Liver-directed therapy in metastatic colorectal cancer

Combining with immunotherapy is an emerging trend for local treatment of colorectal cancer liver metastases: a bibliometric analysis

Background

A growing body of evidence has demonstrated the expanding role of local treatment in managing colorectal cancer liver metastases (CRCLM). To identify current research trends and forecast future directions, we conducted a bibliometric analysis to examine global collaboration patterns and academic influence across countries, institutions, journals, and authors.

Materials and methods

Relevant articles and reviews on CRCLM local therapies were systematically retrieved from the Web of Science Core Collection. The bibliometric package in R software and VOSviewer software were used to analyze countries, institutions, journals, authors, and keywords. The research status and key areas of local treatment of colorectal cancer liver metastases were analyzed by keywords.

Results

The analysis encompassed 2,695 articles published between 2008 and 2023. The United States emerged as the leading contributor, with Memorial Sloan Kettering Cancer Center producing the highest number of publications (n=178). Among journals, Annals of Surgical Oncology ranked first in publication volume, while Journal of Vascular and Interventional Radiology achieved the highest citation count. The local treatment modalities for CRCLM included transarterial therapies (radioembolization and chemoembolization), hepatic artery infusion chemotherapy and immunotherapy, imaging guidance methods, hepatectomy and survival, and ablation and stereotactic body radiotherapy. Recent studies highlighted ablations, microspheres, and immunotherapy as key research areas, with thematic mapping identifying immunotherapy as an emerging niche field.

Conclusion

CRCLM local treatment research focuses on integrating local and systemic therapies. Preclinical studies, RFA with anti - PD - 1 agents, show enhanced anti - tumor immunity and survival. While the synergy of local and immunotherapy is confirmed, large - scale clinical evidence is still needed. Thus, cross - disciplinary cooperation is urgently required to boost translational medical research.

Liver Resection With Extrahepatic Disease: A Population-Based Analysis of Thoughtful Selection

BACKGROUND

The oncologic benefit of liver resection for colorectal liver metastases (CRLM) in the setting of concurrent extrahepatic disease (EHD) is controversial. We performed a population-based, cross-sectional study to determine the practice patterns and overall survival (OS) of patients with CRLM + EHD who underwent liver resection.

METHODS

Patients with CRLM + EHD were identified using the California Cancer Registry from 2000 to 2019. Records were linked to the Office of Statewide Health Planning Inpatient Database. Patient demographics, clinical characteristics, and survival were compared between CRLM + EHD patients with and without liver resection.

RESULTS

Of 170 978 patients with CRLM, 62 003 (36%) had concurrent EHD (CRLM + EHD). In all, 3736 (6%) of CRLM + EHD underwent liver resection compared to 22% of patients with liver limited CRLM. Compared to CRLM + EHD without liver resection, CRLM + EHD with resection were younger, had fewer comorbidities, received higher frequencies of perioperative chemotherapy, and were more likely to have only a single site of EHD rather than multiple sites. Median OS was significantly higher for CRLM + EHD with resection compared to without (52 vs. 27 months, HR 0.46 [95% CI 0.44-0.47], p < 0.001). Regarding the location of EHD, this survival benefit was observed with liver resection for lung, peritoneal, intraabdominal lymph nodes, ovarian, and bone metastases.

CONCLUSIONS

In a large population-based setting, subsets of CRLM + EHD patients that undergo liver resection are associated with prolonged survival. These results support surgery with thoughtful patient selection to optimize survival outcomes in this population.

Enhancing Anti-PD-1 Immunotherapy by Targeting MDSCs via Hepatic Arterial Infusion in Breast Cancer Liver Metastases

BACKGROUND

Surgery, chemotherapy, and radiation often have limited utility for advanced metastatic disease in the liver, and despite its promising activity in select cancers, PD-1 blockade therapy similarly has minimal benefit in this setting. Curaxin, CBL0137, is an experimental anti-cancer drug that disrupts the binding of DNA to histones, destabilizes chromatin, and induces Z-DNA formation which may stimulate anti-tumor immune responses.

