Lack of Efficacy of Two Consecutive Treatments of Radioimmunotherapy With131I-cG250 in Patients With Metastasized Clear Cell Renal Cell Carcinoma

Combination radionuclide therapy: A new paradigm

Targeted molecular radionuclide therapy (MRT) has shown its potential for the treatment of cancers of multiple origins. A combination therapy strategy employing two or more distinct therapeutic approaches in cancer management is aimed at circumventing tumor resistance by simultaneously targeting compensatory signaling pathways or bypassing survival selection mutations acquired in response to individual monotherapies. Combination radionuclide therapy (CRT) is a newer application of the concept, utilizing a combination of radiolabeled molecular targeting agents with chemotherapy and beam radiation therapy for enhanced therapeutic index. Encouraging results are reported with chemotherapeutic agents in combination with radiolabeled targeting molecules for cancer therapy. With increasing awareness of the various survival and stress response pathways activated after radionuclide therapy, different holistic combinations of MRT agents with radiosensitizers targeting such pathways have also been explored. MRT has also been studied in combination with beam radiotherapy modalities such as external beam radiation therapy and carbon ion radiation therapy to enhance the anti-tumor response. Nanotechnology aids in CRT by bringing together multiple monotherapies on a single nanostructure platform for treating cancers in a more precise or personalized way. CRT will be a key player in managing cancers if correctly tailored to the individual patient profile. The success of CRT lies in an in-depth understanding of the radiobiological principles and pathways activated in response.

Novel Agents and Future Perspectives on Theranostics

In the current era of precision medicine, there is renewed interest in radiopharmaceutical therapy and theranostics. The approval of somatostatin receceptor directed therapy and norepinephrine transporter targeted ¹³¹I-MIBG therapies by the FDA and the rapid progress of highly promising beta and alpha emitter tagged PSMA directed therapy of prostate cancer have stimulated clinically impactful changes in practice. Many novel strategies are being explored and novel radiopharmaceutical therapeutic agents including peptide based ligands as well as antibodies or antibody fragments are being developed preclinically or are in early phase clinical trials. While beta particle emitters have most commonly been used for targeted radiotherapy and radioimmunotargeting, there is an emerging interest in alpha emitters that cause greater density of ionization events leading to increased double-strand DNA damage and cluster breaks because of the high-energy particles within a shorter tissue range of penetration and thereby lower toxicity to adjacent normal tissues.

Selectivity Conversion of Protease Inhibitory Antibodies

Solid tumors are inherently difficult to treat because of large regions of hypoxia and are often chemotherapy- or radiotherapy-resistant. It seems that cancer stem cells reside in hypoxic and adjacent necrotic tumor areas. Therefore, new treatments that are highly selective for tumors and can eradicate cells in both hypoxic and necrotic tumor regions are desirable. Antibody α-radioconjugates couple an α-emitting radionuclide with the specificity of a tumor-targeting monoclonal antibody. The large mass and energy of α-particles result in radiation dose delivery within a smaller area independent of oxygen concentration, thus matching key criteria for killing hypoxic tumor cells. With advances in radionuclide production and chelation chemistry, α-radioconjugate therapy is regaining interest as a cancer therapy. Here, we will review current literature examining radioconjugate therapy specifically targeting necrotic and hypoxic tumor cells and outline how α-radioconjugate therapy could be used to treat tumor regions harboring more resistant cancer cell types.

Statement of Significance

Tumor-targeting antibodies are excellent vehicles for the delivery of toxic payloads directly to the tumor site. Tumor hypoxia and necrosis promote treatment recurrence, resistance, and metastasis. Targeting these areas with antibody α-radioconjugates would aid in overcoming treatment resistance.

Selectivity Conversion of Protease Inhibitory Antibodies

Background: Proteases are one of the largest pharmaceutical targets for drug developments. Their dysregulations result in a wide variety of diseases. Because proteolytic networks usually consist of protease family members that share high structural and catalytic homology, distinguishing them using small molecule inhibitors is often challenging. To achieve specific inhibition, this study described a novel approach for the generation of protease inhibitory antibodies. As a proof of concept, we aimed to convert a matrix metalloproteinase (MMP)-14 specific inhibitor to MMP-9 specific inhibitory antibodies with high selectivity. Methods: An error-prone single-chain Fv (scFv) library of an MMP-14 inhibitor 3A2 was generated for yeast surface display. A dual-color competitive FACS was developed for selection on MMP-9 catalytic domain (cdMMP-9) and counter-selection on cdMMP-14 simultaneously, which were fused/conjugated with different fluorophores. Isolated MMP-9 inhibitory scFvs were biochemically characterized by inhibition assays on MMP-2/-9/-12/-14, proteolytic stability tests, inhibition mode determination, competitive ELISA with TIMP-2 (a native inhibitor of MMPs), and paratope mutagenesis assays. Results: We converted an MMP-14 specific inhibitor 3A2 into a panel of MMP-9 specific inhibitory antibodies with dramatic selectivity shifts of 690-4,500 folds. Isolated scFvs inhibited cdMMP-9 at nM potency with high selectivity over MMP-2/-12/-14 and exhibited decent proteolytic stability. Biochemical characterizations revealed that these scFvs were competitive inhibitors binding to cdMMP-9 near its reaction cleft via their CDR-H3s. Conclusions: This study developed a novel approach able to convert the selectivity of inhibitory antibodies among closely related protease family members. This methodology can be directly applied for mAbs inhibiting many proteases of biomedical importance.

Application of chimeric antigen receptor-engineered T cells in ovarian cancer therapy

Due to the critical role of T cells in the immune surveillance of ovarian cancer, adoptive T-cell therapies are receiving increased attention as an immunotherapeutic approach for ovarian cancer. Chimeric antigen receptors (CARs), constructed by incorporating the single-chain Fv fragment to a T-cell signaling domain such as CD3 ζ or Fc receptor γ chain, endow T cell with nonmajor histocompatibility complex-restricted specificity. Dual specificity, trans-signaling CARs and affinity-tuned single-chain Fv fragment have broadened the applicability of CAR-engineered T-cell therapy and may be considered preferential to T cell receptor T-cell therapy in clinical care. As new insights into the CAR-engineered T cells have emerged over the last decade, we review the development of CAR T-cell therapy and discuss the progress and safety concerns regarding its translation from basic research into clinical care of ovarian cancer.

