Sigma-2 receptor ligand as a novel method for delivering a SMAC mimetic drug for treating ovarian cancer.

BACKGROUND: The sigma-2 receptor has been validated as a biomarker for proliferating tumours. Second mitochondria-derived activator of caspase (Smac) is a protein released from mitochondria into the cytosol, leading to apoptosis. In this study, we investigated a sigma-2 ligand as a tumour-targeting drug delivery agent for treating ovarian cancer. METHODS: A sigma-2 ligand, SW 43, was conjugated with a Smac mimetic compound (SMC), SW IV-52s, to form SW III-123. The delivery function of the sigma-2 moiety and cell killing mechanisms of SW III-123 were examined in human ovarian cancer cell lines. RESULTS: SW III-123 internalisation into ovarian cancer cells was mediated by sigma-2 receptors. SW III-123, but not SW IV-52s or SW 43, exhibited potent cytotoxicity in human ovarian cancer cell lines SKOV-3, CaOV-3 and BG-1 after 24-h treatment, suggesting that the sigma-2 ligand successfully delivered SMC into ovarian cancer cells. SW III-123 induced rapid degradation of inhibitor of apoptosis proteins (cIAP1 and cIAP2), accumulation of NF-κB-inducing kinase (NIK) and phosphorylation of NF-κB p65, suggesting that SW III-123 activated both canonical and noncanonical NF-κB pathways in SKOV-3 cells. SW III-123 cleaved caspase-8, -9 and -3. Tumour necrosis factor alpha (TNFα) antibody markedly blocked SW III-123-induced cell death and caspase-3 activity in SKOV-3 cells, indicating that SW III-123 activated both intrinsic and extrinsic apoptotic pathways and induced TNFα-dependent cell death in SKOV-3 cells. CONCLUSION: Sigma-2 ligands are a promising tumour-targeting drug delivery agent. Sigma-2-conjugated SMC exemplifies a novel class of therapeutic drugs for treating ovarian cancer.

Myeloid-derived suppressor cells: general characteristics and relevance to clinical management of pancreatic cancer.

Recent studies describe a heterogeneous population of cells of the myeloid lineage, termed myeloid derived suppressor cells (MDSC), which are observed with increased prevalence in the peripheral blood and tumor microenvironment of cancer patients, including pancreatic cancer. Accumulation of MDSC in the peripheral circulation has been related to extent of disease, and correlates with stage. MDSC have primarily been implicated in promoting tumor growth by suppressing antitumor immunity. There is also compelling evidence MDSC are also involved in angiogenesis and metastatic spread. Two main subsets of MDSC have been identified in cancer patients: a monocytic subset, characterized by expression of CD14, and a granulocytic subset characterized by expression of CD15. Both subsets of MDSC actively suppress host immunity through a variety of mechanisms including production of reactive oxygen species and arginase. Just as in humans, accumulation of monocytic and granulocytic MDSC has been noted in the bone marrow, spleen, peripheral circulation, and tumors of tumor bearing mice. Successful targeting of MDSC in mice is associated with improved immune responses, delayed tumor growth, improved survival, and increased efficacy of vaccine therapy. By further elucidating mechanisms of MDSC recruitment and maintenance in the tumor environment, strategies could be developed to reverse immune tolerance to tumor. We discuss here what is currently known about MDSC as well as some potential strategies targeting MDSC in the context of our work on pancreatic cancer and recent literature. Due to the number of new reports on MDSC, the most pertinent ones have been selected.

Outcomes analysis of laparoscopic resection of pancreatic neoplasms.