METHODS

Murine cell lines of colon (CT26) and breast (4T1) cancer were interrogated for survival and CBL0137-associated DNA changes in vitro. Immunocompetent models of liver metastases followed by CBL0137 hepatic arterial infusion (HAI) were used to examine in vivo tumor cell DNA alterations, treatment responses, and the immune contexture associated with CBL0137, both alone and in combination with anti-PD-1 therapy.

RESULTS

CBL0137 induced immediate changes to favor tumor cell death in vitro and in vivo with an efficient tumor uptake via the HAI route. Toxicity to CBL0137 was minimal and anti-tumor treatment effects were more efficient with HAI compared to intravenous delivery. Immune effects were pronounced with CBL0137 HAI with concurrent depletion of a specific population of myeloid-derived suppressor cells and maintenance of effector T cell populations.

CONCLUSIONS

Combination of CBL0137 HAI with PD-1 blockade improved survival in 4T1 tumors but not in CT26 tumors, and therapeutic efficacy relies on the finding of simultaneous and targeted depletion of myeloid-derived suppressor cells and skewing of T cell populations to produce synergy with PD-1 blockade therapy.

Imaging of the hepatic arterial infusion pump: Primer for radiologists

Hepatic arterial infusion (HAI) pumps are used to deliver liver-directed therapy by allowing the administration of selective chemotherapy to the liver via a catheter implanted most commonly into the gastroduodenal artery connected to a subcutaneous pump. This selective administration helps maximize the chemotherapeutic effect within the hepatic tumors while minimizing systemic toxicity. While HAI therapy has primarily been used to treat liver-only metastatic colorectal cancer, the indications have expanded to other malignancies, including intrahepatic cholangiocarcinoma. Radiologists play an important role in pre-operative planning, assessment of treatment response, and evaluation for potential complications using various imaging studies, including computed tomography angiography, magnetic resonance imaging, and perfusion scintigraphy. This article describes the radiologist's role as part of a multi-disciplinary oncology team to help maximize the success of HAI therapy and also helps radiologists familiarize themselves with various aspects of HAI pumps.

Effect of preoperative liver-directed therapy prior to hepatic resection

INTRODUCTION

Hepatobiliary malignancies present with advanced disease precluding upfront resection. Liver-directed therapy (LDT), particularly Y-90 radioembolization and transarterial chemoembolization (TACE), has become increasingly utilized to facilitate attempt at oncologic resection. However, the safety profile of preoperative LDT is limited.

METHODS

Retrospective review of the ACS NSQIP main and targeted hepatectomy registries for 2014-2016. Primary objective was evaluation of outcomes between preoperative LDT cases and those that received upfront resection.

RESULTS

A total of 8923 cases met selection criteria. 192 cases (2.15%) received either Y-90 or TACE prior to hepatectomy. Multivariate analysis for all study patients revealed preoperative LDT significantly increased the risk of perioperative transfusion (OR 2.19, 95% CI 1.445-3.328, P < 0.0001), sepsis (OR 2.21, 95% CI 1.104-4.411, P = 0.022), and liver failure (OR 2.72, 95% CI 1.562-4.747, P < 0.0001). Subgroup analysis found for primary hepatobiliary malignancies LDT only increased the risk for liver failure. While for secondary hepatic tumors LDT significantly increased perioperative transfusion, sepsis, cardiac failure, renal failure, liver failure, and mortality. The complication profile also significantly increased with advanced T stage. Conversely, on propensity score matching preoperative LDT did not significantly increase perioperative complications.

CONCLUSION

Preoperative LDT has the potential to convert inoperable hepatic tumors into resectable disease but there is a general increased risk for significant postoperative complications, most notable liver failure. However, on controlled analysis preoperative LDT does not increase perioperative complications and should not be considered a contraindication to resection.

