Biological Effective Radiation Dose for Multiple Myeloma Palliation.

Purpose: Various radiation therapy (RT) dose/fractionation schedules are acceptable for palliation in multiple myeloma. Nine years of single-institution RT experience were reviewed to determine the influence of dose/fractionation and other factors pertinent to individualizing therapy. Methods and Materials: In total, 152 items were identified from Current Procedural Terminology codes for multiple myeloma treatment from 2012 through June 30, 2021. After exclusions, 205 sites of radiation in 94 patients were reviewed. Data were captured from treatment planning and clinical records. To statistically assess the association between biological effective dose (BED10) and variables of interest, BED was first dichotomized to <24 Gy versus ≥24 Gy. Multivariate analysis used SAS software and a generalized estimating equation approach to account for multiple observations per patient. Results: Fractions of 1.8 to 8 Gy were used in 1 to 25 fractions. Most patients had no significant toxicity. Grade 1 toxicity was more likely with greater BED radiation courses, as expected (20% vs 12% for BED <24 Gy). Pain relief was complete or very good for most sites, with <3% reporting no pain relief. Eleven sites in 9 patients required retreatment. All retreatment sites had palliation that was lasting, with a median of 22 months to last follow-up or death after repeat course (range, 0.5-106 months). There was a trend for better pain control and less risk of fracture retreatment with BED ≥24 Gy. Conclusions: Most patients had good palliation without toxicity. BED ≥24 Gy caused 8% greater risk of grade 1 toxicity and trended toward better pain control plus reduced risk of fracture retreatment.

MIRD dose estimate report No. 20: radiation absorbed-dose estimates for 111In- and 90Y-ibritumomab tiuxetan.

UNLABELLED: Absorbed-dose calculations provide a scientific basis for evaluating the biologic effects associated with administered radiopharmaceuticals. In cancer therapy, radiation dosimetry supports treatment planning, dose-response analyses, predictions of therapy effectiveness, and completeness of patient medical records. In this study, we evaluated the organ radiation absorbed doses from intravenously administered (111)In- and (90)Y-ibritumomab tiuxetan. METHODS: Ten patients (6 men and 4 women) with non-Hodgkin lymphoma, cared for at 3 different medical centers, were administered the tracer (111)In-ibritumomab tiuxetan and assessed using planar scintillation camera imaging at 5 time points and CT-organ volumetrics to determine patient-specific organ biokinetics and dosimetry. Explicit attenuation correction based on the transmission scan or transmission measurements provided the fraction of (111)In-administered activity in 7 major organs, the whole body, and remainder tissues over time through complete decay. Time-activity curves were constructed, and radiation doses were calculated using MIRD methods and implementing software. RESULTS: Mean radiation absorbed doses for (111)In- and for (90)Y-ibritumomab tiuxetan administered to 10 cancer patients are reported for 24 organs and the whole body. Biologic uptake and retention data are given for 7 major source organs, remainder tissues, and the whole body. Median absorbed dose values calculated by this method were compared with previously published dosimetry for ibritumomab tiuxetan and the product package insert. CONCLUSION: In high-dose radioimmunotherapy, the importance of patient-specific dosimetry becomes obvious when the objective of treatment planning is to achieve disease cures, safely, by limiting radiation dose to any critical normal organ to its maximum tolerable value. Compared with the current package insert, we found differences in median absorbed dose by multiples of 24 in the kidneys, 1.8 in the red marrow, 0.65 in the liver, 0.077 in the intestinal wall, 0.30 in the lungs, 0.46 in the spleen, and 0.34 in the heart wall.

Predictors of distant brain recurrence for patients with newly diagnosed brain metastases treated with stereotactic radiosurgery alone.

