Perspectives on joint EANM/SNMMI/ANZSNM practice guidelines/procedure standards for [18F]FDG PET/CT imaging during immunomodulatory treatments in patients with solid tumors.

Response assessment in the context of immunomodulatory treatments represents a major challenge for the medical imaging community and requires a multidisciplinary approach with involvement of oncologists, radiologists, and nuclear medicine specialists. There is evolving evidence that [18F]FDG PET/CT is a useful diagnostic modality for this purpose. The clinical indications for, and the principal aspects of its standardization in this context have been detailed in the recently published "Joint EANM/SNMMI/ANZSNM practice guidelines/procedure standards on recommended use of [18F]FDG PET/CT imaging during immunomodulatory treatments in patients with solid tumors version 1.0". These recommendations arose from a fruitful collaboration between international nuclear medicine societies and experts in cancer treatment. In this perspective, the key elements of the initiative are reported, summarizing the core aspects of the guidelines for radiologists and nuclear medicine physicians. Beyond the previous guidelines, this perspective adds further commentary on how this technology can advance development of novel therapeutic approaches and guide management of individual patients.

Centralized Clinical Trial Imaging Data Management: Practical Guidance from a Comprehensive Cancer Center's Experience.

Medical imaging is an integral part of clinical trial research and it must be managed properly to provide accurate data to the sponsor in a timely manner (Clune in Cancer Inform 4:33-56, 2007; Wang et al. in Proc SPIE Int Soc Opt Eng 7967, 2011). Standardized workflows for site qualification, protocol preparation, data storage, retrieval, de-identification, submission, and query resolution are paramount to achieve quality clinical trial data management such as reducing the number of imaging protocol deviations and avoiding delays in data transfer. Centralization of data management and implementation of relational databases and electronic workflows can help maintain consistency and accuracy of imaging data. This technical note aims at sharing the practical implementation of our centralized clinical trial imaging data management processes to avoid the fragmentation of tasks among various disease centers and research staff, and enable us to provide quality, accurate, and timely imaging data to clinical trial sponsors.

Yield of bone scintigraphy for the detection of metastatic disease in treatment-naive prostate cancer: a systematic review and meta-analysis.

AIM: To evaluate the yield of staging bone scintigraphy in patients with treatment-naive prostate cancer. MATERIALS AND METHODS: A computerised search of the MEDLINE and EMBASE databases was performed to find relevant original literature. Studies that investigated the positivity of a staging bone scintigraphy according to prostate-specific antigen (PSA) levels and/or Gleason score in patients with treatment-naive prostate cancer were eligible for inclusion. Meta-analytic pooling was performed using the inverse variance method for calculating weights. RESULTS: Fifty-four eligible studies, which included a total sample size of 20,421 patients, were included. The pooled proportions of the positive bone scintigraphy in patients with PSA ≤10, 10 20 were 3.5% (95% confidence interval [CI]: 2.4-5%), 6.9% (95% CI: 4.5-10.3%), and 41.8% (95% CI: 36.3-47.6%). The pooled proportions of the positive bone scintigraphy examinations in patients with Gleason score ≤6, 7, and ≥8 were 4.1% (95% CI: 2-8%), 10% (95% CI: 6.1-15.8%), and 28.7% (95% CI: 21.8-36.8%). Meta-regression analysis revealed that the Gleason score was a significant factor affecting study heterogeneity in patients with PSA ≤10 (p = 0.04). Pooled proportions of positive bone scintigraphy examinations showed 3.4% in patients with a PSA of ≤10 and 3.3% in patients with 10

Prognostic significance of supradiaphragmatic lymph nodes at initial presentation in patients with stage III high-grade serous ovarian cancer.

