Follicular non-Hodgkin's lymphoma.

Follicular non-Hodgkin's lymphoma (NHL) is a unique subtype of NHL, which is indolent, incurable with a high prevalence of residual mass after treatment, and may transform to more aggressive NHL. The aim of this review is to (1) describe the histological and flow cytometry characteristics of follicular NHL; (2) introduce the Follicular Lymphoma International Prognostic Index 2 (FLIPI-2), which allows better treatment selection and patient stratification for clinical trials; (3) illustrate the classic and atypical ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), and positron-emission tomography (PET)/CT appearance of follicular NHL; and (4) characterize the appearance of nodal and extranodal follicular NHL with pathological correlation. Imaging is essential in every step of the management of patients with follicular lymphoma. Overall survival is improved with better predictive tools and new targeted biological therapies. Radiologists should be aware of possible active residual mass, indolent recurrence, transformation, and association with other primary cancers in patients treated for follicular lymphoma.

Estimates of red marrow dose by sacral scintigraphy in radioimmunotherapy patients having non-Hodgkin's lymphoma and diffuse bone marrow uptake.

According to the recommendations of the Dosimetry Task Group of the American Association of Physicists in Medicine, blood-derived estimates of the red marrow (RM) dose from radiolabeled monoclonal antibodies (MAbs) are valid only if the RM is devoid of any specific uptake. There is, therefore, a clear need for an alternative method for estimating the RM dose in patients receiving MAbs that target normal or abnormal (malignant) bone marrow elements. Radiolabeled LL2, an anti-B-cell murine MAb, targets normal B cells and malignant lymphoma cells in the RM. This may result in an increased radiation dose to the RM through neighboring targeted activity. We investigated whether imaging-based estimates of the RM dose, particularly using sacral scintigraphy, correlate with myelotoxicity in non-Hodgkin's lymphoma patients who received 131I-LL2. The sacrum-based RM dose (RMs) was estimated from sacral activity by assuming that 9.9% of the total adult RM is contained in the sacrum. The sacrum was not used if there was focally increased or decreased sacral uptake. Myelotoxicity was assessed based on Radiation Therapy Oncology Group criteria. Twelve of 21 non-Hodgkin's lymphoma patients treated had adequate imaging, dosimetry, and follow-up to evaluate myelotoxicity. Eight of these patients had diffusely increased RM uptake on their MAb scans. The average estimated RMs in the eight patients was 168 +/- 62 cGy (mean +/- SD) with only 50 mCi 131I-LL2. Six of these patients (75%) developed grade 3 or 4 myelotoxicity. In contrast, the average RMs in the four patients who did not have any enhanced uptake on their scans was 71 +/- 30 cGy (P < 0.02). None of these patients developed grade 3 or 4 toxicity. These results suggest that image-based estimates of the RM dose may be predictive of myelotoxicity and should be used in patients with diffuse RM uptake on their scans.

Micropharmacology of monoclonal antibodies in solid tumors: direct experimental evidence for a binding site barrier.

Monoclonal antibodies (MAbs) often distribute nonuniformly in tumors. In part, that observation reflects intrinsic heterogeneity within the tumor; in part, it reflects poor penetration through tumor substance. Several years ago, we proposed the "binding site barrier" hypothesis (J.N. Weinstein, R.R. Eger, D.G. Covell, C.D.V. Black, J. Mulshine, J.A. Carrasquillo, S.M. Larson, and A.M. Keenan, Ann. NY Acad. Sci., 507: 199-210, 1987; K. Fujimori, D.C. Covell, J.E. Fletcher, and J.N. Weinstein, Cancer Res., 49: 5656-5663, 1989), the idea that antibodies (and other ligands) could be prevented from penetrating tumors by the very fact of their successful binding to target antigen. Calculations suggested that this might be a significant factor in the therapy of even microscopic nodules. The higher the affinity and the higher the antigen density, the greater the barrier. Here, we provide direct experimental evidence of such a barrier to the percolation of D3 MAb through intradermally implanted line 10 carcinoma of guinea pigs. After affinity purification using glutaraldehyde-fixed line 10 cells, the D3 had an average immunoreactivity of 88%, a binding constant of 1.6 +/- 0.3 (SEM) x 10(10) M-1, and saturation binding of 355,000 +/- 15,000 molecules/cell. Using a combination of double-label autoradiography and double-chromagen immunohistochemistry, we determined simultaneously the distribution of (a) i.v. injected D3 MAb; (b) coinjected isotype-matched control IgG (BL3); (c) D3 antigen; (d) blood vessels. The previously developed mathematical models aided in the design of these experiments. Double immunochemical staining of the tumors showed antigen-rich patches 100-800 microns across, surrounded by blood vessels. At a low MAb dose (30 micrograms), binding to antigen severely hindered penetration into antigenic patches as small as 200 microns, even at 72 h. Explanation of this finding by a physical barrier was ruled out by the observation that BL3 distributed uniformly in the same patches. At a higher dose (1000 micrograms), the binding site barrier could be partially overcome. The same general principles of micropharmacology may apply to biological ligands other than antibodies, including those secreted by genetically modified cells.

