybrid detection modalities for image-guided surgery

Introduction: Radioguided surgery is an ever-evolving part of nuclear medicine. In fact, this nuclear medicine sub-discipline actively bridges non-invasive molecular imaging with surgical care. Next to relying on the availability of radio- and bimodal-tracers, the success of radioguided surgery is for a large part dependent on the imaging modalities and imaging concepts available for the surgical setting. With this review, we have aimed to provide a comprehensive update of the most recent advances in the field. Areas covered: We have made an attempt to cover all aspects of radioguided surgery: 1) the use of radioisotopes that emit γ, β⁺, and/or β^- radiation, 2) hardware developments ranging from probes to 2D cameras and even the use of advanced 3D interventional imaging solutions, and 3) multiplexing solutions such as dual-isotope detection or combined radionuclear and optical detection. Expert opinion: Technical refinements in the field of radioguided surgery should continue to focus on supporting its implementation in the increasingly complex minimally invasive surgical setting, e.g. by accommodating robot-assisted laparoscopic surgery. In addition, hybrid concepts that integrate the use of radioisotopes with other image-guided surgery modalities such as fluorescence or ultrasound are likely to expand in the future.

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.

Pretargeting CWR22 prostate tumor in mice with MORF-B72.3 antibody and radiolabeled cMORF

PURPOSE

We have now applied our MORF/cMORF pretargeting technology to the targeting of CWR22 prostate tumor in nude mice.

METHODS

The antiTAG-72 antibody B72.3 was conjugated with an 18 mer MORF while the cMORF was radiolabeled with (99m)Tc. The specific binding of the antibody to the CWR22 cells was first confirmed in an assay placing the radiolabeled B72.3 antibody in competition with increasing concentrations of native B72.3. Thereafter, a group of four CWR22 tumored mice intravenously received the MORF-B72.3 and, 3 days later, the (99m)Tc-cMORF, and were killed at 3 h postradioactivity injection. The dosage of the labeled cMORF was selected on the basis of previous experience in LS174T tumored mice. As controls, four animals received only the radiolabeled cMORF and another four received only the (111)In-B72.3. The maximum percent tumor accumulation (MPTA) of the labeled cMORF was subsequently determined by a dosage study of labeled cMORF. Both a multipinhole SPECT image and a planar gamma camera image were obtained of a representative mouse.

RESULTS

The CWR22 tumor was confirmed to be TAG-72-positive. The MPTA of the labeled cMORF in the CWR22 tumor was 2.22%ID/g compared to only 0.12%ID/g in control mice without pretargeting. Both the planar and tomographic images confirmed the success of the CWR22 pretargeting.

CONCLUSIONS

The MORF/cMORF pretargeting approach has been successfully applied to tumor targeting of the prostate xenograft CWR22. However, the MPTA in this tumor model is lower than that in the LS174T tumor model investigated earlier, possibly due to a lower tumor blood supply.

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.

Radioimmunoguided surgery using indium-111 capromab pendetide (PROSTASCINT) to diagnose supraclavicular metastasis from prostate cancer

A 59-year-old man presented with a Gleason score of 4 + 4 = 8 prostate cancer and with multiple bilateral pelvic nodes involved at open pelvic lymph node dissection. On indium-111 capromab pendetide (ProstaScint) scan, there was increased tracer deposition in the prostate, the mesenteric nodes, the right pulmonary hilum, and the left supraclavicular fossa. The ProstaScint injection was repeated, and the gamma probe was used to localize tissue that accumulated radiotracer. Two nodes were excised, one that exhibited increased uptake and one that did not. The radioactive lymph node contained metastatic prostate cancer. No malignancy was found in the second node.

Biodistribution and localization of radiolabeled NR-LU-10 Fab fragment in human breast cancer xenografts

Radioimmunodetection, which takes advantage of tumor-specific or tumor-associated radio-labeled monoclonal antibodies or other biologic molecules to diagnose the extent of disease in cancer patients, has been of limited use in studies to date in patients with breast cancer. The difficulty is in finding an antibody that is both sensitive and specific enough to localize in breast tumors. This study undertook immunohistochemical and in vivo evaluation of tumor localization and biodistribution of NR-LU-10 Fab (antibody fragment) in breast tumors to determine its ability to bind selectively to malignant tissue. NR-LU-10 Fab recognizes a pancarcinoma glycoprotein antigen found on tumors of epithelial cell origin. NR-LU-10 Fab reacted with 6/6 (100%) breast cancer cell lines and 14/16 (87.5%) breast tumors with varying degrees of immunostaining intensities. Athymic mice bearing ZR-75-1 breast cancer xenografts were injected with 125I-labeled NR-LU-10 Fab (12 microg/5 microCi) and sacrificed at fixed time intervals. These studies demonstrated the highest tumor uptake of labeled Fab at 12 h postinjection (4.58+/-1.59% of injected dose/gram [% ID/g] of tissue); this gradually decreased to 0.13+/-0.05% ID/g of tissue by 72 h postinjection of the radiolabeled Fab. Biolocalization to normal tissues was as predicted for a Fab fragment; i.e., initially high in clearance organs (kidney), followed by rapid clearance over the 72-h test period. NR-LU-10 Fab displays adequate breast tumor localization with minimal biolocalization to normal tissues, thus supporting its potential use in radioimmunoscintigraphy and the RIGS system (radioimmunoguided surgery).