PURPOSE: To identify the optimal size threshold and to assess the prognostic significance of supradiaphragmatic lymph nodes at initial presentation of patients with high-grade serous ovarian cancer (HGSC). METHODS: This IRB-approved, HIPAA-compliant retrospective study included baseline pretreatment staging abdominal CTs of 88 women (mean age 62 years, SD 10.4, range 29-85) with FIGO stage III HGSC. Patients with stage IV disease were excluded due to worse prognosis and management guided by distant metastases. Two fellowship-trained radiologists independently reviewed abdominal CTs to record the presence of supradiaphragmatic nodes, abdominal lymphadenopathy, peritoneal carcinomatosis, and ovarian mass. Progression-free survival (PFS) and overall survival (OS) were recorded after median 79 months follow-up (IQR 58-115, range 13-144). The optimal short-axis size threshold for supradiaphragmatic lymphadenopathy was determined by correlating 3, 4, 5, 6, 7, and 10 mm thresholds with PFS and OS using Log-rank test. Prognostic significance of supradiaphragmatic lymphadenopathy was assessed using Cox proportional hazards models. RESULTS: There was good interobserver agreement for presence (κ = 0.65, 95%CI 0.51-0.79) and size (ICC = 0.77, 95%CI 0.66-0.86) of supradiaphragmatic nodes. 5 mm short-axis size threshold was associated with significantly shorter PFS (median 14 months, IQR 11-17 vs. 23 months, IQR 12-59; p = 0.02) and OS (median 44 months, IQR 27-69 vs. 65 months, IQR 45-96; p = 0.03). Total 38/88 (43%) patients had supradiaphragmatic lymphadenopathy. On Cox proportion hazards analysis, supradiaphragmatic lymphadenopathy was significantly associated with shorter PFS (p = 0.02; HR 1.81, 95%CI 1.11-2.96) and OS (p = 0.008; HR 2.11, 95%CI 1.21-3.65). CONCLUSION: In patients with stage III HGSC, supradiaphragmatic lymphadenopathy is associated with shorter PFS and OS. Further studies would help determine its implications on staging, decision regarding neoadjuvant therapy, and surgical technique.

Long-term follow-up results of the multicenter phase II trial of regorafenib in patients with metastatic and/or unresectable GI stromal tumor after failure of standard tyrosine kinase inhibitor therapy.

BACKGROUND: This investigator-initiated trial provided the justification for the phase III GRID study resulting in worldwide regulatory approval of regorafenib as a third-line therapy for patients with metastatic gastrointestinal stromal tumors (GIST). We report the genotype analyses, long-term safety, and activity results from this initial trial of regorafenib in GIST. PATIENTS AND METHODS: The trial was conducted between February 2010 and January 2014, among adult patients with metastatic GIST, after failure of at least imatinib and sunitinib. Patients received regorafenib orally, 160 mg once daily, days 1-21 of a 28-day cycle. Clinical benefit rate (CBR), defined as complete or partial response (PR), or stable disease lasting ≥16 weeks per RECIST 1.1, progression-free survival (PFS), overall survival (OS), long-term safety data, and metabolic response by functional imaging were assessed. RESULTS: Thirty-three patients received at least one dose of regorafenib. The median follow-up was 41 months. CBR was documented in 25 of 33 patients [76%; 95% confidence interval (CI) 58% to 89%], including six PRs. The median PFS was 13.2 months (95% CI 9.2-18.3 months) including four patients who remained progression-free at study closure, each achieving clinical benefit for more than 3 years (range 36.8-43.5 months). The median OS was 25 months (95% CI 13.2-39.1 months). Patients whose tumors harbored a KIT exon 11 mutation demonstrated the longest median PFS (13.4 months), whereas patients with KIT/PDGFRA wild-type, non-SDH-deficient tumors experienced a median 1.6 months PFS (P < 0.0001). Long-term safety profile is consistent with previous reports; hand-foot skin reaction and hypertension were the most common reasons for dose reduction. Notably, regorafenib induced objective responses and durable benefit in SDH-deficient GIST. CONCLUSIONS: Long-term follow-up of patients with metastatic GIST treated with regorafenib suggests particular benefit among patients with primary KIT exon 11 mutations and those with SDH-deficient GIST. Dose modifications are frequently required to manage treatment-related toxicities. CLINICAL TRIAL NUMBER: NCT01068769.

Case report. PET/CT appearance of desmoid tumour of the chest wall.

Desmoid tumours are rare, poorly circumscribed tumours that have a firm consistency and, although benign, have a remarkable tendency to infiltrate into surrounding structures. Extra-abdominal desmoid tumours involve mainly the extremities or the chest wall and are usually managed by wide radical resection. Moreover, desmoid tumours involving the chest wall are locally aggressive tumours with a high recurrence rate. We report a case of a pathologically proven desmoid tumour of the chest wall in a patient with a history of bilateral breast cancer and oesophageal cancer. We discuss the imaging appearances of this tumour on positron emission tomography combined with computed tomography (PET/CT) and magnetic resonance imaging.

