Interventional oncology (abbreviated IO) is a subspecialty field of interventional radiology that deals with the diagnosis and treatment of cancer and cancer-related problems using targeted minimally invasive procedures performed under image guidance. Interventional oncology has developed to a separate pillar of modern oncology and it employs X-ray, ultrasound, computed tomography (CT) or magnetic resonance imaging (MRI) to help guide miniaturized instruments (e.g. biopsy needles, ablation electrodes, intravascular catheters) to allow targeted and precise treatment of solid tumours (also known as neoplasms) located in various organs of the human body, including but not limited to the liver, kidneys, lungs, and bones. Interventional oncology treatments are routinely carried out by interventional radiologists in appropriate settings and facilities.
Interventional oncology procedures are commonly applied to treat primary or metastatic cancer. Interventional oncology may be offered once traditional surgery, chemotherapy or radiotherapy have failed or are not considered safe. IO treatments may be also offered in combination with any of the above oncological therapies in order to augment the therapeutic outcome in more complex or widespread (metastatic) cancer cases. There is an increase in the variety of applications of interventional oncological treatments for primary and metastatic cancer in different human body organs:
- Liver cancer: primary liver tumours known as hepatocellular carcinoma and liver metastases.
- Lung cancer: usually lung metastases or inoperable primary lung cancer.
- Kidney Cancer: usually small kidney tumours known as renal cell carcinoma.
- Bone Cancer: for bone metastases located in the spine, pelvis and long bones.
- Breast Cancer: for small tumours.
- Prostate Cancer: large inoperable tumours.
- Pancreatic cancer: inoperable advanced neoplasms.
- 1930 – First therapeutic embolization procedure (of a carotid-cavernous fistula); described by Brooks.
- 1960s – Radioisotopes such as Yttrium-90 (Y90) started to be investigated for the use in cancer treatments.
- 1966 – Embolization therapy to treat tumors and spinal cord vascular malformations by blocking the blood flow.
- 1969 – The catheter-delivered stenting technique and prototype stent.
- 1970s – Embolisation agents started to be used in palliative care to treat liver tumors.
- 1980 – Cryoablation to freeze liver tumors.
- 1983 – Laser interstitial thermal therapy first performed on a tumour by Bown.
- 1985 – Self-expanding stents are developed for vascular and oncological applications.
- 1990 – Radiofrequency ablation (RFA) technique for liver tumors.
- 1990s – Treatment of bone and kidney tumors by embolization.
- 1990s – RFA for soft tissue tumors, i.e., bone, breast, kidney, lung and liver cancer.
- 1997 – Intra-arterial delivery of tumor-killing viruses and gene therapy vectors to the liver.
- 1997 – HIFU first used to treat prostate cancer.
- 2012 – Pioneering liver chemoperfusion study reported by Delcath for disseminated liver metastases.
Interventional oncology procedures are generally divided between diagnostic procedures that help obtain tissue diagnosis of suspicious neoplasms and therapeutic ones that aim to cure or palliate the tumour. Therapeutic interventional oncology procedures may be classified further into ablation techniques that destroy neoplastic tissues by delivery of some form of heat, cryo or electromagnetic energy and embolization techniques that aim to occlude the blood vessels feeding the tumour and thereby destroy it by means of ischemia. Both ablation and embolization techniques are minimally invasive treatment, i.e. they may be delivered through the skin (in a percutaneous way) without the need for any skin incisions or other form of open surgery. Hence, most treatments are nowadays offered as day case or outpatient appointments and patients may enjoy rapid recovery and minimal pain and discomfort with low rates of complications.
- Fine needle aspiration: biopsy with a fine needle trying to obtain tissue diagnosis by examining the tumour cells.
- Core needle biopsy: similar to fine needle aspiration, only involving the use of larger needles to excise the tissue.
- Vacuum assisted biopsy: similar to core needle aspiration but using vacuum assistance to gather the sample. Vacuum assisted breast biopsy may provide a high diagnostic yield in case of breast tumours.
