Implantation of colon cancer at trocar sites is increased by low pressure pneumoperitoneum.

BACKGROUND: The purpose of this study was to determine the effect of pneumoperitoneum on the implantation of tumor at trocar sites. METHODS: GW-39 human colon cancer cell suspension (0.5 ml of 2.5% v/v) was injected into the peritoneal cavity of golden Syrian hamsters through a 1 cm midline incision. Four 5 mm trocars were inserted through the anterior abdominal wall, and the midline incision was then closed. The animals were randomized to receive pneumoperitoneum (n = 62) or no pneumoperitoneum (n = 60) for 10 minutes. Tumor implantations at trocar sites and midline wound incisions were documented grossly and histologically 8 weeks later. RESULTS: Tumor was identified in 86% (49 of 57) of control animals and 95% (52 of 55) of the experimental group (p = 0.20). Implants increased with pneumoperitoneum at the midline incision from 44% to 71% (p < 0.01) and at trocar sites from 41% to 64% (p < 0.00001). CONCLUSIONS: Pneumoperitoneum significantly increased tumor implantation at trocar sites and midline incisions.

Underlying pathology in mammary Paget's disease.

BACKGROUND: Management of patients with mammary Paget's disease is controversial; recent recommendations range from primary radiotherapy to modified radical mastectomy. This review correlates associated breast findings with disease stage and outcome to help guide evaluation and treatment. METHODS: Retrospective review of clinical, mammographic and pathologic data from 38 women with mammary Paget's disease treated between 1979 and 1995 was performed. Mastectomies were performed on all but two patients with the entire breast and lymph nodes evaluated for histopathologic evidence of carcinoma. RESULTS: Underlying carcinoma (ductal carcinoma in situ and/or invasive ductal cancer) was found in most patients (92%) even when no palpable mass was evident (85%); this carcinoma is often multifocal (73%). Mammography fails to identify the underlying disease in many patients with no palpable mass and multifocal underlying disease (64%). Patients with Paget's disease and a palpable mass have a much greater incidence of invasive cancer, multifocal lesions, and positive lymph nodes, and have worse survival. CONCLUSIONS: Although some patients with Paget's disease might be well treated by breast conservation therapy, many patients have underlying multifocal carcinoma (including invasive cancer), which can be inapparent by examination and mammography. Selecting candidates with disease amenable to complete excision without mastectomy is problematic.

Detection of recurrent and metastatic colorectal cancer: comparison of positron emission tomography and computed tomography.

BACKGROUND: This study evaluates the clinical value of positron emission tomography (PET) with 2-[F-18] fluoro-2-deoxy-D-glucose (FDG) as compared to computed tomography (CT) in patients with suspected recurrent or metastatic colorectal cancer (CRC). METHODS: A retrospective review of the records of 58 patients who had FDG-PET for evaluation of recurrent or advanced primary CRC was performed. FDG-PET results were compared with those of CT and correlated with operative and histopathologic findings, or with clinical course and autopsy reports. RESULTS: Recurrent or advanced primary CRC was diagnosed in 40 and 11 patients, respectively. The sensitivity and specificity of FDG-PET were 91% and 100% for detecting local pelvic recurrence, and 95% and 100% for hepatic metastases. These values were superior to CT, which had sensitivity and specificity of 52% and 80% for detecting pelvic recurrence, and 74% and 85% for hepatic metastases. FDG-PET correctly identified pelvic recurrence in 19 of 21 patients; CT was negative in 6 of these patients and equivocal in 4. FDG-PET was superior to CT in detecting multiple hepatic lesions and influenced clinical management in 10 of 23 (43%) patients. CONCLUSION: FDG-PET is more sensitive than CT in the clinical assessment of patients with recurrent or metastatic CRC, and provides an accurate means of selecting appropriate treatment for these patients.

Radioimmunotherapy with a 64Cu-labeled monoclonal antibody: a comparison with 67Cu.