Past, Present, and Future: Development of Theranostic Agents Targeting Carbonic Anhydrase IX

Theranostics is the integration of diagnostic information with pharmaceuticals to increase effectiveness and safety of cancer treatments. Nuclear medicine provides a non-invasive means to visualize drug target expression across primary and metastatic sites, and assess pharmacokinetics and efficacy of companion therapeutic agents. This is significant given the increasing recognition of the importance of clonal heterogeneity in treatment response and resistance. Carbonic anhydrase IX (CA-IX) has been advocated as an attractive diagnostic and therapeutic biomarker for targeting hypoxia in solid malignancies. CA-IX confers cancer cell survival under low oxygen tension, and is associated with increased propensity for metastasis. As such, CA-IX is overexpressed in a broad spectrum of cancers. Different classes of antigen recognition molecules targeting CA-IX including monoclonal antibodies, peptides, small molecule inhibitors, and antibody mimetics have been radiolabeled for imaging and therapeutic applications. cG250, a chimeric monoclonal antibody, has been labeled with an assortment of radionuclides (¹²⁴I, ¹¹¹In, ⁸⁹Zr, ¹³¹I, ⁹⁰Y, and ¹⁷⁷Lu) and is the most extensively investigated CA-IX radiopharmaceutical. In recent years, there have been tremendous advancements made by the research community in developing alternatives to cG250. Although still in preclinical settings, several small molecule inhibitors and antibody mimetics hold great promise in improving the management of aggressive and resistant cancers.

Treatment of metastatic renal cell carcinoma (mRCC) with CAIX CAR-engineered T-cells-a completed study overview

We studied safety and proof of concept of a phase I/II trial with chimeric antigen receptor (CAR) T-cells in patients with metastatic renal cell carcinoma (mRCC). The CAR was based on the G250 mAb that recognized an epitope of carboxy-anhydrase-IX (CAIX). Twelve patients with CAIX+ mRCC were treated in three cohorts with a maximum of 10 daily infusions of 2×10(7) to 2×10(9) CAR T-cells. Circulating CAR T-cells were transiently detectable in all patients and maintained antigen-specific immune functions following their isolation post-treatment. Blood cytokine profiles mirrored CAR T-cell presence and in vivo activity. Unfortunately, patients developed anti-CAR T-cell antibodies and cellular immune responses. Moreover, CAR T-cell infusions induced liver enzyme disturbances reaching CTC grades 2-4, which necessitated cessation of treatment in four out of eight patients (cohort 1+2). Examination of liver biopsies revealed T-cell infiltration around bile ducts and CAIX expression on bile duct epithelium, adding to the notion of on-target toxicity. No such toxicities were observed in four patients that were pretreated with G250 mAb (cohort 3). The study was stopped due to the advent of competing treatments before reaching therapeutic or maximum tolerated dose in cohort 3. No clinical responses have been recorded. Despite that, from this trial numerous recommendations for future trials and their immune monitoring could be formulated, such as choice of the target antigen, format and immunogenicity of receptor and how the latter relates to peripheral T-cell persistence.

Diagnostic Challenges of Kidney Cancer: A Systematic Review of the Role of Positron Emission Tomography-Computerized Tomography

PURPOSE

Positron emission tomography-computerized tomography is a leading imaging modality for many types of solid tumors. The ability to characterize molecular processes noninvasively during a relatively fast whole-body scan is the major advantage of this technology. We reviewed the literature in an attempt to clarify the usefulness of positron emission tomography-computerized tomography in patients with a renal mass.

MATERIALS AND METHODS

We searched PubMed® for articles published from 2004 through September 2015 using the keywords "renal," "kidney," "mass," "tumor," "cancer," and "PET/CT."

RESULTS

A total of 158 relevant articles were included in the review. Most diagnostic studies used (18)F-fluorodeoxyglucose, a marker of glucose metabolism, as the radiotracer. The results were substandard, with sensitivity rates in the range of 31.5% to 77% for diagnosis of renal cell carcinomas. There were higher success rates for diagnosis of clear cell carcinomas. Carbonic anhydrase IX is an enzyme expressed in 95% of clear cell carcinomas but not in normal renal tissue or in benign or nonclear cell malignancies. A chimeric mouse-human antibody to carbonic anhydrase IX labeled with (124)I-girentuximab was demonstrated to diagnose clear cell tumors with sensitivity of 86.2% and specificity of 85.9%. For diagnosis of metastases positron emission tomography-computerized tomography with (18)F-fluorodeoxyglucose was observed to be more accurate than computerized tomography alone (94% vs 89%). Studies with other tracers also reveal encouraging results. Positron emission tomography-computerized tomography holds great promise in predicting prognosis and response to tyrosine kinase inhibitors. Current tyrosine kinase inhibitor treatments usually induce only mild lesion shrinkage. Thus, assessment of response based on changes in size of metastases is insufficient. Low (18)F-fluorodeoxyglucose uptake before treatment and decreased uptake after 2 cycles of treatment are associated with better survival. Using labeled medications as radiotracers before actual treatment may assist in selection of the most effective medication for a specific patient.

CONCLUSIONS

Positron emission tomography-computerized tomography with (18)F-fluorodeoxyglucose currently has lower sensitivity compared to enhanced computerized tomography for diagnosis of primary renal masses but better sensitivity for diagnosis of metastases. Predicting and monitoring response to targeted therapy could direct the clinician toward drug selection or modification during therapy. The possibility of treating patients with advanced renal cell carcinoma with (124)I-girentuximab attached to (177)Lu, a strong β-emitter, is investigated.

