Marlin O. Thurston

Radioimmunoguided surgery using monoclonal antibody

The potential proficiency of radioimmunoguided surgery in the intraoperative detection of tumors was assessed using labeled monoclonal antibody B72.3 in 66 patients with tissue-proved tumor. Monoclonal antibody B72.3 was injected 5 to 42 days preoperatively, and the hand-held gamma-detecting probe was used intraoperatively to detect the presence of tumor. Intraoperative probe counts of less than 20 every 2 seconds, or tumor-to-adjacent normal tissue ratios less than 2:1 were considered negative (system failure). Positive probe counts were detected in 5 of 6 patients with primary colon cancer (83 percent), in 31 of 39 patients with recurrent colon cancer (79 percent), in 4 of 5 patients with gastric cancer (80 percent), in 3 of 8 patients with breast cancer (37.5 percent), and in 4 of 8 patients with ovarian cancer (50 percent) undergoing second-look procedures. Additional patients in each group were scored as borderline positive. Overall, radioimmunoguided surgery using B72.3 identified tumors in 47 patients (71.2 percent), bordered on positive in 6 patients (9.1 percent), and failed to identify tumor in 13 patients (19.7 percent). Improved selection of patients for antigen-positive tumors, the use of higher affinity second-generation antibodies, alternate routes of antibody administration, alternate radionuclides, and more sophisticatedly bioengineered antibodies and antibody combinations should all lead to improvements in radioimmunoguided surgery.

Method for locating, differentiating, and removing neoplasms

The present invention is addressed to a method for the improved localization, differentiation, and removal of neoplastic tissue in animals. In particular, one aspect of the present invention involves a surgical procedure wherein an animal suspected of containing neoplastic tissue is surgically accessed and the tissue therein examined visually and by palpation for evidence of neoplastic tissue. The improved methodology commences with the administering to the animal of an effective amount of a labelled antibody specific for neoplastic tissue and labelled with a radioactive isotope exhibiting specific photon emissions of energy levels. Next, and importantly, the surgial procedure is delayed for a time interval following said administering for permitting the labelled antibody to preferentially concentrate in any neoplastic tissue present in the animal so as to increase the ratio of photon emissions from neoplastic tissue to background photon emissions in said animal. Thereafter, an operative field of the animal is surgically accessed and tissue within the operative field to be examined for neoplastic tissue has the background photon emission count determined. Once the background photon emission account for tissue within the operative field has been determined, a handheld probe is manually positioned within the operative field adjacent tissue suspected of being neoplastic. The probe is configured for fascile hand positioning and maneuvering within the operative field of the animal. The probe is characterized by having a collimatable radiation detector having a selective photon entrance and having an output deriving discrete signals responsive to photon emissions when said entrance is positioned immediately adjacent thereto. The probe further comprises amplifier means having an input coupled with said radiation detector output and responsive to said discrete signals to provide corresponding amplified output pulses. Finally, the probe comprises readout means responsive to said output pulses and actuable to an initial condition for commencing the provision of a perceptible indication of an indicia corresponding to the number of said output pulses received. From the perceptible indication, the extent of tissue exhibiting a number of output pulses having a value above background output pulses is determined and such determined tissue removed surgically. Thereafter, the probe is manually positioned adjacent tissue surrounding the surgically removed tissue to determined from said perceptible indication whether any of said surrounding tissue still exhibits a number of output pulses having a value above said background output pulses. Any adjacent tissue surrounding the initial surgically removed tissue which does exhibit an increased number of output pulses is surgically removed additonally. Thereafter, the margins again are examined with the probe in order to ensure that all tissue exhibiting a number of output pulses having a value above the background output pulses has been removed.

Radioimmunoguided surgery using the monoclonal antibody B72.3 in colorectal tumors

The authors have developed a hand-held gamma-detecting probe (GDP) for intraoperative use that improves the sensitivity of external radioimmunodetection. Radiolabeled monoclonal antibody (MAb) B72.3 was injected in six patients with primary colorectal cancer and 31 patients with recurrent colorectal cancer an average of 16 days preoperatively. The GDP localized the MAb B72.3 in 83 percent of sites. The technique, known as a radioimmunoguided surgery (RIGSTM) system did not alter the surgical procedure in patients with primary colorectal cancer but did alter the approach in 26 percent (8/31) of patients with recurrent colorectal cancer. Two patients avoided unnecessary liver resections and two underwent extraabdominal approaches to document their disease. The RIGS system may influence the short-term morbidity and mortality of surgery for colorectal cancer. Larger series and longer follow-up are needed to determine whether the RIGS system confers a survival advantage to the patient with colorectal cancer.