67Cu (t1/2 = 62 h) has demonstrated potential as a radionuclide for radioimmunotherapy, but limited availability severely restricts its widespread use. 64Cu (t1/2 = 12.8 h) has been shown to have comparable effectiveness in vitro and in vivo. The present study was undertaken to examine the therapeutic potential of 64Cu- and 67Cu-bromoacetamidobenzyl-1,4,8,11-tetraazacyclotetradeca ne-N, N',N",N"'-tetraacetic acid (BAT)-2-iminothiolane (2IT)-1A3 (1A3 is a mouse anti-human colorectal cancer mAb) for treatment of GW39 human colon carcinoma carried in hamster thighs. Hamsters were injected with 64Cu- or 67Cu-BAT-2IT-1A3 or Cu-labeled nonspecific IgG (MOPC) or saline. Hamsters were killed 6-7 months after therapy or when tumors were > or = 10 g. Of the hamsters with small tumors (mean weight 0.43 +/- 0.25 g), 87.5% were disease-free 7 months after treatment with 2 mCi (1 Ci = 37 GBq) of 64Cu-BAT-2IT-1A3 or 0.4 MCi of 67Cu-BAT-2IT-1A3. The mean tumor doses at these activities of 64Cu- and 67Cu-BAT-2IT-1A3 were 586 and 1269 rad (1 rad = 0.01 Gy), respectively. In contrast, 76% of hamsters treated with 2 mCi of 64Cu-BAT-2IT-MOPC or 0.4 mCi of 67Cu-BAT-2IT-MOPC had to be killed before 6 months because of tumor regrowth. When hamsters with larger tumors (mean weight 0.66 +/- 0.11 g) were treated with 64Cu- or 67Cu-BAT-2IT-1A3, survival was extended compared with controls, but only one animal remained tumor-free to 6 months. These results demonstrate that 64Cu- and 67Cu-BAT-2IT-1A3 given in a single administered dose can eradicate small tumors without significant host toxicity, but additional strategies to deliver higher tumor doses will be needed for larger tumors.

Dosimetry of copper-64-labeled monoclonal antibody 1A3 as determined by PET imaging of the torso.

UNLABELLED: We present biodistribution and dosimetry results for 64Cu-benzyl-TETA-MAb 1A3 from 15 human subjects injected with this tracer as determined by serial PET imaging of the torso. METHODS: PET imaging was used to quantify in vivo tracer biodistribution at two time points after injection. Absorbed dosimetry calculated using MIRD-11 and the updated MIRDOSE3 was compared with estimates obtained using rat biodistribution data. RESULTS: By measuring activity concentrations in the torso, and extrapolating for the whole body using standard organ and tissue volumes, we were able to account for 93% of the injected radiopharmaceutical over a range of imaging times from 0 to 36 hr postinjection. Based on PET imaging and the MIRD-11 schema, the liver and spleen are the critical organs with average absorbed doses of 0.12 and 0.10 mGy/MBq (0.44 and 0.39 rad/mCi). The revised MIRDOSE3 scheme yields similar values for these and other organs but also results in a dose of 0.14 mGy/MBq (0.53 rad/mCi) to the heart wall. In the rat, the large intestine is the critical organ at 0.14 mGy/MBq (0.52 rad/mCi), while liver and kidneys each receive 0.11 mGy/MBq (0.41 rad/mCi). Some disparities in absorbed doses determined by these methods are evident but are a result of dissimilar biodistributions in rats and humans. For most organs, rat extrapolated values are higher than the human measurements with PET. CONCLUSION: This study shows that torso PET imaging can quantitatively measure the whole-body biodistribution of a radiopharmaceutical as long as it has relatively slow pharmacokinetics.

Impact of pneumoperitoneum on trocar site implantation of colon cancer in hamster model.