PURPOSE: To ascertain predictors of distant brain failure (DBF) in patients treated initially with stereotactic radiosurgery alone for newly diagnosed brain metastases. We hypothesize that these factors may be used to group patients according to risk of DBF. METHODS AND MATERIALS: We retrospectively analyzed 100 patients with newly diagnosed brain metastases treated from 2003 to 2005 at our Gamma Knife radiosurgery facility. The primary endpoint was DBF. Potential predictors included number of metastases, tumor volume, histologic characteristics, extracranial disease, and use of temozolomide. RESULTS: One-year actuarial risk of DBF was 61% for all patients. Significant predictors of DBF included more than three metastases (hazard ratio, 3.30; p = 0.004), stable or poorly controlled extracranial disease (hazard ratio, 2.16; p = 0.04), and melanoma histologic characteristics (hazard ratio, 2.14; p = 0.02). These were confirmed in multivariate analysis. Those with three or fewer metastases, no extracranial disease, and nonmelanoma histologic characteristics (N = 18) had a median time to DBF of 89 weeks vs. 33 weeks for all others. One-year actuarial freedom from DBF for this group was 83% vs. 26% for all others. CONCLUSIONS: Independent significant predictors of DBF in our series included number of metastases (more than three), present or uncontrolled extracranial disease, and melanoma histologic characteristics. These factors were combined to identify a lower risk subgroup with significantly longer time to DBF. These patients may be candidates for initial localized treatment, reserving whole-brain radiation therapy for salvage. Patients in the higher risk group may be candidates for initial whole-brain radiation therapy or should be considered for clinical trials.

Locoregionally advanced head and neck cancer treated with primary radiotherapy: a comparison of the addition of cetuximab or chemotherapy and the impact of protocol treatment.

PURPOSE: The addition of platinum-based chemotherapy (ChRT) or cetuximab (ExRT) to concurrent radiotherapy (RT) has resulted in improved survival in Phase III studies for locoregionally advanced head and neck cancer (LAHNC). However the optimal treatment regimen has not been defined. A retrospective study was performed to compare outcomes in patients who were treated definitively with ExRT or ChRT. METHODS: Cetuximab with concurrent RT was used to treat 29 patients with LAHNC, all of whom had tumors of the oral cavity, oropharynx, or larynx. All patients were T2 to T4 and overall American Joint Committee on Cancer Stage III to IVB, with a Karnofsky Performance Status (KPS) score of 60 or greater. ChRT was used to treat 103 patients with similar characteristics. Patients were evaluated for locoregional control (LRC), distant metastasis-free survival (DMFS), disease-specific survival (DSS), and overall survival (OS). Median follow-up for patients alive at last contact was 83 months for those treated with ExRT and 53 months for those treated with ChRT. Cox proportional hazard models were used to assess independent prognostic factors. RESULTS: The LRC, DMFS, and DSS were not significantly different, with 3-year rates of 70.7%, 92.4%, and 78.6% for ExRT and 74.7%, 86.6%, and 76.5% for ChRT, respectively. The OS was significantly different between the two groups (p = 0.02), with 3-year rates of 75.9% for ExRT and 61.3% for ChRT. OS was not significant when patients who were on protocol treatments of ExRT or ChRT were compared. Also, OS was not significant when multivariate analysis was used to control for potential confounding factors. CONCLUSION: In our single-institution retrospective review of patients treated with ExRT or ChRT, no significant differences were found in LRC, DMFS, DSS, or OS.

A method to correct for radioactivity in large vessels that overlap the spine in imaging-based marrow dosimetry of lumbar vertebrae.