Treatment of non-Hodgkin's lymphoma with radiolabeled murine, chimeric, or humanized LL2, an anti-CD22 monoclonal antibody.

LL2 is a murine IgG2a anti-CD22 monoclonal antibody found to react with virtually all non-Hodgkin's lymphomas (NHLs). Twenty-one patients with chemotherapy-resistant NHL received nonmyeloablative doses of 131I-labeled LL2 IgG and F(ab')2 ranging from 15 to 343 mCi given in cycles of 15-50 mCi, for up to seven treatment cycles. The cumulative protein dose ranged from 1.1 mg IgG to 157 mg F(ab')2. Seventeen patients were assessable for treatment response, and antitumor effects were seen in five (one complete remission, two partial remissions, and two minor or mixed responses). In addition, one complete response was seen in a patient who received only "diagnostic" doses of 131I-LL2 IgG. Thus, a total of six patients had responses according to the defined response criteria. Three additional patients have been treated with potentially myeloablative doses of 131I-LL2 IgG at a starting dose level of 90 mCi/m2 (100 mg). Two patients were evaluable, and both had partial remissions lasting 8 and 3 months, respectively. Chimeric and complementarity-determining region-grafted LL2 have been developed. Initial clinical studies have shown that these agents have targeting properties similar to the murine LL2 and, therefore, may be suitable alternatives to murine LL2 in the treatment of NHL. LL2 is a promising agent for the treatment of lymphoma, particularly when the maximum tolerated dose is given either with or without autologous bone marrow transplantation.

Evaluation of a complementarity-determining region-grafted (humanized) anti-carcinoembryonic antigen monoclonal antibody in preclinical and clinical studies.

A complementarity-determining region-grafted (humanized) version of MN-14 (hMN-14), a high-affinity, anti-carcinoembryonic antigen (CEA) murine monoclonal antibody (mMAb), was selected from several clones that differed slightly in their framework composition. One clone was selected based on its similar binding affinity to CEA as that observed with mMN-14 MAb and its production yields. Targeting studies, using 131I-labeled humanized MN-14 (hMN-14)/125I-labeled mMN-14 IgG in GW-39 tumor-bearing nude mice, showed excellent tumor uptake and tumor: nontumor ratios, similar to the mMN-14. A pilot clinical imaging trial was initiated to determine the targeting, pharmacokinetics, and dosimetry for 131I-labeled hMN-14 IgG. Nineteen patients with advanced CEA-producing tumors were given 8 to 30 mCi (0.5 to 20.0 mg). Eleven patients also received 131I-labeled mMN-14 IgG for comparison. The biodistribution, tumor targeting, and pharmacokinetic behavior of the hMN-14 was similar to that seen with the mMN-14. The average time required to clear 50% of the radiolabeled hMN-14 from the blood and total body was 32.9 +/- 25.6 h and 109 +/- 73 h, respectively. Patients with elevated plasma CEA (i.e., > 200 ng/ml) had more than 30% of the labeled antibody complexed within 1 h after injection. In some of these patients, increased complexation resulted in enhanced metabolism of the antibody with more rapid clearance from the blood than that seen in patients with lower plasma CEA. The average radiation absorbed dose measured in 20 tumors (average weight, 204 +/- 205 g) in 14 patients was 7.6 +/- 5.3 cGy/mCi. Tumor: nontumor dose ratios were 2.5 +/- 1.6, 9.5 +/- 5.8, and 2.6 +/- 1.8 for the red marrow, total body, and liver, respectively. One patient, with a highly elevated human anti-mouse antibody response from a prior OncoScint study (murine B72.3 IgG), received 3 injections of the hMN-14 without an adverse experience, and showed no evidence of altered biodistribution characteristic of mMAb-human anti-mouse antibody interactions. An antibody response to hMN-14 (HAhMN14) was not detected in patients who received only the hMN-14 (as many as three injections), but in three patients who received two injections of the mMN-14, a HAhMN14 response was detected. With similar, excellent targeting properties as the mMN-14 and the potential for reduced immunogenicity, hMN-14 is an attractive candidate for further clinical imaging and therapy applications.

Targeting and initial radioimmunotherapy of medullary thyroid carcinoma with 131I-labeled monoclonal antibodies to carcinoembryonic antigen.

