Long-term outcome of radiofrequency thermal ablation (RFA) of liver metastases from colorectal cancer (CRC): size as the leading prognostic factor for survival

Radiofrequency ablation: mechanisms and clinical applications

Radiofrequency ablation (RFA), a form of thermal ablation, employs localized heat to induce protein denaturation in tissue cells, resulting in cell death. It has emerged as a viable treatment option for patients who are ineligible for surgery in various diseases, particularly liver cancer and other tumor-related conditions. In addition to directly eliminating tumor cells, RFA also induces alterations in the infiltrating cells within the tumor microenvironment (TME), which can significantly impact treatment outcomes. Moreover, incomplete RFA (iRFA) may lead to tumor recurrence and metastasis. The current challenge is to enhance the efficacy of RFA by elucidating its underlying mechanisms. This review discusses the clinical applications of RFA in treating various diseases and the mechanisms that contribute to the survival and invasion of tumor cells following iRFA, including the roles of heat shock proteins, hypoxia, and autophagy. Additionally, we analyze‌ the changes occurring in infiltrating cells within the TME after iRFA. Finally, we provide a comprehensive summary of clinical trials involving RFA in conjunction with other treatment modalities in the field of cancer therapy, aiming to offer novel insights and references for improving the effectiveness of RFA.

Evidence on percutaneous radiofrequency and microwave ablation for liver metastases over the last decade

Purpose

This review aimed to summarize the treatment outcomes of percutaneous radiofrequency ablation (RFA) and microwave ablation (MWA) for metastatic liver tumors based on the findings of published studies over the last decade.

Materials and methods

Literature describing the survival outcomes of ablation therapy for liver metastases was explored using the PubMed database on April 26, 2022, and articles published in 2012 or later were selected. The included studies met the following criteria: (i) English literature, (ii) original clinical studies, and (iii) literature describing overall survival (OS) of thermal ablation for metastatic liver tumors. All case reports and cohort studies with fewer than 20 patients and those that evaluated ablation for palliative purposes were excluded.

Results

RFA was the most commonly used method for ablation, while MWA was used in several recent studies. RFA and MWA for liver metastases from various primary tumors have been reported; however, majority of the studies focused on colorectal cancer. The local control rate by RFA and MWA varied widely among the studies, ranging approximately 50–90%. Five-year survival rates of 20–60% have been reported following ablation for colorectal liver metastases by a number of studies, and several reports of 10-year survival rates were also noted.

Conclusion

Comparative studies of local therapies for colorectal liver metastases demonstrated that RFA provides comparable survival outcomes to surgical metastasectomy and stereotactic body radiation therapy.

Microwave Ablation, Radiofrequency Ablation, Irreversible Electroporation, and Stereotactic Ablative Body Radiotherapy for Intermediate Size (3-5 cm) Unresectable Colorectal Liver Metastases: a Systematic Review and Meta-analysis

Purpose of Review

Based on good local control rates and an excellent safety profile, guidelines consider thermal ablation the gold standard to eliminate small unresectable colorectal liver metastases (CRLM). However, efficacy decreases exponentially with increasing tumour size. The preferred treatment for intermediate-size unresectable CRLM remains uncertain. This systematic review and meta-analysis compare safety and efficacy of local ablative treatments for unresectable intermediate-size CRLM (3–5 cm).

Recent Findings

We systematically searched for publications reporting treatment outcomes of unresectable intermediate-size CRLM treated with thermal ablation, irreversible electroporation (IRE) or stereotactic ablative body-radiotherapy (SABR). No comparative studies or randomized trials were found. Literature to assess effectiveness was limited and there was substantial heterogeneity in outcomes and study populations. Per-patient local control ranged 22–90% for all techniques; 22–89% (8 series) for thermal ablation, 44% (1 series) for IRE, and 67–90% (1 series) for SABR depending on radiation dose.

Summary

Focal ablative therapy is safe and can induce long-term disease control, even for intermediate-size CRLM. Although SABR and tumuor-bracketing techniques such as IRE are suggested to be less susceptible to size, evidence to support any claims of superiority of one technique over the other is unsubstantiated by the available evidence. Future prospective comparative studies should address local-tumour-progression-free-survival, local control rate, overall survival, adverse events, and quality-of-life.

