A comparison between radioimmunotherapy and hyperthermic intraperitoneal chemotherapy for the treatment of peritoneal carcinomatosis of colonic origin in rats

Amplifying Curcumin's Antitumor Potential: A Heat-Driven Approach for Colorectal Cancer Treatment

Introduction

Peritoneal metastases from colorectal cancer (CRC) present a significant clinical challenge with poor prognosis, often unresponsive to systemic chemotherapy. Cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is a treatment approach for select patients. The use of curcumin, a natural compound with antitumor properties, in HIPEC is of interest due to its lower side effects compared to conventional drugs and potential for increased efficacy through direct delivery to the peritoneal cavity.

Methods

An in vitro hyperthermic model was developed to simulate clinical HIPEC conditions. Three colon cancer cell lines (SK-CO-1, COLO205, SNU-C1) representing different genetic mutations (p53, KRAS, BRAF) were treated with either curcumin (25 µM) or mitomycin-C (1 µM) for 1, 2, or 3 hours. Post-treatment, cells were incubated at 37°C (normothermia) or 42°C (hyperthermia). Cell viability and proliferation were assessed at 24, 48 and 72 hours post-treatment using Annexin V/PI, MTT assay, trypan blue exclusion, and Hoffman microscopy.

Results

Hyperthermia significantly enhanced the antitumor efficacy of curcumin, evidenced by a two-fold reduction in cell viability compared to normothermia across all cell lines. In the SNU-C1 cell line, which harbors a p53 mutation, mitomycin-C failed to significantly impact cell viability, unlike curcumin, suggesting mutation-specific differences in treatment response.

Discussion

The findings indicate that hyperthermia augments the antitumor effects of curcumin in vitro, supporting the hypothesis that curcumin could be a more effective HIPEC agent than traditional drugs like mitomycin-C. Mutation-associated differences in response to treatments were observed, particularly in p53 mutant cells. While further studies are needed, these preliminary results suggest that curcumin in HIPEC could represent a novel therapeutic strategy for CRC patients with peritoneal metastases. This approach may offer improved outcomes with fewer side effects, particularly in genetically distinct CRC subtypes.

Treating colorectal peritoneal metastases with an injectable cytostatic loaded supramolecular hydrogel in a rodent animal model

Patients with peritoneal metastases (PM) of colorectal cancer have a very poor outcome. Intraperitoneal delivery of chemotherapy is the preferred route for PM treatment. The main limitation of the treatment options is the short residence time of the cytostatic, with subsequent short exposure of the cancer cells. To address this, a supramolecular hydrogel has been developed that allows both local and slow release of its encapsulated drug, mitomycin C (MMC) or cholesterol-conjugated MMC (cMMC), respectively. This experimental study investigates if drug delivery using this hydrogel improves the therapeutic efficacy against PM. PM was induced in WAG/Rij rats (n = 72) by intraperitoneally injecting syngeneic colon carcinoma cells (CC531) expressing luciferase. After seven days, animals received a single intraperitoneal injection with saline (n = 8), unloaded hydrogel (n = 12), free MMC (n = 13), free cMMC (n = 13), MMC-loaded hydrogel (n = 13), or cMMC-loaded hydrogel (n = 13). Primary outcome was overall survival with a maximum follow-up of 120 days. Intraperitoneal tumor development was non-invasive monitored via bioluminescence imaging. Sixty-one rats successfully underwent all study procedures and were included to assess therapeutic efficacy. After 120 days, the overall survival in the MMC-loaded hydrogel and free MMC group was 78% and 38%, respectively. A trend toward significance was found when comparing the survival curves of the MMC-loaded hydrogel and free MMC (p = 0.087). No survival benefit was found for the cMMC-loaded hydrogel compared to free cMMC. Treating PM with our MMC-loaded hydrogel, exhibiting prolonged MMC exposure, seems effective in improving survival compared to treatment with free MMC.

Repeat Cytoreductive Surgery with Hyperthermic Intraperitoneal Chemotherapy for Cancers with Peritoneal Metastasis: A 30-year Institutional Experience

BACKGROUND

Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) improves survival in abdominal cancer patients with metastatic disease limited to the peritoneal cavity. Patients are increasingly being offered repeat CRS-HIPECs for peritoneal recurrence. However, in this rare clinical scenario, the survival benefit of performing repeat CRS-HIPEC operations remains unclear.

METHODS

A retrospective review of the CRS-HIPEC database at Wake Forest Baptist Medical Center was performed over a 30-year timespan. From 1547 patients with appendix cancers, colorectal cancers, mesotheliomas, and other miscellaneous cancers, 156 received more than one CRS-HIPEC. Kaplan-Meier survival analysis was performed using overall survival (OS) from the time of surgery as the primary endpoint. Multi-variable Cox proportional hazards regression modelling was performed on pertinent clinical variables.

RESULTS

Patients who received multiple CRS-HIPECs had significantly better median OS (10.7 years) versus those who received one CRS-HIPEC (2.5 years), with appendix cancers faring best (12.9 years). Resection status R2a or better was achieved in 76.4% of repeat CRS-HIPECs. There were no significant changes in complication rates after repeat CRS-HIPEC. On multivariate analysis of repeat CRS-HIPEC, patients with appendix and colorectal cancers, heart disease, and poor functional status were independently associated with poor OS. Factors not independently associated with OS were age, sex, body mass index, race, diabetes, lung disease, smoking history, and systemic chemotherapy between CRS-HIPECs.

CONCLUSIONS

Performing multiple CRS-HIPEC operations on appropriate surgical candidates may significantly prolong survival. Appendix cancers derived the greatest benefit. Satisfactory resection margins and complication rates are comparable to first cases and achievable in repeat CRS-HIPEC procedures.

Establishment of an Experimental System for Intraperitoneal Chemotherapy in a Rat Model

AIM

To establish an experimental system for comparing different methods of intraperitoneal chemotherapy in a rat model.

MATERIALS AND METHODS

We used six-week-old Sprague-Dawley rats, and created an early postoperative intraperitoneal chemotherapy (EPIC) system using 18-gauge syringes and evacuators, and a hyperthermic intraperitoneal chemotherapy (HIPEC) system using two peristaltic pumps which controlled the flow rate and temperature. Pressurized intraperitoneal aerosol chemotherapy (PIPAC) was achieved using a nozzle for dispersing aerosols at a flow rate up to 41.5 ml/min. The distribution and intensity of 0.2% trypan blue dye was compared among three methods.

RESULTS

The distribution was limited and the intensity was weak after EPIC, and the dye stained moderately in gravity-dependent regions after HIPEC. On the other hand, the distribution was the most comprehensive, and the intensity was the greatest after PIPAC.

CONCLUSION

This experimental system in a rat model may reflect the comparative effect among EPIC, HIPEC and PIPAC in humans.

Effect and safety of intraoperative intraperitoneal chemotherapy on patients suffering from colorectal cancer

Background

Colorectal cancer (CRC), the third most commonly diagnosed malignant carcinoma and the third most common cause of carcinoma-related mortality, continues to be a major international health problem. And approximately 33% of patients suffer from recurrence after radical surgery. Free malignant cell implanting in the peritoneum is generally accepted as one of the main reasons of such outcome. We did this present clinical study with the aim of evaluating the effects and safety of intraoperative intraperitoneal chemotherapy (IOC) on patients suffering from colorectal cancer, with hoping to find a novel, effective, and available approach to deal with malignant cell implanting during surgeries.

