Significance of 18F-fluorocholine PET/CT positive pulmonary lesions in prostate cancer patients.

AIM: To assess the frequency and the significance of incidental pulmonary lesions with 18F-fluorocholine (18F-FCH) PET/CT in prostate cancer (PCa) patients. PATIENTS, METHODS: 225 consecutive PCa patients referred for 18F-FCH PET/CT (median age 68 years) were retrospectively evaluated for the presence of lesions in the lungs: 173 referred for restaging and 52 for initial staging regarding their high risk of extra prostatic extension. The final diagnosis was based on histopathological or on clinical and radiological follow-up. RESULTS: 13 patients had 18F-FCH positive pulmonary and 8 patients malignant lesions: 5 patients (38%) had a primary lung cancer (2 squamous cell carcinomas, 1 papillary adenocarcinoma, 1 typical pulmonary carcinoid, 1 bronchioloalveolar carcinoma) and 3 patients (23%) PCa metastases. Benign lesions were found in 5 subjects (38%). SUVmax and maximum diameter were neither significantly different in primary and metastatic tumors nor between malignant and benign lesions. CONCLUSIONS: Although our results suggest that incidental uptake in the lungs in PCa patients are nonspecific, their detection may have a significant impact on patient management knowing that more than 60% represent malignant disease.

18F-FLT and 125I-IdUrd uptake increase in human tumour cell lines induced by the thymidylate synthase inhibitor FdUrd.

AIM: 5-fluoro-2'-deoxyuridine (FdUrd) depletes the endogenous 5'-deoxythymidine triphosphate (dTTP) pool. We hypothesized whether uptake of exogenous dThd analogues could be favoured through a feedback enhanced salvage pathway and studied the FdUrd effect on cellular uptake of 3'-deoxy-3'-18F-fluorothymidine (18F-FLT) and 5-125I-iodo-2'-deoxyuridine (125I-IdUrd) in different cancer cell lines in parallel. METHODS: Cell uptake of 18F-FLT and 125I-IdUrd was studied in 2 human breast, 2 colon cancer and 2 glioblastoma lines. Cells were incubated with/without 1 µmol/l FdUrd for 1 h and, after washing, with 1.2 MBq 18F-FLT or 125I-IdUrd for 0.3 to 2 h. Cell bound 18F-FLT and 125I-IdUrd was counted and expressed in % incubated activity (%IA). Kinetics of 18F-FLT cell uptake and release were studied with/without FdUrd modulation. 2'-3H-methyl-fluorothymidine (2'-3H-FLT) uptake with/without FdUrd pretreatment was tested on U87 spheroids and monolayer cells. RESULTS: Basal uptake at 2 h of 18F-FLT and 125I-IdUrd was in the range of 0.8-1.0 and 0.4-0.6 Bq/cell, respectively. FdUrd pretreatment enhanced 18F-FLT and 125I-IdUrd uptake 1.2-2.1 and 1.7-4.4 fold, respectively, while co-incubation with excess thymidine abrogated all 18F-FLT uptake. FdUrd enhanced 18F-FLT cellular inflow in 2 breast cancer lines by factors of 1.8 and 1.6, respectively, while outflow persisted at a slightly lower rate. 2'-3H-FLT basal uptake was very low while uptake increase after FdUrd was similar in U87 monolayer cells and spheroids. CONCLUSIONS: Basal uptake of 18F-FLT was frequently higher than that of 125I-IdUrd but FdUrd induced uptake enhancement was stronger for 125I-IdUrd in five of six cell lines. 18F-FLT outflow from cells might be an explanation for the observed difference with 125I-IdUrd.

68Ga-NODAGA-RGDyK for αvß3 integrin PET imaging. Preclinical investigation and dosimetry.