Prognostic significance of the number of bone scan abnormalities at the time of initial bone metastatic recurrence in breast carcinoma.

BACKGROUND: To gain insight into the factors that contribute to the more favorable prognosis associated with recurrence limited to bone in patients with breast carcinoma, the authors analyzed the number of sites of initial involvement identified on radionuclide bone scans in relation to long term outcome. METHODS: Records of 641 patients with clinical Stage I-III breast carcinoma that originally was diagnosed in 1974-1985 were reviewed. During follow-up, 295 patients (46%) experienced distant recurrence, including 116 with bone as the sole initial site of metastatic disease. Radionuclide bone scans identified the initial site(s) of recurrence in 113 of these latter 116 patients, and these studies were categorized by the number of skeletal lesions subsequently confirmed as metastases (1, 2, or > or = 3). Survival from time of recurrence and time of original diagnosis was analyzed using Kaplan-Meier methods, and factors associated with recurrence and mortality were examined using logistic and Cox regression. RESULTS: Median survival from time of recurrence was 35 months in the patients with bone-only metastases, compared with 11-26 months for all other sites of visceral recurrence exclusive of bone. Number of positive lymph nodes and estrogen receptor status were the only predictive variables for recurrence. Median survival from time of recurrence and time of original diagnosis for the 3 bone scan categories was: 1 lesion (n = 47), 53 and 86 months; 2 lesions (n = 22), 38 and 68 months; and > or = 3 lesions (n = 44), 22 and 58 months (P < 0.0001 and P < 0.005 for 1 and 2 lesions vs. > or = 3). In the "bone-only" group, the number of scan lesions was the strongest predictor of length of survival. CONCLUSIONS: Patients with breast carcinoma who experience a recurrence in bone at only one or two sites initially have a survival advantage over those with more extensive (> or = 3 sites) skeletal metastases and those with metastatic disease involving other visceral organs.

The treatment and outcome of cancer patients with thromboses on central venous catheters.

Thromboses are a common complication of central venous catheters in cancer patients. This study was performed to analyze retrospectively the treatment and outcome of all patients with venous thromboses related to central venous catheters at a major cancer center. From 1992 through 1995, 319 oncology patients with central venous catheters underwent radionuclide venography (RNV) at the Dana-Farber Cancer Institute for suspected catheter or venous thrombosis. The treatment and outcome of patients found to have venous thromboses were evaluated. Of the 319 patients, 112 were found to have evidence of venous thrombosis. The median age and platelet counts were not significantly different between the patients with and without thromboses. The most common indication for obtaining RNV was difficulty in aspirating or infusing material through the catheter. Patients who had pain or edema, or both, of the neck or upper extremity were more likely to have a venous thrombosis. Regardless of therapeutic intervention, including anticoagulation with heparin or coumadin, or both; line removal or replacement; or a combination thereof, no patients had a major adverse outcome such as pulmonary embolism, compromise of limb, or death. Only 4 patients did not have resolution of their presenting symptoms, all of whom were treated with line replacement. The overall survival of patients with and without thromboses was not significantly different. Either anticoagulation or removal of the central venous catheter (or both) appears to be adequate treatment for catheter-related thrombosis. A prospective trial to evaluate these approaches may be worthwhile so that the use of unnecessary procedures may be avoided in this patient population.

When is hilar uptake of 67Ga-citrate indicative of residual disease after CHOP chemotherapy?