Next revolution in molecular theranostics: personalized medicine for urologic cancers

Extensive lists of molecular biomarkers are currently evaluated as potential targets for directed cancer therapies. We reviewed three potential candidate biomarkers to play a role in the near future as molecular theranostics for urologic malignancies. Carbonic anhydrase type IX is a surrogate marker of hypoxia highly expressed in cancer cells. Their expression and clinical significance in kidney and urothelial bladder cancer are discussed as well as the main therapeutic approaches that are currently under evaluation. For prostate cancer, available evidence on the use of prostate-specific membrane antigen and neuropeptide receptors radiolabeled analog and the undergoing clinical studies are also analyzed and discussed at different stages of prostate cancer.

Theranostic applications of antibodies in oncology

Targeted therapies, including antibodies, are becoming increasingly important in cancer therapy. Important limitations, however, are that not every patient benefits from a specific antibody therapy and that responses could be short-lived due to acquired resistance. In addition, targeted therapies are quite expensive and are not completely devoid of side-effects. This urges the need for accurate patient selection and response monitoring. An important step towards personalizing antibody treatment could be the implementation of theranostics. Antibody theranostics combine the diagnostic and therapeutic potential of an antibody, thereby selecting those patients who are most likely to benefit from antibody treatment. This review focuses on the clinical application of theranostic antibodies in oncology. It provides detailed information concerning the suitability of antibodies for theranostics, the different types of theranostic tests available and summarizes the efficacy of theranostic antibodies used in current clinical practice. Advanced theranostic applications, including radiolabeled antibodies for non-invasive functional imagining, are also addressed. Finally, we discuss the importance of theranostics in the emerging field of personalized medicine and critically evaluate recent data to determine the best way to apply antibody theranostics in the future.

Tyrosine kinase inhibitor sorafenib decreases 111In-girentuximab uptake in patients with clear cell renal cell carcinoma

Tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of metastatic clear cell renal cell carcinoma (RCC). Although TKIs have demonstrated good clinical efficacy, the lack of complete responses, the chronic nature of the treatment, and the side effects are clear disadvantages. An interesting new approach in the treatment of clear cell RCC is antibody-mediated therapy with the chimeric anti-carbonic anhydrase IX (CAIX) antibody girentuximab (cG250). As the results of several girentuximab trials become available, the question arises of whether TKI treatment can be combined with girentuximab-based therapy. In this study, we assessed the effect of the widely used TKI sorafenib on the tumor-targeting potential of (111)In-labeled girentuximab.

METHODS

(111)In-girentuximab imaging was performed on 15 patients suspected of having a renal malignancy, with surgery being part of their treatment plan. Of these, 10 patients were treated in a neoadjuvant setting with sorafenib (400 mg orally twice daily). Five patients received treatment during 1 wk, and 5 patients received treatment during 4 wk. In both sorafenib-treated groups, baseline and posttreatment tumor targeting of (111)In-girentuximab were compared. Surgery was performed 3 d after the last image acquisition. Five additional patients were included as a control group and had only a single (111)In-girentuximab injection and scintigraphy without any treatment. Distribution of (111)In-girentuximab was determined scintigraphically ex vivo in a 1-cm lamella of the resected tumorous kidney. Expression of CAIX and of the vascular marker CD31 was determined immunohistochemically on specimens of both tumor and normal kidney tissue.

RESULTS

Treatment with sorafenib resulted in a marked decrease of (111)In-girentuximab uptake in the tumor in clear cell RCC patients, especially in the group treated for 4 wk (mean change in both sorafenib-treated groups, -38.4%; range, +9.1% to -79.4%). Immunohistochemical analysis showed markedly reduced CD31 expression and vessel density in the sorafenib-treated groups but no differences in CAIX expression between the sorafenib-treated groups and the nontreated patients.

CONCLUSION

Treatment with sorafenib resulted in a treatment duration-dependent significantly decreased uptake of (111)In-girentumab in clear cell RCC lesions. These results indicate that the efficacy of antibody-mediated treatment or diagnosis modalities is hampered by TKI treatment.

Carbonic anhydrase expression in kidney and renal cancer: implications for diagnosis and treatment

Four different carbonic anhydrases are expressed in the human nephron, the functional unit of the kidney. These are specifically expressed in different nephron segments, emphasizing the critical role carbonic anhydrases play in maintaining the homeostasis of this crucial organ.Whereas the localization of carbonic anhydrases in the kidney has been long established, interest in carbonic anhydrases has increased dramatically for renal cancer, in particular for the clear cell variant of renal cell carcinoma (ccRCC) because carbonic anhydrase IX is specifically expressed in ccRCC. Therefore carbonic anhydrase IX is being studied as potential diagnostic and therapeutic target, despite carbonic anhydrase IX expression in non-renal tissues.

General overview of radioimmunotherapy of solid tumors

Radioimmunotherapy (RIT) represents an attractive tool for the treatment of local and/or diffuse tumors with radiation. In RIT, cytotoxic radionuclides are delivered by monoclonal antibodies that specifically target tumor-associated antigens or the tumor microenvironment. While RIT has been successfully employed for the treatment of lymphoma, mostly with radiolabeled antibodies against CD20 (Bexxar(®); Corixa Corp., WA, USA and Zevalin(®); Biogen Idec Inc., CA, USA and Schering AG, Berlin, Germany), its use in solid tumors is more challenging and, so far, few trials have progressed beyond Phase II. This review provides an update on antibody-radionuclide conjugates and their use in RIT. It also discusses possible optimization strategies to improve the clinical response by considering biological, radiobiological and physical features.

Molecular imaging and carbonic anhydrase IX-targeted radioimmunotherapy in clear cell renal cell carcinoma

Conventional imaging is suboptimal at evaluating disease status in renal cell carcinoma (RCC) because of poor sensitivity. Furthermore, there is an unmet need for the treatment of metastatic RCC, both in terms of improvement of progression-free survival and limitation of toxicity. For this reason, radionuclide imaging and radionuclide therapy are extensively investigated. This review provides an overview of the current progress in molecular imaging and radionuclide therapy in clear cell RCC and will focus on promising detection and therapy strategies targeting the carbonic anhydrase IX antigen, which is expressed in clear cell RCC.