BACKGROUND: Numerous anecdotal reports have documented the spread of colon cancer to trocar sites after laparoscopic-assisted colectomy. We hypothesized that the pneumoperitoneum of laparoscopy potentiated tumor adherence to trocar sites. PURPOSE: This study was designed to determine the effect of CO2 pneumoperitoneum on the rate of tumor implantation at trocar sites. METHODS: Viable GW-39 human colon cancer cells were injected into the abdominal cavity of hamsters (2 x 10(6) cells/hamster). A midline laparotomy, insertion of four 5-mm trocars, injection of viable cells into the mesentery of the cecum, and free peritoneal cavity was performed in two groups: one control group (41) who did not receive a pneumoperitoneum and a comparison group (50) who underwent pneumoperitoneum for ten minutes at an insufflation pressure of 10 mmHg. Animals were killed at six weeks, and hematoxylin and eosin-stained sections of trocar wounds, midline wound, small intestine, cecum, liver, and lung were examined by a veterinary pathologist, who was blinded to operation. RESULTS: Pneumoperitoneum increased tumor implantation in the cecal mesentery and the midline incision (P < 0.05) but did not effect recurrence in the liver, lung, or jejunum. Trocar site implantation tripled with the addition of pneumoperitoneum increased implantation of pneumoperitoneum (26 vs. 75 percent) (P < 0.0001). CONCLUSION: Pneumoperitoneum increased implantation of free intra-abdominal cancer cells at wound sites on the abdominal wall or within the abdominal cavity in this animal model. The use of pneumoperitoneum during laparoscopy in patients with colon cancer should only be performed in a protocol setting to evaluate the effect of pneumoperitoneum on the treatment of cancer.

RadioimmunoPET: detection of colorectal carcinoma with positron-emitting copper-64-labeled monoclonal antibody.

UNLABELLED: Detection of tumor foci may be improved by combining the selective tumor-targeting properties of a monoclonal antibody with the superior sensitivity and contrast resolution of PET. METHODS: An anti-colorectal carcinoma monoclonal antibody (MAb 1A3) was labeled with 64Cu, a positron-emitting radionuclide, by use of a bifunctional chelate (bromoacetamidobenzyl-TETA) and evaluated in 36 patients with suspected advanced primary or metastatic colorectal cancer. After radiopharmaceutical injection (5-20 mg protein, 10 mCi 64Cu), PET was performed once or twice, 4 to 36 hr later. All patients had CT scans and 18 patients were also studied with [18F]fluorodeoxyglucose (FDG) PET. RESULTS: In 29 patients, one or more tumor sites (n = 56) were proven, in 5 patients the absence of active tumor was confirmed and in the remaining 2, tumor status is not yet confirmed. Of the 56 confirmed tumor sites, 40 were detected by MAb-PET as foci of increased activity (sensitivity 71%). The positive predictive value of MAb-PET was excellent, ranging from 89% (40/45) to 96% (43/45), depending on the ultimate classification of three image-positive, but as yet unconfirmed tumor sites. Also, MAb-PET detected 11 new occult tumor sites, including 9 small abdominopelvic foci less than 2.0 cm in diameter that were not detected by CT or MRI. There were no complications, but significantly elevated HAMA titers were found in 28% of the 29 patients tested 1 to 12 mo after injection. There was no apparent dose-related effect from 5 to 20 mg MAb 1A3. CONCLUSION: These Phase I/II results suggest that PET with radiolabeled MAbs (radioimmunoPET) may have important applications in clinical oncology, particularly for detecting smaller colorectal tumor foci in the abdomen or pelvis and for determining accurate dosimetry.

Preparation, biodistribution and dosimetry of copper-64-labeled anti-colorectal carcinoma monoclonal antibody fragments 1A3-F(ab')2.