The targeting potential of 131I-labeled NP-4 and MN-14 anti-CEA (carcinoembryonic antigen) monoclonal antibodies (MAbs) was assessed in 19 patients with metastatic medullary thyroid cancer (MTC). Seventeen of these patients also entered pilot radioimmunotherapy studies with nonmyeloablative doses of 131I-anti-CEA MAbs. Tumor targeting was possible in all 19 patients, with an overall lesion sensitivity of 91%. Tumor dosimetry with 131I-MN-14 IgG or F(ab)2 was very favorable, with tumor doses of 14.3 +/- 8.3 cGy/mCi and tumor:red marrow dose ratios exceeding 3:1 for most lesions. Limited antitumor effects lasting up to 26+ months, based on physical exam, tumor markers, computed tomography, or a followup MAb scan, were seen in 5 of 11 assessable patients given relatively low doses of 131I-labeled anti-CEA MAbs. We conclude that anti-CEA MAbs are excellent agents for targeting metastatic MTC. The high tumor uptake of the 131I-anti-CEA antibodies and evidence of tumor response in some patients suggest that radioimmunotherapy with radioiodinated anti-CEA MAbs may be an effective treatment for MTC, particularly when the maximum tolerated dose is given alone or in combination with autologous red marrow or peripheral stem cell support.

Factors influencing the pharmacokinetics, dosimetry, and diagnostic accuracy of radioimmunodetection and radioimmunotherapy of carcinoembryonic antigen-expressing tumors.

The aim of this study was to examine factors that may influence the pharmacokinetics, diagnostic accuracy, and dosimetry in radioimmunodetection and radioimmunotherapy with anti-carcinoembryonic antigen (CEA) monoclonal antibodies (mAbs). Data from 275 patients with CEA expressing tumors were analyzed retrospectively. Of these, 69 patients devoid of human antimouse antibody (i.e., 31 colorectal, 9 lung, 7 breast, 4 ovarian, 6 pancreatic, 9 medullary thyroid, 1 gallbladder, and 1 salivary gland cancer, and 1 primary tumor of unknown origin) underwent a low-protein-dose diagnostic study (0.3-2.6 mg of protein; 6.8-28.8 mCi 131I-labeled IgG or fragments), followed within 4 weeks by a high-protein-dose therapy injection (4.0-27.5 mg of protein; 29.8-238.9 mCi). The anti-CEA antibodies NP-4 (Ka=10(8)M-1) and MN-14 (ka=10(9)M-1) were used. Plasma clearance, the molecular composition of radioactivity in the plasma, and the cumulated activity in organs and tumors were determined. Radiation doses were derived from the Medical Internal Radiation Dose scheme. At a low-protein dose and over a similar range of plasma CEA, a significantly higher percentage of MN-14 than of NP-4 was complexed with circulating CEA, consistent with its higher affinity. Complexation was reduced with increasing protein doses. However, the targeting sensitivity was not affected. Profound differences were found in the clearance of the antibody between different types of cancer. Colorectal cancer patients cleared the antibody significantly faster from blood (T1/2=17.6+/-12.6 versus 44.2 +/- 23.7 h) and whole body (t1/2= 53.2 +/- 30.1 versus 114.6+/-59.7 h) than all other tumor types (P <0.001). Consequently, significantly lower red marrow (2.1 +/- 1.0 cGy/mCi versus 4.3 +/- 1.6 cGy/mCi) and whole-body doses (0.5 +/- 0.3 cGy/mCi versus 1.0 +/- 0.4 cGy/mCi) were seen in colorectal cancer patients as compared with other tumor types (P < 0.001). This clearance is probably due to hepatic metabolism of the immune complexes. Clearance rates were especially high in patients with colorectal cancer having large liver metastases and elevated liver enzymes (rapid hepatic clearance with liberation of free I-). In contrast, a disease-stage and plasma CEA-matched cohort of colorectal cancer patients, examined with the 131 I-labeled anti-colon-specific antigen p mAb Mu-9, showed normal murine IgG pharmacokinetics (n=22;3 of them compared intraindividually to MN-14). Only in colorectal cancer patients did complexes between mAb and CEA tend to clear rapidly, whereas Mu-9 had normal kinetics in these patients. This suggests that different CEA-expressing cancer types may produce heterogeneous CEA molecules and that the variability in mAb clearance is due to varying clearance rates of these different circulating CEA subspecies. Disease-related alterations in antibody metabolism are unlikely, given that only anti-CEA antibodies exhibit this phenomenon.

Reduction of the renal uptake of radiolabeled monoclonal antibody fragments by cationic amino acids and their derivatives.