AIM: To visualize neovasculature and/or tumour integrin αvß3 we selected the binding moiety Arg-Gly-Asp-D-Tyr-Lys (RGDyK) coupled to NODAGA for labeling with 68Ga. METHODS: NODAGA-RGDyK (ABX) was labeled with the 68Ga eluate from the 68Ge generator IGG100 using the processor unit PharmTracer. Biodistribution was measured in female Hsd mice sacrificed 10, 30, 60 and 90 min after i.v. injection of 68Ga-NODAGA-RGDyK for OLINDA dosimetry extrapolated to humans. Tumour targeting was studied in SCID mice bearing A431 and other tumour transplants using microPET and biodistribution measurements. RESULTS: Effective half-life of 68Ga-NODAGA-RGDyK was ~25 min for total body and most organs except liver and spleen that showed stable activity retention. With a bladder voiding interval of 0.5 h the calculated effective dose (ED) was 0.012 and 0.016 mSv/MBq for males and females, respectively. Rapid uptake within 10 min was observed in A431 tumours with dynamic PET followed by a slow release. Biodistribution measurements showed a 68Ga-NODAGA-RGDyK uptake in A431 tumours of 3.4±0.4 and 2.7±0.3%ID/g at 1 and 2 h, respectively. Similar uptakes were observed in a mouse and human breast and ovarian cancer xenografts. Co-injection of excess (5 mg/kg) unlabeled NODAGA-RGDyK with the radiotracer reduced tumour uptake at one hour to 0.23±0.01%ID/g, but similarly decreased uptake in normal organs as well. When unlabeled peptide was injected 15 min after 68Ga-NODAGA-RGDyK, uptake diminished particularly in tumour and adrenals, suggestive of a different binding mode compared with other normal tissues. CONCLUSION: NODAGA-RGDyK was reliably labeled with 68Ga and revealed a predicted ED of 0.014 mSv/MBq. Tumour uptake was rapid and significant and was chased with unlabeled RGDyK in a similar manner as adrenal uptake.

Benefit of anti-HER2-coated paclitaxel-loaded immuno-nanoparticles in the treatment of disseminated ovarian cancer: Therapeutic efficacy and biodistribution in mice.

The benefit of polymeric immuno-nanoparticles (NPs-Tx-HER), consisting of paclitaxel (Tx)-loaded nanoparticles coated with anti-HER2 monoclonal antibodies (Herceptin, trastuzumab), in cancer treatment was assessed in a disseminated xenograft ovarian cancer model induced by intraperitoneal inoculation of SKOV-3 cells overexpressing HER2 antigens. The study was focused on the evaluation of therapeutic efficacy and biodistribution of NPs-Tx-HER compared to other Tx formulations. The therapeutic efficacy was determined by two methods: bioluminescence imaging and survival rate. The treatment regimen consisted in an initial dose of 20mg/kg Tx administered as 10mg/kg intravenously (IV) and 10mg/kg intraperitonealy (IP), followed by five alternative IP and IV injections of 10mg/kg Tx every 3 days. The bioluminescence study has clearly shown the superior anti-tumor activity of NPs-Tx-HER compared to free Tx. As a confirmation of these results, a significantly longer survival of mice was observed for NPs-Tx-HER treatment compared to free Tx, Tx-loaded nanoparticles coated with an irrelevant mAb (Mabthera, rituximab) or Herceptin alone, indicating the potential of immuno-nanoparticles in cancer treatment. The biodistribution pattern of Tx was assessed on healthy and tumor bearing mice after IV or IP administration. An equivalent biodistribution profile was observed in healthy mice for Tx encapsulated either in uncoated nanoparticles (NPs-Tx) or in NPs-Tx-HER. No significant difference in Tx biodistribution was observed after IV or IP injection, except for a lower accumulation in the lungs when NPs were administered by IP. Encapsulated Tx accumulated in the organs of the reticulo-endothelial system (RES) such as the liver and spleen, whereas free Tx had a non-specific distribution in all tested organs. Compared to free Tx, the single dose injection (IV or IP) of encapsulated Tx in mice bearing tumors induced a higher tumor accumulation. However, no difference in overall tumor accumulation between NPs-Tx-HER and NPs-Tx was observed. In conclusion, the encapsulation of Tx into NPs-Tx-HER immuno-nanoparticles resulted in an improved efficacy of drug in the treatment of disseminated ovarian cancer overexpressing HER2 receptors.