Current Surgical Management Strategies for Colorectal Cancer Liver Metastases

Simple Summary

Colorectal cancer is one of the most common cancer diagnoses in the world. At least half of patients diagnosed with colorectal cancer will develop metastatic disease, with most being identified in the liver. Surgical resection of colorectal liver metastases (CRLM) is potentially curative. Surgical resection of CRLM, however, remains underutilized despite the continued expansion of operative strategies available. This is likely due to differing views on resectability. Resectability is a surgical assessment, and the classification of CRLM as unresectable should only be made by an experienced hepatobiliary surgeon. Obtaining a surgical evaluation at the time of liver metastasis discovery may help mitigate the challenge of assessing resectability and the determination of potential operative time windows within current multimodal management strategies. The aim of this review is to help facilitate discussions surrounding resectability as well as the timing and sequencing of both surgical and non-surgical therapies.

Abstract

Colorectal cancer is the third most common cancer diagnosis in the world, and the second most common cause of cancer-related deaths. Despite significant progress in management strategies for colorectal cancer over the last several decades, metastatic disease remains difficult to treat and is often considered incurable. However, for patients with colorectal liver metastases (CRLM), surgical resection offers the best opportunity for survival, can be curative, and remains the gold standard. Unfortunately, surgical treatment options are underutilized. Misperceptions regarding resectable and unresectable CRLM likely play a role in this. The assessment of factors that impact resectability status like medical fitness, technical considerations, and disease biology can be difficult, necessitating careful multidisciplinary input and discussion. The identification of ideal operative time windows that align with the multimodal management of these patients can also be perplexing. For all patients with CRLM it may therefore be advantageous to obtain surgical evaluation at the time of discovering liver metastases to mitigate these challenges and minimize the risk of undertreatment. In this review we summarize current surgical management strategies for CRLM and discuss factors to be considered when determining resectability.

Evolutions of the Management of Colorectal Cancer Liver Metastasis: A Bibliometric Analysis

Background: Tremendous progress has been made in the treatment of colorectal cancer liver metastasis (CRCLM) in recent decades, and thousands of papers have been published. Therefore, we conducted a bibliometric analysis of articles related to CRCLM treatment to explore its evolution. Materials and Methods: The Clarivate Analytics Web of Science (WOS) Core Collection database was searched through June 2020 using terms related to CRCLM treatment. We analyzed the bibliographic information of the literature related to CRCLM treatment and explored the research topics to understand its evolution over time. Results: We identified 3436 records related to CRCLM treatment in the WOS database. The total number of times these documents were cited ranged 0-2352, and the years of publication spanned 1976-2020. The greatest numbers of articles were published in the United States, Japan, and France. Among institutions, Memorial Sloan-Kettering Cancer Center, MD Anderson Cancer Center, and Oslo University Hospital published the most articles. Regarding authors, Jarnagin WR, Adam R, Vauthey JN published the most articles. The research topics of these articles included systemic chemotherapy, molecular targeted therapy, the outcome of liver resection, prognosis prediction, hepatic artery infusion, radiofrequency ablation, and two-stage hepatectomy. Conclusion: Bibliometric analysis of studies related to CRCLM treatment can help doctors and researchers quickly understand the development trend in this field. These data emphasize the current management of patients with CRCLM, and they can potentially guide the direction of future research.

18F FDG PET/MRI with hepatocyte-specific contrast agent for M staging of rectal cancer: a primary economic evaluation

Purpose

Rectal cancer is one of the most frequent causes of cancer-related morbidity and mortality in the world. Correct identification of the TNM state in primary staging of rectal cancer has critical implications on patient management. Initial evaluations revealed a high sensitivity and specificity for whole-body PET/MRI in the detection of metastases allowing for metastasis-directed therapy regimens. Nevertheless, its cost-effectiveness compared with that of standard-of-care imaging (SCI) using pelvic MRI + chest and abdominopelvic CT is yet to be investigated. Therefore, the aim of this study was to analyze the cost-effectiveness of whole-body ¹⁸F FDG PET/MRI as an alternative imaging method to standard diagnostic workup for initial staging of rectal cancer.