UNLABELLED: Antibody fragments labeled with a radiometal using bifunctional chelates generally undergo renal clearance followed by trapping of the metabolites, leading to high radiation doses to the kidneys. Copper-64-labeled BAT-2IT-1A3-F(ab')2 was recently reported to accumulate in colorectal tumors in an animal model, however, kidney uptake was also high. In this study, the preparation of 64Cu-BAT-2IT-1A3-F(ab')2 was optimized to reduce the renal uptake. METHODS: The bifunctional chelate 6-bromoacetamidobenzyl-1,4,8,11-tetraazacyclotetradecane-N,N ',N",N'"-tetraacetic acid (BAT) was conjugated to 1A3-F(ab')2 using the linking agent 2-iminothiolane (2IT). The conjugation reaction produced 20% of a lower molecular weight (molecular wieght) impurity found to be TETA-1A3-Fab'. The conjugation procedure was optimized to include FPLC purification of the BAT-2IT-1A3-F(ab')2 from TETA-1A3-Fab' after conjugation prior to labeling with 64Cu. The biodistribution of 64Cu-labeled FPLC-purified and unpurified conjugates was determined in normal Sprague-Dawley rats and tumor bearing Golden Syrian hamsters. Human absorbed doses were calculated from rat biodistribution data and PET imaging of a baboon. RESULTS: Upon FPLC purification of the BAT-2IT-1A3-F(ab')2, the immunoreactivity of 64Cu-labeled 1A3-F(ab')2 was significantly improved over that of non-FPLC-purified 64Cu-BAT-2IT-1A3-F(ab')2, and the kidney uptake was decreased in normal rats. The biodistribution in hamsters showed some improvement in both tumor uptake and kidney clearance with FPLC-purified 64Cu-BAT-2IT-1A3-F(ab')2. CONCLUSION: The improved dosimetry of 64Cu-labeled FPLC purified BAT-2IT-1A3-F(ab')2 should more readily allow this agent to be investigated clinically to image colorectal cancer using PET.

Factors influencing cosmetic results after conservation therapy for breast cancer.

PURPOSE: Host, tumor, and treatment-related factors influencing cosmetic outcome are analyzed for patients receiving breast conservation treatment. METHODS AND MATERIALS: Four-hundred and fifty-eight patients with evaluable records for cosmesis evaluation, a subset of 701 patients treated for invasive breast cancer with conservation technique between 1969 and 1990, were prospectively analyzed. In 243 patients, cosmetic evaluation was not adequately recorded. Cosmesis evaluation was carried out from 3.7 months to 22.3 years, median of 4.4 years. By pathologic stage, tumors were 62% T1N0, 14% T1N1, 15%, T2N0, and 9% T2N1. The majority of patients were treated with 4-6 MV photons. Cosmetic evaluation was rated by both patient and physician every 4-6 months. A logistic regression analysis was completed using a stepwise logistic regression. P-values of 0.05 or less were considered significant. Excellent cosmetic scores were used in all statistical analyses unless otherwise specified. RESULTS: At most recent follow-up, 87% of patients and 81% of physicians scored their cosmetic outcome as excellent or good. Eighty-two percent of physician and patient evaluations agreed with excellent-good vs. fair-poor rating categories. Analysis demonstrated a lower proportion of excellent cosmetic scores when related to patient age > 60 years (p = 0.001), postmenopausal status (p = 0.02), black race (p = 0.0034), and T2 tumor size (p = 0.05). Surgical factors of importance were: volume of resection > 100 cm3 (p = 0.0001), scar orientation compliance with the National Surgical Adjuvant Breast Project (NSABP) guidelines (p = 0.0034), and > 20 cm2 skin resected (p = 0.0452). Extent of axillary surgery did not significantly affect breast cosmesis. Radiation factors affecting cosmesis included treatment volume (tangential breast fields only vs. three or more fields) (p = 0.034), whole breast dose in excess of 50 Gy (p = 0.0243), and total dose to tumor site > 65 Gy (p = 0.06), as well as optimum dose distribution with compensating filters (p = 0.002). Daily fraction size of 1.8 Gy vs. 2.0 Gy, boost vs. no boost, type of boost (brachytherapy vs. electrons), total radiation dose, and use of bolus were not significant factors. Use of concomitant chemotherapy with irradiation impaired excellent cosmetic outcome (p = 0.02). Use of sequential chemotherapy or adjuvant tamoxifen did not appear to diminish excellent cosmetic outcomes (p = 0.31). Logistic regression for excellent cosmetic outcome analysis was completed for age, tumor size, menopausal status, race, type of surgery, volume of breast tissue resected, scar orientations, whole breast radiation dose, total radiation dose, number of radiation fields treated, and use of adjuvant chemotherapy. Significant independent factors for excellent cosmetic outcome were: volume of tissue resected (p = 0.0001), type of surgery (p = 0.0001), breast radiation dose (p = 0.005), race (p = 0.002), and age (p = 0.007). CONCLUSIONS: Satisfactory cosmesis was recorded in 81% of patients. Impaired cosmetic results are more likely with improper orientation of tylectomy and axillary incisions, larger volume of breast resection, radiation dose to the entire breast in excess of 50.0 Gy, and concurrent administration of chemotherapy. Careful selection of treatment procedures for specific patients/tumors and refinement in surgical/irradiation techniques will enhance the cosmetic results in breast conservation therapy.