Reassessing target antigens for adoptive T-cell therapy

Adoptive T cell therapy can target and kill widespread malignant cells thereby inducing durable clinical responses in melanoma and selected other malignances. However, many commonly targeted tumor antigens are also expressed by healthy tissues, and T cells do not distinguish between benign and malignant tissues if both express the target antigen. As such, autoimmune toxicity from T-cell-mediated destruction of normal tissue has limited the development and adoption of this otherwise promising type of cancer therapy. A review of the unique biology of T-cell therapy and of recent clinical experience compels a reassessment of target antigens that traditionally have been viewed from the perspective of weaker immunotherapeutic modalities. In selecting target antigens for adoptive T-cell therapy, expression by tumors and not by essential healthy tissues is of paramount importance. The risk of autoimmune adverse events can be further mitigated by generating antigen receptors using strategies that reduce the chance of cross-reactivity against epitopes in unintended targets. In general, a circumspect approach to target selection and thoughtful preclinical and clinical studies are pivotal to the ongoing advancement of these promising treatments.

Application of monoclonal antibody G250 recognizing carbonic anhydrase IX in renal cell carcinoma

Monoclonal antibody G250 (mAbG250) recognizes a determinant on carbonic anhydrase IX (CAIX). CAIX is expressed by virtually all renal cell carcinomas of the clear cell type (ccRCC), but expression in normal tissues is restricted. The homogeneous CAIX expression in ccRCC and excellent targeting capability of mAbG250 in animal models led to the initiation of the clinical evaluation of mAbG250 in (metastatic) RCC (mRCC) patients. Clinical studies confirmed the outstanding targeting ability of mAbG250 and cG250 PET imaging, as diagnostic modality holds great promise for the future, both in detecting localized and advanced disease. Confirmation of the results obtained in the non-randomized clinical trials with unmodified cG250 is needed to substantiate the value of cG250 treatment in mRCC. cG250-Based radio immuno-therapy (RIT) holds promise for treatment of patients with small-volume disease, and adjuvant treatment with unmodified cG250 may be of value in selected cases. In the upcoming years, ongoing clinical trials should provide evidence for these assumptions. Lastly, whether cG250-based RIT can be combined with tyrosine kinase inhibitors, which constitutes the current standard treatment for mRCC, needs to be established.

Phase II study of Lutetium-177-labeled anti-prostate-specific membrane antigen monoclonal antibody J591 for metastatic castration-resistant prostate cancer

PURPOSE

To assess the efficacy of a single infusion of radiolabeled anti-prostate-specific membrane antigen (PSMA) monoclonal antibody J591 (lutetium-177; (177)Lu) by prostate-specific antigen (PSA) decline, measurable disease response, and survival.

EXPERIMENTAL DESIGN

In this dual-center phase II study, two cohorts with progressive metastatic castration-resistant prostate cancer received one dose of (177)Lu-J591 (15 patients at 65 mCi/m(2), 17 at 70 mCi/m(2)) with radionuclide imaging. Expansion cohort (n = 15) received 70 mCi/m(2) to verify response rate and examine biomarkers.

RESULTS

Forty-seven patients who progressed after hormonal therapies (55.3% also received prior chemotherapy) received (177)Lu-J591. A total of 10.6% experienced ≥50% decline in PSA, 36.2% experienced ≥30% decline, and 59.6% experienced any PSA decline following their single treatment. One of 12 with measurable disease experienced a partial radiographic response (8 with stable disease). Sites of prostate cancer metastases were targeted in 44 of 47 (93.6%) as determined by planar imaging. All experienced reversible hematologic toxicity, with grade 4 thrombocytopenia occurring in 46.8% (29.8% received platelet transfusions) without significant hemorrhage. A total of 25.5% experienced grade 4 neutropenia, with one episode of febrile neutropenia. The phase I maximum tolerated dose (70 mCi/m(2)) resulted in more 30% PSA declines (46.9% vs. 13.3%, P = 0.048) and longer survival (21.8 vs. 11.9 months, P = 0.03), but also more grade 4 hematologic toxicity and platelet transfusions. No serious nonhematologic toxicity occurred. Those with poor PSMA imaging were less likely to respond.

CONCLUSION

A single dose of (177)Lu-J591 was well tolerated with reversible myelosuppression. Accurate tumor targeting and PSA responses were seen with evidence of dose response. Imaging biomarkers seem promising.

ImmunoPET imaging of renal cell carcinoma with (124)I- and (89)Zr-labeled anti-CAIX monoclonal antibody cG250 in mice

INTRODUCTION

Monoclonal antibody (mAb) cG250 recognizes carbonic anhydrase IX (CAIX), overexpressed on clear cell renal cell carcinoma (ccRCC). (124)I-cG250 is currently under clinical investigation for the detection of ccRCC. However, the (124)I label is rapidly excreted from the tumor cells after internalization of the radiolabeled mAb. We hypothesized that labeling cG250 with the residualizing positron emitter (89)Zr would lead to higher tumor uptake and more sensitive detection of ccRCC lesions.

MATERIALS AND METHODS

Nude mice with CAIX-expressing ccRCC xenografts (SK-RC-52 or NU-12) were i.v. injected with (89)Zr-cG250 or (124)I-cG250. To determine specificity of (89)Zr-cG250 uptake in ccRCC, one control group was i.v. injected with (89)Zr-MOPC21 (irrelevant mAb). PET images were acquired using a small animal PET camera and the biodistribution of the radiolabeled mAb was determined.

RESULTS

The ccRCC xenografts were clearly visualized after injection of (89)Zr-cG250 and (124)I-cG250. Tumor uptake of (89)Zr-cG250 was significantly higher compared with (124)I-cG250 in the NU-12 tumor model (114.7% ± 25.2% injected dose per gram (%ID/g) vs. 38.2 ± 18.3%ID/g, p=0.029), but in the SK-RC-52 the difference in tumor uptake was not significant (48.7 ± 15.2%ID/g vs. 32.0 ± 22.9%ID/g, p=0.26). SK-RC-52 tumors were not visualized with (89)Zr-MOPC21 (tumor uptake 3.0%ID/g). Intraperitoneal SK-RC-52 lesions as small as 7 mm(3) were visualized with (89)Zr-cG250 PET.