UNLABELLED: The purpose of this study was to evaluate the prevalence and characterize the patterns of hilar uptake (HU) on 67Ga-citrate imaging after cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy regimens for non-Hodgkin's lymphoma (NHL), to differentiate hilar lymphoma (HL) from HU of benign etiology. METHODS: A total of 930 studies (698 planar, 232 thoracic SPECT) was reviewed retrospectively in 100 NHL patients (29 low-grade, 60 intermediate-grade, and 11 high-grade) treated with CHOP and followed up longitudinally with serial gallium studies (planar: median, 7; range, 3-16 studies in 100 patients; SPECT: median, 1; range, 0-11 studies in 72 patients) over a median duration of 36 mo (range, 6-112 mo) from diagnosis. Clinical outcome and size changes over time on correlative CT and/or radiographs were used to evaluate benign versus malignant changes within the hila. RESULTS: HU after CHOP was present in 79% of patients (90% confidence interval [CI], 71%-85%), with 33% showing HU on SPECT alone. Once present, HU persisted for a median of 27 mo (range, 2-84 mo) from onset. The prevalence of HU and HL at various time points was as follows: baseline HU, 52% with HL 60%; mid-CHOP HU, 59% with HL2%; post-CHOP HU, 52% with HL6%; follow-up HU, 76% with HL 9%. HU of benign etiology was not significantly correlated with CHOP dosage. HU was symmetric in 90% of patients (90% CI, 82%-95%) and less intense than the original disease in 89% of patients (90% CI, 80%-95%), and these features were highly predictive of benign etiology (negative predictive value [NPV], 98.6% if symmetric; NPV, 96.5% if less than original disease; NPV, 100% if both present). Asymmetric HU equal in intensity to the original disease, however, was highly predictive of HL (positive predictive value [PPV], 87.5% if asymmetric; PPV, 85.7% if equal to original disease; PPV, 100% if both present). CONCLUSION: HU after CHOP is common (overall incidence, 79%), often seen only on SPECT, and most likely of benign etiology when symmetric and less intense than the original disease. Asymmetric HU that equals the intensity of the original disease, however, is a possible indicator for HL.

Uptake of radiolabeled somatostatin analog is detectable in patients with metastatic foci of sarcoma.

BACKGROUND: Somatostatin receptors are present on many types of epithelial tumors, and ligands targeting these receptors are used to treat patients with neuroendocrine malignancies. Preclinical studies have demonstrated the presence of somatostatin receptors on a variety of mesenchymal tumors by in vitro receptor autoradiography. The use of radiolabeled somatostatin analogs to assess the presence of somatostatin receptors in vivo has been established, but use of this technique to evaluate human sarcomas has not been reported previously. METHODS: Seventeen patients (13 females and 4 males) with metastatic sarcoma underwent imaging via somatostatin-receptor scintigraphy. Scans were performed using indium -111 pentetreotide. Planar studies and single photon emission computed tomography imaging were performed at 4 and 24 hours, and results of scintigraphy were correlated with computed tomography findings. RESULTS: Twelve of 17 scans showed increased uptake in regions of known metastatic disease. There was no apparent correlation with scan positivity and patient age, histology, site of disease, or duration of diagnosis. CONCLUSIONS: Seventy-one percent of patients with advanced soft-tissue sarcomas had positive scintigraphy scans demonstrating tumor expression of somatostatin receptors subtype 2 in vivo. Imaging with indium-111 pentetreotide could be studied as an adjunct to conventional imaging modalities for assessment of sarcoma patients. Further research is needed to determine the prognostic implications of somatostatin receptor subtype 2 positivity, including larger studies to evaluate any potential correlation with metastatic behavior and other clinical outcomes.

Return of lymphatic function after flap transfer for acute lymphedema.

OBJECTIVE: The goals of this work were to develop animal models of lymphedema and tissue flap transfer, and to observe physiologic changes in lymphatic function that occur in these models over time, both systemically with lymphoscintigraphy (LS) and locally using fluorescence microlymphangiography (FM). SUMMARY BACKGROUND DATA: Although lymphedema has been managed by a combination of medical and surgical approaches, no effective long-term cure exists. Surgical attempts aimed at reconnecting impaired lymphatic channels or bypassing obstructed areas have failed. METHODS: The tails of rats (A groups) and mice (B groups) were used because of their different features. Lymphedema was created by ligation of the lymphatics at the tail base and quantified by diameter measurements there. In the experimental group, rectus abdominis myocutaneous flap was transferred across the ligation. In addition to the ligation (A1 and B1) and ligation + flap (A2 and B2) groups, three control groups were included: sham flap with ligation (B4), sham flap alone (B5), and normal (A3 and B3) animals. Observations were made at weekly time points for lymphatic function and continuity. RESULTS: Lymphedema was successfully created in the mouse ligation groups (B1 and B4) and sustained for the entire length of observation (up to 14 weeks). Lymphatic continuity was restored in those animals with transferred flaps across the ligation site (A2 and B2), as seen both by LS and FM. Sham flaps did not visibly affect lymphatic function nor did they cause any visible swelling in the tail. CONCLUSIONS: Acute lymphedema developing after ligation of tail lymphatics in mice can be prevented by myocutaneous flap transfer. Restored lymphatic continuity and function were demonstrable using lymphoscintigraphy and fluorescence microlymphangiography.