Intraoperative radioimmunodetection of colorectal tumor with a hand-held radiation detector

A hand-held gamma detection probe was used intraoperatively to localize primary and recurrent colorectal tumors in 28 patients 48 to 72 hours after they received an intravenous injection of 2.2 mCi of iodine-131 labeled anticarcinoembryonic antigen polyclonal baboon antibody. Preoperative evaluation included determination of serum carcinoembryonic antigen, barium enema, colonoscopy, chest film, computerized axial tomography, liver, spleen, and bone scans, and endoscopy when indicated. Preoperative whole-body imaging correctly localized primary tumors in only 33 percent of the patients, whereas it correctly demonstrated tumor in 64 percent of those with recurrent disease. Intraoperative tumor-to-background ratios derived from the detector probe were elevated in all patients, averaging 3.97:1 in primary lesions and 4.18:1 in recurrent tumors. Postoperatively, carcinoembryonic antigen was localized in tissues with the avidin-biotin peroxidase staining technique to confirm intraoperative readings. Variations in stain uptake in a patient could be correlated with variations in radiation detector readings in the same patient. Results support our previous work in nude mice, demonstrating the improved sensitivity and specificity of the hand-held gamma detection device over whole-body imaging for intraoperative localization of immunoradiolabeled tumors.

A gamma-detecting probe for radioimmune detection of CEA-producing tumors

The detection of tumors with radiolabeled antibodies against CEA is possible; however, current nuclear medicine scanning cameras rarely detect tumors smaller than 2 cm in diameter. One of the limitations to tumor detection is the inability to place a detecting camera near a deeply seated intra-abdominal tumor. A hand-held gamma-detecting probe, suitable for intraoperative use, was designed to locate radioactive tumors. Experimental work with CEA-producing colon tumor xenografts in nude mice suggests this probe is more sensitive than external scanners in detecting small tumors. A case report documents the clinical use of this new intraoperative probe.

The impact of radioimmunoguided surgery (RIGSTM) 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 (NeoprobeTM 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.

Portable gamma probe for radioimmune localization of experimental colon tumor xenografts

Tumor radioimmune detection as presently practiced utilizes a gamma scintillation camera to image tumors. A major clinical limitation is the inability to detect tumors smaller than 2 cm. This limitation is due in part to the inverse square law which states: the number of detected radioactive counts is inversely proportional to the square of the distance separating a radioactive source from the detecting device. A hand-held gamma-detecting probe (GDP) suitable for intraoperative use has been developed. The GDP can be placed near radioactive tumors and take advantage of the inverse square law in a way not possible with external scanning cameras. The use of radiolabeled baboon carcinoembryonic antigen (CEA)-specific antisera produced increased tumor isotope localization in CEA-producing tumors compared to the injection of nonspecific antisera. Tumor isotope-antisera localization was not influenced by tumor volume or time since tumor implantation. The GDP probe counts demonstrated a high degree of correlation with gamma well tissue counts. The probe was able to detect preferential tumor localization in doses lower than could be detected with external scintillation cameras.

Localization by hand-held gamma probe of tumor labeled with antibody “cocktail”

Five groups (n = 4) of congenitally athymic female nude mice bearing subcutaneous implants of CX-1 and/or SW-1116 tumor in the hind limbs received iodine-125 radio-labeled monoclonal antibodies (MoAbs) B72.3 (two groups), 17-1A (two groups), and cocktail (one group) (iodogen method, 50 microCi/10 micrograms/mouse). Daily probe counts were made in duplicate with a hand-held detector over each tumor site and the front leg (background) for 21 days. Animals were sacrificed and appropriate well counts were obtained. All the single MoAb preparations localized well in both tumor cell lines. Uptake of monoclonal antibody 17-1A was similar in the two tumor cell lines, with counts initially high and slowly decreasing over the 21-day period. Tumor/background ratios continued to increase over time, indicating that both tumor lines have similar antigenic expression for the monoclonal antibody 17-1A. This was not the case for monoclonal antibody B72.3, which showed a preferential uptake by the CX-1 tumor, with higher initial counts and prolonged binding of the antibody, giving rise to higher tumor/background ratios. The mixture of monoclonal antibodies B72.3 and 17-1A markedly improved the uptake by the CX-1 tumor cell line but not that by the SW-1116 cell line, where the effect was negative when compared to the uptake of the single MoAb preparations. The use of a monoclonal antibody mixture can enhance targeting of some tumor sites. Due to the heterogeneity of tumor cell lines, even within the same animal, different mixtures of monoclonal antibodies are needed to increase the targeting of tumor.

Radioimmunoguided surgery: A new intraoperative approach to the detection of tumor

Tumors marked with a radiolabeled antibody may be located by two different techniques. The first is the diagnostic use of a gamma camera to produce an image. The second is the clinical use of a gamma-sensitive probe to ‘home in’ on tumors intraoperatively. Since the two techniques are quite different, it is not surprising that they differ in advantages, limitations, and design.

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.