Immunoscintigraphy with a new indium-111-labeled monoclonal antibody (MAb 1A3) in patients with colorectal cancer.

PURPOSE: This study was designed to evaluate a new anticolorectal carcinoma monoclonal antibody (1A3), conjugated with the bifunctional chelating agent N,N'-bis(2-hydroxybenzyl)1(4-bromoacetamidobenzyl)1,2-ethylenediam ine-N,N'- diacetic acid and labeled with indium-111, in a Phase I/II study involving 38 patients with localized or advanced colorectal cancer. METHODS: Patients were injected with indium-111-N,N'-bis(2-hydroxybenzyl) 1(4-bromoacetamidobenzyl)1,2-ethylenediamine-N,N'-diacetic acid-monoclonal antibody 1A3 (1-50 mg, 1-5 mCi) and imaged at two or three sessions one to five days later. Scintigraphic findings were compared with radiologic, pathologic, surgical, and other clinical findings to assess the accuracy of radioimmunoscintigraphy. RESULTS: At least one known tumor site was clearly defined by planar scintigraphy in 29 (76 percent) patients. Increased radioactivity was seen in 40 of 63 known tumor sites (37/43 abdominal-pelvic, 3/15 hepatic, and 0/5 pulmonary sites) without any apparent dose-related effects. Nineteen previously undetected sites were considered positive by imaging, and, of these, six were biopsy-proven tumor sites, four were probable tumor sites, three were definitely false positive sites, and six were probable false positive sites. Radioimmunoscintigraphy detected proven tumor in 15 of 16 patients with negative or equivocal computed tomography results. Of of the 28 patients with rectosigmoid cancer, 25 (89 percent) had positive studies with 34 of 47 tumor sites showing definite uptake on the scintigrams. This included 3 of 9 hepatic metastases. The only adverse reaction occurred in one patient who developed transient hives. Human anti-mouse antibody responses occurred in approximately one-half of the patients injected with doses of 10 or 50 mg. CONCLUSION: This study shows that radioimmunoscintigraphy with this indium-111-labeled monoclonal antibody is safe, it can detect most nonhepatic abdominal-pelvic tumors with a positive predictive value of 83 (44/53) percent, and it should prove to be useful, particularly in the diagnosis of recurrent rectal carcinoma.

Management of locally advanced carcinoma of the breast. I. Noninflammatory.