Methods

In total, 391 patients who went through colorectal radical surgery were considered eligible between June 1, 2017, and December 31, 2018. 220 patients were treated with surgery without IOC, while other 171 patients received surgery plus IOC. Clinical characteristics, operative findings, postoperative short-term outcomes, disease-free survival (DFS), and overall survival (OS) were compared between these above 2 groups in the selected population.

Result

The present research included 391 patients (251 men and 140 women) who underwent surgery without IOC (n = 171) or surgery plus IOC (n = 220), with a mean (SD) age of 60.4 (9.7) years in the surgery without IOC group and 60.6 (8.7) in the surgery plus IOC group (P=.85). No significant differences were witnessed between the two groups in surgery-related information and postoperative complications. It is worth noting that IOC independent of other factors was associated with a favor prognosis in CRC patients with stage II/III (HR 0.50, 95%CI 0.30–0.82, P=.006). Moreover, for patients with stage II colorectal carcinoma, DFS did not differ between two groups (P=.553, Kaplan-Meier log-rank), and OS was no exception. In stage III CRC patients, the estimated DFS rate for patients receiving IOC was 82.2% and patients without IOC was 66.4% after 3 years, which demonstrated that IOC was associated with a favorable prognosis in stage III patients (P=.012, Kaplan-Meier log-rank). Furthermore, the differences were still remained between the two groups when considering the influence about postoperative chemotherapy (P=.014, Kaplan-Meier log-rank). IOC can also significantly improve patients’ overall survival whether they get treatment with POC (P=.006, Kaplan-Meier log-rank; P=.025, Kaplan-Meier log-rank).

Conclusions

In the present study, we have found that surgery plus IOC generated a favorable prognosis for stage III CRC patients but not stage II without any side-effects when the dosage of lobaplatin was 0.1g/L. As a new, safe, and simple procedure, IOC therapy is easily performed—and does not require any special devices or techniques. Thus, IOC is a promising and exciting therapeutic strategy for patients with CRC.

Laparoscopic Hyperthermic Intraperitoneal Perfusion Chemotherapy for Patients With Malignant Ascites Secondary to Unresectable Gastric Cancer

BACKGROUND

To compare the efficacy of 3 chemotherapeutic combinations for laparoscopic hyperthermic intraperitoneal perfusion chemotherapy (HIPPC) in the treatment of malignant ascites secondary to unresectable gastric cancer (GC).

MATERIALS AND METHODS

From January 2010 to December 2013, 38 GC patients were randomly divided into 3 groups and treated by laparoscopic HIPPC with 1 of the 3 following chemotherapy combinations: raltitrexed (Ra) with oxaliplatin (L-OHP), Ra with cisplatin (DDP), and Ra with mitomycin C (MMC). Perioperative complications, patients' quality of life, and survival were recorded and compared among the 3 groups.

RESULTS

The intraoperative course was successful in all patients, and no perioperative death or complication related to laparoscopic HIPPC was documented. The median follow-up period was 9 months and the median survival was 7.5 months for all patients. Patients in the Ra/L-OHP group had a median survival of 8.7 months, the Ra/DDP group had a median survival of 5.6 months, and the Ra/MMC group had a median survival of 7.5 months. Patients' median survival in the Ra/L-OHP group and Ra/MMC group is significantly longer than Ra/DDP group (P<0.05). No significant difference was found in total remission rate of ascites, increase in the Karnofsky performance scale, and incidence rate of port-site metastases among the 3 groups.

CONCLUSIONS

Laparoscopy-assisted HIPPC provide modest yet encouraging efficacy for malignant ascites secondary to disseminated GC. Our preliminary data indicate that the chemotherapeutical combination of Ra/L-OHP and Ra/MMC might be more beneficial compared with Ra/DDP in terms of patients' survival.

The Effect of Pancreatoduodenectomy Plus Intraperitoneal Hyperthermic Perfusion on Resectable Pancreatic Head Cancer: Cohort Study

BACKGROUND

Intraperitoneal hyperthermic perfusion (IPHP) has achieved positive results in treating various abdominal cancers but infrequently reported in resectable pancreatic head cancer. This study was designed to explore the safety and efficacy of pancreaticoduodenectomy plus intraperitoneal hyperthermic perfusion (PD + IPHP) in patients with pancreatic cancer.

METHODS

Data of pancreatic cancer patients undergoing pancreaticoduodenectomy were retrospectively analyzed, including PD + IPHP (n = 28) and PD group (n = 29). IPHP was performed during surgery, on postoperative day (POD) 2, and POD 4 with normal saline as the perfusion solution. Complications and overall survival of these patients were observed and recorded.

RESULTS

There was no significant difference in the incidence of major postoperative complications between PD + IPHP group and PD group. The median overall survival (OS) time of the PD + IPHP group was 19.0 months, the 1-year survival rate was 82.35%, and the 2-year survival rate was 49.41%. The median OS time of the PD group was 13.0 months, the 1-year survival rate was 51.00%, and the 2-year survival rate was 27.33% (Log-rank, P = 0.030; Breslow, P = 0.039). Cox proportional risk model showed that IPHP was an independent factor to improve survival outcomes of these patients (hazard ratio = 0.363, 95% confidence interval: 0.14-0.94; P = 0.038).

CONCLUSIONS

Intraperitoneal hyperthermic perfusion significantly improves the survival outcomes of pancreatic head cancer patients undergoing PD and does not bring extra risks of complications.

Spectral photon-counting CT imaging of colorectal peritoneal metastases: initial experience in rats

Computed tomography imaging plays a major role in the preoperative assessment of tumor burden by providing an accurate mapping of the distribution of peritoneal metastases (PM). Spectral Photon Counting Computed Tomography (SPCCT) is an innovative imaging modality that could overcome the current limitations of conventional CT, offering not only better spatial resolution but also better contrast resolution by allowing the discrimination of multiple contrast agents. Based on this capability, we tested the feasibility of SPCCT in the detection of PM at different time of tumor growth in 16 rats inoculated with CC531 cells using dual-contrast injection protocols in two compartments (i.e. intravenous iodine and intraperitoneal gadolinium or the reverse protocol), compared to surgery. For all peritoneal regions and for both protocols, sensitivity was 69%, specificity was 100% and accuracy was 80%, and the correlation with surgical exploration was strong (p = 0.97; p = 0.0001). No significant difference was found in terms of diagnostic performance, quality of peritoneal opacification or diagnostic quality between the 2 injection protocols. We also showed poor vascularization of peritoneal metastases by measuring low concentrations of contrast agent in the largest lesions using SPCCT, which was confirmed by immunohistochemical analyses. In conclusion, SPCCT using dual-contrast agent injection protocols in 2 compartments is a promising imaging modality to assess the extent of PM in a rat model.