Oncological outcomes and predictors of radiofrequency ablation of colorectal cancer liver metastases

BACKGROUND

Surgical resection is considered the standard treatment option for long-term survival in colorectal cancer liver metastasis (CRLM) patients, but only a small number of patients are suitable for resection following diagnosis. Radiofrequency ablation (RFA) is an accepted alternative therapy for CRLM patients who are not suitable for resection. However, the relatively high rate of local tumor progression (LTP) is an obstacle to the more widespread use of RFA.

AIM

To determine the oncological outcomes and predictors of RFA in CRLM patients.

METHODS

A retrospective analyze was performed on the clinical data of 85 consecutive CRLM patients with a combined total of 138 liver metastases, who had received percutaneous RFA treatment at our institution from January 2013 to December 2018. Contrast-enhanced computed tomography was performed the first month after RFA to assess the technique effectiveness of the RFA and to serve as a baseline for subsequent evaluations. The Kaplan-Meier method was used to calculate overall survival (OS) and LTP-free survival (LTPFS). The log-rank test and Cox regression model were used for univariate and multivariate analyses to determine the predictors of the oncological outcomes.

RESULTS

There were no RFA procedure-related deaths, and the technique effectiveness of the treatment was 89.1% (123/138). The median follow-up time was 30 mo. The LTP rate was 32.6% (45/138), and the median OS was 36 mo. The 1-, 3-, and 5-year OS rates were 90.6%, 45.6%, and 22.9%, respectively. Univariate analysis revealed that tumor size and ablative margin were the factors influencing LTPFS, while extrahepatic disease (EHD), tumor number, and tumor size were the factors influencing OS. Multivariate analysis showed that tumor size larger than 3 cm and ablative margin of 5 mm or smaller were the independent predictors of shorter LTPFS, while tumor number greater than 1, size larger than 3 cm, and presence of EHD were the independent predictors of shorter OS.

CONCLUSION

RFA is a safe and effective treatment method for CRLM. Tumor size and ablative margin are the important factors affecting LTPFS. Tumor number, tumor size, and EHD are also critical factors for OS.

Literature Review of Current Management of Colorectal Liver Metastasis

Colorectal cancer is a leading cause of cancer mortality in the United States, and metastasis to the liver is a frequent sequela. Currently, surgical resection is the best option for curative treatment and/or long-term survival after colorectal liver metastasis (CRLM), but unfortunately, not all patients are surgical candidates. Alternative and adjunct therapies commonly used in the treatment of CRLM include chemotherapy, biologic therapy, radio-embolization, and radiofrequency ablation. The aim of this review was to report the various treatment modalities and outcomes currently used in the treatment of CRLM.

Does the Site of the Primary Affect Outcomes When Ablating Colorectal Liver Metastases with Radiofrequency Ablation?

PURPOSE

To determine whether primary tumor side was a predictor of radiofrequency ablation (RFA) outcome in colorectal liver metastases (CRLM).

MATERIALS AND METHODS

The institutional review board approved this retrospective study. Written informed consent was obtained from all patients. From January 2007 to December 2013, 102 patients underwent RFA of metachronous CRLM were enrolled in this study with propensity score matching method. Recurrence rate (RR) and overall survival (OS) were analyzed between two patients cohorts with primary left-side colorectal cancer (LSCRC) or primary right-side colon cancer (RSCC).

RESULTS

The total RR was 59.8% in all patients. Patients in LSCRC cohort had lower RR and non-local recurrence (NLR) rate than those in RSCC patients' cohort (49.0 vs 70.6%, p = 0.026 and 21.6 vs 41.2%, p = 0.033). Five-year OS was 14 and 30% for RSCC and LSCRC, respectively. There was a significant difference between two cohorts in median OS (29.4 vs 40.3 months for RSCC and LSCRC, respectively, p = 0.042). Univariate analysis showed that primary tumor side, the number of liver metastases, tumor size, carcinoembryonic antigen level, differentiation, TNM stage, active chemotherapy and RFA boundary were significant in predicting OS. When these variables were subsequently entered in a multivariate model, RSCC (p < 0.001; hazard ratio [HR], 6.2) and tumor size (> 3 cm) (p = 0.006; HR, 3.9) were significant.