Methods

For estimation of quality-adjusted life years (QALYs) and lifetime costs of diagnostic modalities, a decision model including whole-body ¹⁸F FDG PET/MRI with a hepatocyte-specific contrast agent and pelvic MRI + chest and abdominopelvic CT was created based on Markov simulations. For obtaining model input parameters, review of recent literature was performed. Willingness to pay (WTP) was set to $100,000/QALY. Deterministic sensitivity analysis of diagnostic parameters and costs was applied, and probabilistic sensitivity was determined using Monte Carlo modeling.

Results

In the base-case scenario, the strategy whole-body ¹⁸F FDG PET/MRI resulted in total costs of $52,186 whereas total costs of SCI were at $51,672. Whole-body ¹⁸F FDG PET/MRI resulted in an expected effectiveness of 3.542 QALYs versus 3.535 QALYs for SCI. This resulted in an incremental cost-effectiveness ratio of $70,291 per QALY for PET/MRI. Thus, from an economic point of view, whole-body ¹⁸F FDG PET/MRI was identified as an adequate diagnostic alternative to SCI with high robustness of results to variation of input parameters.

Conclusion

Based on the results of the analysis, use of whole-body ¹⁸F FDG PET/MRI was identified as a feasible diagnostic strategy for initial staging of rectal cancer from a cost-effectiveness perspective.

Prognostic and predictive value of circulating DNA for hepatic arterial infusion of chemotherapy for patients with colorectal cancer liver metastases

Hepatic arterial infusion (HAI) of chemotherapy is an experimental treatment option for patients with colorectal cancer liver metastases (CRCLM). The current study aimed to investigate the predictive and prognostic value of cell free DNA (cfDNA) in patients with CRCLM receiving HAI with oxaliplatin and systemic capecitabine. Plasma samples from 62 patients were investigated who were included into a single arm phase II study investigating HAI treatment for patients with CRCLM. The clinical outcome of the trial has been presented previously. In brief, treatment consisted of intrahepatic infusion of oxaliplatin 100 mg/m² every second week with concomitant oral capecitabine 3,500 mg/m² every second week for up to 12 cycles. Blood samples were drawn at baseline and follow-up and plasma was analyzed for cell free DNA using a direct fluorescent assay. The baseline level of plasma cfDNA was 0.92 ng/µl (95% CI 0.84-1.00). Patients with a baseline value of cfDNA above the 75th quartile had a median overall survival of 2.4 years (95% CI 0.7-2.8), compared with 3.9 years (95% CI 2.8-5.9) for patients below the 75th quartile (P=0.02). The baseline level of cfDNA was significantly lower (0.91 ng/µl, 95% CI 0.76-0.98) in patients who achieved an objective response compared to non-responders (1.79 ng/µl; 95% CI 0.99-2.57; P=0.02). The current study demonstrated a possible prognostic and predictive value of cfDNA for patients with CRCLM undergoing HAI with oxaliplatin and concomitant capecitabine.

Fatty change of the liver microenvironment influences the metastatic potential of colorectal cancer