CONCLUSION

ImmunoPET imaging with cG250 visualized s.c. and i.p. ccRCC lesions in murine models. This confirms the potential of cG250 immunoPET in the diagnosis and (re)staging of ccRCC. PET imaging of ccRCC tumors with (89)Zr-cG250 could be more sensitive than (124)I-cG250-PET.

Incidence and prognostic significance of second primary cancers in renal cell carcinoma

BACKGROUND

The survival of patients with renal cell carcinoma (RCC) has improved in recent years. However, data on the risk of developing a second cancer after a diagnosis of RCC is limited. We used the data available in the Surveillance Epidemiology and End Results (SEER) database to estimate the risk of second metachronous primary cancers in patients diagnosed with RCC between 1973 and 2006. Furthermore, we also investigated the effect of the second primary cancers (SPCs) on the survival of RCC patients.

RESULTS

A total of 3795 cases of SPCs were registered in the SEER between 1973 and 2006. The ratio of observed/expected number of SPCs in RCC was 1.18, which was significantly greater than expected. Solid tumors comprised 90% of all second malignancies in RCC patients, with the most second cancers reported in the prostate gland and the digestive and respiratory systems. The overall risk of second primaries was highest in patients aged over 30 years at the time of diagnosis. The site-specific risk of second cancers varied with the age at diagnosis, sex, race of the patient, size of the primary renal tumor, and history of radiation therapy. Patients with second primaries had a significantly longer overall survival than those without second malignancies. An interval of <1 year between the diagnosis of RCC and the second primary was the strongest predictor of poor overall survival in RCC patients with a second malignancy.

CONCLUSIONS

Patients with RCC are at a significantly higher risk of developing a second malignancy, suggesting the need for careful surveillance for their early detection and management.

Treatment of metastatic renal cell carcinoma with CAIX CAR-engineered T cells: clinical evaluation and management of on-target toxicity

Autologous T cells genetically modified to express a chimeric antibody receptor (CAR) against carboxy-anhydrase-IX (CAIX) were administered to 12 patients with CAIX-expressing metastatic renal cell carcinoma (RCC). Patients were treated in three cohorts with a maximum of 10 infusions of a total of 0.2 to 2.1 × 10(9) CAR T cells. CTC grade 2-4 liver enzyme disturbances occurred at the lowest CAR T cell doses, necessitating cessation of treatment in four out of eight patients in cohorts 1 and 2. Examination of liver biopsies revealed CAIX expression on bile duct epithelium with infiltration of T cells, including CAR T cells. Subsequently four patients were pre-treated with CAIX monoclonal antibody (mAb) G250 to prevent CAR-specific toxicity and showed no liver toxicities and indications for enhanced peripheral T cell persistence. No clinical responses were recorded. This report shows that CAIX-targeting CAR T cells exerted antigen-specific effects in vivo and induced liver toxicity at the lowest dose of 0.2 × 10(9) T cells applied, illustrating the potency of receptor-modified T cells. We provide in-patient proof that the observed "on-target" toxicity is antigen-directed and can be prevented by blocking antigenic sites in off-tumor organs and allowing higher T cell doses.

Potential role of (124)I-girentuximab in the presurgical diagnosis of clear-cell renal cell cancer

Renal cell carcinoma (RCC) is a biologically heterogeneous disease, with many small renal masses (SRMs) exhibiting an indolent natural history, while others progress more rapidly to become life-threatening. Existing multiphase contrast-enhanced imaging methods, such as computed tomography or magnetic resonance imaging, cannot definitively distinguish between benign and malignant solid tumors or identify histologic subtype, and early results of molecular imaging studies (positron emission tomography [PET]) in the evaluation of SRMs have not improved on these established modalities. Alternative molecular markers/agents recognizing aberrant cellular pathways of cellular oxidative metabolism, DNA synthesis, and tumor hypoxia tracers are currently under development and investigation for RCC assessment, but to date none are yet clinically applicable or available. In contrast, immuno-PET offers highly selective binding to cancer-specific antigens, and might identify radiographically recognizable and distinct molecular targets. A phase I proof-of-concept study first demonstrated the ability of immuno-PET to discriminate between clear-cell RCC (ccRCC) and non-ccRCC, utilizing a chimeric monoclonal antibody to carbonic anhydrase IX (cG250, girentuximab) labeled with ¹²⁴I (¹²⁴I-girentuximab PET); the study examined patients with renal masses who subsequently underwent standard surgical resection. A follow-up phase III multicenter trial confirmed that ¹²⁴I-cG250-PET can accurately and noninvasively identify ccRCC with high sensitivity (86%), specificity (87%), and positive predictive value (95%). In the challenge to appropriately match treatment of an incidentally identified SRM to its biological potential, this highly accurate and histologically specific molecular imaging modality demonstrates the ability of imaging to provide clinically important preoperative diagnostic information, which can result in optimal and personalized therapy.

Phase 1 radioimmunotherapy study with lutetium 177-labeled anti-carbonic anhydrase IX monoclonal antibody girentuximab in patients with advanced renal cell carcinoma

BACKGROUND

Patients with metastatic clear cell renal cell carcinoma (ccRCC) have a dismal prognosis. Therefore, new and less toxic treatments are needed.

OBJECTIVE

We determined the maximum tolerated dose (MTD) and potential therapeutic efficacy of multiple infusions of lutetium 177 ((177)Lu)-girentuximab (cG250) on various dose levels in a phase 1 trial in patients with progressive metastasized ccRCC.

DESIGN, SETTING, AND PARTICIPANTS

In this uncontrolled case series in 23 patients with progressive ccRCC metastases, cG250 accumulation was verified by diagnostic indium 111-cG250 imaging. Patients then received a high-activity dose of (177)Lu-cG250.