CONCLUSION

LSCRC and tumor size (≤ 3 cm) are independent predictors of RFA in CRLM and yield the better oncologic outcomes.

Longterm effects of palliative local treatment of incurable metastatic lesions in colorectal cancer patients

We assessed the value of palliative local treatment of incurable metastatic lesions in colorectal cancer patients. Consecutive patients with metastatic colorectal cancer treated between 2003 and 2014 were retrospectively reviewed. Propensity score matching was used to create comparable palliative local treatment and chemotherapy alone groups (n = 272 in each group). The primary endpoint was overall survival, which was calculated using Kaplan-Meier survival analyses. Factors possibly influencing survival were evaluated by univariate and subsequently by multivariate analyses. Palliative local treatment prolonged survival as compared with chemotherapy alone (38.73 vs. 19.8 months, p < 0.01). Univariate and subsequent multivariate analyses showed that primary stage IV at initial diagnosis; high CA199 level and LDH at the time of diagnosis were independent factors for a poor prognosis. Palliative local treatment improved survival better than chemotherapy alone in patients with 0, 1, 2, or 3 of the prognostic factors (p < 0.01). Patients administered treatment for pulmonary metastases survived longer than those treated for metastases elsewhere (56.77 vs. 35.43 months, p = 0.01). Surgical treatment provided marginally longer survival than non-surgical treatment (44.87 vs. 35.43 months, p = 0.05). These findings suggest palliative local treatment has survival benefit for selected patients with incurable metastatic colorectal cancer.

New Developments in Interventional Oncology: Liver Metastases From Colorectal Cancer

Colorectal cancer is the third leading cause of cancer death in the United States. Although hepatic excision is the first-line treatment for colorectal liver metastasis (CRLM), few patients are candidates. Locoregional therapy (LRT) encompasses minimally invasive techniques practiced by interventional radiology. These include ablative treatments (radiofrequency ablation, microwave ablation, and cryosurgical ablation) and transcatheter intra-arterial therapy (hepatic arterial infusion chemotherapy, transarterial "bland" embolization, transarterial chemoembolization, and radioembolization with yttrium 90). The National Comprehensive Cancer Network recommends LRT for unresectable CRLM refractory to chemotherapy. The following is a review of LRT in CRLM, including salient features, advantages, limitations, current roles, and future considerations.

Image-guided high-dose-rate brachytherapy of malignancies in various inner organs - technique, indications, and perspectives

In the last few years, minimally invasive tumor ablation performed by interventional radiologists has gained increasing relevance in oncologic patient care. Limitations of thermal ablation techniques such as radiofrequency ablation (RFA), microwave ablation (MWA), and laser-induced thermotherapy (LITT), including large tumor size, cooling effects of adjacent vessels, and tumor location near thermosensitive structures, have led to the development of image-guided high-dose-rate (HDR) brachytherapy, especially for the treatment of liver malignancies. This article reviews technical properties of image-guided brachytherapy, indications and its current clinical role in multimodal cancer treatment. Furthermore, perspectives of this novel therapy option will be discussed.

Tumour eradication using synchronous thermal ablation and Hsp90 chemotherapy with protein engineered triblock biopolymer-geldanamycin conjugates

PURPOSE

Hepatocellular carcinoma (HCC) suffers high tumour recurrence rate after thermal ablation. Heat shock protein 90 (Hsp90) induced post-ablation is critical for tumour survival and progression. A combination therapy of thermal ablation and polymer conjugated Hsp90 chemotherapy was designed and evaluated for complete tumour eradication of HCC.

MATERIALS AND METHODS

A thermo-responsive, elastin-like polypeptide (ELP)-based tri-block biopolymer was developed and conjugated with a potent Hsp90 inhibitor, geldanamycin (GA). The anti-cancer efficacy of conjugates was evaluated in HCC cell cultures with and without hyperthermia (43 °C). The conjugates were also administered twice weekly in a murine HCC model as a single treatment or in combination with single electrocautery as the ablation method.