Fatty liver is the most common cause of liver disease, and its prevalence has been increasing globally. Colorectal cancer (CRC) accounts for approximately 10% of all cancers and metastasizes most commonly to the liver. Paget's ‘Seed and Soil’ theory of metastasis proposed that the secondary growth of cancer cells is dependent on the distal organ microenvironment. This implies that the risk of metastasis may change due to changes in the microenvironment of target organs. However, the association between steatosis, fatty change in the liver microenvironment, and liver metastasis has not been clarified. Here, we induced fatty liver conditions in BALB/c mice using a choline‐deficient high‐fat diet with 0.1% methionine (CDAHFD) and then injected the CT26 cells to produce experimental metastasis. The number of metastatic tumours was significantly increased in mice with severe fatty liver as compared to control mice. The average size of metastatic tumours was smaller in mice with moderate fatty liver than in control mice. The stromal components, including cancer‐associated fibroblasts, tumour‐associated macrophages and tumour‐infiltrating lymphocytes, were also examined. Metastatic tumours in fatty liver showed invasive growth patterns without a fibrotic capsule. Compared to control groups, the polarization of macrophages and subtypes of tumour‐infiltrating lymphocytes differed depending on the extent of fatty liver progression. These results indicated that fatty changes in the liver influenced liver metastasis of CRC. Although moderate fatty changes suppress the growth of metastatic tumours in the liver, a severe fatty microenvironment may promote invasion and metastasis through alteration of the tumour microenvironment (TME).

Role of Hepatic Artery Infusion Chemotherapy in Treatment of Initially Unresectable Colorectal Liver Metastases: A Review

Importance

Although liver metastasis develops in more than half of patients with colorectal cancer, only 15% to 20% of these patients have resectable liver metastasis at presentation. Moreover, patients with initially unresectable colorectal liver metastasis (IU-CRLM) who progress on first-line systemic chemotherapy have limited treatment options. Hepatic arterial infusion chemotherapy (HAIC), in combination with systemic chemotherapy, leverages a multimodality approach to achieving control of hepatic disease and/or expanding resectability in patients with liver-only disease or liver-dominant disease.

Observations

Intra-arterial delivery of agents with high first-pass hepatic extraction (eg, floxuridine) limits systemic toxic effects and allows for administration of systemic chemotherapy at near-full doses. Hepatic arterial infusion chemotherapy in conjunction with systemic chemotherapy augments response rates up to 92% in patients who are chemotherapy naive, and up to 85% in pretreated patients with IU-CRLM. In turn, these responses translate into encouraging rates of conversion to resectability (CTR). Prospective trials have reported CTR rates as high as 52% in heavily pretreated patients with IU-CRLM who have an extensive hepatic disease burden. As such, CTR remains a compelling indication for liver-directed chemotherapy in this subset of patients. This review discusses the biological rationale for HAIC, evolution of rational combinations with systemic chemotherapy, contemporary evidence for CTR using HAIC and systemic chemotherapy, juxtaposition with rates of CTR using systemic chemotherapy alone, and morbidity and toxic effect profiles of HAIC.

Conclusions and Relevance

The argument is made for consideration of earlier initiation of HAIC in patients with IU-CRLM who are chemotherapy naive and for adoption of HAIC strategies to augment rates of resectability in patients who have failed first-line systemic chemotherapy before proceeding to second-line or third-line regimens.

Neutron-activated biodegradable samarium-153 acetylacetonate-poly-L-lactic acid microspheres for intraarterial radioembolization of hepatic tumors

BACKGROUND

Liver cancer is the 6^th most common cancer in the world and the 4^th most common death from cancer worldwide. Hepatic radioembolization is a minimally invasive treatment involving intraarterial administration of radioembolic microspheres.

AIM

To develop a neutron-activated, biodegradable and theranostics samarium-153 acetylacetonate (¹⁵³SmAcAc)-poly-L-lactic acid (PLLA) microsphere for intraarterial radioembolization of hepatic tumors.

METHODS

Microspheres with different concentrations of ¹⁵²SmAcAc (i.e., 100%, 150%, 175% and 200% w/w) were prepared by solvent evaporation method. The microspheres were then activated using a nuclear reactor in a neutron flux of 2 × 10¹² n/cm²/s¹, converting ¹⁵²Sm to Samarium-153 (¹⁵³Sm) via ¹⁵²Sm (n, γ) ¹⁵³Sm reaction. The SmAcAc-PLLA microspheres before and after neutron activation were characterized using scanning electron microscope, energy dispersive X-ray spectroscopy, particle size analysis, Fourier transform infrared spectroscopy, thermo-gravimetric analysis and gamma spectroscopy. The in-vitro radiolabeling efficiency was also tested in both 0.9% sodium chloride solution and human blood plasma over a duration of 550 h.