UNLABELLED: Accurate marrow dosimetry for radionuclide therapy based on imaging methods has been challenging because of a variety of factors. One of the uncertainties in image quantification of lumbar vertebrae is correction for radioactivity in large blood vessels anterior to the vertebrae. We developed a method to correct for background radioactivity contributed from blood in large vessels and tested it in a pilot study. METHODS: CT images of 26 patients receiving (111)In- or (131)I-labeled conjugates were used to measure the inside diameters of the aorta and inferior vena cava (IVC) at the top of L2 and the bottom of L4 and to measure the length of this vessel segment. The volume was calculated for this vessel segment, and then the radioactivity in that volume at each imaging time was determined using a time-variant blood radioactivity concentration as established by serial blood samples. This vessel segment typically overlapped with lumbar vertebrae in anterior and posterior whole-body images. The contribution of this background radioactivity to the cumulated activity of the lumbar spine region of interest (ROI) from serial gamma-camera images was determined, taking into account differences in attenuation between vessel segments and lumbar vertebrae. RESULTS: The total blood volumes varied from 25 to 94 mL, with a mean of 51 mL. This mean is 76% of the mean marrow volume of 3 lumbar vertebrae measured in some of these patients. Thirteen of the 14 patients evaluated for aortic position had the aortic segment completely within the L2-L4 ROI. For the IVC, a mean of 72% was in the L2-L4 ROI. Adjusting for radioactivity in major blood vessels that were in the ROI led to lower marrow dose estimates. CONCLUSION: To improve the accuracy of lumbar spine imaging-based marrow dosimetry, one can adjust radioactivity in the large vessels by methods that measure the volume, position, and depth of vessels in the ROI.

MIRD pamphlet No. 20: the effect of model assumptions on kidney dosimetry and response--implications for radionuclide therapy.

UNLABELLED: Renal toxicity associated with small-molecule radionuclide therapy has been shown to be dose-limiting for many clinical studies. Strategies for maximizing dose to the target tissues while sparing normal critical organs based on absorbed dose and biologic response parameters are commonly used in external-beam therapy. However, radiopharmaceuticals passing though the kidneys result in a differential dose rate to suborgan elements, presenting a significant challenge in assessing an accurate dose-response relationship that is predictive of toxicity in future patients. We have modeled the multiregional internal dosimetry of the kidneys combined with the biologic response parameters based on experience with brachytherapy and external-beam radiation therapy to provide an approach for predicting radiation toxicity to the kidneys. METHODS: The multiregion kidney dosimetry model of MIRD pamphlet no. 19 has been used to calculate absorbed dose to regional structures based on preclinical and clinical data. Using the linear quadratic model for radiobiologic response, we computed regionally based surviving fractions for the kidney cortex and medulla in terms of their concentration ratios for several examples of radiopharmaceutical uptake and clearance. We used past experience to illustrate the relationship between absorbed dose and calculated biologically effective dose (BED) with radionuclide-induced nephrotoxicity. RESULTS: Parametric analysis for the examples showed that high dose rates associated with regions of high activity concentration resulted in the greatest decrease in tissue survival. Higher dose rates from short-lived radionuclides or increased localization of radiopharmaceuticals in radiosensitive kidney subregions can potentially lead to greater whole-organ toxicity. This finding is consistent with reports of kidney toxicity associated with early peptide receptor radionuclide therapy and (166)Ho-phosphonate clinical investigations. CONCLUSION: Radionuclide therapy dose-response data, when expressed in terms of biologically effective dose, have been found to be consistent with external-beam experience for predicting kidney toxicity. Model predictions using both the multiregion kidney and linear quadratic models may serve to guide the investigator in planning and optimizing future clinical trials of radionuclide therapy.

Targeted radionuclide therapy.

Targeted radionuclide therapy (TRT) seeks molecular and functional targets within patient tumor sites. A number of agents have been constructed and labeled with beta, alpha, and Auger emitters. Radionuclide carriers spanning a broad range of sizes; e.g., antibodies, liposomes, and constructs such as nanoparticles have been used in these studies. Uptake, in percent-injected dose per gram of malignant tissue, is used to evaluate the specificity of the targeting vehicle. Lymphoma (B-cell) has been the primary clinical application. Extension to solid tumors will require raising the macroscopic absorbed dose by several-fold over values found in present technology. Methods that may effect such changes include multistep targeting, simultaneous chemotherapy, and external sequestration of the agent. Toxicity has primarily involved red marrow so that marrow replacement can also be used to enhance future TRT treatments. Correlation of toxicities and treatment efficiency has been limited by relatively poor absorbed dose estimates partly because of using standard (phantom) organ sizes. These associations will be improved in the future by obtaining patient-specific organ size and activity data with hybrid SPECT/CT and PET/CT scanners.