Hyperthermic intraperitoneal chemotherapy with recombinant mutant human TNF-α and raltitrexed in mice with colorectal-peritoneal carcinomatosis

Peritoneum is one of the most common metastatic sites of colorectal cancer (CRC). It has been reported that cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy (HIPEC) prolongs the lifespan of patients with peritoneal carcinomatosis of colorectal origin (CRC-PC), while the drugs used for HIPEC are limited. We investigated the application of recombinant mutant human tumor necrosis factor-α (rmhTNF) combined with raltitrexed in the HIPEC treatment in a mice model with CRC-PC. In vitro, we detected the cytotoxicity and apoptosis of human colorectal cancer cells by 3–(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, Western blot, and TdT-mediated dUTP Nick End Labeling (TUNEL) assay. In vivo, we established xenograft models of CRC-PC and assessed the antitumor effect by in vivo imaging, peritoneal cancer index scoring, and TUNEL assay. The results showed that the combination of rmhTNF and raltitrexed under hyperthermia with a temperature of 42°C inhibited the growth of colorectal cancer cells significantly in vitro, and after HIPEC treatments with rmhTNF and raltitrexed, peritoneal tumor growth was prohibited in vivo. Our findings about the efficacy of rmhTNF and raltitrexed used for HIPEC to treat CRC-PC will provide experimental data and basis for their potential clinical application.

Impact statement

Colorectal peritoneal carcinomatosis exhibits poor prognosis and presents a treatment challenge. At present, the main treatment is surgery, supplemented by hyperthermic intraperitoneal chemotherapy (HIPEC), but the drugs used for HIPEC are limited. Our study found that the combination of recombinant mutant human TNF-α (rmhTNF) and raltitrexed (RTX) under hyperthermia with a temperature of 42°C had antitumor effect both in vitro and vivo. The findings will provide experimental data and basis for the potential clinical application of rmhTNF and RTX, which might offer patients a new choice of therapeutic drugs.

Intraperitoneal mitomycin C improves survival compared to cytoreductive surgery alone in an experimental model of high-grade pseudomyxoma peritonei

Pseudomyxoma peritonei (PMP) is a rare cancer commonly originating from appendiceal neoplasms that presents with mucinous tumor spread in the peritoneal cavity. Patients with PMP are treated with curative intent by cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). The value of adding HIPEC to CRS has not been proven in randomized trials, and the objective of this study was to investigate the efficacy of intraperitoneal mitomycin C (MMC) and regional hyperthermia as components of this complex treatment. Xenograft tissue established from a patient with histologically high-grade PMP with signet ring cell differentiation was implanted intraperitoneally in 65 athymic nude male rats and the animals were stratified into three treatment groups; the cytoreductive surgery group (CRSG, CRS only), the normothermic group (NG, CRS and intraperitoneal chemotherapy perfusion (IPEC) with MMC at 35 ºC), and the hyperthermic group (HG, CRS and IPEC at 41 ºC). The main endpoints were survival and tumor weight at autopsy. Adequate imitation of the clinical setting and treatment approach was achieved. The median survival was 31 days in the CRSG, 60 days in NG and 67 days in HG. The median tumor weights at autopsy were 34 g in CRSG, 23 g NG and 20 g in HG. In conclusion, the addition of IPEC with MMC after CRS doubled the survival time and reduced tumor growth compared to CRS alone. Adding regional hyperthermia resulted in a modest improvement of treatment outcome.

Pretargeted radioimmunotherapy and SPECT imaging of peritoneal carcinomatosis using bioorthogonal click chemistry: probe selection and first proof-of-concept

Rationale: Pretargeted radioimmunotherapy (PRIT) based upon bioorthogonal click chemistry has been investigated for the first time in the context of peritoneal carcinomatosis using a CEA-targeting 35A7 mAb bearing trans-cyclooctene (TCO) moieties and several ¹⁷⁷Lu-labeled tetrazine (Tz) radioligands. Starting from three Tz probes containing PEG linkers of varying lengths between the DOTA and Tz groups (i.e. PEG_n = 3, 7, or 11, respectively, for Tz-1, Tz-2, and Tz-3), we selected [¹⁷⁷Lu]Lu-Tz-2 as the most appropriate for pretargeted SPECT imaging and demonstrated its efficacy in tumor growth control. Methods: An orthotopic model of peritoneal carcinomatosis (PC) was obtained following the intraperitoneal (i.p.) injection of A431-CEA-Luc cells in nude mice. Tumor growth was assessed using bioluminescence imaging. Anti-CEA 35A7 mAb was grafted with 2-3 TCO per immunoglobulin. Pretargeted SPECT imaging and biodistribution experiments were performed to quantify the activity concentrations of [¹⁷⁷Lu]Lu-Tz-1-3 in tumors and non-target organs to determine the optimal Tz probe for the PRIT of PC. Results: The pharmacokinetic profiles of [¹⁷⁷Lu]Lu-Tz-1-3 alone were determined using both SPECT imaging and biodistribution experiments. These data revealed that [¹⁷⁷Lu]Lu-Tz-1 was cleared via both the renal and hepatic systems, while [¹⁷⁷Lu]Lu-Tz-2 and [¹⁷⁷Lu]Lu-Tz-3 were predominantly excreted via the renal system. In addition, these results illuminated that the longer the PEG linker, the more rapidly the Tz radioligand was cleared from the peritoneal cavity. The absorbed radiation dose corresponding to pretargeting with 35A7-TCO followed 24 h later by [¹⁷⁷Lu]Lu-Tz-1-4 was higher for tumors following the administration of [¹⁷⁷Lu]Lu-Tz-2 (i.e. 0.59 Gy/MBq) compared to either [¹⁷⁷Lu]Lu-Tz-1 (i.e. 0.25 Gy/MBq) and [¹⁷⁷Lu]Lu-Tz-3 (i.e. 0.18 Gy/MBq). In a longitudinal PRIT study, we showed that the i.p. injection of 40 MBq of [¹⁷⁷Lu]Lu-Tz-2 24 hours after the systemic administration of 35A7-TCO significantly slowed tumor growth compared to control mice receiving only saline or 40 MBq of [¹⁷⁷Lu]Lu-Tz-2 alone. Ex vivo measurement of the peritoneal carcinomatosis index (PCI) confirmed that PRIT significantly reduced tumor growth (PCI = 15.5 ± 2.3 after PRIT vs 30.0 ± 2.3 and 30.8 ± 1.4 for the NaCl and [¹⁷⁷Lu]Lu-Tz-2 alone groups, respectively). Conclusion: Our results clearly demonstrate the impact of the length of PEG linkers upon the biodistribution profiles of ¹⁷⁷Lu-labeled Tz radioligands. Furthermore, we demonstrated for the first time the possibility of using bioorthogonal chemistry for both the pretargeted SPECT and PRIT of peritoneal carcinomatosis.

Body surface area-based versus concentration-based intraperitoneal perioperative chemotherapy in a rat model of colorectal peritoneal surface malignancy: pharmacologic guidance towards standardization

Worldwide, cytoreductive surgery (CRS) and hyperthermic intraperitoneal perioperative chemotherapy (HIPEC) are used in current clinical practice for colorectal peritoneal surface malignancy (PSM) treatment. Although, there is an acknowledged standardization regarding the CRS, we are still lacking a much-needed standardization amongst the various intraperitoneal (IP) chemotherapy protocols, including the HIPEC dosing regimen. We should rely on pharmacologic evidence building towards such a standardization. The current IP chemotherapy dosing regimens can be divided into body surface area (BSA)-based and concentration-based protocols. A preclinical animal study was designed to evaluate pharmacologic advantage (PA), efficacy and survival. WAG/Rij rats were IP injected with the rat colonic carcinoma cell line CC-531. Animals were randomized into three groups: CRS alone or CRS combined with oxaliplatin-based HIPEC (either BSA- or concentration-based). There was no difference in PA between the two groups (p=0.283). Platinum concentration in the tumor nodule was significantly higher in the concentration-based group (p<0.001). Median survival did not differ between the treatment groups (p<0.250). This preclinical study, in contrast to previous thinking, clearly demonstrates that the PA does not provide any information about the true efficacy of the drug and emphasizes the importance of the tumor nodule as pharmacologic endpoint.

