Radioimmunotherapy prevents local recurrence of colonic cancer in an experimental model

Effectiveness of combined (131)I-chTNT and radiofrequency ablation therapy in treating advanced hepatocellular carcinoma

To investigate the effectiveness of monoclonal antibody ((131)I-chTNT) and radiofrequency ablation (RFA) combination therapy in treating middle-advanced stage hepatocellular carcinoma (HCC). Thirty-four patients diagnosed with HCC patients, divided into two groups comprised of 22 and 12 cases were included in this retrospective study. The two groups received RFA with or without ((131)I-chTNT) therapy, respectively. The patients in these groups were followed up for a median of 31 and 35 months, respectively. Patient survival was evaluated using Kaplan-Meier method and safety profiles were determined by analyzing liver, thyroid, and bone marrow toxicities. This retrospective study showed that survival time of the patients who received combination therapy was significantly longer than that of the RFA group (P = 0.052). The median progress-free survival of patients in the two groups was 23 and 7 months, respectively, and the difference was significant (P = 0.04). Tumor recurred in 3.5-8.7 months in four of the combination group patients, among which three had newly developed lesions. The red blood cells and platelets counts were not altered on day 7 and 1 month of the treatment, however, number of white blood cells was significantly increased on day 7 which was reversed back to the normal range in 2 weeks. The ALT and AST were also not significantly altered on day 7 and 1 month of therapy. In middle-advanced stage HCC patients, the combination of (131)I-chTNT and RFA therapy was found to be significantly more effective than the RFA treatment alone as assessed in short-term follow-up. However, the dose we used was insufficient to completely block the local recurrence of the lesions with a diameter of 5 cm or larger.

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.

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.

Adjuvant radioimmunotherapy after radiofrequency ablation of colorectal liver metastases in an experimental model

PURPOSE

Radiofrequency ablation (RFA) has shown to improve survival in patients not eligible for surgical resection of colorectal liver metastases. However, recurrences after RFA are a major problem. Adjuvant radioimmunotherapy (RIT) after surgical resection of liver metastases has shown to improve survival. The aim of the present study was to test the hypothesis that adjuvant RIT might be an effective way to prevent recurrent liver metastases after RFA in an experimental model.

METHODS

Tumours in the liver were induced by intrahepatic injection of 300,000 CC531 cells in male Wag/Rij rats (n = 60). Ten days later, the intrahepatic tumours were treated with RFA. Adjuvant RIT ((177)Lu-labelled monoclonal antibody MG1 at 300 MBq/kg) was administered intravenously either at the day of RFA (day 10) or 7 days later. Control rats received no treatment. Primary endpoint was survival.

RESULTS

Administration of (177)Lu-MG1 resulted in a transient decrease in body weight, compared to no adjuvant treatment. However, no other signs of clinical discomfort were registered. Log rank test showed that the survival curves of the groups treated with RIT, either at day 10 or day 17, did not differ significantly from the survival curve of the rats that did not receive adjuvant treatment (P = 0.902).

CONCLUSION

This study shows that adjuvant RIT does not increase survival after RFA of colorectal liver metastases in rats.

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.

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.