INTERVENTION

Groups of three patients received (177)Lu-cG250, starting at a dose level of 1110 MBq/m(2)(177)Lu-cG250, with dose increments of 370 MBq/m(2) per group. In the absence of persistent toxicity, progressive disease, and accelerated blood clearance, patients were eligible for retreatment after 3 mo with 75% of the previous activity dose. Patients could receive a total of three treatment cycles.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Determination of the MTD was the primary and therapeutic efficacy was the secondary outcome measurement of the study.

RESULTS AND LIMITATIONS

The MTD was 2405 MBq/m(2) because higher doses resulted in dose-limiting myelotoxicity. Some patients received second (13 of 23 [56%]) and third (4 of 23 [17%]) treatment cycles. Most patients (17 of 23 [74%]) demonstrated stable disease 3 mo after the first treatment, and one patient showed a partial response that lasted for 9 mo. Mean growth of target tumor lesions was reduced from 40.4% (95% confidence interval [CI], ± 17.0) during the last 3 mo before study entry to 5.5% (95% CI, ± 5.3; p<0.001) at 3 mo after the first treatment cycle. No major nonhematologic side effects were observed.

CONCLUSIONS

(177)Lu-cG250 radioimmunotherapy in metastatic ccRCC patients is well tolerated at an activity dose level as high as 2405 MBq/m(2) (MTD). Radioimmunotherapy with (177)Lu-cG250 may stabilize previously progressive metastatic ccRCC.

Multimodal imaging and detection strategy with 124 I-labeled chimeric monoclonal antibody cG250 for accurate localization and confirmation of extent of disease during laparoscopic and open surgical resection of clear cell renal cell carcinoma

Renal cell carcinoma (RCC) accounts for approximately 85% to 90% of all primary kidney malignancies, with clear cell RCC (ccRCC) constituting approximately 70% to 85% of all RCCs. This study describes an innovative multimodal imaging and detection strategy that uses ¹²⁴I-labeled chimeric monoclonal antibody G250 (¹²⁴I-cG250) for accurate preoperative and intraoperative localization and confirmation of extent of disease for both laparoscopic and open surgical resection of ccRCC. Two cases presented herein highlight how this technology can potentially guide complete surgical resection and confirm complete removal of all diseased tissues. This innovative ¹²⁴I-cG250 (ie, ¹²⁴I-girentuximab) multimodal imaging and detection approach, which would be clinically very useful to urologic surgeons, urologic medical oncologists, nuclear medicine physicians, radiologists, and pathologists who are involved in the care of ccRCC patients, holds great potential for improving the diagnostic accuracy, operative planning and approach, verification of disease resection, and monitoring for evidence of disease recurrence in ccRCC patients.

Clinical radioimmunotherapy--the role of radiobiology

Conventional external-beam radiation therapy is dedicated to the treatment of localized disease, whereas radioimmunotherapy represents an innovative tool for the treatment of local or diffuse tumors. Radioimmunotherapy involves the administration of radiolabeled monoclonal antibodies that are directed specifically against tumor-associated antigens or against the tumor microenvironment. Although many tumor-associated antigens have been identified as possible targets for radioimmunotherapy of patients with hematological or solid tumors, clinical success has so far been achieved mostly with radiolabeled antibodies against CD20 ((131)I-tositumomab and (90)Y-ibritumomab tiuxetan) for the treatment of lymphoma. In this Review, we provide an update on the current challenges aimed to improve the efficacy of radioimmunotherapy and discuss the main radiobiological issues associated with clinical radioimmunotherapy.

Immune responses to transgene and retroviral vector in patients treated with ex vivo-engineered T cells

Adoptive transfer of immune effector cells that are gene modified by retroviral transduction to express tumor-specific receptors constitutes an attractive approach to treat cancer. In patients with metastatic renal cell carcinoma, we performed a study with autologous T cells genetically retargeted with a chimeric antibody receptor (CAR) directed toward carbonic anhydrase IX (CAIX), an antigen highly expressed in renal cell carcinoma. In the majority of patients, we observed distinct humoral and/or cellular anti-CAIX-CAR T-cell immune responses in combination with a limited peripheral persistence of transferred CAIX-CAR T cells in the majority of patients. Humoral immune responses were anti-idiotypic in nature and neutralized CAIX-CAR-mediated T-cell function. Cellular anti-CAIX-CAR immune responses were directed to the complementarity-determining and framework regions of the CAR variable domains. In addition, 2 patients developed immunity directed against presumed retroviral vector epitopes. Here, we document the novel feature that therapeutic cells, which were ex vivo engineered by means of transduction with a minimal γ-retroviral vector, do express immunogenic vector-encoded epitopes, which might compromise persistence of these cells. These observations may constitute a critical concern for clinical ex vivo γ-retroviral gene transduction in general and CAR-retargeted T-cell therapy in particular, and underscore the need to attenuate the immunogenicity of both transgene and vector.

Carbonic anhydrase 9 in clear cell renal cell carcinoma: a marker for diagnosis, prognosis and treatment

Carbonic anhydrase 9 (CA9) is a transmembrane member of the carbonic anhydrase family. It catalyses the reversible hydration of carbon dioxide into bicarbonate and a proton, thus enabling tumour cells to maintain a neutral pH despite an acidic microenvironment. CA9 is not expressed in healthy renal tissue but is expressed in most clear cell renal cell carcinomas (CCRCC) through HIF-1α accumulation driven by hypoxia and inactivation of the VHL gene. CA9 expression can be detected in the tumour by immunohistochemistry (IHC), in blood and tissue by ELISA assay and RT-PCR. It has a 100% diagnostic specificity in solid renal tumours, while ELISA assays on aspiration fluids may help in atypical cysts. Blood-based assays, ELISA for CA9 antigen and RT-PCR for CA9 mRNA are promising for the prognosis and follow-up of localised CCRCC. In metastatic disease, high CA9 expression by IHC was reported to be a powerful prognostic marker with better survival and sensitivity to IL-2, but this is still debated. Almost no data are currently available on the association of CA9 expression and outcome to targeted drugs. The prognostic value of CA9 in CCRCC could be explained by the frequent VHL gene inactivation driving an early activation of the HIF pathway. The poorer prognosis associated with low CA9 expressing tumours could be due to the simultaneous overexpression of EGFR contributing to the activation of AkT and mTOR pathways. Targeting CA9 by inhibitors, radioimmunotherapy, monoclonal antibodies or vaccination is promising and offers new avenues for clinical research.

