Interventional Oncology: The Fastest Growing Field in Interventional Radiology

1. Introduction

Interventional oncology (IO) represents a paradigm shift in the treatment of cancer, utilizing minimally invasive, image-guided techniques to diagnose and treat tumors. As the third pillar of oncology, alongside surgical oncology, medical oncology, and radiation oncology, IO provides novel, localized treatments that are often alternatives or adjuncts to systemic therapies and conventional surgery. It has proven to be particularly valuable in the management of liver, lung, kidney, and bone cancers, where localized therapies are essential for controlling disease progression.

The increasing prominence of IO has been driven by technological innovations, improved imaging modalities, and the growing need for individualized, targeted cancer therapies. This review outlines the fundamental techniques used in interventional oncology, discusses their applications in cancer care, and highlights future directions in this rapidly evolving field.

2. Techniques in Interventional Oncology

The primary techniques in IO can be broadly categorized into ablative therapies, embolization, and targeted drug delivery. These approaches are often used alone or in combination with systemic therapies to maximize efficacy.

2.1 Ablation Therapies

Thermal ablation involves the use of extreme temperatures to destroy tumor cells. Techniques include radiofrequency ablation (RFA), microwave ablation (MWA), and cryoablation. These therapies are typically used for small tumors and are highly effective for hepatocellular carcinoma (HCC), lung metastases, and renal cell carcinoma (RCC).

·       Radiofrequency ablation (RFA): RFA uses alternating electrical currents to generate heat and induce coagulative necrosis in tumors. It is commonly used for the treatment of liver and kidney tumors, particularly for patients who are not surgical candidates .

·       Microwave ablation (MWA): MWA produces higher temperatures over a shorter duration compared to RFA, leading to larger ablation zones. This makes it particularly effective for larger tumors, especially in the liver and lungs .

·       Cryoablation: Cryoablation uses extreme cold (liquid nitrogen or argon gas) to freeze and destroy tumor cells. It is frequently applied to renal, lung, and bone metastases. One advantage of cryoablation is the ability to monitor the ice-ball formation in real-time during the procedure.

2.2 Embolization Techniques

Embolization therapies involve the occlusion of blood vessels feeding the tumor, depriving it of nutrients and oxygen. These techniques are particularly useful in the treatment of liver cancer and are often combined with systemic therapies for enhanced efficacy.

·       Transarterial chemoembolization (TACE): TACE involves the injection of chemotherapy agents directly into the artery feeding the tumor, followed by the infusion of embolic agents to block the blood supply. This technique is primarily used in the treatment of HCC and liver metastases from colorectal cancer .

·       Radioembolization (Y-90): In this approach, radioactive microspheres containing Yttrium-90 are injected into the tumor's arterial supply, delivering localized radiation to the tumor while sparing surrounding tissues. It is particularly useful for unresectable liver tumors.

2.3 Targeted Drug Delivery

In targeted drug delivery, interventional radiologists use image guidance to deliver therapeutic agents directly to the tumor site. This technique allows for higher concentrations of the drug to reach the tumor, minimizing systemic side effects.

·       Drug-eluting beads (DEB-TACE): This variant of TACE uses microspheres that elute chemotherapeutic drugs over time, providing a sustained local concentration of the drug within the tumor .

·       Immuno-oncology and combination therapies: The integration of IO techniques with immune checkpoint inhibitors and other systemic therapies is an exciting frontier in cancer treatment. Emerging evidence suggests that local tumor destruction by IO can trigger systemic anti-tumor immune responses .

3. Applications of Interventional Oncology

3.1 Liver Cancer

Hepatocellular carcinoma (HCC) is one of the most common indications for IO procedures. Ablation therapies such as RFA and MWA are often used for early-stage HCC in patients who are not candidates for surgery. For intermediate or advanced-stage disease, TACE and radioembolization (Y-90) are effective palliative treatments that can prolong survival and improve quality of life .

3.2 Lung Cancer

Lung metastases and primary lung tumors can be treated with ablative techniques, particularly MWA and cryoablation. These therapies offer a less invasive alternative to surgery for patients with early-stage non-small cell lung cancer (NSCLC) or those who are medically inoperable .

3.3 Renal Cancer

Renal cell carcinoma (RCC) is often managed with ablative techniques, particularly in patients who are not surgical candidates due to comorbidities or poor kidney function. Cryoablation is commonly used because of its precision and the ability to preserve renal function .

3.4 Bone Metastases

Interventional oncology has a growing role in the palliative treatment of painful bone metastases. RFA, cryoablation, and cementoplasty are frequently used to alleviate pain and stabilize bone lesions, improving patients' quality of life.

4. Future Directions and Challenges

4.1 Technological Innovations

Advances in imaging modalities, such as real-time MRI-guided ablation and fusion imaging, are likely to enhance the precision and safety of IO procedures. Artificial intelligence (AI) is also poised to play a key role in improving patient selection, treatment planning, and procedural accuracy.

4.2 Integration with Immunotherapy

There is increasing interest in the combination of IO with immunotherapy. Ablation and embolization therapies can potentially induce an immune response by releasing tumor antigens, which can be harnessed in combination with immune checkpoint inhibitors. Early clinical studies show promising results, but further research is needed to optimize these combination strategies.

4.3 Access and Training

One of the major challenges for the widespread adoption of IO is the availability of specialized training and resources. Interventional oncologists require expertise in both imaging techniques and cancer biology, necessitating dedicated fellowship programs and multidisciplinary collaboration.

5. Conclusion

Interventional oncology is revolutionizing the management of cancer, offering minimally invasive, targeted therapies that complement traditional oncological treatments. With advancements in technology and growing integration with systemic therapies, IO is poised to become an essential component of personalized cancer care. Future research will continue to refine these techniques, improve outcomes, and expand their application to a broader range of cancers.