Iodine-131 Lipiodol: A Re-Emerging Therapeutic Agent in Hepatocellular Carcinoma Treatment

Summary: ¹³¹I-Lipiodol, also known as ¹³¹I-Ethiodized Oil, is a therapeutic agent initially authorised in 1995 under the name Lipiocis®. After its withdrawal in 2010 due to observed lung toxicity, the product re-entered the market in India in 2018 and is also available in Brazil. This article explores the history, mechanism of action, clinical applications, and future prospects of ¹³¹I-Lipiodol in the treatment of hepatocellular carcinoma (HCC), particularly in cases involving portal vein thrombosis.

Introduction to Iodine-131 Lipiodol

Hepatocellular carcinoma (HCC) is one of the most common primary liver cancers worldwide. Treatment options for HCC are often limited, especially in cases where the tumour is non-resectable and the patient is unfit for transplantation. ¹³¹I-Lipiodol has emerged as a valuable therapeutic agent in such scenarios. This article looks into the journey of ¹³¹I-Lipiodol, from its initial approval to its withdrawal and eventual reintroduction, and examines its role in modern oncology.

History of 131I-Lipiodol

Initial Approval and Use

First authorised in 1995 under the brand name Lipiocis®, ¹³¹I-Lipiodol gained recognition for its efficacy in treating HCC. It is a radiopharmaceutical agent, created by labelling Lipiodol—a contrast agent used in radiology—with radioactive iodine-131 (¹³¹I).

Withdrawal Due to Lung Toxicity

In October 2010, ¹³¹I-Lipiodol was withdrawn from the market following observations of lung toxicity in patients. Concerns over its safety profile led to a re-evaluation of its use in clinical settings.

Reintroduction to the Market

After rigorous assessments and regulatory approvals, ¹³¹I-Lipiodol made a comeback on the Indian market in 2018, following approval in March 2017. It is also available in Brazil, signalling a renewed interest in its therapeutic potential.

Composition and Mechanism of Action

Lipiodol as a Carrier

Lipiodol is a mixture of iodinated ethyl esters of fatty acids derived from poppy seed oil. Traditionally used as a contrast agent in radiology, Lipiodol has a high affinity for fatty acid-containing tissues, making it an ideal carrier for targeted therapy.

Radioactive Labelling with ¹³¹I

When labelled with iodine-131, Lipiodol becomes ¹³¹I-Lipiodol. The radioactive isotope emits beta electrons (β^–), which have cytotoxic effects on tumour cells. This targeted delivery allows for high concentrations of radiation within the tumour while minimising exposure to surrounding healthy tissue.

Targeting Fatty Acid-Containing Tissues

¹³¹I-Lipiodol selectively accumulates in HCC tissues due to their rich vascularity and lipophilic nature. The fatty acid components of Lipiodol facilitate this selective uptake, enhancing the therapeutic efficacy.

Clinical Applications

Treatment of Hepatocellular Carcinoma

¹³¹I-Lipiodol is primarily used in the treatment of HCC, especially in patients with portal vein thrombosis where surgical options are limited. Its ability to deliver targeted radiation makes it a valuable tool in reducing tumour size and controlling disease progression.

Non-Resectable and Untransplantable Cases

For patients who are not candidates for surgical resection or liver transplantation, ¹³¹I-Lipiodol offers a palliative treatment option. It can improve survival rates and quality of life by slowing tumour growth.

Safety Profile and Toxicity

Observations of Lung Toxicity

The initial withdrawal of ¹³¹I-Lipiodol was due to reports of lung toxicity. Patients experienced adverse pulmonary effects, prompting further investigation into the safety of the drug.

Current Understanding and Management

With improved dosing protocols and patient monitoring, the incidence of lung toxicity has been reduced. Clinicians now have a better understanding of risk factors and can implement strategies to mitigate adverse effects.

Global Availability and Regulatory Status

Approval in India and Brazil

¹³¹I-Lipiodol received approval in India in March 2017 and became available on the market in 2018. It is also available in Brazil, indicating a growing acceptance of its use in oncology.

Future Prospects in Other Regions

There is potential for ¹³¹I-Lipiodol to be approved in other countries, pending further clinical trials and regulatory reviews. Its re-emergence may influence treatment protocols for HCC globally.

Comparison with Other Therapeutic Agents

Advantages over Conventional Therapies

Compared to systemic chemotherapy, ¹³¹I-Lipiodol offers targeted therapy with fewer systemic side effects. Its selective uptake by tumour tissues enhances efficacy while reducing harm to healthy cells.

Integration into Multimodal Treatment Plans

¹³¹I-Lipiodol can be integrated with other treatment modalities, such as transarterial chemoembolisation (TACE) or radiofrequency ablation (RFA), to enhance therapeutic outcomes.

Patient Selection and Treatment Protocols

Identifying Suitable Candidates

Not all patients with HCC are suitable for ¹³¹I-Lipiodol therapy. Ideal candidates are those with non-resectable tumours, portal vein thrombosis, and no significant extrahepatic disease.

Administration Techniques

The drug is administered via intra-arterial injection, typically through the hepatic artery. This method ensures direct delivery to the liver tumour, maximising the therapeutic effect.

Research and Clinical Trials

Ongoing Studies

Current research focuses on optimising dosing regimens, improving safety profiles, and combining ¹³¹I-Lipiodol with other therapies to enhance efficacy.

Outcomes and Efficacy Data

Clinical trials have demonstrated improved survival rates and tumour control in patients treated with ¹³¹I-Lipiodol. Ongoing studies aim to solidify these findings and expand its clinical applications.

Conclusion

¹³¹I-Lipiodol represents a significant advancement in the treatment of hepatocellular carcinoma, particularly for patients with limited options. Its reintroduction into the market offers hope for improved patient outcomes. Continued research and clinical experience will further define its role in oncology, potentially leading to broader adoption in treatment protocols worldwide.

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