Fluorodeoxyuridine mediated cell cycle synchronization in S-phase increases the Auger radiation cell killing with 125I-iododeoxyuridine.

AIM: 125I-iododeoxyuridine is a potential Auger radiation therapy agent. Its incorporation in DNA of proliferating cells is enhanced by fluorodeoxyuridine. Here, we evaluated therapeutic activities of 125I-iododeoxyuridine in an optimized fluorodeoxyuridine pre-treatment inducing S-phase synchronization. METHODS: After S-phase synchronization by fluorodeoxyuridine, cells were treated with 125I-iododeoxyuridine. Apoptosis analysis and S-phase synchronization were studied by flow cytometry. Cell survival was determined by colony-forming assay. Based on measured growth parameters, the number of decays per cell that induced killing was extrapolated. RESULTS: Treatment experiments showed that 72 to 91% of synchronized cells were killed after 0.8 and 8 kBq/ml 125I-iododeoxyuridine incubation, respectively. In controls, only 8 to 38% of cells were killed by corresponding 125I-iododeoxyuridine activities alone and even increasing the activity to 80 kBq/ml gave only 42 % killing. Duplicated treatment cycles or repeated fluorodeoxyuridine pre-treatment allowed enhancing cell killing to >95 % at 8 kBq/ml 125I-iododeoxyuridine. About 50 and 160 decays per S-phase cells in controls and S-phase synchronization, respectively, were responsible for the observed cell killing at 0.8 kBq/ml radio-iododeoxyuridine. CONCLUSION: These data show the successful application of fluorodeoxyuridine that provided increased 125I-iododeoxyuridine Auger radiation cell killing efficacy through S-phase synchronization and high DNA incorporation of radio-iododeoxyuridine.

Nanomedicines for active targeting: physico-chemical characterization of paclitaxel-loaded anti-HER2 immunonanoparticles and in vitro functional studies on target cells.

Paclitaxel (Tx)-loaded anti-HER2 immunonanoparticles (NPs-Tx-HER) were prepared by the covalent coupling of humanized monoclonal anti-HER2 antibodies (trastuzumab, Herceptin) to Tx-loaded poly (dl-lactic acid) nanoparticles (NPs-Tx) for the active targeting of tumor cells that overexpress HER2 receptors. The physico-chemical properties of NPs-Tx-HER were compared to unloaded immunonanoparticles (NPs-HER) to assess the influence of the drug on anti-HER2 coupling to the NP surface. The immunoreactivity of sulfo-MBS activated anti-HER2 mAbs and the in vitro efficacy of NPs-Tx-HER were tested on SKOV-3 ovarian cancer cells that overexpress HER2 antigens. Tx-loaded nanoparticles (NPs-Tx) obtained by a salting-out method had a size of 171+/-22 nm (P.I.=0.1) and an encapsulation efficiency of about of 78+/-10%, which corresponded to a drug loading of 7.8+/-0.8% (w/w). NPs-Tx were then thiolated and conjugated to activated anti-HER2 mAbs to obtain immunonanoparticles of 237+/-43 nm (P.I.=0.2). The influence of the activation step on the immunoreactivity of the mAbs was tested on SKOV-3 cells using 125I-radiolabeled mAbs, and the activity of the anti-HER2 mAbs was minimally affected after sulfo-MBS functionalization. Approximately 270 molecules of anti-HER2 mAbs were bound per nanoparticle. NPs-Tx-HER exhibited a zeta potential of 0.2+/-0.1 mV. The physico-chemical properties of the Tx-loaded immunonanoparticles were very similar to unloaded immunonanoparticles, suggesting that the encapsulation of the drug did not influence the coupling of the mAbs to the NPs. No drug loss was observed during the preparation process. DSC analysis showed that encapsulated Tx is in an amorphous or disordered-crystalline phase. These results suggest that Tx is entrapped in the polymeric matrix and not adsorbed to the surface of the NPs. In vitro studies on SKOV-3 ovarian cancer cells demonstrated the greater cytotoxic effect of NPs-Tx-HER compared to other Tx formulations. The results showed that at 1 ng Tx/ml, the viability of cells incubated with drug encapsulated in NP-Tx-HER was lower (77.32+/-5.48%) than the viability of cells incubated in NPs-Tx (97.4+/-12%), immunonanoparticles coated with Mabthera, as irrelevant mAb (NPs-Tx-RIT) (93.8+/-12%) or free drug (92.3+/-9.3%).