The renal uptake of radiolabeled antibody fragments and peptides is a problem in radioimmunodetection and radioimmunotherapy, especially with intracellular retained radiometals. The aim of this study was to develop suitable methods to reduce this kidney uptake. BALB/c mice or nude mice bearing the human GW-39 colon carcinoma xenograft were given i.p. injections of basic amino acids or a range of different basic amino acid derivatives, amino sugars, as well as cationic peptides. The effect of these agents on the biodistribution of Fab' and F(ab')2 fragments of different mAbs radiolabeled with 99mTc, 188Re, 111In, 88Y, or 125I was studied. Tumor and organ uptake was determined and compared to untreated mice. The kidney uptake of Fab' fragments was reduced 5-6-fold in a dose-dependent manner as compared to untreated controls. The uptake in all other organs, as well as the tumor, was unaffected. A similar reduction in renal retention was seen for all other intracellularly retained isotopes, as well as for F(ab')2 fragments. D- and L-isomers of lysine were equally effective whether given i.p. or p.o. D-glucosamine was effective, but its N-acetyl derivative was not. Basic polypeptides (e.g., poly-L-lysine) were also effective; their potency increased with increasing molecular weight. HPLC of the urine taken from treated animals showed the excretion of intact Fab', in contrast to mostly low-molecular-weight metabolites in the control group. These studies indicate that a variety of basic compounds is capable of inhibiting the tubular reabsorption of peptides and proteins, thus lowering the kidney uptake of antibody fragments significantly. On a molecular basis, the effect seems to essentially rely on the presence of a positively charged amino group. By reducing renal retention of antibody fragments, their role as imaging and therapeutic agents may be expanded.

Improved detection of medullary thyroid cancer with radiolabeled antibodies to carcinoembryonic antigen.

PURPOSE: This investigation was undertaken to assess the targeting of established and occult medullary thyroid cancer (MTC) with radiolabeled monoclonal antibodies (MAbs) reactive with carcinoembryonic antigen (CEA). PATIENTS AND METHODS: Twenty-six assessable patients with known (n = 17) or occult (n = 9) MTC were studied with radiolabeled anti-CEA MAbs. Scintigraphic images were collected to determine targeting of tumor lesions. RESULTS: The targeting results of technetium 99m (99mTc)-,iodine 123 (123I)-, and iodine 131 (131I)-labeled anti-CEA antibodies (all directed against the same epitope of CEA) indicated that all these reagents were capable of detecting established and occult MTC. The sensitivity for detection of known sites of disease ranged from 76% to 100% for the various anti-CEA MAbs used, when compared with computed tomography (CT), magnetic resonance imaging (MRI), bone scan, or other imaging modalities. Moreover, the antibody scan was positive in seven of nine patients with occult disease (patients with negative conventional imaging studies, but who had elevated calcitonin and/or CEA levels). Three of seven patients underwent surgery and the disease was confirmed by histopathology in all three. CONCLUSION: Anti-CEA MAbs are excellent agents for imaging recurrent, residual, or metastatic MTC. The high lesion sensitivity in patients with known lesions, combined with the ability to detect disease, may make these agents ideal for staging patients, monitoring disease pretherapy or posttherapy, and especially for evaluating patients with recurrent or persistent hypercalcitonemia or CEA elevations after primary surgery. Analogous to radioiodine in the evaluation of patients with differentiated thyroid cancer, radiolabeled anti-CEA MAbs may achieve a similar role in diagnosing and monitoring patients with MTC.

Assessment of combined radioimmunotherapy and chemotherapy for treatment of medullary thyroid cancer.

We have shown previously significant antitumor effects using 90Y-MN-14 anti-CEA monoclonal antibody (MAb) for radioimmunotherapy (RAIT) of human medullary thyroid cancer (MTC) xenografts using the TT cell line. The purpose of this investigation was to determine the effect of combining chemotherapy and RAIT with 90Y-MN-14 in MTC. In particular, the toxicity and efficacy of various dose schedules of RAIT and doxorubicin were examined and compared with that at the maximum tolerated dose (MTD) of each single modality treatment. The MTD of RAIT of 105 microCi of 90Y-MN-14 was given alone and combined with 100 and 75% of the MTD of doxorubicin (60 mg/m2); and the MTD of doxorubicin was given alone and combined with 100 and 75% of the MTD of RAIT. In addition, 75% of each agent was also administered in combination. The MTD of RAIT was also evaluated in combination with 58 and 78% of the MTD of Taxol. Whereas 90Y-MN-14 (105 microCi) led to significant antitumor effects (P < 0.0001), doxorubicin at 60 mg/m2 or Taxol at 225 mg/m2 yielded only a slight tumor growth delay. The combinations of 100% of the MTD of RAIT and 75% of the MTD of doxorubicin and 100% of the MTD of doxorubicin and 75% of the MTD of RAIT were equitoxic to the MTD of RAIT alone and appear to result in improved efficacy compared with either RAIT or doxorubicin alone. For the 100% RAIT and 75% doxorubicin combination, the therapeutic efficacy was similar when doxorubicin was administered on the same day or 1 day after RAIT, but the treatment was less effective when doxorubicin was administered 2 days after RAIT (P < 0.03). Prolonged retardation of tumor progression was also observed in animals treated with the MTD of RAIT combined with 175 mg/m2 of Taxol, without increases in toxicity above that observed with RAIT alone. In conclusion, the combination of RAIT and chemotherapy appears to augment the antitumor effects of either treatment alone without a significant increase in toxicity. In addition, the timing of drug administration relative to RAIT in the combined therapy appears to be important.