Brief overview of preclinical and clinical studies in the development of intraperitoneal radioimmunotherapy for ovarian cancer.

Due to the generally slow and incomplete transit of i.p. infused agents into the circulation, treating disease confined to the peritoneal cavity with chemotherapy, biologics, and/or radionuclides provides a pharmacologic advantage. A higher i.p. concentration can be achieved than could be tolerated by systemic administration. An advantage of i.p. versus i.v. administration for localization of radiolabeled antibodies to small peritoneal surface disease has been shown in animal model and human biopsy studies (1, 2). A recent phase III Gynecologic Oncology Group chemotherapy trial has confirmed a survival advantage for i.p. delivery among women undergoing initial therapy for advanced ovarian cancer (3). Although the therapy was more difficult to tolerate such that 60% of patients randomized to the i.p. arm did not complete the entire regimen, there was a 16-month survival advantage. I.p. radionuclide therapy has been used in treatment of ovarian cancer for more than three decades, but side effects have been problematic in non-tumor-targeted 32P therapy (4). Efforts to improve specificity have used a number of antigens expressed on ovarian cancer cells as targets for selective delivery of radionuclide-conjugates. Mouse models and cell culture have been prominent for preclinical study of agents and strategies in the development of i.p. targeted radionuclide therapy for ovarian cancer. Animal studies, which have directed clinical trials, have shown clear improvement in survival with various modifications including combination chemotherapy, pretargeting, and combination of antibodies over simply delivery of a radiolabeled antibody via i.p. route.

Safety and Outcome Measures of First-in-Human Intraperitoneal α Radioimmunotherapy With 212Pb-TCMC-Trastuzumab.

PURPOSE: One-year monitoring of patients receiving intraperitoneal (IP) Pb-TCMC-trastuzumab to provide long-term safety and outcome data. A secondary objective was to study 7 tumor markers for correlation with outcome. METHODS: Eighteen patients with relapsed intra-abdominal human epidermal growth factor receptor-2 expressing peritoneal metastases were treated with a single IP infusion of Pb-TCMC-trastuzumab, delivered <4 h after 4 mg/kg IV trastuzumab. Seven tumor markers were studied for correlation with outcome. RESULTS: Six dose levels (7.4, 9.6, 12.6, 16.3, 21.1, 27.4 MBq/m) were well tolerated with early possibly agent-related adverse events being mild, transient, and not dose dependent. These included asymptomatic, abnormal laboratory values. No late renal, liver, cardiac, or other toxicity was noted up to 1 year. There were no clinical signs or symptoms of an immune response to Pb-TCMC-trastuzumab, and assays to detect an immune response to this conjugate were negative for all tested. Tumor marker studies in ovarian cancer patients showed a trend of decreasing Cancer antigen 72-4 (CA 72-4) aka tumor-associated glycoprotein 72 (TAG-72) and tumor growth with increasing administered radioactivity. Other tumor markers, including carbohydrate antigen (CA125), human epididymis protein 4 (HE-4), serum amyloid A (SAA), mesothelin, interleukin-6 (IL-6), and carcinoembryonic antigen (CEA) did not correlate with imaging outcome. CONCLUSIONS: IP Pb-TCMC-trastuzumab up to 27 MBq/m seems safe for patients with peritoneal carcinomatosis who have failed standard therapies. Serum TAG-72 levels better correlated to imaging changes in ovarian cancer patients than the more common tumor marker, CA125.

Ongoing investigations and new uses of radioimmunotherapy in the treatment of non-Hodgkin's lymphoma.