Three-phase 18F-fluorocholine PET/CT in the evaluation of prostate cancer recurrence.

AIM: Contribution of 3-phase 18F-fluorocholine PET/CT in suspected prostate cancer recurrence at early rise of PSA. PATIENTS, METHODS: Retrospective analysis was performed in 47 patients after initial treatment with radiotherapy (n=30) or surgery (n=17). Following CT, 10 minutes list-mode PET acquisition was done over the prostate bed after injection of 300 MBq of 18F-fluorocholine. Three timeframes of 3 minutes each were reconstructed for analysis. All patients underwent subsequent whole body PET/CT. Delayed pelvic PET/CT was obtained in 36 patients. PET/CT was interpreted visually by two observers and SUVmax determined for suspicious lesions. Biopsies were obtained from 13 patients. RESULTS: Biopsies confirmed the presence of cancer in 11 of 13 patients with positive PET for a total of 15 local recurrences in which average SUVmax increased during 14 minutes post injection and marginally decreased in delayed scanning. Conversely inguinal lymph nodes with mild to moderate metabolic activity on PET showed a clearly different pattern with decreasing SUVmax on dynamic images. Three-phase PET/CT contributed to the diagnostic assessment of 10 of 47 patients with biological evidence of recurrence of cancer. It notably allowed the discrimination of confounding blood pool or urinary activity from suspicious hyperactivities. PET/CT was positive in all patients with PSA>or=2 ng/ml (n=34) and in 4/13 patients presenting PSA values<2 ng/ml. CONCLUSION: 18F-fluorocholine 3-phase PET/CT showed a progressively increasing SUVmax in biopsy confirmed cancer lesions up to 14 minutes post injection while decreasing in inguinal lymph nodes interpreted as benign. Furthermore, it was very useful in differentiating local recurrences from confounding blood pool and urinary activity.

Sentinel lymph node involvement and a high Breslow index are independent factors of risk for early relapse of melanoma.

AIM: The clinical relevance of sentinel lymph node (SLN) analysis was evaluated prospectively and compared with other known risk factors of relapse in early stage melanoma. METHODS: Surgery was guided by lymphoscintigraphy, blue dye and gamma probe detection. SLN were analysed by haematoxylin eosin (HE) histochemistry and multimarker immunohistochemistry (IHC). Disease free survival (DFS) was evaluated with Kaplan-Meier plots according to different parameters and Cox analyses of variance. RESULTS: From 210 patients a total of 381 SLN were excised. Lymphoscintigraphy identified all excised SLN with only 2 false positive lymphatic lakes. Fifty patients (24%) had tumour positive SLN. With a mean follow-up of 31.3 months, 29 tumour recurrences were observed, 19 (38%) in 50 SLN positive and 10 (6%) in 160 SLN negative patients. Strong predictive factors for early relapse (p < 0.0005) were SLN positivity and a high Breslow index. CONCLUSION: SLN tumour positivity is an independent factor of high risk for early relapse with a higher power of discrimination than the Breslow index.

Differential tumor cell targeting of anti-HER2 (Herceptin) and anti-CD20 (Mabthera) coupled nanoparticles.