Importance of timing of radioimmunotherapy after granulocyte colony-stimulating factor administration for peripheral blood stem cell harvest.

Nine radioimmunotherapy (RAIT)-naive patients with medullary thyroid cancer received high doses of 131I-MN-14 F(ab)2 anti-carcinoembryonic antigen monoclonal antibody (232-486 mCi), five in combination with bone marrow harvest, without prior granulocyte colony stimulating factor (G-CSF) injections (group 1) and the other four using peripheral blood stem cell harvest (PBSCH) preceded by G-CSF administration of 10 microg/kg per day for 5 days for stem cell mobilization, 6-8 days before RAIT (group 2). The amounts of radioactivity (mCi) given in both groups were similar (312 +/- 93 versus 424 +/- 65; P = NS). The percent platelet loss at nadir, duration of grade 4 thrombocytopenia, and time to complete recovery (TTCR, measured from the day of treatment), were 83 +/- 17%, 2.5 +/- 0.7 days, and 45 +/- 8 days in group 1, respectively, compared with 88 +/- 6%, 3.0 +/- 2.6 days, and 50 +/- 24 days in group 2 (P = NS), respectively. In contrast, the percent WBC loss at nadir, duration of grade 4 leukopenia, and TTCR of WBCs were 72 +/- 12%, 0.0 +/- 0.0 day, and 42 +/- 12 days in group 1, respectively, compared with 93 +/- 3%, 8.0 +/- 3.6 days, and 263 +/- 136 days in group 2, respectively (P < 0.02, 0.03, and 0.05 for differences of percent loss, duration of nadir, and TTCR, respectively). The difference in WBC toxicity after RAIT with bone marrow harvest and PBSCH is thought to be due to the administration of G-CSF for stem cell mobilization within 1 week before RAIT, which may sensitize the "endogenous" granulocyte precursors to subsequent RAIT. Preclinical data of RAIT in mice showed that the time of G-CSF administration before RAIT is critical: increased WBC toxicity was seen in mice given RAIT 3 or 7 days after a 5-day course of G-CSF (81 and 57% WBC loss, respectively) compared with those given no G-CSF or G-CSF 10 or 14 days before RAIT (45-50%) WBC loss). In conclusion, our data indicate that the timing of RAIT after the administration of G-CSF for PBSCH may influence WBC toxicity and recovery after this treatment and may have important implications on the design of high-dose RAIT trials combined with PBSCH.

Pharmacokinetics, dosimetry, and initial therapeutic results with 131I- and (111)In-/90Y-labeled humanized LL2 anti-CD22 monoclonal antibody in patients with relapsed, refractory non-Hodgkin's lymphoma.

The pharmacokinetics, dosimetry, and immunogenicity of 131I- and (111)In-/90Y-humanized LL2 (hLL2) anti-CD22 monoclonal antibodies were determined in patients with recurrent non-Hodgkin's lymphoma. Fourteen patients received tracer doses of 131I-hLL2 followed 1 week later by therapeutic doses intended to deliver 50-100 cGy to the bone marrow. Another eight patients received (111)In-hLL2 followed by therapy with 90Y-hLL2 also delivering 50 or 100 cGy to the bone marrow. The blood T(1/2) (hours) for the tracer infusions of 131I-hLL2 was 44.2 +/- 10.9 (mean +/- SD) compared with 54.2 +/- 25.0 for the therapy infusions, whereas the values were 70.7 +/- 17.6 for (111)In-hLL2 and 65.8 +/- 15.0 for 90Y-hLL2. The estimated average radiation dose from 131I-hLL2 in tumors >3 cm was 2.4 +/- 1.9 cGy/mCi and was only 0.9-, 1.0-, 1.1-, and 1.0-fold that of the bone marrow, lung, liver, and kidney, respectively. In contrast, the estimated average radiation dose from 90Y-hLL2 in tumors >3 cm was 21.5 +/- 10.0 cGy/mCi and was 3.7-, 2.5-, 1.8-, and 2.5-fold that of the bone marrow, lung, liver, and kidney, respectively. No evidence of significant anti-hLL2 antibodies was seen in any of the patients. Myelosuppression was the only dose-limiting toxicity and was greater in patients who had prior high-dose chemotherapy. Objective tumor responses were seen in 2 of 13 and 2 of 7 patients given 131I-hLL2 or 90Y-hLL2, respectively. In conclusion, 90Y-hLL2 results in a more favorable tumor dosimetry compared with 131I-hLL2. This finding, combined with the initial anti-tumor effects observed, encourage further studies of this agent in therapeutic trials.