BACKGROUND: Experience with laparoscopic resection of pancreatic neoplasms remains limited. The purpose of this study is to critically analyze the indications for and outcomes after laparoscopic resection of pancreatic neoplasms. METHODS: The medical records of all patients undergoing laparoscopic resection of pancreatic neoplasms from July 2000 to February 2006 were reviewed. Data are expressed as mean +/- standard deviation. RESULTS: Laparoscopic pancreatic resection was performed in 22 patients (M:F, 8:14) with a mean age of 56.3 +/- 15.1 years and mean body mass index (BMI) of 26.3 +/- 4.5 kg/m2. Nine patients had undergone previous intra-abdominal surgery. Indications for pancreatic resection were cyst (1), glucagonoma (1), gastrinoma (2), insulinoma (3), metastatic tumor (2), IPMT (4), nonfunctioning neuroendocrine tumor (3), and mucinous/serous cystadenoma (6). Mean tumor size was 2.4 +/- 1.6 cm. Laparoscopic distal pancreatectomy was attempted in 18 patients and completed in 17, and enucleation was performed in 4 patients. Laparoscopic ultrasound (n = 10) and a hand-assisted technique (n = 4) were utilized selectively. Mean operative time was 236 +/- 60 min and mean blood loss was 244 +/- 516 ml. There was one conversion to an open procedure because of bleeding from the splenic vein. The mean postoperative LOS was 4.5 +/- 2.0 days. Seven patients experienced a total of ten postoperative complications, including a urinary tract infection (UTI) (1), lower-extremity deep venous thrombosis (DVT) and pulmonary embolus (1), infected peripancreatic fluid collection (1), pancreatic pseudocyst (1), and pancreatic fistula (6). Five pancreatic fistulas were managed by percutaneous drainage. The reoperation rate was 4.5% and the overall pancreatic-related complication rate was 36.4%. One patient developed pancreatitis and a pseudocyst 5 months postoperatively, which was managed successfully with a pancreatic duct stent. There was no 30-day mortality. CONCLUSIONS: Laparoscopic pancreatic resection is safe and feasible in selected patients with pancreatic neoplasms. With a pancreatic duct leak rate of 27%, this problem remains an area of development for the minimally invasive technique.

Clinicopathologic analysis of patients with adult rhabdomyosarcoma.

BACKGROUND: Rhabdomyosarcoma (RMS) in adults (age > or = 16 years) is rare, accounting for less than 3% of adult soft tissue sarcomas. There is little information describing the disease biology or clinicopathologic factors that influence survival in adults with RMS. The objective of this study was to define the factors in patients with adult RMS that predict outcome, disease progression, and survival. METHODS: Eighty-four adult patients with a pathologic diagnosis of RMS that was confirmed by immunohistochemistry were identified by a prospective inpatient data base during the period 1982--1999 and were analyzed for disease specific survival and metastasis free survival using the Kaplan-Meier actuarial method. Statistical significance was evaluated using the log-rank test for univariate influence and a Cox regression model for multivariate influence. RESULTS: The median disease specific survival was 22 months. Patient age, extent of disease, tumor size at the time of diagnosis, and margin status after resection were significant predictors of disease specific survival. Patients who underwent a complete resection had a significantly longer median survival (105 months) compared with any other subgroup of patients. The histologic subtype did not predict patient survival but did vary with patient age. Most notably, the proportion of the pleomorphic subtype increased with advancing age, accounting for 42% of RMS in patients over the age of 40 years. CONCLUSIONS: The most important predictors of outcome in patients with adult RMS are patient age, tumor size, extent of disease, and margin status after resection. In contrast to patients with pediatric RMS, no association was noted between survival and histologic subtype in this group of patients with adult RMS. All histologic subtypes of RMS are aggressive malignancies with poor disease specific survival despite aggressive multimodality management.

Immunotherapeutic approach to cancer with cutaneous DNA vaccination.

Innovations for the development of cancer vaccines are emerging from advances in molecular immunology and cancer biology (1). Of these, DNA-based vaccination has become a powerful and potentially versatile method for eliciting an immune response against cancer. One method for DNA immunization involves the delivery of plasmid DNA by particle bombardment. Originally developed for plant hybridization, this approach has proven to be readily transferable to mammalian applications (2-3). Otherwise known as the gene gun, this method allows for the introduction of exogenous "naked" DNA into skin (4) (Fig. 1). Fig. 1. Photograph of the helium-driven gene gun. This is a hand-held device attached to a high pressure helium line and electrical source which operates the trigger. As shown, plastic bullets containing gold particles coated with plasmid DNA are measured and cut to fit within a cartridge. The cartridge, filled with 12 bullets, is easily placed within the barrel of the gun.

Effects of preexisting immunity on the response to herpes simplex-based oncolytic viral therapy.