Two types of antibody-labeled nanoparticles (mAb-NPs) were prepared with the aim to achieve specific tumor targeting. Anti-HER2 and anti-CD20 monoclonal antibodies (mAb) were used as model ligands. Small poly(dl-lactic acid) nanoparticles (PLA NPs) with a mean size of about 170 nm were prepared by the salting out method. Thereafter, the coating of PLA NPs with mAbs was performed in two steps. First, thiol groups (-SH) were introduced on the surface of PLA-NPs by a two-step carbodiimide reaction. The number of -SH groups on the surface of NPs increased from 150 to 400 mmol-SH/mol PLA when cystamine concentrations of 25-1518 mol cystamine/mol PLA were used during the thiolation reaction. In the second step, covalent coupling of antibodies to thiolated NPs (NPs-SH) was obtained via a bifunctional cross-linker, m-maleimidobenzoyl-N-hydroxy-sulfosuccinimide ester (sulfo-MBS). For both mAbs anti-HER2 and anti-CD20, respectively, the number of -SH functions on the NPs had no influence on the amount of mAb coupled to the NPs. Approximately, 295 anti-HER2 and 557 anti-CD20 molecules, respectively, were covalently coupled per nanoparticle. The NPs size after the coupling reactions was about 250 nm. The specific interaction between tumor cells and mAb-NPs was determined by confocal microscopy using two cell lines: SKOV-3 human ovarian cancer cells (overexpressing HER2) and Daudi lymphoma cells (overexpressing CD20). The results showed the selective targeting of mAb-NPs to tumor cells overexpressing the specific antigen. While anti-CD20 labeled NPs (anti-CD20 NPs) bound to and remained at the cellular surface, anti-HER2 labeled NPs (anti-HER2 NPs) were efficiently internalized. The mAb-NPs represent a promising approach to improve the efficacy of NPs in active targeting for cancer therapy while the choice of the antibody-target system defines the fate of the mAb-NPs after their binding to the cells.

Long-term complete responses after 131I-tositumomab therapy for relapsed or refractory indolent non-Hodgkin's lymphoma.

We present the long-term results of 18 chemotherapy relapsed indolent (N = 12) or transformed (N = 6) NHL patients of a phase II anti-CD20 (131)I-tositumomab (Bexxar) therapy study. The biphasic therapy included two injections of 450 mg unlabelled antibody combined with (131)I-tositumomab once as dosimetric and once as therapeutic activity delivering 75 or 65 cGy whole-body radiation dose to patients with normal or reduced platelet counts, respectively. Two patients were not treated due to disease progression during dosimetry. The overall response rate was 81% in the 16 patients treated, including 50% CR/CRu and 31% PR. Median progression free survival of the 16 patients was 22.5 months. Median overall survival has not been reached after a median observation of 48 months. Median PFS of complete responders (CR/CRu) has not been reached and will be greater than 51 months. Short-term side effects were mainly haematological and transient. Among the relevant long-term side effects, one patient previously treated with CHOP chemotherapy died from secondary myelodysplasia. Four patients developed HAMA. In conclusion, (131)I-tositumomab RIT demonstrated durable responses especially in those patients who achieved a complete response. Six of eight CR/CRu are ongoing after 46-70 months.

A new method of thermoablation with hot water vapour for localized tumours.

BACKGROUND: A new method of thermoablation with hot water vapour based on a new type of microtube was developed. This approach allows tumours, with volume and anatomical positions not accessible to other techniques (cryoablation, radiofrequency ablation, laser ablation) to be treated. MATERIALS AND METHODS: The method was tested on a human colon carcinoma grafted subcutaneously in Swiss nude mice and the experiment monitored under magnetic resonance imaging. RESULTS: It was found that 2.52 cal s(-1) per cm3 of tumour were necessary to reduce tumour size. The microtube is built to withstand a large range of temperatures and pressures and is biocompatible. CONCLUSION: A specific feature of this technique is that, besides hot vapour, several types of drugs can be delivered through the same microtube depending of the location, type or size of the tumour. These properties make it a unique device for multi-therapeutic treatments.

Targeted alpha therapy in vivo: direct evidence for single cancer cell kill using 149Tb-rituximab.

This study demonstrates high-efficiency sterilisation of single cancer cells in a SCID mouse model of leukaemia using rituximab, a monoclonal antibody that targets CD20, labelled with terbium-149, an alpha-emitting radionuclide. Radio-immunotherapy with 5.5 MBq labelled antibody conjugate (1.11 GBq/mg) 2 days after an intravenous graft of 5.10(6) Daudi cells resulted in tumour-free survival for >120 days in 89% of treated animals. In contrast, all control mice (no treatment or treated with 5 or 300 micro g unlabelled rituximab) developed lymphoma disease. At the end of the study period, 28.4%+/-4% of the long-lived daughter activity remained in the body, of which 91.1% was located in bone tissue and 6.3% in the liver. A relatively high daughter radioactivity concentration was found in the spleen (12%+/-2%/g), suggesting that the killed cancer cells are mainly eliminated through the spleen. This promising preliminary in vivo study suggests that targeted alpha therapy with (149)Tb is worthy of consideration as a new-generation radio-immunotherapeutic approach.