BACKGROUND: The treatment of patients with locally advanced noninflammatory breast cancer has evolved substantially over the past 30 years. From 1968 to 1989, 281 women were treated at Mallinckrodt Radiation Oncology Center with four different treatment methods. Median follow-up was 6.2 years (range 3-22 years); no patient was lost to follow-up. METHODS: Retrospective review of records and analysis of data on a computer file were carried out. Thirty-five patients were treated with irradiation alone, 33 with irradiation and adjuvant chemotherapy, 81 with mastectomy and irradiation, and 132 with mastectomy, irradiation, and chemotherapy (triple-modality). RESULTS: Actuarial 5- and 10-year disease free survival (DFS) rates were 45% and 36%, respectively, with triple-modality therapy, 31% and 10% with irradiation and chemotherapy, 32% and 19% with irradiation and mastectomy, and 19% and 11% with irradiation alone. Cause specific survival (CSS) paralleled DFS in the four groups. Locoregional tumor control at 5 years was 91% for irradiation, mastectomy, and chemotherapy, 80% for irradiation and mastectomy, 54% for irradiation and chemotherapy, and 31% for irradiation alone. Systemic therapy and/or irradiation given before mastectomy yielded better locoregional tumor control, DFS, and CSS (not statistically significant). No difference in results was noted with radical, modified radical, or total mastectomy. In the triple-modality group, no chest wall failures occurred with chest wall doses greater than 5040 cGy. Grade 2 or higher treatment sequelae were noted in 10-42% of patients, depending on treatment modality. CONCLUSIONS: Triple-modality therapy yielded improved locoregional tumor control, DFS, and CSS compared with other modalities. Patients treated with surgery had better locoregional tumor control than those who received irradiation alone or in combination with chemotherapy, but the impact on DFS and CSS was less impressive. Additional clinical trials are needed to define further the role and optimal use of the various therapeutic modalities in the management of locally advanced breast cancer.

Evaluation of a direct method for technetium labeling intact and F(ab')2 1A3, an anticolorectal monoclonal antibody.

A direct method for 99mTc-labeling monoclonal antibodies (MAb) has been evaluated for labeling intact and F(ab')2 1A3, an anticolorectal carcinoma MAb. The method employs ascorbic acid to reduce the MAbs. By altering the reaction conditions for 99mTc-1A3, a maximum radiolabeling yield of 48% was obtained with an immunoreactivity (IR) value of 87%; and for 99mTc-1A3-F(ab')2, a yield of 49% and an IR value of 70% was obtained. Biodistribution of 99mTc-labeled 1A3 MAbs was performed in a Golden Syrian hamster model and compared to 125I-labeled 1A3 MAbs. Tumor uptake (%ID/g) was significantly better for the intact 125I-1A3 at 24 h post-injection compared to the intact 99mTc-1A3. For 99mTc-1A3-F(ab')2, %ID/g tumor was low, and did not increase over 24 h. High %ID/g kidney persisted at 24 h for both 99mTc-labeled intact and F(ab')2 1A3. Serum stability was performed in Sprague-Dawley rats for the 99mTc-labeled 1A3 MAbs, and compared to 125I-labeled 1A3 MAbs, which showed intact 99mTc-1A3 cleared similarly to 125I-1A3, and 99mTc-1A3-F(ab')2 cleared more rapidly than 125I-1A3-F(ab')2 indicating instability of the 99mTc-labeled 1A3-F(ab')2.

Copper-64-labeled antibodies for PET imaging.