5-[125I]iodo-2'-deoxyuridine in the radiotherapy of brain tumors in rats.

UNLABELLED: Glial neoplasms of the human central nervous system have defied treatment, in part because of the limited selectivity of available cytotoxic agents. The thymidine analog 5-iodo-2'-deoxyuridine radiolabeled with the Auger electron emitter 125I (125IUdR) is highly toxic to dividing cells when it is deoxyribonucleic acid incorporated, but it is relatively innocuous when located outside the nucleus. Previous studies have shown that 125IUdR has significant antineoplastic potential against mammalian cells in vitro and direct administration of 125IUdR is effective therapy for ovarian ascites tumors in mice and neoplastic meningitis in rats. Studies using external gamma imaging and autoradiography have also shown that direct intratumoral administration of 123IUdR/125IUdR into intracerebral 9L gliosarcomas in rats results in selective uptake of the radionuclide into tumor cells. Based on these encouraging results, we have evaluated the therapeutic potential of 125IUdR in rats bearing intracerebral 9L gliosarcomas. METHODS: Iodine-125-IUdR was infused intracerebrally over a 2-day period into rats bearing 1-day-old 9L tumors and over a 6-day period into animals with 9-day-old 9L tumors; equimolar concentrations of 127IUdR were infused into control animals. Tumor growth was monitored by contrast-enhanced 1H MRI and animal survival was followed over time. RESULTS: Intracerebral tumors (3-7 mm) were readily detected by MRI. Tumor-bearing rats treated with 127IUdR succumbed within 17-24 days, whereas tumor-bearing animals treated with 125IUdR survived significantly longer, and 10%-20% of the animals were cured of tumors. CONCLUSION: These data substantiate the antineoplastic potential of 5-[125I]iodo-2'-deoxyuridine and indicate that it may be a useful agent for the therapy of solid tumors that are accessible to direct radiopharmaceutical administration.

An investigation of lymphatic function following free-tissue transfer.

Despite microsurgical advances in the repair of severed arteries, veins, and nerves, disrupted lymphatics are not usually identified or reconnected during replantation. Although temporary swelling of a replanted part is attributed to lymphedema, this condition resolves without microsurgical intervention. Spontaneous regeneration or reconnection of lymphatics is thought to occur in such situations. Microsurgical free-flap transfer is clinically analogous to replantation in that it also results in a complete division of all lymphatic channels exiting the flap. The ability of lymphatics to regenerate after flap reconstruction, either pedicled or free, has received little attention because safe and accurate techniques for visualization and evaluation of the status of these structures have not been available. As a result of recent advances in radiocolloid lymphoscintigraphic imaging techniques, it is possible to demonstrate lymphatic flow in a physiologic, anatomic, and noninvasive manner. These methods can be applied to free-flap models to document lymphatic function after surgical treatment and determine when and to what extent such a process of growth occurs. We studied 10 consecutive patients having free-flap reconstruction. These flaps were performed for chronic osteomyelitis (6) and unstable wound coverage (4). Microvascular flaps used were latissimus dorsi, scapular-parascapular fasciocutaneous, lateral arm, rectus abdominis, temporoparietal, and free toe. Radiocolloid lymphoscintigraphy with technetium-99m-antimony trisulfide colloid (Sb2S3) was done on all patients by injection directly into the free-flap dermis. All patients were studied between 8 and 44 days (mean 23.6) after free-flap transfer. Following injection into each flap, rapid egress of the radiotracer along lymphatic pathways with progression to locoregional nodes was observed in all patients. Reestablishment of lymphatic pathways following microvascular free-tissue transfer was demonstrated by radionuclide lymphoscintigraphic techniques in 10 consecutive patients who had reconstruction for extremity wounds.

Intratumoral administration of 5-[123I]iodo-2'-deoxyuridine in a patient with a brain tumor.