A balanced deoxyribonucleoside mixture increased the rate of DNA incorporation of 5-[125I]Iodo-2'-deoxyuridine in glioblastoma cells.

Administration of nucleotide mixtures has been shown to restore and sustain the proliferation of leukocytes and enterocytes. Since it has been suggested that cancer cells use exogenous nucleotides more efficiently than normal cells, we hypothesized that administration of nucleotide mixtures would also stimulate the proliferation of cancer cells, thereby increasing the number of cells targeted by the thymidine analog 5-[(125)I]iodo-2'-deoxyuridine ([(125)I]IUdR). We first evaluated the influence of different deoxyribonucleoside mixtures on the DNA incorporation of [(125)I]IUdR in 3 human glioblastoma cell lines. Results showed that a 4-h coincubation with a mixture of identical concentration (10 microM) of deoxyadenosine, deoxyuridine, deoxyguanosine and deoxycytidine (AUGC) increased by 8.5-, 6.2-, and 2.0-fold the rate of DNA incorporation of [(125)I]IUdR in exponentially growing LN229, U87 and U251 cells, respectively. Replacing deoxyuridine by thymidine (ATGC) reversed the effect of the mixture, whereas removing deoxyuridine allowed a mixture of 10 microM AGC to increase by 2.2-fold the rate of DNA incorporation of [(125)I]IUdR in LN229 cells. Furthermore, the rate of DNA incorporation of [(125)I]IUdR in LN229 and U87 cells was increased up to 19.9- and 9.4-fold, respectively, by extending the coincubation time with 10 microM AUGC to 9 h, and up to 40.9- and 26.8-fold by incubating confluent cells for 4 h with 10 microM AUGC. Flow cytometry analysis showed that exposure of confluent cells to AUGC increased the percentage of cells in S phase of the cell cycle. Thus, co-administration of a balanced deoxyribonucleoside mixture may improve the use of radiolabeled nucleotide analogs, such as [(125)I]IUdR, for the targeting of cancer cells.

Fluorodeoxyuridine improves imaging of human glioblastoma xenografts with radiolabeled iododeoxyuridine.

Use of radiolabeled nucleotides for tumor imaging is hampered by rapid in vivo degradation and low DNA-incorporation rates. We evaluated whether blocking of thymidine (dThd) synthesis by 5-fluoro-2'-deoxyuridine (FdUrd) could improve scintigraphy with radio-dThd analogues, such as 5-iodo-2'-deoxyuridine (IdUrd). We first show in vitro that coincubation with FdUrd substantially increased incorporation of [125I]IdUrd and [3H]dThd in the three tested human glioblastoma lines. Flow cytometry analysis showed that a short coincubation with FdUrd (1 h) produces a signal increase per labeled cell. We then measured biodistribution 24 h after i.v. injection of [125I]IdUrd in nude mice s.c. xenografted with the three glioblastoma lines. Compared with animals given [125I]IdUrd alone, i.v. preadministration for 1 h of 10 mg/kg FdUrd increased the uptake of [125I]IdUrd in the three tumors 4.8-6.8-fold. Compatible with previous reports, there were no side effects in mice observed for 2 months after receiving such a treatment. The tumor uptake of [125I]IdUrd was increased < or =13.6-fold when FdUrd preadministration was stepwise reduced to 1.1 mg/kg. Uptake increases remained lower (between 1.7- and 5.8-fold) in normal proliferating tissues (i.e., bone marrow, spleen, and intestine) and negligible in quiescent tissues. DNA extraction showed that 72-80% of radioactivity in tumor and intestine was bound to DNA. Scintigraphy of xenografted mice was performed at different times after i.v. injection of 3.7 MBq [125I]IdUrd. Tumor detection was significantly improved after FdUrd preadministration while still equivocal after 24 h in mice given [125I]IdUrd alone. Furthermore, background activity could be greatly reduced by p.o. administration of KClO4 in addition to potassium iodide. We conclude that FdUrd preadministration may improve positron or single photon emission tomography with cell division tracers, such as radio-IdUrd and possibly other dThd analogues.