Murine Models of Intraperitoneal Perfusion for Disseminated Colorectal Cancer

BACKGROUND

Reproduction of the perfusion used in therapy (hyperthermic intraperitoneal chemotherapy) procedures preclinically represents a valuable asset for investigating new therapeutic agents that may improve patient outcomes. This article provides technical descriptions of our execution of closed and open "coliseum" abdominal perfusion techniques in a mouse model of peritoneal carcinomatosis of colorectal cancer.

MATERIALS AND METHODS

BALB/c mice presenting with disseminated colorectal cancer (CT26-luciferin cells) underwent 30-min perfusions mimicking either the closed perfusion or the coliseum perfusion technique. Disease burden was monitored by bioluminescence signaling using an in vivo imaging system. Perfusion circuits consisted of single inflow lines with either a single or dual outflow line.

RESULTS

Twelve mice presenting with disseminated disease underwent the closed perfusion technique. Surgical complications included perfusate leakage and organ constriction/suction into the outflow line(s). Nine mice underwent the coliseum perfusion technique with surgical debulking, using bipolar cauterization to remove tumors attached to the peritoneum. All mice survived the coliseum perfusion with limited intraoperative complications.

CONCLUSIONS

Fewer intraoperative complications were experienced with our coliseum perfusion technique than the closed perfusion. The methods described here can be used as a guideline for developing future perfusion murine models for investigating perfusion models useful for delivery of chemotherapy or other tumor-sensitization agents, including selective targeted agents, nanoparticles, and heat.

Antibody PEGylation in bioorthogonal pretargeting with trans-cyclooctene/tetrazine cycloaddition: in vitro and in vivo evaluation in colorectal cancer models

Bioorthogonal chemistry represents a challenging approach in pretargeted radioimmunotherapy (PRIT). We focus here on mAb modifications by grafting an increase amount of trans-cyclooctene (TCO) derivatives (0 to 30 equivalents with respect to mAb) bearing different polyethylene glycol (PEG) linkers between mAb and TCO (i.e. PEG₀ (1), PEG₄ (2) and PEG₁₂ (3)) and assessing their functionality. We used colorectal xenograft (HT29/Ts29.2) and peritoneal carcinomatosis (A431-CEA-Luc/35A7) as tumor cells/mAbs models and fluorescent tetrazines (TZ). MALDI-TOF MS shows that grafting with 2,3 increases significantly the number of TCO per mAb compared with no PEG. In vitro immunofluorescence showed that Ts29.2 and 35A7 labeling intensity is correlated with the number of TCO when using 1,3 while signals reach a maximum at 10 equivalents when using 2. Under 10 equivalents conditions, the capacity of resulting mAbs-1–3 for antigen recognition is similar when reported per grafted TCO and comparable to mAbs without TCO. In vivo, on both models, pretargeting with mAbs-2,3 followed by TZ injection induced a fluorescent signal two times lower than with mAbs-1. These findings suggest that while PEG linkers allow a better accessibility for TCO grafting, it might decrease the number of reactive TCO. In conclusion, mAb-1 represents the best candidate for PRIT.

Animal models of colorectal peritoneal metastasis

Colorectal cancer remains an important cause of mortality worldwide. The presence of peritoneal carcinomatosis (PC) causes significant symptoms and is notoriously difficult to treat. Therefore, informative preclinical research into the mechanisms and possible novel treatment options of colorectal PC is essential in order to improve the prognostic outlook in these patients. Several syngeneic and xenograft animal models of colorectal PC were established, studying a wide range of experimental procedures and substances. Regrettably, more sophisticated models such as those giving rise to spontaneous PC or involving genetically engineered mice are lacking. Here, we provide an overview of all reported colorectal PC animal models and briefly discuss their use, strengths, and limitations.

Therapeutic Efficacy of Alpha-RIT Using a (213)Bi-Anti-hCD138 Antibody in a Mouse Model of Ovarian Peritoneal Carcinomatosis

Purpose

Ovarian peritoneal carcinomatosis is a pathology for which effective cures are currently lacking. New research protocols seek to eradicate residual micrometastases following cytoreductive surgery by using hyperthermic intraperitoneal chemotherapy (HIPEC) or radioimmunotherapy (RIT). This study aims to first develop alpha-RIT using an anti-CD138 mAb radiolabeled with an alpha-emitter, bismuth-213 (²¹³Bi-B-B4) and HIPEC in a nude mouse model and second to compare and combine these techniques.

Material and methods

A murine model of postoperative ovarian peritoneal carcinomatosis was established. A pilot group of six mice received an intraperitoneal injection of luciferase-tagged SHIN-3 cells and bioluminescence was measured every day. Cytoreductive surgery was performed at day 14 (n = 4) and 29 (n = 2). Because the residual bioluminescence signal measured after surgery was equivalent to that obtained 3 days after the graft, HIPEC or alpha-RIT treatments were applied 3 days after the graft. Ten mice were treated by HIPEC with cisplatine (37.5 mg/mL), 11 with 7.4 MBq of ²¹³Bi-B-B4, seven with 11.1 MBq of ²¹³Bi-B-B4, and 10 mice were treated with the combined therapy (HIPEC + 7.4 MBq of ²¹³Bi-B-B4). Eleven mice received no treatment. Bioluminescence imaging and survival were assessed.

Results

Alpha-RIT 7.4 MBq and 11.1 MBq significantly improved survival (p = 0.0303 and p = 0.0070, respectively), whereas HIPEC and HIPEC + alpha-RIT treatments did not significantly ameliorate survival as compared to the control group.

Conclusion

Survival was significantly increased by alpha-RIT treatment in mice with peritoneal carcinomatosis of ovarian origin; however, HIPEC alone or in combination with alpha-RIT had no significant effect.

Intraperitoneal chemotherapy (IPC) for peritoneal carcinomatosis: review of animal models

The development of suitable animal models is essential to experimental research on intraperitoneal chemotherapy (IPC). This review of the English literature (MEDLINE) presents a detailed analysis of current animal models and gives recommendations for future experimental research. Special consideration should be given to cytotoxic drug dose and concentration, tumor models, and outcome parameters.

Comparison between internalizing anti-HER2 mAbs and non-internalizing anti-CEA mAbs in alpha-radioimmunotherapy of small volume peritoneal carcinomatosis using 212Pb

Background and Purpose

We assessed the contribution of antibody internalization in the efficacy and toxicity of intraperitoneal α-radioimmunotherapy (RIT) of small volume carcinomatosis using ²¹²Pb-labeled monoclonal antibodies (mAbs) that target HER2 (internalizing) or CEA (non-internalizing) receptors.