In the imaging of tumors using radiolabeled monoclonal antibodies, the use of PET gives increased sensitivity over conventional gamma camera imaging techniques. Copper-64, a positron-emitting radionuclide, has been labeled to 1A3, an anticolorectal carcinoma monoclonal antibody, and its fragments 1A3-F(ab')2 utilizing the bifunctional chelate Br-benzyl-TETA. The 64Cu-labeled intact 1A3 and 1A3-F(ab')2 have been evaluated as potential imaging agents for PET. Biodistribution studies of 64Cu-benzyl-TETA-1A3 and 64Cu-benzyl-TETA-1A3-F(ab')2 in tumor-bearing hamsters were compared with those of 111In-Br phi HBED-1A3, 111In-Br phi HBED-1A3-F(ab')2 and 125I-labeled intact 1A3 and 1A3-F(ab')2. Tumor uptake of 64Cu-labeled intact 1A3 and fragments in the hamster model was superior to both 111In- and 125I-labeled intact 1A3 and fragments. Human dosimetry data for 64Cu- and 123I-labeled 1A3 and 1A3-F(ab')2 were calculated from biodistribution data in rats. High kidney uptake of 64Cu-benzyl-TETA-1A3-F(ab')2 precludes clinical study at this time; however, the data shows that 64Cu-benzyl-TETA-1A3 would be suitable for positron tomography imaging of colorectal cancer in patients.

Tumor localization and radioimaging with mixtures of radioiodinated monoclonal antibodies directed to different colon cancer associated antigens.

After demonstrating enhanced tumor cell binding with a mixture of monoclonal antibodies (MAbs) in vitro, biodistribution and immunoscintigraphy studies with 3 radioiodinated anti-colon cancer MAbs and a non-specific control MAb (MOPC) were conducted in a human colon cancer (GW-39)-hamster model system. Each of the specific MAbs, but not MOPC, demonstrated extensive tumor binding and in scintigrams affected visualization of all large tumors (greater than 0.85 g) over background. Using single MAbs, few small tumors (0.19-0.50 g) were defined above background (0-29%). However, with combinations of these specific MAbs small tumors were more frequently defined in scintigrams (43-67%). Radioimages using higher doses of MAbs and small, younger tumors more clearly demonstrated the superiority of a MAb mixture. These results confirmed that combinations of MAbs to different antigens can detect smaller tumors with better tumor localization when compared to component MAbs used singly. This study supports the concept that tumor targeting and detection may be enhanced with appropriate mixtures of MAbs.

N,N'-bis(2-hydroxybenzyl)-1-(4-bromoacetamidobenzyl)-1,2 -ethylenediamine-N,N'-diacetic acid: a new bifunctional chelate for radiolabeling antibodies.

N,N'-Bis(2-hydroxybenzyl)-1-(4-bromoacetamidobenzyl)-1,2 -ethylenediamine-N,N'-diacetic acid (Br phi HBED) was synthesized to bind trivalent metals with high stability constants and to bifunctionally link the radiometal with antibodies (Ab). This ligand has advantages over our previously reported N-(2-hydroxy-3,5-dimethylbenzyl)-N'-(2-hydroxy-5- bromoacetamidobenzyl)ethylenediamine-N,N'-diacetic acid (BrMe2HBED). Br phi HBED has the protein coupling group BrCH2CONH removed from the sterically hindered ring position with the addition of a benzyl group in the linker arm; this provides further distance between the protein and the chelate. We have also observed that the chelate was more stable than BrMe2HBED, so it can be stored longer without loss of observed chemical properties. The improved chelate design allows for more rapid radiolabeling with [111In]indium citrate (1 h at room temperature) with higher radiochemical yields. Br phi HBED was conjugated with an anticolorectal carcinoma monoclonal antibody (1A3) where radiolabeling yields of 75-90% were obtained and the antibody retained its immunoreactivity (ca. 90%) under all labeling conditions studied. Biodistribution studies in a hamster transplanted tumor (GW39) model demonstrated a high tumor uptake when compared to those of 125I-1A3 or 111In-DTPA cyclic anhydride-1A3. Blood clearance of 111In-Br phi HBED-1A3 was rapid and combined with its high target uptake has higher target to nontarget ratios in vivo at various time intervals when compared with that of 1A3 radiolabeled with either 111In-DTPA cyclic anhydride or 125I.

Biodistribution and histological localization of anti-human colon cancer monoclonal antibody (MAb) 1A3: the influence of administered MAb dose on tumor uptake.