Fractionated irradiation combined with carbogen breathing and nicotinamide of two human glioblastomas grafted in nude mice.

This study addressed the potential radiosensitizing effect of nicotinamide and/or carbogen on human glioblastoma xenografts in nude mice. U-87MG and LN-Z308 tumors were irradiated with either 20 fractions over 12 days or 5 fractions over 5 days in air-breathing mice, mice injected with nicotinamide, mice breathing carbogen, or mice receiving nicotinamide plus carbogen. The responses to treatment were assessed using local control and moist desquamation. In U-87MG tumors, the enhancement ratios (ERs) at the radiation dose required to produce local tumor control in 50% of the treated mice (TCD(50)) with nicotinamide and/or carbogen ranged from 1.13 to 1.24 for irradiation in 20 fractions over 12 days. In LN-Z308 tumors, the ERs at the TCD(50) with nicotinamide and/or carbogen ranged from 1.22 to 1.40 for irradiation in 5 fractions over 5 days and from 1.11 to 1.30 in 20 fractions over 12 days, respectively. Skin injury was slightly enhanced, with ERs ranged from 1.06 to 1.15 when radiation was combined with carbogen and/or nicotinamide. Thus carbogen and nicotinamide can slightly improve the radiation response of human glioblastoma xenografts.

Biokinetics of a F(ab')3 iodine-131 labeled antigen binding construct (Mab 35) directed against CEA in patients with colorectal carcinoma.

UNLABELLED: An 131I labeled trivalent antigen binding construct, formed from 3 Fab' fragments of murine anti-CEA monoclonal antibody (Mab) 35, has shown favorable biokinetics in animal studies. OBJECTIVES: The aim of this study was to evaluate biodistribution and tumor uptake of 131I-F(ab')3 in patients and its potential utility for radioimmunotherapy of CEA expressing tumors. PATIENTS AND METHODS: Six patients (5 M, 1 F; age 62 +/- 13 y) with liver metastases of colorectal cancer, scheduled for hepatic surgery were studied by 2-3 whole body scans immediately post infusion of 111-137 MBq of 131I labeled Mab 35 F(ab')3 and up to 72 h. Circulating CEA ranged from 1.2 to 1930 ng/ml. We evaluated plasma and whole body clearance, activity accumulation by post-surgical ex-vivo tissue measurement in primary tumor (T) and metastases (M), and calculated M to blood (M/B) and M to liver (M/L) ratios. RESULTS: All known tumor sites were detected by immunoscintigraphy and confirmed at surgery. Whole body effective T1/2 calculated in two patients was 51.5 h and 55.6 h respectively. Effective serum T1/2 was mono-exponential in 3 patients (short observation interval) with 20.9 +/- 7 h and bi-exponential in three with alpha T1/2 of 6.3 +/- 1 h and beta T1/2 of 38.6 +/- 5 h. In a patient with concomitant colic and hepatic lesions uptake of primary tumor was 0.0071% injected dose per gram of tissue (%ID/g) and mean metastases activity was 0.0275 %ID/g at 48 h. In the 3 patients who had surgery at 48 h, mean uptake in metastases and normal liver was 0.0182 %ID/g and 0.0021 %ID/g, respectively (M/L 8.67). In the single subject followed until 7 days post infusion, residual activity in liver metastases was 10 times higher than in normal parenchyma. CONCLUSIONS: Tumor uptake and tumor to blood ratio, as well as serum clearance of the triconstruct are similar to those observed with intact iodinated anti-CEA antibodies. In the patient studied for 7 days the tumor residence time was favorable. Further improvements, however, need to be obtained before considering this approach for radioimmunotherapy.

[Immunotargeting of tumors: state of the art and prospects in 2000]. / Immunociblage des tumeurs: situation et perspectives en 2000.