Role of radiation dosimetry in radioimmunotherapy planning and treatment dosing.

Cancer-seeking antibodies (Abs) carrying radionuclides can be powerful drugs for delivering radiotherapy to cancer. As with all radiotherapy, undesired radiation dose to critical organs is the limiting factor. It has been proposed that optimization of radioimmunotherapy (RIT), that is, maximization of therapeutic efficacy and minimization of normal tissue toxicity, depends on a foreknowledge of the radiation dose distributions to be expected. The necessary data can be acquired by established tracer techniques, in individual patients, using quantitative radionuclide imaging. Object-oriented software systems for estimating internal emitter radiation doses to the tissues of individual patients (patient-specific radiation dosimetry), using computer modules, are available for RIT, as well as for other radionuclide therapies. There is general agreement that radiation dosimetry (radiation absorbed dose distribution, cGy) should be utilized to establish the safety of RIT with a specific radiolabeled Ab in the early stages (i.e. phase I or II) of drug evaluation. However, it is less well established that radiation dose should be used to determine the radionuclide dose (amount of radioactivity, GBq) to be administered to a specific patient (i.e. radiation dose-based therapy). Although treatment planning for individual patients based upon tracer radiation dosimetry is an attractive concept and opportunity, particularly for multimodality RIT with intent to cure, practical considerations may dictate simpler solutions under some circumstances.

Distribution of deoxyglucose and technetium-99m-glucarate in the acutely ischemic myocardium.

The regional myocardial distribution of 99mTc-glucarate was compared to 3H-deoxyglucose in 22 rabbits with left circumflex marginal artery occlusion. In 12 rabbits, tissue radioactivity measurements were compared to the results of triphenyl tetrazolium chloride staining and light microscopy. In 10 additional rabbits, the myocardial sodium space (24NaCl), an indicator of tissue edema induced by injury, was compared to the distribution of deoxyglucose and glucarate. Technetium-99m-glucarate accumulated in injured myocardium within 6 hr after coronary ligation and myocardial concentration was greatest in the most severely injured zones (TTC unstained). Hydrogen-3-deoxyglucose behaved as a marker of ischemia but concentrated in tissue with injury ranging from mild ischemia (TTC stained) to transmural infarction (TTC unstained). Both 99mTc-glucarate and 3H-deoxyglucose concentrated in acute, severely injured myocardial tissue. These studies suggest that 99mTc-glucarate is a useful tracer for evaluating myocardial injury. In addition, it appears that 99mTc-glucarate and 3H-deoxyglucose demarcate different points in the spectrum of myocardial injury.

Pharmacokinetics, dosimetry and toxicity of rhenium-188-labeled anti-carcinoembryonic antigen monoclonal antibody, MN-14, in gastrointestinal cancer.

UNLABELLED: The biodistribution, pharmacokinetics and dosimetry of 188Re-labeled MN-14, an IgG anti-carcinoembryonic antigen monoclonal antibody (MAb), were assessed in patients in advanced gastrointestinal cancer. In addition, the dose-limiting toxicity (DLT) and maximum tolerated dose of fractionated doses of this agent were determined. METHODS: Eleven patients were administered radioactive doses of directly labeled 188Re-MN-14 IgG, ranging from 20.5 mCi to 161.0 mCi (2.0 mg-4.9 mg). Ten of these patients received two or three MAb infusions, given 3-4 days apart, delivering total doses of 30 mCi/m2-80 mCi/m2. External scintigraphy was used to evaluate the MAb biodistribution, and quantitative external scintigraphic methods were used to determine the organ and tumor radiation doses. RESULTS: The biodistribution studies showed enhanced 188Re-MN-14 uptake in the liver, spleen and kidneys, compared to that of 131I-MN-14. The biological T(1/2) values for 188Re-MN-14 in the blood and whole body (in hours) were 8.2 +/- 4.1 (n = 7) and 107.8 +/- 104.2 (n = 9), respectively (mean +/- s.d.). The radiation absorbed doses (cGy/mCi) delivered to the total body, red marrow, lungs, liver, spleen and kidneys were 0.5 +/- 0.05, 3.6 +/- 1.6, 2.0 +/- 0.8, 5.9 +/- 2.5, 7.1 +/- 1.9 and 8.5 +/- 2.8, respectively. Red marrow suppression was the only DLT observed. The maximum tolerated dose of fractionated doses of 188Re-MN-14 was estimated to be 60 mCi/m2. CONCLUSION: Despite its relatively increased renal and hepatic uptake, red marrow suppression is the only DLT of 188Re-MN-14. The feasibility of administering relatively high doses of 188Re on a completely outpatient basis may make this agent a preferred candidate for radioimmunotherapy.