Materials and Methods

Athymic nude mice bearing 2–3 mm intraperitoneal tumor xenografts were intraperitoneally injected with similar activities (370, 740 and 1480 kBq; 37 MBq/mg) of ²¹²Pb-labeled 35A7 (anti-CEA), trastuzumab (anti-HER2) or PX (non-specific) mAbs, or with equivalent amounts of unlabeled mAbs, or with NaCl. Tumor volume was monitored by bioluminescence and survival was reported. Hematologic toxicity and body weight were assessed. Biodistribution of ²¹²Pb-labeled mAbs and absorbed dose-effect relationships using MIRD formalism were established.

Results

Transient hematological toxicity, as revealed by white blood cells and platelets numbering, was reported in mice treated with the highest activities of ²¹²Pb-labeled mAbs. The median survival (MS) was significantly higher in mice injected with 1.48 MBq of ²¹²Pb-35A7 (non-internalizing mAbs) (MS = 94 days) than in animals treated with the same activity of ²¹²Pb-PX mAbs or with NaCl (MS = 18 days). MS was even not reached after 130 days when follow-up was discontinued in mice treated with 1.48 MBq of ²¹²Pb-trastuzumab. The later efficacy was unexpected since final absorbed dose resulting from injection of 1.48 MBq, was higher for ²¹²Pb-35A7 (35.5 Gy) than for ²¹²Pb-trastuzumab (27.6 Gy). These results also highlight the lack of absorbed dose-effect relationship when mean absorbed dose was calculated using MIRD formalism and the requirement to perform small-scale dosimetry.

Conclusions

These data indicate that it might be an advantage of using internalizing anti-HER2 compared with non-internalizing anti-CEA ²¹²Pb-labeled mAbs in the therapy of small volume xenograft tumors. They support clinical investigations of ²¹²Pb-mAbs RIT as an adjuvant treatment after cytoreductive surgery in patients with peritoneal carcinomatosis.

Emerging trends for radioimmunotherapy in solid tumors

Due to its ability to target both known and occult lesions, radioimmunotherapy (RIT) is an attractive therapeutic modality for solid tumors. Poor tumor uptake and undesirable pharmacokinetics, however, have precluded the administration of radioimmunoconjugates at therapeutically relevant doses thereby limiting the clinical utility of RIT. In solid tumors, efficacy of RIT is further compromised by heterogeneities in blood flow, tumor stroma, expression of target antigens and radioresistance. As a result significant efforts have been invested toward developing strategies to overcome these impediments. Further, there is an emerging interest in exploiting short-range, high energy α-particle emitting radionuclides for the eradication of minimal residual and micrometastatic disease. As a result several modalities for localized therapy and models of minimal disease have been developed for preclinical evaluation. This review provides a brief update on the recent efforts toward improving the efficacy of RIT for solid tumors, and development of RIT strategies for minimal disease associated with solid tumors. Further, some of promising approaches to improve tumor targeting, which showed promise in the past, but have now been ignored are also discussed.

Multivariate comparison of B-ultrasound guided and laparoscopic continuous circulatory hyperthermic intraperitoneal perfusion chemotherapy for malignant ascites

OBJECTIVE

Clinical efficacy of B-ultrasound-guided and laparoscopy-assisted continuous hyperthermic intraperitoneal perfusion chemotherapy (CHIPC) for treatment of malignant ascites was investigated.

METHODS

Sixty-two patients with malignant ascites induced by ovarian or gastrointestinal cancers were randomly treated with B-ultrasound-guided CHIPC (therapeutic group) or laparoscopy-assisted CHIPC (control group) performed at the same center. Hospitalization costs and surgical duration were evaluated. Follow-up was conducted for 21 months with B-ultrasound or computed tomography at least once per month for assessment of ascites amount and tumor progression. Clinical efficacy was assessed by modified World Health Organization criteria. Survival time, Karnofsky performance score (KPS) of quality of life (QOL), and complications were recorded for all patients.

RESULTS

Overall condition, primary disease type, and ascites amounts were comparable between groups. Significantly shorter mean duration of perfusion catheter placement (35 vs. 85 min) and mean hospitalization cost (36,000 vs. 55,000 ¥/patient) were observed in the therapeutic group than the control group (P < 0.01). Significantly different KPS scores were not observed before or after CHIPC (23.13 vs. 22.64 %) in both groups (P > 0.05). No significant differences in objective remission rates of malignant ascites (93.75 vs. 93.34 %), median survival times (9 vs. 8 months), or stamp hole metastasis rates (18.75 vs. 18.15 %) were observed between groups (P > 0.05).

CONCLUSIONS

B-ultrasound-guided and laparoscopy-assisted CHIPC have similar clinical efficacy for improving QOL and prolonging patient survival. B-ultrasound-guided CHIPC may, however, shorten operation times and reduce hospitalization costs, making the treatment available to a broader patient population, although port hole metastasis remains an issue.

Cytoreductive surgery plus hyperthermic perioperative chemotherapy to treat peritoneal metastases from colorectal cancer: standard of care or an experimental approach?

Peritoneal carcinomatosis is a common presentation in patients with metastatic colorectal cancer and the overall survival is poor. In most patients, the disease remains limited to the peritoneal cavity. Therefore, investigators have applied cytoreductive surgery and hyperthermic perioperative chemotherapy as the standard approach for selected patients with peritoneal metastases from colorectal cancer. Overall, very promising long-term survival has been shown in a subset of patients with a limited extent of peritoneal disease before treatment. Whether randomised, controlled trials are needed to definitively show the magnitude of benefit, if any, of this approach is an important question. This Debate outlines the arguments on each side of this issue.

B ultrasound-guided hyperthermic intraperitoneal perfusion chemotherapy for the treatment of malignant ascites

To minimize invasive surgery, we employed B ultrasound to guide the placement of the catheters used in continuous circulatory hyperthermic intraperitoneal perfusion chemotherapy (CHIPC) in malignant ascites treatment. Thirty-two patients with malignant ascites were treated with CHIPC guided by B-mode ultrasound. Ascites were originally from ovarian cancer (11 cases), gastric cancer (10 cases), colorectal cancer (9 cases) and pancreatic cancer (2 cases). The CHIPC was carried out at 43˚C for 90 min with 0.9% saline solution as a carrier containing cisplatin and doxorubicin or mitomycin-C as therapeutic reagents depending on the type of the primary tumor. The therapeutic efficacy, postoperative complications and survival period of these patients were assessed with follow-up examinations. Among all participates to be assessed with ascites, 26 and 4 patients showed complete remission (CR) and partial remission (PR) respectively, with an objective remission rate (ORR) of 93.75%. The KPS scores were elevated by 23.1±9.0 after 3 sessions of ultrasound guided CHIPC and the quality of life (QOF) of patients was significantly improved (p<0.01). The median survival time was 9 months and 18 patients survived between 3 and 30 months after CHIPC treatment. Additionally, patients with different types of cancers significantly differed in the survival time (p<0.01). A novel approach of using B ultrasound guided CHIPC for the treatment of malignant ascites demonstrated satisfactory outcomes. The approach shows benefit in minimizing invasive surgery, improving the patient QOF and prolonging survival time.