UNLABELLED: We have initiated a study in which patients suspected of having primary gliomas are given a single intracerebral injection of the thymidine analog 5-[123I]iodo-2'-deoxyuridine ([123I]IUdR). The purpose of the study is to determine the biodistribution of the radiopharmaceutical and to calculate dose estimates to the tumor and normal tissues. METHODS: A patient with a cystic glioma was injected with [123I]IUdR. Whole-body scans and brain scans were obtained at various times after injection, and blood, urine and stools were collected and assayed for radioactivity to assess its biodistribution and clearance. RESULTS: Scintigraphic imaging demonstrated that the distribution of radiolabeled IUdR was mainly confined to the tumor (injection site), stomach and bladder. Disappearance from the tumor site and blood clearance were delayed probably due to collection in the cystic lesion. Eighty percent of the injected dose was recovered in the urine. CONCLUSION: The pharmacokinetics of [123I]IUdR locoregionally administered to a human glioma in situ resembled those observed in a rat glioma model where administration of the radiopharmaceutical radiolabeled with the Auger electron emitter 125I was therapeutically effective.

Tumor-targeting potential of radioiodinated iododeoxyuridine in bladder cancer.

UNLABELLED: Since bladder cancer arises in the superficial lining of the urothelium, it is a likely candidate for site-directed administration of 5-iodo-2'-deoxyuridine radiolabeled with the Auger electron emitter 123I or 125I (*IUdR). METHODS: We instilled *IUdR for 2 hr directly within the bladder lumen of rats bearing N-methyl-N-nitrosourea (NMU)-induced bladder cancer and conducted scintigraphic, biodistribution and autoradiography (ARG) studies 48 hr and 1 wk later. Control animals were not subjected to the carcinogen but were instilled with *IUdR. RESULTS: Two groups of animals were identified after instillation of MNU: Group A consisted of rats with hyperplasia and Group B of rats with papillary carcinoma (stages Ta and T1). Scintigraphic detection of carcinomas was achieved with high sensitivity and specificity, and increased tumor-to-normal tissue ratios were obtained in both groups. Moreover, ARG demonstrated that (1) the uptake of *IUdR was observed in the hyperplastic and carcinomatous urothelium but not in the normal urothelium; (2) uptake was detected at a very early stage of tumor development (hyperplasia stage); (3) *IUdR was able to penetrate deep within the bladder wall; and (4) other normal dividing tissues, such as the bone marrow, the small intestine and the large intestine, were free of silver grains (i.e., no DNA-incorporated *IUdR). CONCLUSION: Since this carrier of Auger electron emitters has antineoplastic effects ([123I]IUdR and [125I]IUdR) in addition to its scintigraphic potential ([123I]IUdR and [131I]IUdR), it holds promise for therapy and early diagnosis of bladder cancer.

pI-dependent isolation of antibody isoforms by semipreparative isoelectric focusing.

A procedure based on isoelectric point (pI) was developed to separate immunoreactive antibody isoforms. A polyclonal IgG, rabbit anti-human serum albumin (R-HSA), was subjected to free-flow isoelectrophoresis using a semipreparative isoelectric focusing apparatus that fractionates proteins by pI. Twenty fractions were collected and their pH, protein content, and immunoreactivity determined. The development of a pH gradient and separation of proteins took place within 3 hours with about 93% protein recovery. The protein concentration of the individual fractions varied. Isoelectric focusing of fractions in agarose slab gels confirmed the clear separation of antibody isoforms. Enzyme-linked immunosorbent assay demonstrated significantly higher immunoreactivity (P < or = 0.03) of the majority of the antibody isoform fractions compared with native R-HSA IgG. The procedure is capable of isolating immunoreactive antibody isoform fractions from immunologically irrelevant and low-affinity antibodies.

Tumor targeting potential and metabolism of 5-[125I]iodo-2'-deoxyuridine injected intratumorally in patients with breast cancer.