Cholescintigraphy in the diagnosis of acute cholecystitis: morphine augmentation is superior to delayed imaging.

Morphine-augmented radionuclide hepatobiliary imaging has been used as an alternative to delayed imaging for the diagnosis of acute cholecystitis. Previous studies have indicated that the morphine-augmentation is as useful as, or more useful than, delayed imaging. A careful comparison of the efficacy of the two techniques appears warranted because: (1) most early studies did not compare the efficacy of the two techniques in a single report using comparable patient populations; (2) the reported efficacy of morphine-augmentation is based primarily on study designs which excluded cases of early gallbladder visualization without morphine, while most delayed imaging protocols included these cases; and (3) there were concerns about the potential consequences of a false-negative morphine examination. This study compared the efficacy of morphine-augmentation with delayed imaging in those cases in which the gallbladder was not visualized during the first hour of study. Of 306 consecutive patients who were scanned to rule out acute cholecystitis, the gallbladder was visualized within 1 hr in 215 cases. In the remaining 91 cases, 46 patients had delayed imaging (17 true-positive, 10 true-negative, 19 false-positive and 0 false-negative), and 45 had morphine-augmentation (24 true-positive, 15 true-negative, 4 false-positive and 2 false-negative). The data indicate that delayed imaging has a significantly lower specificity and positive-predictive value for acute cholecystitis than morphine-augmentation and a slightly higher (statistically insignificant) sensitivity and negative-predictive value. These results appear to be supported by a reanalysis of the data that has already been reported in the literature.

Initial experience with high-dose radioimmunotherapy of metastatic medullary thyroid cancer using 131I-MN-14 F(ab)2 anti-carcinoembryonic antigen MAb and AHSCR.

UNLABELLED: This phase I study was initiated to determine the toxicity and therapeutic potential of high-dose 131I-MN-14 F(ab)2 anti-carcinoembryonic antigen monoclonal antibody (MAb) combined with autologous hematopoietic stem cell rescue (AHSCR) in patients with rapidly progressing metastatic medullary thyroid cancer. METHODS: Twelve patients were entered into the study. Dose escalation was based on prescribed radiation doses to critical organs (i.e., kidney, lung, and liver). Starting doses were 900 cGy to the kidney and no more than 1200 cGy to the lung and liver, with dose increments of 300 cGy until the maximum tolerable dose is determined. Tumor targeting was assessed by external scintigraphy, toxicity was assessed according to the common toxicity criteria of the National Cancer Institute, and therapy responses were assessed by CT, serum carcinoembryonic antigen, and calcitonin. RESULTS: One patient received 9.95 GBq 131I-MN-14 F(ab)2, for an initial dose of 656 cGy to critical organs, 8 received 900 cGy (8.69-17.98 GBq), and 3 received 1200 cGy (15.17-17.69 GBq). The MAb scans of all patients showed positive findings. Autologous hematopoietic stem cells were given to all patients 1-2 wk after therapy, when the total body radiation exposure was less than 5.2 x 10(-7) C/kg/h. Dose-limiting toxicity, defined as grade 3 or 4 nonhematologic toxicity, was not seen in the patient who received the 656-cGy dose, and only 1 of the 8 patients treated at the 900-cGy dose level had grade 3 toxicity, which was gastrointestinal and reversible. No dose-limiting toxicity was seen in the 3 patients treated at the 1200-cGy dose level. Except for the instance of grade 3 gastrointestinal toxicity, nonhematologic toxicity was relatively mild, with only grade 1 or 2 toxicity observed in 9 patients. No renal toxicity was seen. Of the 12 patients, 1 had partial remission for 1 y, another had a minor response for 3 mo, and 10 had stabilization of disease lasting between 1 and 16 months. CONCLUSION: The results show the safety of administering high myeloablative doses of 131I-MN-14 F(ab)2 with AHSCR in patients with metastatic medullary thyroid cancer. The antitumor responses in patients with aggressive, rapidly progressing disease are encouraging and warrant further research to optimize the effectiveness of this new treatment.

Regression of advanced refractory ovarian cancer treated with iodine-131-labeled anti-CEA monoclonal antibody.