Hyperthermia and intraperitoneal chemotherapy for the treatment of peritoneal carcinomatosis: an experimental study

OBJECTIVE

Hyperthermic intraperitoneal chemotherapy (HIPEC) with mitomycin C can improve survival if used as an adjunct to cytoreductive surgery (CS) for treatment of peritoneal carcinomatosis (PC). It remains unclear if both hyperthermia and chemotherapy are essential for the reported survival benefit.

METHODS

Eighty WAG/Rij rats were inoculated intraperitoneally with the rat colon carcinoma cell line CC-531. Animals were randomly assigned to 1 of the 4 treatment groups (n = 20): CS only, CS followed by HIPEC (mitomycin 35 mg/m(2) at 41°C), CS followed by intraperitoneal mitomycin perfusion at 37°C, CS followed by intraperitoneal saline perfusion at 41°C. Survival was the primary outcome with a maximum follow up of 126 days.

RESULTS

Median survival was 62 days in rats treated with CS only and 57 days in rats treated with CS followed by hyperthermic saline perfusion. Rats receiving HIPEC had a median survival of 121 days (P = 0.022 when compared with CS only). In the group treated with chemotherapy at 37°C, 13 of 20 animals were still alive at the end of the experiment so median survival was not reached. (CS vs. IPEC: P = 0.002, hazard ratio 0.36, 95% CI 0.19-0.69) Rats treated with hyperthermic saline perfusion did not have an increased survival as compared with CS only.

CONCLUSIONS

The effectiveness of intraoperative intraperitoneal perfusion after CS is highly dependent on the presence of chemotherapeutic agents in the perfusate but not on hyperthermia. The need to include hyperthermia in the adjuvant intraoperative treatment after CS for PC should be further investigated.

Intraoperative versus early postoperative intraperitoneal chemotherapy after cytoreduction for colorectal peritoneal carcinomatosis: an experimental study

BACKGROUND

Perioperative intraperitoneal chemotherapy is used as an adjunct to cytoreductive surgery (CS) for peritoneal carcinomatosis (PC) in order to prolong survival. Worldwide, hyperthermic intraperitoneal chemotherapy (HIPEC), early postoperative intraperitoneal chemotherapy (EPIC), and combinations of the two are used. It remains unclear which regimen is most beneficial.

METHODS

The rat colon carcinoma cell line CC-531 was injected into the peritoneal cavity of 80 WAG/Rij rats to induce PC. Animals were randomized into four treatment groups (n = 20): CS only, CS followed by HIPEC (mitomycin 35 mg/m(2) at 41.5°C), CS followed by EPIC during 5 days (i.p. injection of mitomycin on day 1 and 5-fluorouracil on days 2-5), and CS followed by HIPEC plus EPIC. Primary outcome was survival.

RESULTS

In rats treated with CS only, median survival was 53 days (95% confidence interval (CI) 49-57 days). In rats treated with CS followed by HIPEC, survival was significantly (P = 0.001) increased (median survival 94 days, 95% CI 51-137 days). In the group treated with EPIC after CS, 12 out of 20 rats were still alive at the end of the experiment (P < 0.001 as compared with CS only). In the group receiving both treatments, 11 rats died of toxicity, and therefore this group was not included in the survival analysis.

CONCLUSIONS

Both EPIC and HIPEC were effective in prolonging survival. The beneficial effect of EPIC on survival seemed to be more pronounced than that of HIPEC. Further research is indicated to evaluate and compare the possible benefits and adverse effects associated with both treatments.

Adjuvant radioimmunotherapy improves survival of rats after resection of colorectal liver metastases

OBJECTIVE

The aim of this study was to test the hypothesis that adjuvant radioimmunotherapy (RIT) prevents recurrent liver metastases and/or results in improved survival after tumorectomy in an experimental model.

BACKGROUND

Although partial hepatectomy can improve 5-year survival of patients with colorectal liver metastases up to 58%, recurrent tumor growth in the liver occurs frequently. Radioimmunotherapy using radiolabeled monoclonal antibodies directed against tumor-associated antigens is considered most suited for treating minimal residual disease and could therefore serve as an adjuvant after surgery.

METHODS

Liver metastases were induced in male Wag/Rij rats by a mini-laparotomy with intrahepatic injection of 0.3 × 106 CC531 tumor cells. The biodistribution of the radiolabeled monoclonal antibody MG1, directed against a 80-kDa cell surface antigen on CC531 tumors, in this model was determined at 1, 3, and 7 days after intravenous administration. The therapeutic efficacy of 177Lu-MG1 was compared with that of a sham antibody (UPC10), labeled with the same activity dose of Lu-177, and saline only. Radioimmunotherapy was administered either at the day of the tumorectomy (day 14 after tumor cell inoculation) or 7 days later. Primary endpoint was survival.

RESULTS

Radiolabeled MG1 preferentially accumulated in tumor lesions in the liver reaching a maximum 3 days postinjection (8.7 ± 0.6% injected dose per gram). Both the administration of 177Lu-MG1 and 177Lu-UPC10 resulted in a transient decrease in body weight. No other signs of clinical discomfort were registered. The survival curves of the group that received 177Lu-UPC10 and the group that received saline only did not differ (P=0.886). Administration of RIT immediately after surgery improved survival compared to administration of the control antibody (hazard ratio [HR], 1.54; P = 0.051), which was even more pronounced when survival was adjusted for the weight of the resected tumor (HR, 1.71; P = 0.027). A therapeutic efficacy of delayed treatment seemed likely (HR, 2.34; P = 0.055). Survival after early administration did not differ from delayed administration (HR, 1.16; P = 0.763).

CONCLUSION

This study provides proof of principle that RIT can be an effective adjuvant treatment modality after surgical treatment of colorectal liver metastases.

Experimental study of radioimmunotherapy versus chemotherapy for colorectal cancer

BACKGROUND

Radioimmunotherapy (RIT) has been shown to reduce the incidence of local recurrence of colorectal cancer in an experimental model. The aim of the present study was to investigate the survival benefit of RIT compared with chemotherapy.

METHODS

An anastomosis was constructed in male Wag/Rij rats after intraluminal injection of CC531 tumour cells. The therapeutic efficacy of (177) Lu-labelled MG1 (single intravenous dose of 300 MBq/kg, n = 20) was compared with that of 5-fluorouracil-based chemotherapy (6 weekly cycles administered intraperitoneally, n = 20) and no treatment (n = 20). The primary endpoint was survival. Toxicity was monitored by bodyweight measurement.

RESULTS

Both chemotherapy and RIT affected bodyweight, but the weight of animals in the RIT group remained significantly higher than in the chemotherapy group (median slope of bodyweight plot 0·48 versus 0·30 g/day; P < 0·001). Kaplan-Meier analysis showed that overall survival in the RIT and chemotherapy groups was significantly better than that in the control group (50 and 46 per cent versus 25 per cent respectively after 170 days; P = 0·024 and P = 0·029). Survival after treatment with RIT did not differ from that after chemotherapy (P = 0·911).

CONCLUSION

RIT is as effective as chemotherapy in experimental colorectal cancer.

Brief intraperitoneal radioimmunotherapy of small peritoneal carcinomatosis using high activities of noninternalizing 125I-labeled monoclonal antibodies

We assessed the efficiency and toxicity of brief intraperitoneal radioimmunotherapy using high activities of (125)I-labeled monoclonal antibody (mAb) in the treatment of small-volume peritoneal carcinomatosis.