RESULTS

The SmAcAc-PLLA microspheres with different SmAcAc contents remained spherical before and after neutron activation. The mean diameter of the microspheres was about 35 µm. Specific activity achieved for ¹⁵³SmAcAc-PLLA microspheres with 100%, 150%, 175% and 200% (w/w) SmAcAc after 3 h neutron activation were 1.7 ± 0.05, 2.5 ± 0.05, 2.7 ± 0.07, and 2.8 ± 0.09 GBq/g, respectively. The activity of per microspheres were determined as 48.36 ± 1.33, 74.10 ± 1.65, 97.87 ± 2.48, and 109.83 ± 3.71 Bq for ¹⁵³SmAcAc-PLLA microspheres with 100%, 150%, 175% and 200% (w/w) SmAcAc. The energy dispersive X-ray and gamma spectrometry showed that no elemental and radioactive impurities present in the microspheres after neutron activation. Retention efficiency of ¹⁵³Sm in the SmAcAc-PLLA microspheres was excellent (approximately 99%) in both 0.9% sodium chloride solution and human blood plasma over a duration of 550 h.

CONCLUSION

The ¹⁵³SmAcAc-PLLA microsphere is potentially useful for hepatic radioembolization due to their biodegradability, favorable physicochemical characteristics and excellent radiolabeling efficiency. The synthesis of the formulation does not involve ionizing radiation and hence reducing the complication and cost of production.

Safety and Feasibility of Radiation Therapy to the Primary Tumor in Patients With Metastatic Castration-resistant Prostate Cancer

INTRODUCTION

The objective of this study was to evaluate the safety and feasibility of radiation therapy (RT) to the primary tumor in patients with metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

This retrospective study included 105 patients with mCRPC who were treated between April 2004 and May 2019. We divided the patients into 2 groups: patients treated with RT to the primary tumor after they developed CRPC (RT group) and without (non-RT group). The primary purpose was safety assessed using the Common Terminology Criteria for Adverse Events. The secondary purpose included prostate-specific antigen (PSA) response, cancer-specific survival (CSS), and overall survival (OS). Background-adjusted multivariate analyses, with the inverse probability of treatment weighting (IPTW) method, were performed to evaluate impact of RT on CSS and OS.

RESULTS

The median age at CRPC diagnosis was 75 years, and the median follow-up period after CRPC diagnosis was 21 months. The adverse events rates related to RT in any grade and grade ≥ 3 were 55% and 23%, respectively. Nine (29%) patients achieved ≥ 30% PSA decline with RT. In multivariate analyses with the IPTW method, the CSS and OS in the RT group were significantly longer than those in the non-RT group. In subgroup analyses with the IPTW method, RT was significantly associated with improved OS in patients aged ≥ 75 years and patients with initial PSA ≥ 500 ng/mL, cT4, Gleason score ≥ 8, and high-volume metastatic burden.

CONCLUSIONS

RT to the primary tumor is safe and feasible, and it has potential benefits on oncologic outcomes in patients with mCRPC.

MicroRNA-216b suppresses the cell growth of hepatocellular carcinoma by inhibiting Ubiquitin-specific peptidase 28 expression

MicroRNA-216b (miR-216b) has been reported to be downregulated in several tumors, its mechanism is still little-studied in hepatocellular carcinoma (HCC). In the present study, we found that miR-216b was downregulated in HCC, but Ubiquitin-specific peptidase 28 (USP28) was upregulated. In addition, Kaplan-Meier-plotter analysis indicated that liver cancer patients with high miR-216b expression had a longer overall survival, but patients with high USP28 had a shorter overall survival. Further studies showed that overexpression of miR-216b inhibited HCC cell growth, and molecular investigations revealed that miR-216b targeted USP28 and inhibited its expression in HCC cells. In addition, overexpression of miR-216b suppressed the substrates' expression of USP28, for example, c-Myc, and miR-216b overexpression also inhibited Cyclin E expression as well as upregulating p27 expression, both of which were the downstream signals of c-Myc. These results indicated that miR-216b downregulated USP28/c-Myc signaling in HCC cells. Collectively, this study demonstrated that miR-216b/c-Myc axis could be as a potential target for HCC therapy in the future.