- Chemical Ablation: one of the earliest ablative techniques involving the injection of substances such as ethanol or acetic acid into a tumour to cause protein denaturation and cell death.
- Radiofrequency ablation: tissue destruction through delivery of electricity that produces ionic friction.
- Irreversible electroporation: delivery of electrical fields to disrupt cellular membranes and cause cell death or apoptosis or enhance targeted drug delivery.
- Cryoablation: instant cell death by tissue freezing to temperatures as low as -20 Celsius.
- Microwave ablation: electromagnetic energy produces high frequency oscillation of water molecules leading to tissue coagulation by heat.
- High-intensity focused ultrasound (HIFU): targeted beam of focused ultrasonic waves that accumulates high energy and burns the tissue.
- Laser ablation (Interstitial laser therapy): tissue coagulation by a laser beam.
- Bland embolization: delivery of sub-millimiter microparticles through a catheter inserted in the groin and advanced into the liver under X-ray guidance to get access into the tumor vasculature.
- Transarterial chemoembolization (TACE): delivery of intra-arterial chemotherapy to the liver through a catheter in combination with embolic material to produce ischemia.
- Drug eluting bead chemoembolization (DEB-TACE): delivery of microparticles that are themselves loaded with the chemotherapy agent – doxorubicin – and allow for prolonged elution into the tumour microvessels.
- Selective internal radiation therapy (also known as SIRT or radioembolization): microspheres loaded with a radioactive isotope (Yttrium-90) are injected into the blood vessels feeding a tumour and deliver a lethal dose of radiation into the vessels feeding the tumour thereby causing cell death.
- Intra-arterial chemotherapy: high dose chemotherapy is administered directly into the tumor-feeding arteries.
- Portal vein embolization (PVE): delivery of bland embolic material into the portal vein of the hepatic lobe containing the tumor of interest to induce hypertrophy in the contralateral hepatic lobe for the purposes of improving outcomes from planned surgical resection.
- Radiation Lobectomy: injection of small radioactive beads loaded with yttrium-90 into the hepatic artery feeding the hepatic lobe in which the tumor is located. This is done with the intent of inducing growth in the contralateral hepatic lobe, not dissimilarly from portal vein embolization.
Interventional oncology has long been used to provide palliative care for patients. IO procedures can help reduce cancer-related pain and improve patients’ quality of life. Tumours can intrude into various ducts and blood vessels of the body, obstructing the vital passage of food, blood or waste. The interventional radiological treatment known as stenting can be used to re-open blockages, for example of the esophagus or bile ducts in cases of esophageal cancer or cholangiocarcinoma, respectively, considerably relieving the patient’s adverse symptoms.
While the surgical resection of tumours is generally accepted to offer the best long-term solution, it is often not possible due the size, number or location of the tumour. IR therapies may be applied to shrink the tumour, making a surgical or interventional treatment possible. Some patient groups may also be too weak to undergo open surgery. IR treatments can be applied in these complex cases to provide effective and milder forms of treatment. Interventional oncological techniques can also be used in combination with other treatments to help increase their efficacy. For example, IO techniques can be used to shrink large tumours making them easier to excise. Chemotherapeutic drugs can also be administered intra-arterially, increasing their potency and removing the harsh effects of system-wide application. Patients can greatly benefit from IO treatments. The minimally invasive nature of the treatments means they cause less pain, fewer side effects and shorter recovery times. Many IO procedures can be performed on an outpatient basis, freeing up hospital beds and reducing costs.
Cancer is a multifaceted disease group that requires a multidisciplinary approach to treatment. Numerous studies have shown that cancer patients treated in multidisciplinary environments benefit greatly from the combined expertise. Interventional Radiologists are seen as playing a major role in multidisciplinary cancer teams where they provide innovative solutions to improve combined therapies and to treat complications.
Proper patient selection is the key element for the success of any medical procedure and improper conduct can have fatal consequences. Patient selection protocols must be strictly followed before treating patients with IO procedures.
IO treatments are carried out under image guidance. For this reason practitioners must have attained solid training in radiation protection.
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