Following 15 years of experimental studies, tumor immunotargeting using monoclonal antibodies directed against tumor associated antigens shows now important monoclonal antibodies directed against tumor associated antigens shows now important clinical developments. This is mainly due to encouraging therapeutic results which have obtained using humanized antibodies such as the anti-CD20 rituximab in follicular B lymphomas and the anti-DrbB2 herceptin in breast carcinomas. Thanks to genetic engineering it is possible to graft variable or hypervariable regions from murine antibodies to human IgG, and even to obtain fully human antibodies by using either transgenic mice containing a large part of the human repertoire of human IgG, or selection of human antibody fragments expressed by phages. Radiolabeling of antibodies played a major role to demonstrate the tumor immunotargeting specificity and remains attractive for the diagnosis by immunoscintigraphy as well as for the treatment by radioimmunotherapy of some cancers. In this review, the current results and the prospects of diagnostic and therapeutic uses of anti-tumor antibodies and their fragments will be described. Concerning diagnosis, 123-iodine or 99m-technetium labeled Fab fragments allowed very demonstrative tumor images but this technique has a limited effect upon the therapeutic attitude. Immuno-PET (positron emission tomography) could enhance the sensitivity of this imaging method. Radio-immunoguided surgery and immunophotodetection are attractive techniques still under evaluation. Concerning therapy, 131-iodine labeled anti-CD20 antibodies gave spectacular results in non-Hodgkin's B lymphomas. In solid tumors which as less radiosensitive, radioimmunotherapy could concern small tumors and need the use of two-steps targeting and/or alpha emitters radioisotopes. Some other strategies will be described such as bispecific antibodies directed against tumors and immune effector cells, some antibody fragments expressed on T cells called T-bodies or some biological studies using intrabodies. Published data and works in progress demonstrate that immunotargeting of tumors will have a growing place in the treatments of cancer patients.

Unlabelled iododeoxyuridine increases the cytotoxicity and incorporation of [1251]-iododeoxyuridine in two human glioblastoma cell lines.

Iododeoxyuridine (IUdR), labelled with radioiodines emitting Auger, alpha or beta- radiation, has been proposed as a therapeutic tool in the treatment of cancer. However, the low per cent incorporation in tumour cells and limited cytotoxicity are major obstacles for such an application. Using unlabelled IUdR as a modulator, we have studied the in vitro cytotoxicity of [125I]-IUdR in two human glioblastoma cell lines. Surprisingly, an enhanced cytotoxicity of [125I]-IUdR was observed in the presence of 0.3-10 microM concentrations of unlabelled IUdR in U251 glioblastoma cells and to a lesser extent in LN229 cells. The presence of unlabelled IUdR unexpectedly increased the incorporation of [125I]-IUdR in both cell lines. Thymidine competitively blocked the cytotoxic effects of combined unlabelled and [125I]-labelled IUdR in these cells and DNA-incorporation of radiolabelled IUdR.

Combined radioimmunotherapy and radiotherapy of liver metastases from colorectal cancer: a feasibility study.

BACKGROUND: A combination of radioimmunotherapy (RIT) and radiotherapy (RT) should allow one to increase the dose of radiation targeting a particular tumour without the concomitant increase of toxic side effects. This might be obtained if the dose limiting side effect of each individual radiation therapy concerned different organs. METHODS: Six patients with limited liver metastatic disease from colorectal cancer were treated with 6.9 GBq (range 4.7 to 8.4 GBq) 131I-labelled anti-CEA MAb F(ab')2 fragments combined with 20 Gy RT to the liver. Both treatments were given in close association, according to timing schedules evaluated in animals that gave the best results. RESULTS: Reversible bone marrow and liver toxicity was observed in 6 and 5 patients, respectively. Three patients who first received 20 Gy RT to the liver, showed a significant platelet drop upon completion of RT. Repeat computerized tomography (CT) after 2 months showed a minor response in 1 patient and stable disease in 3 patients. CONCLUSION: The study shows potential ways of combining RIT and RT, suggesting that this combination is feasible for the treatment of liver metastases.