Radiolabeled somatostatin analogs in prostate cancer

Vapreotide (RC-160), a somatostatin analog, was labeled with 99mTC by a direct method and also by using CPTA [1,4,8,11-tetraazacyclotetradecane] as a bifunctional chelating agent. The labeled compounds were evaluated in nude mice bearing experimental human prostate cancers. In these studies, 111In-DTPA-D-Phe-Octreotide (111In-DTPA-octreotide) served as a standard and 99mTc-oxytocin as a receptor-non-specific control. 99mTc-octreotide was also used. The 24 htumor uptake of 99mTc-RC-160 was nearly 400% higher, (p < 0.05), than that of 111In-DTPA-octreotide and diminished upon receptor blocking. In all tissues except the kidneys, the uptake of 99mTc-RC-160 was also higher than that of 111In-DTPA-octreotide. The uptake of 99mTc-RC-160 was influenced by the amount of peptide injected and the best tumor/muscle and tumor/blood ratios were obtained when only one micrograms of the peptide (200 Ci/mmol) was administered.

B72.3 immunoreactivity in benign abdominal lymph nodes associated with gastrointestinal disease

PURPOSE

Immunolocalization of the tumor-associated glycoprotein 72 antigen with the monoclonal antibody B72.3 has been used as a "cancer marker" in radioimmunoscintigraphy and radioimmunoguided surgery (RIGS). Radioimmunoscintigraphy and RIGS have been used to detect occult metastatic deposits from colorectal adenocarcinoma. It has been suggested that RIGS is superior to histologic examination in detecting lymph node metastases from colorectal cancer. To determine the specificity of immunodetection of the tumor-associated glycoprotein-72 antigen as a marker for metastatic adenocarcinoma, we studied benign intra-abdominal lymph nodes with B72.3 and an immunohistochemical technique.

METHODS

Formaldehyde-fixed, paraffin-embedded sections of 276 benign abdominal lymph nodes, resected with 35 cases of colonic adenocarcinoma and 33 cases of benign gastrointestinal disorders, were evaluated for B72.3 immunoreactivity using an avidin-biotin complex immunohistochemical technique. Lymph nodes from cases of colonic carcinoma were also studied with cytokeratin immunostaining to help eliminate occult micrometastases.

RESULTS

B72.3 immunoreactivity was seen in the germinal centers of benign lymph nodes associated with 49 percent of the cases of colonic adenocarcinoma and 12 percent of the cases of benign gastrointestinal disease.

CONCLUSIONS

B72.3 immunoreactivity can be seen in benign abdominal lymph nodes associated with gastrointestinal disease. We advise caution in the use of diagnostic techniques that equate B72.3 immunoreactivity with the presence of adenocarcinoma.

Tumor associated glycoprotein-72 is highly expressed in prostatic adenocarcinomas

We examined the expression of two well-characterized oncofetal antigens, the tumor associated glycoprotein-72 (TAG-72) and carcinoembryonic antigen (CEA), in malignant prostatic tissues. Three specific monoclonal antibodies, B72.3, CC49 and CC83, were used to examine the expression of TAG-72. Immunoreactivity was detected in 63% of the malignant specimens using B72.3. CC49 and CC83 were more sensitive than B72.3 in detecting TAG-72 expression. Immunoreactivity was detected in approximately 80% of prostatic adenocarcinomas with CC49 or CC83. The pattern and localization of TAG-72 immunoreactivity were similar for the three antibodies with most immunoreactivity observed within the cytoplasm of malignant cells and within the lumens of malignant glands. TAG-72 immunoreactivity was not detected within benign epithelium or stroma, with the exception of focal epithelial expression in areas of acute prostatitis. The COL-1 antibody to CEA did not detect CEA in benign glands, stroma, or malignant cells of prostate specimens resected for prostatic adenocarcinoma. These results demonstrate that TAG-72, but not CEA, is frequently expressed in prostatic adenocarcinomas.

Reactivity of B72.3 with adenocarcinomas. An immunohistochemical study of 476 cases

BACKGROUND

The monoclonal antibody B72.3 has been shown to react with several common types of adenocarcinoma. However, the distribution of B72.3 reactivity in adenocarcinomas has not been well-enough defined to determine whether B72.3 immunostaining would be helpful in the diagnosis of adenocarcinoma of unknown origin.

METHODS

Formaldehyde fixed, paraffin-embedded tissue from 476 adenocarcinomas from a variety of primary sites were studied using B72.3 and an avidin-biotin complex immunohistochemical technique.

RESULTS

B72.3 immunoreactivity was seen in 75-100% of the adenocarcinomas from the ovary, endocervix, endometrium, distal esophagus/stomach, colon, lung, breast, prostate, pancreas, and bile ducts. Positive reactions were unusual in thyroid carcinomas (7%) and renal cell carcinomas (11%). B72.3 reactivity was not seen in the 20 hepatocellular carcinomas or 4 adrenal cortical carcinomas studied.

CONCLUSIONS

B72.3 reacts with a wide variety of adenocarcinomas. Immunostaining with B72.3 may be helpful in excluding hepatocellular carcinoma in certain clinical settings.