RESULTS

ELP-GA conjugates displayed enhanced cytotoxicity in vitro and effective heat shock inhibition under hyperthermia. The conjugates alone significantly slowed the tumour growth without systemic toxicity. Four doses of thermo-responsive ELP-GA conjugates with concomitant simple electrocautery accomplished significant Hsp90 inhibition and sustained tumour suppression.

CONCLUSION

Hsp90 inhibition plays a key role in preventing the recurrence of HCC, and the combination of ablation with targeted therapy holds great potential to improve prognosis and survival of HCC patients.

Understanding the current status of image-guided ablation for metastatic colorectal disease

Colorectal metastases to the liver are increasingly being detected and accurately characterized at an earlier stage and even at the subcentimeter level. The oncological case for surgical resection of this disease is widely accepted. The advent of smaller volume disease has encouraged the development of in situ ablative technologies over the last two decades and the oncological efficacy of these procedures has continued to improve through stepwise developments in ablation devices and image guidance. This article provides an overview of these techniques, currently available and future technologies, and the imaging findings encountered. It also sets out the current position image-guided ablation merits alongside chemotherapy and surgical resection. In selected cases ablation for colorectal metastases can produce oncological outcomes equivalent to surgery and critically with less morbidity in an increasingly older patient population. We examine whether with careful patient selection, optimal technology, meticulous technique, and diligent follow-up, consistently reproducible high quality outcomes will be achieved in the next few years.

Debulking treatment with CT-guided percutaneous radiofrequency ablation and hepatic artery infusion of floxuridine improves survival of patients with unresectable pulmonary and hepatic metastases of colorectal cancer

The survival of most patients with both unresectable hepatic and pulmonary metastases of colorectal cancer is poor. In this retrospective study, we investigated the efficacy of computed tomography (CT)-guided radiofrequency ablation (RFA) and systemic chemotherapy plus hepatic artery infusion of floxuridine (HAI-FUDR). Sixty-one patients were selected from 1,136 patients with pulmonary and hepatic metastases from colorectal cancer. Patients were treated with RFA and systemic chemotherapy plus HAI-FUDR (ablation group, n = 39) or systemic chemotherapy plus HAI-FUDR (FUDR group, n = 22). Patients in the two groups were matched by sex, age, number of metastases, and calendar year of RFA or FUDR. Survival data were evaluated by using univariate and multivariate analyses. Clinical characteristics were comparable between the two groups. All patients in the ablation group underwent RFA and chemotherapy. Median follow-up was 56.8 months. The 1-, 3-, and 5-year overall survival (OS) rates were 97%, 64%, and 37%, respectively, for the ablation group, and 82%, 32%, and 19%, respectively, for the FUDR group. The 1-, 3-, and 5-year survival rates after metastasis were 97%, 49%, and 26% for the ablation group, and 72%, 24%, and 24% for the FUDR group, respectively. The median OS times were 45 and 25 months for the ablation and FUDR groups, respectively. In the multivariate analysis, treatment allocation was a favorable independent prognostic factor for OS (P = 0.001) and survival after metastasis (P = 0.009). These data suggest that the addition of RFA to systemic chemotherapy plus HAI-FUDR improves the survival of patients with both unresectable hepatic and pulmonary metastases from colorectal cancer.

Therapeutic efficacy comparison of radiofrequency ablation in hepatocellular carcinoma and metastatic liver cancer

The aim of this study was to evaluate the effect of radiofrequency ablation (RFA) on malignant hepatic tumors and compare its therapeutic efficacy in hepatocellular carcinoma (HCC) and metastatic liver cancer (MLC). A total of 56 patients with malignant hepatic tumors (34 patients with HCC and 22 patients with MLC) underwent RFA treatment. Two weeks following the RFA treatment, contrast-enhanced abdominal computed tomography scans were used to investigate whether the ablation of the tumors was complete. The patients were followed up for a period ranging from 1 to 93 months, to compare recurrence rates, distant recurrence rates and survival rates. The HCC group exhibited an initial complete ablation rate of 94.1% compared with 95.4% for the MLC group; the difference in ablation rates was not identified to be statistically significant. The recurrence and distant recurrence rates were 14.7% and 11.8%, respectively, for the HCC group and 9.1% and 36.4%, respectively, for the MLC group. The 1-, 3- and 5-year survival rates of the patients with HCC were 86.2, 71.4 and 60.0%, respectively, whereas those for the patients with MLC were 73.9%, 45.4% and 37.5%, respectively. The survival rates of the two groups were identified to be significantly different (P=0.002). RFA treatment was therefore shown to be effective in treating small (<5 cm) malignancies, which is clinically significant.