We have previously demonstrated the high tumor targeting potential of the thymidine analogue 125IUdR in experimental animal models following direct intratumoral or locoregional (intracavitary) administration. The aim of the present work was to evaluate the metabolism and selectivity (based on differential cell proliferation kinetics) of 125IUdR incorporation in patients with breast cancer following a similar approach. 125IUdR (4-8 MBq) was injected intratumorally by ultrasound-guided percutaneous injection in 7 patients with breast cancer 24 hours before ablative surgery. Blood and urine samples were collected up to 72 hours after injection and analyzed by HPLC using a C18 reversed-phase column and methanol:water (20:80) as the mobile phase. Following resection, the radioactivity of the tumor and the surrounding tissues was measured in a gamma counter, and microautoradiography was performed on semithin tissue sections to determine the site of tracer incorporation at the cellular level. Activity in plasma peaked at 0.5 to 1 hour after 125IUdR injection (4.96 +/- 1.08% of injected dose/liter), declining thereafter with a mean T1/2 of 11.24 +/- 2.78 hours. By HPLC analysis, undegraded 125IUdR was about 15-30% of total plasma activity, with a biphasic pattern peaking at both 1-3 hours and approximately 12 hours. In addition to free 125I-, about 10% of early plasma activity was constituted by a labeled metabolite (tentatively identified as radio-iodouracil), rising to about 50-60% at later time points. About 70-90% of urinary radioactivity was 125I-, and 5-20% was undegraded 125IUdR in the first 24-hour samples, while the remainder was iodouracil. High tumor/nontumor ratios were obtained (mean 147.4 +/- 125.2, range 27-397) with average tumor/blood ratios at the time of surgery equal to 32.7 +/- 18.6 (range 5-56). An average 0.0244 +/- 0.0189% of the injected dose was present per gram of tumor (range 0.001-0.061% ID/g). Microautoradiography confirmed the high values of tumor/nontumor incorporation ratios and demonstrated the specificity of 125IUdR incorporation mostly in the tumor cell nuclei, with only occasional incorporation by normal-appearing tubular cells. These results suggest the potential of radiolabeled IUdR for tumor targeting in humans, to be used whenever a satisfactory route of locoregional administration allowing for homogeneous tracer distribution within the tumor mass is accessible and in the presence of favorable tumor cell proliferations kinetics.

Tumor targeting in vivo and metabolic fate of 5-[iodine-125]iodo-2'-deoxyuridine following intratumoral injection in patients with colorectal cancer.

Previous studies have demonstrated the tumor-targeting potential of radioiodinated 5-iodo-2'-deoxyuridine (IUdR) in experimental animal models following direct intratumoral or intracavitary administration. The aim of this study was to measure the tumor uptake and metabolic fate of 5-[125I]iodo-2'-deoxyuridine ([125I]UdR) in humans after a single intratumoral injection. Ten patients with colorectal cancer were injected intratumorally with [125I]UdR) (0.24-3.9 MBq) during endoscopy 24 hr before ablative surgery. Blood and urine samples were collected up to 72 hr after [125I]UdR injection. Following resection, the radioactivity in the tumor and the surrounding tissues was measured in a gamma counter, and microautoradiography was performed on semi-thin tissue sections to assess localization of the radiopharmaceutical at the cellular level. An average of 0.234% of the injected dose was present per gram of tumor (range 0.009-0.918, median value 0.147), and tumor-to-nontumor radioactivity incorporation ratios were high for colonic mucosa when the nontumor tissue was taken at 1 cm (mean 629, range 27-2391) and 15 cm (mean 2387, range 122-12674) from the injection site. Microautoradiography confirmed these high tumor-to-nontumor ratios and demonstrated localization of [125I]UdR in the tumor cell nuclei. These results suggest that radioiodinated IUdR might have potential as a tumor-targeting agent in humans, provided homogeneous intratumoral distribution of the radiopharmaceutical by a suitable route of loco-regional administration can be achieved.

N-(m-[125I]iodophenyl)maleimide: an agent for high yield radiolabeling of antibodies.

In an effort to radiolabel antibodies, N-(m-[125I]iodophenyl)maleimide (m-[125I]IPM) was prepared by the demetallation of an N-[m-tri-(n-butyl)stannylphenyl]maleimide intermediate. The unlabeled intermediate was synthesized in greater than or equal to 75% yield using a palladium catalyzed reaction of hexabutylditin with m-bromoaniline, followed by reaction with maleic anhydride and ring annulation. All products were confirmed by NMR and elemental analysis. Labeling with 125I was carried out in a biphasic mixture containing chloramine-T (radiochemical yield greater than or equal to 70%). Rabbit IgG modified with the heterobifunctional crosslinking agent N-succinimidyl-3-(2-pyridyldithio)propionate (SPDP) and bovine serum albumin were conjugated with m-[125I]IPM (yield: 40 and 80%, respectively). In addition, m-[125I]IPM was conjugated to rabbit IgG subunits (HL) in 70% yield. The in vitro stability of the radiolabeled proteins in serum showed less than 1% deiodination over 24 h.