Survival Outcomes After Surgical Management of the Primary Tumor With and Without Radiotherapy for Metastatic Rectal Adenocarcinoma: A National Cancer Database (NCDB) Analysis

BACKGROUND

With advances in systemic therapies, the role of primary tumor resection may be of increased importance in patients with metastatic rectal cancer. The role of combining pelvic radiotherapy with surgical resection in the metastatic setting is unknown. We utilized the National Cancer Database to examine outcomes in patients with metastatic rectal adenocarcinoma with primary tumor resection with and without pelvic radiotherapy.

MATERIALS AND METHODS

We queried the National Cancer Database from 2004 to 2014 for patients with stage IV rectal adenocarcinoma receiving chemotherapy. We identified 4051 patients in that group that had primary tumor resection. Patients were then stratified by receipt of pelvic radiotherapy (yes = 1882; no = 2169) Univariable and multivariable analyses identified characteristics predictive of overall survival. Propensity-adjusted Cox proportional hazard ratios for survival were used to account for indication bias.

RESULTS

The median patient age was 63 years (range, 18-90 years) with a median follow-up of 32.3 months (range, 3.02-151.29 months). There were proportionately more patients with T3/T4 disease or N1 disease in the surgery plus radiotherapy arm. The median survival was 46.3 months versus 35.3 months in favor of addition of radiotherapy (P < .001). The 2- and 5-year overall survival was 68.4% and 24.8% for surgical resection alone compared with 77.2% and 39.6% for surgery + radiotherapy. On propensity-adjusted multivariable analysis, radiotherapy was associated with a statistically significant reduction in risk of death (hazard ratio, 0.722; 95% confidence interval, 0.0665-0.784).

CONCLUSION

This analysis indicates that in patients with metastatic rectal adenocarcinoma receiving chemotherapy, pelvic radiotherapy in addition to primary tumor resection may be of significant benefit.

Radioactive holmium phosphate microspheres for cancer treatment

The aim of this study was the development of radioactive holmium phosphate microspheres (HoPO₄-MS) with a high holmium content and that are stable in human serum for selective internal radiation therapy (SIRT) of liver cancer. To this end, holmium acetylacetonate microspheres (HoAcAc-MS) were prepared (34.2 ± 1.0 µm in diameter, holmium content of 46.2 ± 0.8 and density of 1.7 g/cm³) via an emulsification and solvent evaporation method. The concentration of HoAcAc in the organic solvent, the temperature of emulsification and the stirring speed were varied for the preparation of the HoAcAc-MS to obtain microspheres with different diameters ranging from 11 to 35 µm. Subsequently, the AcAc ligands of the HoAcAc-MS were replaced by phosphate ions by simply incubating neutron irradiated HoAcAc-MS in a phosphate buffer solution (0.116 M, pH 4.2) to yield radioactive HoPO₄-MS. The obtained microspheres were analyzed using different techniques such as SEM-EDS, ICP-OES and HPLC. The prepared HoPO₄-MS (29.5 ± 1.2 µm in diameter and a density of 3.1 g/cm³) present an even higher holmium content (52 wt%) than the HoAcAc-MS precursor (46 wt%). Finally, the stability of the HoPO₄-MS was tested by incubation in human serum at 37 °C which showed no visible changes of the microspheres morphology and only 0.1% of holmium release was observed during the 2 weeks period of incubation. In conclusion, this study shows that stable radioactive HoPO₄-MS can be prepared with suitable properties to be used for cancer therapy.