METHODS

Brief intraperitoneal radioimmunotherapy consisted of a 185-MBq (740 MBq/mg) intraperitoneal injection of (125)I-35A7 (an anti-carcinoembryonic antigen mAb) into athymic nude mice 4 d after peritoneal tumor xenografting and, after 1 h, abundant washing of the peritoneal cavity with saline solution to remove unbound radioactivity. Another group of mice received this treatment plus a 37-MBq intravenous injection of (125)I-35A7 on day 7 or 11 after grafting. Control groups received a brief treatment followed by an additional intravenous injection on day 7 of either saline solution or irrelevant (125)I-PX. Tumor growth was monitored by bioluminescence imaging and SPECT/CT, and hematologic toxicity was evaluated by complete blood counts. Survival time was reported, and the mice were sacrificed when the bioluminescence signal reached 4.5 × 10(7) photons/s. The biodistribution of (125)I-35A7 mAb after intravenous or brief treatment was assessed, and the mean absorbed irradiation dose by organs and tumors was calculated using the MIRD formalism.

RESULTS

Mild, transient hematologic toxicity was observed after the brief treatment plus intravenous (125)I-mAb, with no weight loss. Median survival increased from 32 d in the control groups, to 46 d in the brief treatment group, to 66 d in the group additionally receiving intravenous treatment on day 11, to 73 d in the group additionally receiving intravenous treatment on day 7. The brief treatment alone resulted in a 3-fold higher tumor-to-blood uptake ratio than did the standard intravenous treatment, and the mean absorbed irradiation doses by tumors were 11.6 Gy for the brief treatment and 16.7 Gy for the additional intravenous treatment. For healthy tissues other than blood, the mean absorbed irradiation dose did not exceed 1 Gy after brief treatment and 4.2 Gy after intravenous treatment.

CONCLUSION

The efficiency, low toxicity, and high tumor-to-healthy tissue uptake ratio associated with brief intraperitoneal (125)I-35A7 radioimmunotherapy suggest that this method can be used in combination with radiation-synergistic drugs in the therapy of small-volume peritoneal carcinomatosis after cytoreductive surgery.

Intraoperative hyperthermic intraperitoneal chemotherapy after cytoreductive surgery for peritoneal carcinomatosis in an experimental model

BACKGROUND

The combination of cytoreductive surgery (CS) and hyperthermic intraperitoneal chemotherapy (HIPEC) is the treatment of choice for selected patients with peritoneal carcinomatosis (PC) of colorectal origin. However, it remains to be proven whether the addition of HIPEC to CS is essential for the reported survival benefit.

METHODS

Sixty WAG/Rij rats were inoculated intraperitoneally with the rat colonic carcinoma cell line CC-531. Animals were randomized into three treatment groups: CS alone, CS followed by HIPEC (mitomycin 15 mg/m(2) ) and CS followed by HIPEC (mitomycin 35 mg/m(2) ). Survival was the primary outcome parameter.

RESULTS

The median survival of rats treated with CS alone was 43 days. Rats receiving HIPEC 15 mg/m(2) and HIPEC 35 mg/m(2) both had a significantly longer median survival of 75 days (P = 0·003) and 97 days (P < 0·001) respectively. Rats receiving HIPEC showed a significantly lower tumour load at autopsy compared with rats treated with CS alone.

CONCLUSION

A combination of CS and HIPEC results in longer survival than CS alone in rats with PC of colorectal origin.

Chemotherapy with laparoscope-assisted continuous circulatory hyperthermic intraperitoneal perfusion for malignant ascites

AIM: To investigate the procedure, feasibility and effects of laparoscope-assisted continuous circulatory hyperthermic intraperitoneal perfusion chemotherapy (CHIPC) in treatment of malignant ascites induced by peritoneal carcinomatosis from gastric cancers.

METHODS: From August 2006 to March 2008, the laparoscopic approach was used to perform CHIPC on 16 patients with malignant ascites induced by gastric cancer or postoperative intraperitoneal seeding. Each patient underwent CHIPC three times after laparoscope-assisted perfusion catheters placing. The first session was completed in operative room under general anesthesia, 5% glucose solution was selected as perfusion liquid, and 1500 mg 5-fluorouracil (5-FU) and 200 mg oxaliplatin were added in the perfusion solution. The second and third sessions were performed in intensive care unit, 0.9% sodium chloride solution was selected as perfusion liquid, and 1500 mg 5-FU was added in the perfusion solution alone. CHIPC was performed for 90 min at a velocity of 450-600 mL/min and an inflow temperature of 43 ± 0.2°C.

RESULTS: The intraoperative course was uneventful in all cases, and the mean operative period for laparoscope-assisted perfusion catheters placing was 80 min for each case. No postoperative deaths or complications related to laparoscope-assisted CHIPC occurred in this study. Clinically complete remission of ascites and related symptoms were achieved in 14 patients, and partial remission was achieved in 2 patients. During the follow-up, 13 patients died 2-9 mo after CHIPC, with a median survival time of 5 mo. Two patients with partial remission suffered from port site seeding and tumor metastasis,and died 2 and 3 mo after treatment. Three patients who are still alive today survived 4, 6 and 7 mo, respectively. The Karnofsky marks of patients (50-90) increased significantly (P < 0.01) and the general status improved after CHIPC. Thus satisfactory clinical efficacy has been achieved in these patients treated by laparoscopic CHIPC.

CONCLUSION: Laparoscope-assisted CHIPC is a safe, feasible and effective procedure in the treatment of debilitating malignant ascites induced by unresectable gastric cancers.

Multimodal approach for treatment of peritoneal surface malignancies in a tumour-bearing rat model

PURPOSE

Surgical cytoreduction of peritoneal surface malignancy of colorectal origin in combination with hyperthermic intraoperative peritoneal chemotherapy (HIPEC) has become an established treatment approach. Only a few of animal models for scientific research on various therapeutic strategies have been described yet. The feasibility of an established rat model with a peritoneal surface malignancy from colorectal origin for treatment investigation should be examined in this study.

METHODS

Peritoneal surface malignancy of colonic origin was induced in 90 male BD IX rats. Animals were randomised into six groups (15 animals per one control and five treatment groups). One treatment group underwent only surgical debulking. The animals of the other four treatment groups received additional interventions: hyperthermic intraperitoneal chemotherapy with mitomycin or gemcitabine, photodynamic therapy or taurolidine lavage. Twenty-one days after treatment, the intraperitoneal status was investigated. Tumour weight, count of tumour nodules and experimental Peritoneal Carcinosis Index (ePCI) were detected.

RESULTS

Extended surgical cytoreduction and additional treatments including HIPEC were feasible in this rat model. All treatment groups had a significant lower tumour weight, account of tumour nodes and ePCI if compared with the control group. Comparing the additional therapies only HIPEC with mitomycin lead to relevant tumour reduction after surgery.

CONCLUSION

This rat model is suitable for research on the multimodal treatment of peritoneal malignancies. A persisting cytoreductive effect of surgical tumour debulking could be proven. Only additional HIPEC therapy with mitomycin showed a significant tumour reduction. This animal model provides the opportunity to investigate different therapeutic strategies.