Studies in radiation oncology are focusing on the optimal use of systemic targeted radionuclide therapy (STaRT) in the treatment of patients with cancer. The two approved radioimmunotherapy agents, yttrium-90 ibritumomab tiuxetan and iodine-131 tositumomab, are being studied in a range of lymphoid malignancies, from low-grade to aggressive B-cell non-Hodgkin's lymphomas. Studies of standard- and escalated-dose radioimmunotherapy with or without stem cell support are reviewed, as are radioimmunotherapy with other therapeutic modalities in these settings. The results of these trials have important implications for clinical practice, and it is hoped that they will further clarify the optimal timing and dosing of these agents.

Logistics of therapy with the ibritumomab tiuxetan regimen.

Radioimmunotherapy is an important new modality for treating patients with B-cell non-Hodgkin's lymphoma (NHL). Clinical trials have shown the safety and efficacy of agents that deliver radiation directly to malignant cells by attaching the (131)I or (90)Y radionuclide to monoclonal antibodies against CD20. In clinical trials, (90)Y ibritumomab tiuxetan has produced rates of response as high as 83% in patients with relapsed or refractory CD20+ NHL. The ibritumomab tiuxetan regimen is conveniently given in an outpatient setting over the course of 7-9 days. This article describes the logistics for initiating treatment, coordinating a multidisciplinary team, identifying eligible patients, and delivering the imaging and therapeutic doses of ibritumomab tiuxetan. The standard radiation safety procedures to protect family members and healthcare professionals involved in the care of patients treated with (90)Y ibritumomab tiuxetan are also reviewed. Treatment with the ibritumomab tiuxetan regimen involves only standard precautions needed to minimize radiation exposure to other persons.

Clinical development of radioimmunotherapy for B-cell non-Hodgkin's lymphoma.

Over the past several decades, several biomolecules have been investigated for their ability to deliver radiation to cancer cells, but antibodies have been the carriers of choice in systemic targeted radionuclide therapy (STaRT). Two radioimmunotherapy agents that target the CD20 antigen, (131)I-tositumomab and (90)Y-ibritumomab tiuxetan, have been approved by the U.S. Food and Drug Administration for the treatment of patients with relapsed or refractory B-cell non-Hodgkin's lymphoma (NHL), and clinical trials have shown that they are effective as monotherapies in the salvage setting, producing response rates that are often higher and durations of response that are often longer than those with chemotherapy. Escalated doses of these agents can be supported with stem cell transplantation and can produce high rates of complete response and greater survival in patients with relapsed NHL. The quality and duration of responses are greater with radioimmunotherapy when it is used earlier in the course of treatment.

Pretargeted radioimmunotherapy.

This brief review covers the concept of pretargeted radioimmunotherapy and summarize the results obtained in preclinical animal models and initial phase I clinical trials. Reagents studied have been a bifunctional antibody prepared by crosslinking Fab' fragments from two antibodies with different specificity, one binding the target antigen expressed on tumors and the other binding a radiolabeled peptide. The alternative system is a conjugate of streptavidin linked to the pretargeting agent and radiolabeled biotin. After reaching optimal tumor targeting of the pretargeting agent, a synthetic mono-biotin poly N-acetyl-galactosamine compound was used to clear unbound targeting agent from the circulation before the injection of radiolabeled biotin. Promising therapeutic responses were obtained in various tumor xenograft models in athymic nude mice. A phase I study of an anti-CD20/streptavidin pretargeting agent and 15 mCi/m(2)(90)Y-biotin produced objective responses with minimal toxicity among lymphoma patients, with an average tumor-to-whole-body radiation dose ratio of 49. Pretargeting radioimmunotherapy approaches have shown higher tumor-to-whole-body ratios than that usually obtained with one-step radioimmunotherapy.

Overview of dosimetry for Systemic Targeted Radionuclide Therapy (STaRT).