Repetitive chemoembolization of hypovascular liver metastases from the most common primary sites

AIM

To evaluate tumor response in patients with hypovascular liver metastases from the most common primary sites treated with chemoembolization.

MATERIALS & METHODS

Chemoembolization was performed in 190 patients (five groups) who had hypovascular liver metastases from the colon (n = 66), breast (n = 40), uveal malignant melanoma (n = 20), pancreas (n = 48) and stomach (n = 16). Surgical resection of primary sites had been performed for all included patients. Tumor response, survival statistics from the first chemoembolization using Kaplan-Meier method and progression rate of embolized lesions were evaluated by analysis of variance with Tukey's post hoc test.

RESULTS

Multiple comparison between the groups showed no statistical significant difference in local tumor response (H: 9.23; p > 0.05). Survival indices of the patients, including survival rate, progression-free survival rate, median survival time and time to progression, demonstrated significant difference between the groups during the follow-up period (H: 9.7; p = 0.045). The progression rate of treated liver metastases from colon, breast, uvea, pancreas and stomach were 16.6, 17.5, 30.0, 25.0 and 32.0%, respectively (p = 0.002).

CONCLUSION

Hypovascular liver metastases treated with chemoembolization may demonstrate equal local response, but are significantly different in rate of progression and survival.

Percutaneous CT-guided radiofrequency ablation for unresectable hepatocellular carcinoma pulmonary metastases

PURPOSE

This study aimed to evaluate the safety and efficacy of percutaneous CT-guided radiofrequency ablation (RFA) for unresectable hepatocellular carcinoma pulmonary metastases (HCCPM) and to identify the prognostic factors for survival.

MATERIALS AND METHODS

We reviewed the medical records of 320 patients with HCCPM treated between January 2005 and January 2012. Among them, 29 patients with 68 lesions of unresectable HCCPM underwent 56 RFA sessions. Safety, local efficacy, survival and prognostic factors were evaluated. Survival was analysed using the Kaplan-Meier method. Univariate analyses were evaluated by the log-rank test.

RESULTS

Pneumothorax requiring chest tube placement occurred in five (8.9%, 5/56) RFA sessions. During the median follow-up period of 23 months (range 6-70), 18 patients (62.1%, 18/29) died of tumour progression and 11 (37.9%, 11/29) were alive. The 1-, 2- and 3-year overall survival rates were 73.4%, 41.1% and 30%, respectively. The median progression-free survival was 18 months (95% confidence interval (CI) 9.8-26.2) and the median overall survival time was 21 months (95%CI, 9.7-32.3). The maximum tumour diameter ≤3 cm (p = 0.002), the number of pulmonary metastases ≤3 (p = 0.014), serum AFP level ≤400 ng/mL (p = 0.003), and the controlled status of intrahepatic tumour after lung RFA (p = 0.001) were favourable prognostic factors for overall survival.

CONCLUSIONS

Our study indicates that percutaneous CT-guided RFA, as an alternative treatment procedure to pulmonary metastasectomy, can be a safe and effective therapeutic option for unresectable HCCPM.

Advances in treatment of liver metastases of colorectal cancer

Liver metastasis of colorectal cancer has a high incidence and mortality and is the main factor affecting prognosis, which necessitates the development of more reasonable therapeutic strategy for this condition. Nowadays, surgical resection is the only probable curative method; however, surgical intervention is indicated in only a few patients. The development of medical technology and accumulation of clinical experience have led to the wide use of multimodal treatment for liver metastases of colorectal cancer. Multimodal treatment includes surgical resection, neoadjuvant chemotherapy, transcatheter hepatic arterial chemoembolization, radiation therapy, radiofrequency ablation, cryotherapy, percutaneous ethanol injection, and Chinese medicine treatment. The combined application of the above treatments can improve the survival rate and the quality of life of patients. This article summarizes the advances in comprehensive treatment for colorectal liver metastases.