'Image and treat': an individualized approach to urological tumors

PURPOSE OF REVIEW

The current treatment options for advanced urologic cancers demonstrate limited efficacy. To obtain optimal clinical results, there is a need for new, individualized, therapeutic strategies, which have only recently been applied to these malignancies. Nuclear medicine plays an important role in establishing imaging biomarkers necessary for personalized medicine. This review focuses on the current status of the 'image and treat' approach combining molecular imaging with targeted radionuclide therapy of urological malignancies

RECENT FINDINGS

Tumor-specific targets in uro-oncology are showing promising results for development of personalized therapy using positron emission tomography/computed tomography (PET/CT) molecular imaging and radioimmunotherapy. The antibody cG250, which binds to carbonic anhydrase IX, is being evaluated as a radiolabeled imaging and therapeutic agent in clear-cell renal cell carcinoma. I-cG250 PET/CT has demonstrated excellent targeting of clear-cell renal cell carcinoma. Prostate-specific membrane antigen is a promising target for both PET/CT and radioimmunotherapy of prostate cancer. HER2 may be another potential target in bladder and prostate cancer.

SUMMARY

Tumor-specific targets and biomarkers are being studied for PET/CT and radioimmunotherapy. This may lead to development of new therapeutic strategies. However, considerable investment in new research will be required for personalized medicine to be routinely used in uro-oncology.

Highlights of the annual congress of the European Association of Nuclear Medicine, Copenhagen 2007

INTRODUCTION

The Annual Congress of the European Association of Nuclear Medicine took place in Copenhagen on October 13-17, 2007. The event is the major scientific and professional effort in the field of nuclear medicine in Europe. The most important developments in the fields of instrumentation, radionuclide production, radiochemistry, radiotherapy, as well as the clinical imaging fields of neurology, cardiology, oncology, and general sciences were reported.

OBJECTIVE

This paper emphasizes the major findings and trends at this important gathering. This review is, however, only a brief summary of the large amount of data discussed.

Antibody therapy in renal cell carcinoma

The treatment of metastasized renal cell carcinoma (RCC) still represents a formidable challenge, despite the development of small molecule, tyrosine kinase inhibitors (TKI) that have made a major impact on the disease. Although the percentage of patients achieving a partial response or stabilization of disease has been impressive, these effects are mostly non-durable. Additionally, drug-related side effects can be quite severe. Alternative treatment modalities might be monoclonal antibodies (mAbs). mAbs against RCC-associated antigens have been developed and have shown promise. Additionally, current efforts focus on Bevacizumab that recognizes vascular endothelial growth factor (VEGF). VEGF overexpression in RCC provides the opportunity to inhibit this proangiogenic pathway. Also with Bevacizumab, promising results have been obtained, particularly in combination with other treatment modalities. It is likely that mAbs, either as single agents or in combination with other agents, may become useful additions to the armamentarium to diagnose and treat RCC.

Anti-cancer therapies targeting the tumor stroma

For anti-tumor therapy different strategies have been employed, e.g., radiotherapy, chemotherapy, or immunotherapy. Notably, these approaches do not only address the tumor cells themselves, but also the tumor stroma cells, e.g., endothelial cells, fibroblasts, and macrophages. This is of advantage, since these cells actively contribute to the proliferative and invasive behavior of the tumor cells via secretion of growth factors, angiogenic factors, cytokines, and proteolytic enzymes. In addition, tumor stroma cells take part in immune evasion mechanisms of cancer. Thus, approaches targeting the tumor stroma attract increasing attention as anti-cancer therapy. Several molecules including growth factors (e.g., VEGF, CTGF), growth factor receptors (CD105, VEGFRs), adhesion molecules (alphavbeta3 integrin), and enzymes (CAIX, FAPalpha, MMPs, PSMA, uPA) are induced or upregulated in the tumor microenvironment which are otherwise characterized by a restricted expression pattern in differentiated tissues. Consequently, these molecules can be targeted by inhibitors as well as by active and passive immunotherapy to treat cancer. Here we discuss the results of these approaches tested in preclinical models and clinical trials.

Radiolabeled antibodies in renal cell carcinoma

Renal cell carcinoma (RCC) is a radio- and chemotherapy resistant tumor, which has a very high morbidity and mortality when metastasized. The current treatment options demonstrate limited efficacy and severe side-effects. Therefore, there is a need for new therapeutic strategies for RCC. As for other malignancies, monoclonal antibodies (mAbs) targeting tumor-associated antigens have been developed for RCC. One of these, mAb G250, targets the MN/CAIX/G250 antigen, which is ubiquitously expressed in clear cell RCC (ccRCC). ccRCC is the most common form of RCC with a prevalence of 80%. Expression of G250 in normal tissue is restricted to the gastrointestinal mucosa and related structures, thereby making it a suitable candidate for targeting ccRCC. In several clinical studies the efficient accumulation of mAb G250 in ccRCC has been demonstrated, resulting in high contrast images. G250-imaging could prove to be a valuable tool in diagnosing metastases in patients with a G250-antigen positive primary tumor and/or in the differential diagnosis of suspect kidney lesions. Furthermore, the therapeutic efficacy of radiolabeled G250 has been investigated in a series of studies. Thus far, most efforts have been devoted to G250 labeled with high doses of ¹³¹I. Other radionuclides which may enhance the therapeutic index of this radiolabeled mAb are currently under investigation. In our institution, an activity dose escalation study is currently ongoing to investigate the therapeutic potential of ¹⁷⁷Lu-labeled G250 in metastatic ccRCC patients. In this review, the current status of the diagnostic and therapeutic properties of radiolabeled antibodies in RCC is described.