The purposes of systemic targeted radionuclide therapy dosimetry include compiling a database of normal organ radiation-absorbed doses that are carrier- and radionuclide-specific, and assuring that the normal organ radiation doses are within a safe range before therapy. Also of importance is quantitation of radiation delivery to tumors vs. normal tissues to correlate absorbed dose with tumor control. For agents with significant and variable excretion, estimates of individual patient distribution/clearance may be needed to optimize the dose-response relationship.

166Ho-DOTMP radiation-absorbed dose estimation for skeletal targeted radiotherapy.

UNLABELLED: 166Ho-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene-phosphonate (DOTMP) is a tetraphosphonate molecule radiolabeled with 166Ho that localizes to bone surfaces. This study evaluated pharmacokinetics and radiation-absorbed dose to all organs from this beta-emitting radiopharmaceutical. METHODS: After two 1.1-GBq administrations of 166Ho-DOTMP, data from whole-body counting using a gamma-camera or uptake probe were assessed for reproducibility of whole-body retention in 12 patients with multiple myeloma. The radiation-absorbed dose to normal organs was estimated using MIRD methodology, applying residence times and S values for 166Ho. Marrow dose was estimated from measured activity retained after 18 h. The activity to deliver a therapeutic dose of 25 Gy to the marrow was determined. Methods based on region-of-interest (ROI) and whole-body clearance were evaluated to estimate kidney activity, because the radiotracer is rapidly excreted in the urine. The dose to the surface of the bladder wall was estimated using a dynamic bladder model. RESULTS: In clinical practice, gamma-camera methods were more reliable than uptake probe-based methods for whole-body counting. The intrapatient variability of dose calculations was less than 10% between the 2 tracer studies. Skeletal uptake of 166Ho-DOTMP varied from 19% to 39% (mean, 28%). The activity of 166Ho prescribed for therapy ranged from 38 to 67 GBq (1,030-1,810 mCi). After high-dose therapy, the estimates of absorbed dose to the kidney varied from 1.6 to 4 Gy using the whole-body clearance-based method and from 8.3 to 17.3 Gy using the ROI-based method. Bladder dose ranged from 10 to 20 Gy, bone surface dose ranged from 39 to 57 Gy, and doses to other organs were less than 2 Gy for all patients. Repetitive administration had no impact on tracer biodistribution, pharmacokinetics, or organ dose. CONCLUSION: Pharmacokinetics analysis validated gamma-camera whole-body counting of 166Ho as an appropriate approach to assess clearance and to estimate radiation-absorbed dose to normal organs except the kidneys. Quantitative gamma-camera imaging is difficult and requires scatter subtraction because of the multiple energy emissions of 166Ho. Kidney dose estimates were approximately 5-fold higher when the ROI-based method was used rather than the clearance-based model, and neither appeared reliable. In future clinical trials with 166Ho-DOTMP, we recommend that dose estimation based on the methods described here be used for all organs except the kidneys. Assumptions for the kidney dose require further evaluation.

A phase 2 study of radiosurgery and temozolomide for patients with 1 to 4 brain metastases.

PURPOSE: To determine if temozolomide reduces the risk of distant brain failure (DBF, metachronous brain metastases) in patients with 1 to 4 brain metastases treated with radiosurgery without whole-brain radiation therapy (WBRT). METHODS AND MATERIALS: Twenty-five patients with newly diagnosed brain metastases were enrolled in a single institution phase 2 trial of radiosurgery (15-24 Gy) and adjuvant temozolomide. Temozolomide was continued for a total of 12 cycles unless the patient developed DBF, unacceptable toxicity, or systemic progression requiring other therapy. RESULTS: Twenty-five patients were enrolled between 2002 and 2005; 3 were not evaluable for determining DBF. Of the remaining 22 patients, tumor types included non-small cell lung cancer (n = 8), melanoma (n = 7), and other (n = 7). Extracranial disease was present in 10 (45%) patients. The median number of tumors at the time of radiosurgery was 3 (range, 1-6). The median overall survival was 31 weeks. The median radiographic follow-up for patients who did not develop DBF was 33 weeks. Six patients developed DBF. The 1-year actuarial risk of DBF was 37%. CONCLUSIONS: In this study, there was a relatively low risk of distant brain failure observed in the nonmelanoma subgroup receiving temozolamide. However, patient selection factors rather than chemotherapy treatment efficacy are more likely the reason for the relatively low risk of distant brain failure observed in this study. Future trial design should account for these risk factors.