Herpes simplex viruses (HSV) type 1 are the basis of a number of anticancer strategies that have proven efficacious in animal models. They are natural human pathogens and the majority of adults have anti-HSV immunity. The current study examined the effect of preexisting immunity on the response to herpes-based oncolytic viral treatment of hepatic metastatic cancer in a murine model designed to simulate a clinical approach likely to be utilized for nonneurological tumors. Specifically, the anticancer effects of NV1020 or G207, two multimutated HSV-1 oncolytic viruses, were tested in immunocompetent mice previously immunized with a wild-type herpes simplex type 1 virus. Mice were documented to have humoral as well as cell-mediated immunity to HSV-1. Tumor response to oncolytic therapy was not measurably abrogated by immunity to HSV at the doses tested. The influence of route of viral administration was also tested in models of regional hepatic arterial and intravenous therapy. Route of viral administration influenced efficacy, as virus delivered intravenously produced some detectable attenuation while hepatic arterial therapy remained unaffected. These results demonstrate that when given at appropriate doses and in reasonable proximity to tumor targets, HSV-based oncolytic therapy can still be expected to be effective treatment for patients with hepatic malignancies.

Desmoid tumors of the head and neck--a clinical study of a rare entity.

BACKGROUND: Desmoid tumors are are, nonmalignant neoplasms that show locally aggressive growth but lack the potential to metastasize. Common anatomic sites include the extremity, abdominal wall, and mesentery. Little is reported about clinical features and outcome of desmoid tumors of the head and neck. METHODS: Twenty-one patients with desmoid tumors of the head and neck treated at MSKCC between July 1982 and June 1999 were identified from our inpatient tumor database. All patients underwent surgical resection and were prospectively followed. Clinicopathologic features and treatment modalities were evaluated. RESULTS: Patient age at diagnosis was 22 to 76 years, with a female-male ratio of 16:5. Most tumors were located in the supraclavicular fossa or the muscles of the neck (n = 19). Patients most commonly had a painless mass (n = 13) or neurologic symptoms including pain or neurologic deficit (n = 8). Extent of resection was limited to the tumor in nine patients. In the other 12, structures including the accessory or phrenic nerve, parts of the brachial plexus, or bony structures were resected. Persistent neurologic or functional deficits after surgery were noted in 12 patients. Five of 21 patients had recurrences (24%). Eleven patients received radiation therapy. In this small population, no obvious benefit for patients receiving radiation vs patients who were not irradiated, regardless of their surgical margin status, was seen. Treatment for recurrence was re-resection or re-resection plus radiation. Eighteen patients remained free of disease after treatment, two patient have stable disease and one died of other causes. No patients died of their disease. CONCLUSIONS: Desmoid tumors of the head and neck are rare, fibrous neoplasms with a good prognosis but significant morbidity. Function-preserving surgery should be a primary goal to minimize morbidity. In this small group of patients, the benefits of radiation therapy in patients with positive margins could not be clearly demonstrated and should be balanced against radiation-related morbidity.

LROC analysis of detector-response compensation in SPECT.

Localization ROC (LROC) observer studies examined whether detector response compensation (DRC) in ordered-subset, expectation-maximization (OSEM) reconstructions helps in the detection and localization of hot tumors. Simulated gallium (Ga-67) images of the thoracic region were used in the study. The projection data modeled the acquisition of attenuated 93- and 185-keV photons with a medium-energy parallel-hole collimator, but scatter was not modeled. Images were reconstructed with five strategies: 1) OSEM with no DRC; 2) OSEM preceded by restoration filtering; 3) OSEM with iterative DRC; 4) OSEM with an ideal DRC; and 5) filtered backprojection (FBP) with no DRC. All strategies included attenuation correction. There were four LROC studies conducted. In a study using a single tumor activity, the ideal DRC offered the best performance, followed by iterative DRC, restoration filtering, OSEM with no DRC, and FBP. Statistical significance at the 5% level was found between all pairs of strategies except for restoration filtering and OSEM with no DRC. A similar ranking was found for a more realistic study using multiple tumor activities. Additional studies considered the effects of OSEM iteration number and tumor activity on the detection improvement that iterative DRC offered with respect to OSEM with no DRC.

Immunization with DNA coding for gp100 results in CD4 T-cell independent antitumor immunity.

BACKGROUND: Xenogeneic DNA immunization can exploit small differences in expressed protein sequence resulting in immune recognition of self-molecules. We hypothesized that immunizing mice with xenogeneic DNA coding for the human melanosomal membrane glycoprotein gp100 would overcome immune ignorance or tolerance and result in tumor immunity. We also investigated the immunologic mechanisms of the antitumor immunity. METHODS: C57BL/6 mice were immunized with DNA coding for human gp100, mouse gp100, or control vector by gene gun. After immunization, mice were challenged with a syngeneic melanoma expressing gp100, and tumor growth was analyzed. Mice deficient in major histocompatibility complex class I or class II molecules were similarly studied to assess the immunologic mechanism of the tumor protection. RESULTS: There was significant tumor protection after vaccination with xenogeneic human gp100 DNA. Class I, but not class II, major histocompatibility complex molecules were required for tumor immunity. In addition, mice immunized with human gp100 demonstrated autoimmunity manifested as coat color depigmentation. CONCLUSIONS: Immunization with xenogeneic DNA coding for the melanosomal glycoprotein gp100 results in tumor protection and autoimmune depigmentation. These results show that xenogeneic DNA vaccines can lead to cancer immunity without CD4(+) T-cell help with potential implications for rational vaccine design.