Targeted therapy in nuclear medicine—current status and future prospects

In recent years, a number of new developments in targeted therapies using radiolabeled compounds have emerged. New developments and insights in radioiodine treatment of thyroid cancer, treatment of lymphoma and solid tumors with radiolabeled monoclonal antibodies (mAbs), the developments in the application of radiolabeled small receptor-specific molecules such as meta-iodobenzylguanidine and peptides and the position of locoregional treatment in malignant involvement of the liver are reviewed. The introduction of recombinant human thyroid-stimulating hormone and the possibility to enhance iodine uptake with retinoids has changed the radioiodine treatment protocol of patients with thyroid cancer. Introduction of radiolabeled mAbs has provided additional treatment options in patients with malignant lymphoma, while a similar approach proves to be cumbersome in patients with solid tumors. With radiolabeled small molecules that target specific receptors on tumor cells, high radiation doses can be directed to tumors in patients with disseminated disease. Radiolabeled somatostatin derivatives for the treatment of neuroendocrine tumors are the role model for this approach. Locoregional treatment with radiopharmaceuticals of patients with hepatocellular carcinoma or metastases to the liver may be used in inoperable cases, but may also be of benefit in a neo-adjuvant or adjuvant setting. Significant developments in the application of targeted radionuclide therapy have taken place. New treatment modalities have been introduced in the clinic. The concept of combining therapeutic radiopharmaceuticals with other treatment modalities is more extensively explored.

Percutaneous ultrasound-guided radiofrequency ablation for kidney tumors in patients with surgical risk

OBJECTIVE

The aim of this study was to describe our experience with percutaneous ultrasound-guided radiofrequency ablation of kidney tumors.

METHODS

From July 2002 to August 2005, 45 radiofrequency ablations (RFA) in 42 selected patients with kidney tumor were performed. The patients had either contraindications to surgery procedures or had a solitary kidney. The average tumor size was 37.5 mm (range, 18-59 mm) with the mean age of 68 years (range, 28-83 years). RFA were performed based on radiographic findings. Needle biopsy was made only twice. Monopolar Cool-tip Tyco or bipolar Celon Olympus radiofrequency devices were used. The procedure was performed under conscious sedation with local anesthesia. Treatment efficacy was assessed by computed tomography and by Doppler ultrasound. The absence of contrast enhancement on computed tomography was considered to be a successful treatment.

RESULTS

The average follow up was 14 months (range, 3-36 months). In 42 tumors (93%), total absence of contrast enhancement was obtained after the initial RFA and in three tumors (7%) after the second ablation session. There were no complications following 41 procedures, including all ablations in small (<35 mm) renal masses. In four procedures, minor complications were observed. All patients are alive. There has been no need for chronic hemodialysis and, until now, we have not observed any local recurrences with the exception of one metastasis to an ipsilateral adrenal gland.

CONCLUSIONS

RFA of kidney tumors is a promising alternative treatment which could be considered for patients who are not suitable for surgery.

Antibody-guided radiation therapy of cancer

Radioimmunotherapy (RIT) using radiolabeled monoclonal antibodies (MAbs) directed against tumor-associated antigens has evolved from an appealing concept to one of the standard treatment options for patients with non-Hodgkin's lymphoma (NHL). Inefficient localization of radiolabeled MAbs to nonhematological cancers due to various tumor-related factors, however, has refrained RIT from outgrowing the experimental stage in solid tumors. Still, small volume or minimal residual disease has been recognized as a potentially suitable target for radiolabeled antibodies. Several strategies are being explored aimed at improving the targeting of radiolabeled MAbs to solid tumors thus improving their therapeutic efficacy. In this review, a historical overview of the application of RIT is given and various aspects of the application of radiolabeled MAbs as anti-cancer agents are discussed. Finally, the clinical results of RIT of NHL, colorectal cancer, ovarian cancer, breast cancer, and renal cell cancer are reviewed.

Radioimmunotherapy with [131I]cG250 in patients with metastasized renal cell cancer: dosimetric analysis and immunologic response

PURPOSE

A study was designed to define the therapeutic efficacy, safety, and toxicity of two sequential high-dose treatments of radioimmunotherapy with [131I]cG250 in patients with metastasized renal cell carcinoma. Here, we report the dosimetric analysis and the relationship between the development of a human antichimeric antibody response and altered pharmacokinetics.

EXPERIMENTAL DESIGN

Patients (n = 29) with progressive metastatic renal cell carcinoma received a low dose (222 MBq) of [131I]cG250 for dosimetric analysis, followed by the first radioimmunotherapy with 2,220 MBq/m2 [131I]cG250 (n = 27) 1 week later. If no grade 4 hematologic toxicity was observed, a second low dose of [131I]cG250 (n = 20) was given 3 months later. Provided that no accelerated blood clearance was observed, a second radioimmunotherapy of [131I]cG250 was administered at an activity-dose level of 1,110 MBq/m2 (n = 3) or 1,665 MBq/m2 (n = 16). After each administration, whole-body images were obtained and the pharmacokinetics and the development of human antichimeric antibody responses were determined. Radiation-absorbed doses were calculated for whole body, red marrow, organs, and metastases.

RESULTS

No correlation was found between hematologic toxicity and radiation-absorbed dose to the whole body or bone marrow, nor administered activity (MBq and MBq/kg). The tumor-absorbed doses varied largely. An inverse relation between tumor size and radiation-absorbed dose was found. Most tumor lesions received <10 Gy, whereas only lesions <5 g absorbed >50 Gy. A relatively high number of patients developed a human antichimeric antibody response (8 of 27) with altered pharmacokinetics, hampering additional radioimmunotherapies in four of these patients.

CONCLUSIONS

Dosimetric analysis did not adequately predict the degree of bone marrow toxicity. When human antichimeric antibody developed, the rapid clearance of radioactivity from the blood and body prohibited further treatment. According to the calculated absorbed dose in metastatic lesions, future radioimmunotherapy studies with radiolabeled cG250 should aim at treatment of small-volume disease or treatment in an adjuvant setting.