MIRD Pamphlet No. 26: Joint EANM/MIRD Guidelines for Quantitative 177Lu SPECT Applied for Dosimetry of Radiopharmaceutical Therapy.

The accuracy of absorbed dose calculations in personalized internal radionuclide therapy is directly related to the accuracy of the activity (or activity concentration) estimates obtained at each of the imaging time points. MIRD Pamphlet no. 23 presented a general overview of methods that are required for quantitative SPECT imaging. The present document is next in a series of isotope-specific guidelines and recommendations that follow the general information that was provided in MIRD 23. This paper focuses on (177)Lu (lutetium) and its application in radiopharmaceutical therapy.

Patient-specific dosimetry of pretargeted radioimmunotherapy using CC49 fusion protein in patients with gastrointestinal malignancies.

UNLABELLED: Pretargeted radioimmunotherapy (RIT) using CC49 fusion protein, comprised of CC49-(scFv)4 and streptavidin, in conjunction with 90Y/111In-DOTA-biotin (DOTA = dodecanetetraacetic acid) provides a new opportunity to improve efficacy by increasing the tumor-to-normal tissue dose ratio. To our knowledge, the patient-specific dosimetry of pretargeted 90Y/111In-DOTA-biotin after CC49 fusion protein in patients has not been reported previously. METHODS: Nine patients received 3-step pretargeted RIT: (a) 160 mg/m2 of CC49 fusion protein, (b) synthetic clearing agent (sCA) at 48 or 72 h later, and (c) 90Y/111In-DOTA-biotin 24 h after the sCA administration. Sequential whole-body 111In images were acquired immediately and at 2-144 h after injection of 90Y/111In-DOTA-biotin. Geometric-mean quantification with background and attenuation correction was used for liver and lung dosimetry. Effective point source quantification was used for spleen, kidneys, and tumors. Organ and tumor 90Y doses were calculated based on 111In imaging data and the MIRD formalism using patient-specific organ masses determined from CT images. Patient-specific marrow doses were determined based on radioactivity concentration in the blood. RESULTS: The 90Y/111In-DOTA-biotin had a rapid plasma clearance, which was biphasic with <10% residual at 8 h. Organ masses ranged from 1,263 to 3,855 g for liver, 95 to 1,009 g for spleen, and 309 to 578 g for kidneys. The patient-specific mean 90Y dose (cGy/37 MBq, or rad/mCi) was 0.53 (0.32-0.78) to whole body, 3.75 (0.63-6.89) to liver, 2.32 (0.58-4.46) to spleen, 7.02 (3.36-11.2) to kidneys, 0.30 (0.09-0.44) to lungs, 0.22 (0.12-0.34) to marrow, and 28.9 (4.18-121.6) to tumors. CONCLUSION: Radiation dose to normal organs from circulating radionuclide is substantially reduced using pretargeted RIT. Tumor-to-normal organ dose ratios were increased about 8- to 11-fold compared with reported patient-specific mean dose to liver, spleen, marrow, and tumors from 90Y-CC49.

A Phase I study of combined modality (90)Yttrium-CC49 intraperitoneal radioimmunotherapy for ovarian cancer.