Using a murine monoclonal antibody MAb 1A3, which binds to a lipid antigen found enriched in human colon cancer, and MOPC-21 antibody, as a non-specific control, we examined the effect of increasing doses of 125I-labelled MAbs (5 micrograms to 2,000 micrograms) on tumor localization. Biodistribution studies in hamsters with small GW-39 human colon carcinoma tumors [0.44 g +/- 0.014 (SEM)] demonstrated functional saturation of antigen binding sites in tumors when large doses of MAb 1A3 were used. The percentage injected dose bound per gram of tumor (ID/g tumor) remained constant for doses of intact MAb 1A3 less than or equal to 100 micrograms but decreased with doses greater than 100 micrograms, suggesting that a population of antigen binding sites had been saturated. While the percentage ID/g tumor decreased for doses of MAb 1A3 greater than 100 micrograms, the absolute amount specifically bound/g turnover increased (up to the 1,000 micrograms dose), suggesting that another population of less accessible 1A3 antigen could continue to bind MAb 1A3. In contrast, MOPC demonstrated a relatively constant percentage ID/g of tumor (2.26% +/- 0.11) throughout the dose range which was 2-3 times lower than MAb 1A3 (6.8% +/- 0.14) at plateau doses (5-100 micrograms). These data suggest that specific saturation of tumor binding sites was a biphasic phenomenon. Blood and normal tissues did not show binding kinetics suggesting saturation. Results of dose response experiments using MAb 1A3 F(ab')2 fragments (5 micrograms to 1,000 micrograms) closely paralleled those obtained with intact MAb 1A3, but with lower percentages of ID/g tumor, blood and non-tumor tissues as in previous studies with MAb 1A3 and other MAb F(ab')2 fragments. Histological examinations demonstrated that non-specific binding of MOPC or MAb 1A3 to tumor or normal tissues was of such low affinity as to be largely undetected after histological procedures. In contrast, MAb 1A3 (but not MOPC) showed specific cell-binding patterns to tumor but not normal tissues at all doses.

Magnetic resonance imaging using gadolinium labeled monoclonal antibody.

Gadolinium was attached to antibodies and tested in vitro and in vivo for its effect on proton relaxation enhancement. Using the cyclic anhydride method, diethylenetriaminepentaacetic acid (DTPA) was attached to albumin, IgG and anti-CEA monoclonal antibody. Gadolinium (Gd) was then chelated to the protein complexes forming protein-DTPA-Gd complex. With this technique approximately 9 atoms of Gd could be attached to each albumin molecule, 4 to each IgG molecule and 1.5 to each monoclonal antibody molecule. The minimal in vitro concentration of Gd in the form of IgG-DTPA-Gd necessary to produce proton relaxation enhancement at 0.35 tesla was 10(-1) mM. An in vivo experiment using anticarcinoembryonic antigen (CEA) monoclonal antibody-DTPA-Gd in hamsters implanted with human colon carcinoma resulted in a tumor concentration of Gd of less than 10(-4) mM. No enhancement of the tumors was detected at that concentration. For monoclonal antibodies to function as selective MR contrast agents, substantial advances in technology must occur.

Improved radioimaging and tumor localization with monoclonal F(ab')2.

Monoclonal anti-tumor antibodies have great promise for radioimmunodetection and localization of tumors. Fab and F(ab')2 fragments, which lack the Fc fragment of antibody (Ab), are cleared more rapidly from the circulation and may have less nonspecific tissue binding than intact Ab. In radioimaging studies using a murine monoclonal antibody to carcinoembryonic antigen in a human colon carcinoma xenografted into hamsters, F(ab')2 fragments were shown superior to Fab fragments and intact antibody for scintiscanning. In double-label experiments with anti-CEA antibody and control monoclonal IgG, F(ab')2 fragments were found to give better and more rapid specific tumor localization than intact antibody or Fab fragments. F(ab')2 fragments offer significant promise for tumor imaging and possibly therapy.