Dermatofibrosarcoma protuberans: A clinicopathologic analysis of patients treated and followed at a single institution.

BACKGROUND: Despite optimal surgical therapy for patients with dermatofibrosarcoma protuberans (DFSP), some patients still continue to develop local recurrence. The authors' objective was to identify and analyze clinicopathologic factors for disease free survival in a large group of patients who were followed prospectively at a single institution. METHODS: Prospectively collected data and pathology slides were available for review from 159 patients with primary or recurrent DFSP who underwent treatment between July 1950 and July 1998. The study group was comprised of patients with either the "classic" form of DFSP or the fibrosarcomatous "high grade" variant of DFSP (FS-DFSP). Patient, tumor, pathologic, and treatment factors were analyzed using the log rank test for univariate influence and Cox regression analysis for multivariate influence. Local recurrence free survival was determined by the Kaplan-Meier actuarial method. RESULTS: Of the 159 patients who comprised the current study group, 134 (84%) had the classic form of DFSP. The FS-DFSP variant was found in the remaining 25 patients (16%). The overall 5-year local recurrence free survival rate was 75%, with a median follow-up of 4. 75 years. The 5-year recurrence free survival rate for each group was 81% and 28%, respectively. On univariate analysis, age > 50 years, very close (< 1 mm) to positive microscopic margins, FS-DFSP variant, high mitotic rate, and increased cellularity were unfavorable prognostic factors. Multivariate analysis determined very close (< 1 mm) to positive microscopic margins and FS-DFSP variant to be independent adverse prognostic factors. For the 34 patients who developed a recurrence after surgical resection (21%), the median time to local recurrence was 32 months. Of the patients in this group, two died from metastatic disease. CONCLUSIONS: The prognosis after surgical resection with negative and sometimes positive microscopic margins for patients with DFSP is very good. However, increased age, high mitotic index, and increased cellularity are predictors of poor clinical outcome. The FS-DFSP variant represents a much more aggressive tumor with metastatic potential. Patients who are treated with curative intent for FS-DFSP should undergo aggressive attempts at complete surgical resection. Patients with recurrent classic DFSP without evidence of adverse prognostic features may benefit from conservative management, especially in the setting of potentially unresectable disease.

Coupling and uncoupling of tumor immunity and autoimmunity.

Self-antigens, in the form of differentiation antigens, are commonly recognized by the immune system on melanoma and other cancers. We have shown previously that active immunization of mice against the melanocyte differentiation antigen, a tyrosinase-related protein (TRP) gp75(TRP-1) (the brown locus protein) expressed by melanomas, could induce tumor immunity and autoimmunity manifested as depigmentation. In this system, tumor immunity and autoimmunity were mediated by autoantibodies. Here, we characterize immunity against another tyrosinase family glycoprotein TRP-2 (the slaty locus protein), using the same mouse model and method of immunization. As observed previously for gp75(TRP-1), immunity was induced by DNA immunization against a xenogeneic form of TRP-2, but not against the syngeneic gene, and depended on CD4(+) cells. Immunization against TRP-2 induced autoantibodies and autoreactive cytotoxic T cells. In contrast to immunization against gp75(TRP-1), both tumor immunity and autoimmunity required CD8(+) T cells, but not antibodies. Only autoimmunity required perforin, whereas tumor immunity proceeded in the absence of perforin. Thus, immunity induced against two closely related autoantigens that are highly conserved throughout vertebrate evolution involved qualitatively different mechanisms, i.e., antibody versus CD8(+) T cell. However, both pathways led to tumor immunity and identical phenotypic manifestations of autoimmunity.

Injection of DNA encoding granulocyte-macrophage colony-stimulating factor recruits dendritic cells for immune adjuvant effects.