PURPOSE: The purpose of this study was to determine the feasibility and maximum tolerated dose of (90)Yttrium-CC49 ((90)Y-CC49) as the radioimmunotherapy (RIT) component of an i.p. combined modality treatment for recurrent ovarian cancer. EXPERIMENTAL DESIGN: A Phase I trial of (90)Y-CC49 RIT was conducted in ovarian cancer patients who had persistent or recurrent intra-abdominal disease, had failed one or two prior chemotherapy regimens, and demonstrated TAG-72 expression. Patients were treated with a previously established combined modality treatment protocol of s.c. IFN alpha2b, i.p. paclitaxel, and increasing dosages of i.p. (90)Y-CC49. Patients were monitored for toxicity, generation of human antimouse antibody response, and clinical efficacy. RESULTS: Twenty eligible patients were treated per study specifications. All patients had been treated with debulking and paclitaxel/carboplatin-based chemotherapy at initial diagnosis. The patients included 11 patients with persistent disease at the time of second look laparotomy and 9 patients with delayed recurrence. Patients were treated with i.p. (90)Y-CC49 given in combination with s.c. IFN alpha2b (dose of 3 x 10(6) units for a total of four doses) and i.p. paclitaxel (dose of 100 mg/m(2)). RIT treatment was associated with primarily hematological toxicity. The maximum tolerated dose of i.p. (90)Y-CC49 was established at 24.2 mCi/m(2) in this combined regimen. Of nine patients with measurable disease, two had partial responses lasting 2 and 4 months. Of 11 patients with nonmeasurable disease, median time to progression was 6 months in 7 patients who recurred; 4 of these patients remain no evidence of disease at 9+, 18+, 19+, and 23+ months. CONCLUSIONS: (90)Yttrium-CC49-based RIT in combination with IFN alpha2b and i.p. paclitaxel is feasible and well tolerated at a dose of < or =24.2 mCi/m(2).

Phase I study of 90Y-CC49 monoclonal antibody therapy in patients with advanced non-small cell lung cancer: effect of chelating agents and paclitaxel co-administration.

PURPOSE: This trial was designed to evaluate strategies to improve the efficacy of a radiolabeled monoclonal antibody (mCC49) against tumor-associated glycoprotein-72 (TAG-72) in patients with non-small cell lung cancer (NSCLC). The aims of this study were to determine: safety and maximum tolerated dose (MTD) of (90)Y-mCC49 in combination with interferon alpha2beta (IFN); whether calcium disodium versonate (EDTA) or diethylenetriamine penta-acetic acid (DTPA) could reduce myelosuppression; and safety and MTD of paclitaxel (Taxol) in combination with (90)Y-mCC49. EXPERIMENTAL DESIGN: Patients with advanced (TAG-72 positive) non-small cell lung cancer were entered in three phases; the first was the dose escalation of a single agent (90)Y-mCC49. In the second phase, the dose escalation of (90)Y-mCC49 was attempted with concurrent EDTA or DTPA chelator therapy. In the third phase, radiosensitization with a continuous infusion of paclitaxel (96-hour) was administered with (90)Y-mCC49. All patients received IFN for TAG-72 up-regulation. RESULTS: Thirty-four patients were evaluable. Reversible Grade 4 neutropenia and thrombocytopenia were the dose-limiting toxicities (DLTs). The MTD of (90)Y-mCC49/IFN was 14 mCi/m(2). EDTA did not alter toxicity, while there was a modest reduction of myelosuppression with DTPA. The MTD of continuous infusion paclitaxel in combination with 14 mCi/m(2) of (90)Y-CC49 was 60 mg/m(2). There were no objective tumor responses. CONCLUSIONS: (90)Y-mCC49/IFN was well tolerated at a dose of 14 mCi/m(2). The clinical effect of adjunctive chelating therapy with DTPA was modest. The MTD of coadministered continuous infusion (96-hour) paclitaxel was 60 mg/m(2). Because of the immunogenicity of the murine compound, future studies are planned using a humanized version of CC49.