Noninternalizing monoclonal antibodies are suitable candidates for 125I radioimmunotherapy of small-volume peritoneal carcinomatosis

We have previously shown that, in vitro, monoclonal antibodies (mAbs) labeled with the Auger electron emitter (125)I are more cytotoxic if they remain at the cell surface and do not internalize in the cytoplasm. Here, we assessed the in vivo biologic efficiency of internalizing and noninternalizing (125)I-labeled mAbs for the treatment of small solid tumors.

METHODS

Swiss nude mice bearing intraperitoneal tumor cell xenografts were injected with 37 MBq (370 MBq/mg) of internalizing (anti-HER1) (125)I-m225 or noninternalizing (anti-CEA) (125)I-35A7 mAbs at days 4 and 7 after tumor cell grafting. Nonspecific toxicity was assessed using the irrelevant (125)I-PX mAb, and untreated controls were injected with NaCl. Tumor growth was followed by bioluminescence imaging. Mice were sacrificed when the bioluminescence signal reached 4.5 x 10(7) photons/s. Biodistribution analysis was performed to determine the activity contained in healthy organs and tumor nodules, and total cumulative decays were calculated. These values were used to calculate the irradiation dose by the MIRD formalism.

RESULTS

Median survival (MS) was 19 d in the NaCl-treated group. Similar values were obtained in mice treated with unlabeled PX (MS, 24 d) and 35A7 (MS, 24 d) or with (125)I-PX mAbs (MS, 17 d). Conversely, mice treated with unlabeled or labeled internalizing m225 mAb (MS, 76 and 77 d, respectively) and mice injected with (125)I-35A7 mAb (MS, 59 d) showed a significant increase in survival. Irradiation doses were comparable in all healthy organs, independently from the mAb used, whereas in tumors the irradiation dose was 7.4-fold higher with (125)I-labeled noninternalizing than with internalizing mAbs. This discrepancy might be due to iodotyrosine moiety release occurring during the catabolism of internalizing mAbs associated with high turnover rate.

CONCLUSION

This study indicates that (125)I-labeled noninternalizing mAbs could be suitable for radioimmunotherapy of small solid tumors and that the use of internalizing mAbs should not be considered as a requirement for the success of treatments with (125)I Auger electrons.

Can antibody galactosylation be used to improve radioimmunotherapy of induced peritoneal carcinomatosis of colonic origin in the rat?

In radioimmunotherapy (RIT), hematologic toxicity is the dose-limiting toxicity due to the long circulatory half-life of the antibody. Although intraperitoneal (i.p.) RIT results in high uptake of i.p. growing tumors, the radiolabeled antibody enters the circulation, resulting in bone marrow toxicity. Carbohydrate modification of antibodies could induce accelerated clearance of the antibody via the hepatic asialoglycoprotein receptor, thereby reducing exposure to normal tissues. In this study, we investigated whether galactosylation of an antibody in a model of peritoneal carcinomatosis (PC) of colonic origin could be used to improve targeting of i.p. growing tumors. Therefore, the biodistribution of the galactosylated and nongalactosylated anti-CC531 antibody, MG1, after i.p. injection was determined in a model of peritoneal carcinomatosis of CC-531 colon tumors in Wag/Rij rats. Uptake of the radiolabeled antibodies in the tumor and relevant organs was determined at 2, 4, 24, and 48 hours after injection. Galactosylation of the antibody did not affect the binding affinity of MG1. Remarkably, the uptake of Gal-MG1 in tumors was higher than that of MG1 at 2 and 4 hours after injection. After 24 and 48 hours, uptake of Gal-MG1 in tumor tissue was lower than that of MG1. Gal-MG1 cleared from the blood within hours after administration. At 2-24 hours after administration, tumor-to-blood ratios obtained with Gal-MG1 were significantly higher than those obtained with unmodified MG1. Antibody galactosylation resulted in improved tumor-non-tumor ratios after i.p. injection in a model of PC. This could improve the efficiency of RIT, especially in combination with short-lived nonresidualizing radionuclides.

Radioimmunotherapy improves survival of rats with microscopic liver metastases of colorectal origin

Background

Half of the patients with colorectal cancer develop liver metastases during the course of their disease. The aim of the present study was to assess the efficacy of radioimmunotherapy (RIT) with a radiolabeled monoclonal antibody (mAb) to treat experimental colorectal liver metastases.

Methods

Male Wag/Rij rats underwent a minilaparotomy with intraportal injection of 1 × 10⁶ CC531 tumor cells. The biodistribution of ¹¹¹In-labeled MG1, 1 day after intravenous administration, was determined in vivo and compared with that of an isotype-matched control antibody (UPC-10). The maximal tolerated dose (MTD) of ¹⁷⁷Lu-labeled MG1 was determined and the therapeutic efficacy of ¹⁷⁷Lu-MG1 at MTD was compared with that of ¹⁷⁷Lu-UPC-10 and saline only. RIT was administered either at the day of tumor inoculation or 14 days after tumor inoculation. Primary endpoint was survival.

Results

¹¹¹In-MG1 preferentially accumulated in CC531 liver tumors (9.2 ± 3.7%ID/g), whereas ¹¹¹In-UPC-10 did not (0.8 ± 0.1%ID/g). The MTD of ¹⁷⁷Lu-MG1 was 400 MBq/kg body weight. Both the administration of ¹⁷⁷Lu-MG1 and ¹⁷⁷Lu-UPC-10 had no side-effects except a transient decrease in body weight. The survival curves of the group that received ¹⁷⁷Lu-UPC-10 and the group that received saline only did not differ (P = 0.407). Administration of ¹⁷⁷Lu-MG1 RIT immediately after surgery improved survival significantly compared with administration of ¹⁷⁷Lu-UPC-10 (P = 0.009) whereas delayed treatment did not (P = 0.940).

Conclusion

This study provides proof of principle that RIT can be an effective treatment modality for microscopic liver metastases, whereas RIT is not effective in larger tumors.

Radioimmunotherapy prevents local recurrence of colonic cancer in an experimental model

Background

Radioimmunotherapy (RIT) is suitable for the treatment of microscopic residual disease and might therefore have an adjuvant role after colonic cancer surgery.

Methods

An anastomosis was constructed in male Wag/Rij rats after intraluminal injection of 2 × 106 CC531 tumour cells. The biodistribution of 111In-labelled MG1 monoclonal antibody was assessed after intraperitoneal administration. The therapeutic efficacy of 177Lu-labelled MG1 (74 MBq per rat), administered on the day of surgery (D0, n = 13) or 5 days later (D5, n = 13), was compared with that of carrier only (n = 13). The primary endpoint was perianastomotic tumour growth 28 days after surgery.

Results

111In-labelled MG1 preferentially accumulated in perianastomotic CC531 tumours. RIT resulted in a transient reduction in bodyweight in both treatment groups compared with controls, but there were no other signs of clinical discomfort. No macroscopic or microscopic perianastomotic tumour growth was found in eight of 11 animals in the D0 group and 11 of 13 in the D5 group, whereas 11 of 13 controls had macroscopic tumour (P = 0·011 and P = 0·001 respectively).

Conclusion

This study suggests that RIT may be an effective adjuvant treatment for preventing local recurrence after resection of colonic cancer.