An important issue for effective vaccines is the development of potent adjuvants that can facilitate induction or augmentation of immunity. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a growth factor for myeloid progenitors of monocytes and dendritic cells (DC), which upon maturation are antigen-presenting cells (APC). The adjuvant effects of inoculation of DNA encoding GM-CSF into skin were studied. Initial experiments examined whether the GM-CSF gene injected into the skin of mice could affect the density of epidermal DC (Langerhans cells). DNA encoding GM-CSF delivered by particle bombardment into skin resulted in a significant increase of epidermal DC at the inoculation site. Kinetic analysis of epidermal recruitment after GM-CSF inoculation showed an increase in DC that peaked at seven days. This increase was accompanied by recruitment of DC into draining lymph nodes. The adjuvant effects of DNA encoding GM-CSF inoculated into skin were measured by the ability to augment antibody and T-cell responses against poorly immunogenic tumor antigens. Peptide immunization at skin sites containing epidermal DC newly recruited by GM-CSF DNA elicited T-cell responses against mutant p53, whereas peptide immunization of control skin sites did not elicit any detectable T-cell responses. Likewise, generation of antibodies following immunization with DNA encoding human gp75TRP1, a tyrosinase family member expressed by melanomas, was accelerated and protection from tumor challenge augmented by GM-CSF DNA.

Patient-specific dosimetry of indium-111- and yttrium-90-labeled monoclonal antibody CC49.

UNLABELLED: The objective of this work was to develop patient-specific dosimetry for patients with metastatic gastrointestinal tract cancers who received 111In-CC49 IgG for imaging before therapy with 90Y-CC49 IgG. METHODS: Whole-body imaging of 12 patients, who received 111-185 MBq (3-5 mCi) of 111In-CC49, commenced in < 2 hr postinfusion and was continued daily for 4-5 days. SPECT data were acquired at 24 and 72 hr to determine the range of 111In-CC49 activity concentrations in tumors and normal organs. Time-activity curves were generated from the image data and scaled from 111In-CC49 to 90Y-CC49 for dosimetric purposes. Absorbed-dose calculations for 90Y-CC49 included the mean and range in tumor and normal organs. Computed 90Y-CC49 activity concentrations were compared with measurements on 10 needle biopsies of normal liver and four tumor biopsies. RESULTS: In 9 of 10 normal liver samples, the range of computed 90Y-CC49 activity concentrations bracketed measured values. This was also the case for 3 of 4 tumor biopsies. Absorbed-dose calculations for 90Y-CC49 were based on patients' images and activities in tissue samples and, hence, were patient-specific. CONCLUSION: For the radiolabeled antibody preparations used in this study, quantitative imaging of 111In-CC49 provided the data required for 90Y-CC49 dosimetry. The range of activities in patients' SPECT images was determined for a meaningful comparison of measured and computed values. Knowledge of activity distributions in tumors and normal organs was essential for computing mean values and ranges of absorbed dose and provided a more complete description of the absorbed dose from 90Y-CC49 than was possible with planar methods.

Patient-specific dosimetry using quantitative SPECT imaging and three-dimensional discrete Fourier transform convolution.

UNLABELLED: The objective of this study was to develop a three-dimensional discrete Fourier transform (3D-DFT) convolution method to perform the dosimetry for 131I-labeled antibodies in soft tissues. METHODS: Mathematical and physical phantoms were used to compare 3D-DFT with Monte Carlo transport (MCT) calculations based on the EGS4 code. The mathematical and physical phantoms consisted of a sphere and a cylinder, respectively, containing uniform and non-uniform activity distributions. Quantitative SPECT reconstruction was carried out using the circular harmonic transform (CHT) algorithm. RESULTS: The radial dose profile obtained from MCT calculations and the 3D-DFT convolution method for the mathematical phantom were in close agreement. The root mean square error (RMSE) for the two methods was < 0.1%, with a maximum difference < 21%. Results obtained for the physical phantom gave a RMSE < 0.1% and a maximum difference of < 13%; isodose contours were in good agreement. SPECT data for two patients who had undergone 131I radioimmunotherapy (RIT) were used to compare absorbed-dose rates and isodose rate contours with the two methods of calculation. This yielded a RMSE < 0.02% and a maximum difference of < 13%. CONCLUSION: Our results showed that the 3D-DFT convolution method compared well with MCT calculations. The 3D-DFT approach is computationally much more efficient and, hence, the method of choice. This method is patient-specific and applicable to the dosimetry of soft-tissue tumors and normal organs. It can be implemented on personal computers.