Advanced chemotherapy-resistant ovarian cancer has a poor prognosis, thus requiring new therapeutic modalities. A complete clinical remission, using two cycles of 131I-labeled murine MN-14 anti-CEA monoclonal antibody (MAb), given intravenously, is reported in a patient with advanced ovarian cancer refractory to paclitaxel (Taxol) therapy. The patient first received radioimmunotherapy with approximately 74 mCi 131I-MN-14 IgG, followed 4 mo later by a similar dose of radiolabeled MAb. A partial remission was seen by CT 1 mo after the first radioimmunotherapy, and a further objective response was documented after the second radioimmunotherapy. CT scans performed 6 and 11 mo after the second radioimmunotherapy showed stable and minimal residual changes. However, a whole-body PET scan with [18F]fluorodeoxyglucose (FDG-PET) was negative in these regions. The CA-125 also decreased to only 13 U/ml, compared to the baseline value of 7700 U/ml. Based on CT, FDG-PET, serum CA-125 and physical exam, the patient was in complete clinical remission for 8 mo when the CA-125 levels rose. CT also showed a new suspicious lesion, presumably a peritoneal implant. No toxicity was seen after the first injection, and only Grade 1 thrombocytopenia and Grade 2 leukopenia developed after the second injection, both reversing within 6 wk. This is a report of a complete clinical remission with radiolabeled anti-CEA antibodies in a patient with chemotherapy-refractive metastatic ovarian cancer.

Reduction of renal uptake of monoclonal antibody fragments by amino acid infusion.

UNLABELLED: The renal uptake of radiolabeled antibody fragments and peptides presents a problem in radioimmunodetection and therapy, compromising lesion sensitivity, especially with intracellularly-retained isotopes. Previously, we showed that cationic amino acids and their derivatives are capable of significantly reducing kidney uptake in animals. We report our initial clinical results of successful renal uptake reduction in five patients who underwent cancer radioimmunodetection with 99mTc-anti-CEA Fab' fragments. METHODS: The patients were infused with two liters of a commercially-available nutritive amino acid solution (containing approximately 2.25 g/liter lysine-glutamate and 2.50 g/liter arginine), whereas 75 control patients received the same volume of saline (quantification of organ and tumor kinetics from conjugate whole-body views by ROI technique). RESULTS: The renal uptake in the amino acid group was significantly lower (p<0.05) than in the control group (11.1 +/- 2.0% injected dose versus 17.7 +/- 7.0% injected dose at 24 hr postinjection), whereas the uptake of all other organs remained unaffected. Gel filtration chromatography of the urine taken from amino-acid-treated patients showed that a significantly higher amount of excreted activity was bound to intact Fab' (53% of excreted activity) in contrast to only less than 10% in the control group. CONCLUSION: The renal uptake of monoclonal antibody fragments in patients can be reduced significantly by amino acid infusion, even at considerably lower doses than those that were safe and effective in animals. As was found in animals, the mechanism seems to rely on an inhibition of the re-absorption of tubularly-filtered proteins by the proximal tubule cells. These results encourage further clinical trials to lower the renal uptake experienced in radioimmunodetection, as well as in therapeutic trials with antibody fragments and peptides.

Variables influencing tumor dosimetry in radioimmunotherapy of CEA-expressing cancers with anti-CEA and antimucin monoclonal antibodies.

UNLABELLED: In this study, we examined the factors that may influence tumor dosimetry in the radioimmunotherapy of solid, CEA-expressing cancers. METHODS: Data from 119 tumors in 93 patients with CEA-expressing cancers were analyzed. The patients underwent radioimmunotherapy with the 131I-labeled IgG1 anti-CEA antibodies NP-4 (Ka = 10(8) M-1) or MN-14 (Ka = 10(9) M-1), its humanized form hMN-14, as well as the anticolon-specific antigen-p (CSAp) antibody, Mu-9. For dosimetry, the biodistribution, targeting kinetics and cumulated activity of tumors and organs were determined from planar and SPECT imaging. RESULTS: An inverse logarithmic relationship between tumor size and antibody uptake was found for both anti-CEA antibodies, whereas no such relationship was found for Mu-9. The absolute tumor uptake was identified as the most important factor determining the radiation dose to the tumor (r = 0.9), with the biological half-life of the antibody in the tumor being of secondary importance (r = 0.5). No significant difference in tumor uptake was found between both anti-CEA antibodies, despite their tenfold difference in affinity. At comparable masses, colorectal and medullary thyroid cancers had significantly higher tumor uptakes (p = 0.02), as well as tumor-to-red marrow dose ratios, than other cancer types. The tumor half-lives of the anti-CEA antibodies were significantly lower in colorectal than in all other tumor types (p = 0.01). CONCLUSION: In radioimmunotherapy, tumor uptake appears to be the most important dose-determining factor. Differences in antibody affinity are reflected by differences in the biological half-life, not the absolute uptake. Especially favorable conditions for anti-CEA antibodies seem to prevail in colorectal cancer patients having minimal disease, as well as in medullary thyroid cancer, where cytotoxic tumor doses might be expected. Antimucin antibodies may have a particular advantage in the treatment of patients with larger colorectal tumors.