SPECT imaging of fluorine-18.

UNLABELLED: The objective of this work was to determine the potential clinical usefulness of SPECT to image 511-keV annihilation photons. METHODS: A triple-headed gamma camera equipped with ultra-high-energy collimators was used to image 18F. Sensitivity measurements were carried out and the FWHM and FWTM were determined in air and for a unit-density scattering medium. Additionally, tomographic phantom studies were acquired to evaluate image quality. RESULTS: The sensitivities of the three cameras were, for all practical purposes, identical. At a source-to-collimator distance of 100 mm, the FWHM and FWTM were 13 and 29 mm, respectively. A tomographic phantom study demonstrated that spheres with a diameter of 20 mm were well resolved when filled with 18F activity and placed inside a water-filled phantom. CONCLUSION: The triple-headed SPECT camera in this investigation is a practical means of acquiring tomographic 18F images. The reconstructed slices were of sufficient quality to be of value in some clinical studies.

Nutritional support of the septic patient.

Nutrition and metabolic support is just one of many weapons at the clinician's disposal in the battle against infection. Much has been learned in the past several decades concerning the host's response to infection and the competition among substrates during health and disease. Despite these advances, we still are remarkably ineffective at preventing the muscle wasting that accompanies sepsis and other chronic catabolic conditions. This likely is the result of our lack of understanding concerning the molecular mechanisms responsible for changes in protein metabolism. It is anticipated that the optimal or preferred mixture of glucose, fat, and protein will be better defined in the future, and that new supplements (e.g., MCTs, amino acids, growth factors, antioxidants) will prove beneficial, so the protein-catabolic response to sepsis can be ameliorated and patient outcome improved. Until that time, nutritional interventions should be initiated early in the septic episode and be assessed and altered frequently. Specific guidelines for nutritional support are presented in Table 3.

The effect of intrinsic attenuation correction methods on the stationarity of the 3-D modulation transfer function of SPECT.

The application of stationary restoration techniques to SPECT images assumes that the modulation transfer function (MTF) of the imaging system is shift invariant. It was hypothesized that using intrinsic attenuation correction (i.e., methods which explicitly invert the exponential radon transform) would yield a three-dimensional (3-D) MTF which varies less with position within the transverse slices than the combined conjugate view two-dimensional (2-D) MTF varies with depth. Thus the assumption of shift invariance would become less of an approximation for 3-D post- than for 2-D pre-reconstruction restoration filtering. SPECT acquisitions were obtained from point sources located at various positions in three differently shaped, water-filled phantoms. The data were reconstructed with intrinsic attenuation correction, and 3-D MTFs were calculated. Four different intrinsic attenuation correction methods were compared: (1) exponentially weighted backprojection, (2) a modified exponentially weighted backprojection as described by Tanaka et al. [Phys. Med. Biol. 29, 1489-1500 (1984)], (3) a Fourier domain technique as described by Bellini et al. [IEEE Trans. ASSP 27, 213-218 (1979)], and (4) the circular harmonic transform (CHT) method as described by Hawkins et al. [IEEE Trans. Med. Imag. 7, 135-148 (1988)]. The dependence of the 3-D MTF obtained with these methods, on point source location within an attenuator, and on shape of the attenuator, was studied. These 3-D MTFs were compared to: (1) those MTFs obtained with no attenuation correction, and (2) the depth dependence of the arithmetic mean combined conjugate view 2-D MTFs.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative SPECT for indium-111-labeled antibodies in the livers of beagle dogs.

Results are presented for SPECT computations of liver volumes and 111In-labeled antibody activities in the livers of eight normal beagle dogs. Administered activities ranged from 1 to 2 mCi. SPECT studies were acquired 1 day postinjection using a rotating gamma camera system with elliptical orbits in a 360-degree rotation (128 views, 15 sec/view, 64 x 64 matrices). Uniformity-corrected images were reconstructed by use of the circular harmonic transform algorithm with computer software developed in-house. Liver volumes and activities were computed from transverse slices, 1 pixel (6.25 mm) in thickness. Comparison of SPECT and autopsy data demonstrated that absolute values of percent differences between measured and computed liver volumes ranged from 1.0% to 7.2%. Absolute values of percent differences between autopsy data and computed 111In activities in the liver ranged from 2.3% to 7.5%. These results suggest that quantitative SPECT has the potential of becoming an important tool in clinical trials for determining activities and localization volumes of radiolabeled antibodies directly from radionuclide images.