What are the working principles underlying Regional Chemotherapy?
The aim of the modern Regional Chemotherapy (RCT) cancer treatment method is to maximize damage to the tumour, while minimizing side effects to the patients. Regional chemotherapy is effective as a treatment for cancers that produce “solid tumours.” However, not every type of tumour responds equally well to RCT. As well, there are different Regional Chemotherapy techniques. Each of them is more effective for particular types of tumors, depending on the tumor location.
Some tumours require extremely high concentrations of cytotoxic medications, while others respond at lower concentrations. To cause permanent damage to a solid tumour, the concentration of about six times of that used in conventional systemic chemotherapy is required. With a number of different RCT techniques, it is possible to reach concentrations of cytostatic agents that are up to eighty times as high as those in conventional systemic chemotherapy.
A crucial element in the success of treating cancer with regional chemotherapy is the quality of the blood supply to the tumor. If a tumour is poorly vascularized (perfused, or has poor blood supply), it also poorly absorbs cytostatic agents. Therefore the desired effect and the outcome of the procedure diminish. Even by using a direct arterial approach, the outcome is limited. Perfusion can also be diminished or reduced by various secondary factors, such as a scar formation from a prior surgery or from previous irradiation treatments (radiation therapy).
The goals of all Regional Chemotherapy techniques
The goals of all Regional Chemotherapy techniques are to destroy tumor or to reduce its size. Following the reduction in size the surgery can often be the next step. Reducing the tumor size can allow to transform a non-resectable (not operable) tumor into a resectable one (one that can be removed surgically). At the same time tumor reduction can help to minimize the extent of the surgical procedure. In the best case scenario, the tumour disappears completely following RCT procedure, avoiding the need for additional surgical intervention.
What are regional chemotherapy techniques ?
There is a number of regional chemotherapy techniques that can be used to deliver medication to the tumor. All of them are designed to minimize surgical interventions and to optimize the effectiveness of the procedure. The choice of the technique has to do with the type of cancer and its location in the body.
Arterial infusion through an angiocatheter
The first example of regional chemotherapy techniques is arterial infusion. To perform arterial infusion, a catheter is inserted into an artery. This is done under regional anaesthesia. During the insertion, the tip of the angiocatheter is directed into the tumour region under X-ray monitoring and placed there.
- Advantage: No surgery required.
- Disadvantage: During and immediately following the treatment (3-4 days), the patient has to remain in bed on a recovery rest.
- Illustration: Angiocatheter in the celiac trunk for regional chemotherapy of liver metastases from a carcinoid tumour of the small bowel. These metastases are so well vascularized that they can be visualized with contrast material injected into the artery.
Arterial infusion through a surgically implanted port catheter
As the name implies, a port catheter is surgically implanted directly into the vessel supplying the tumour with blood. This option makes it possible to deliver treatments as often as necessary over a prolonged period of time. After the implantation of the catheter, there is no need for any additional surgical involvement with it.
- Advantage: Following the the patient remains mobile. The arterial infusion can be performed by puncturing the port when the procedure is required. The operation provides an opportunity to explore and to gather additional information about the extent of the tumour.
- Disadvantage: Surgery is required, and it comes with attendant risks.
- Intra-arterial infusion through a Jet Port Allround subclavian artery catheter to treat carcinoma of the right breast. The procedure permits arterial therapy with high concentrations of the cytostatic agent in the area of the right chest wall, axilla and side of the neck, thereby including all the lymphatic drainage areas.
- Jet Port Allround subclavian artery catheter. The tip of the catheter is located in the artery, and the port (injection portion, injection chamber) is placed under the skin. This provides comfortable access for intra-arterial chemotherapy.
Chemoembolization is one of the best known regional chemotherapy techniques. It is most useful primarily for liver tumours and metastases. Thus, this procedure allows to block the thinnest blood vessels (capillaries) with microparticles in order to deliver and retain cytostatic agent in the tumour area. In addition, blocking the blood vessels deprives the tumour area of its oxygen supply, contributing to improved response.
Also developed in 1950s, isolated regional perfusion, one more of the regional chemotherapy techniques, became the model for induction chemotherapy. This particular technique helped to solve some of the drug delivery and toxicity issues. Regional perfusion allowed to significantly increase the delivery of the drug dose to a tumor region. The increase can be six to ten times over the dose attainable with traditional systemic chemotherapy.
Isolated perfusion is performed as a part of a surgical operation. In this procedure, an organ or a region of the body is isolated using catheter systems. Then, this region is perfused with a high concentration of a cytostatic agent. A specialized external pump allows to perform such perfusion procedure.
Sometimes during or just prior to the procedure, it can be beneficial to raise the temperature of the tumour. Such procedure is called hyperthermia. On the other hand, in some cases, reducing the oxygen content in the blood, after administration of a cytostatic agent can be effective as well. Hypoxia is the procedure of reduction of the oxygen in the blood. With some cytostatic agents, hypoxia can result in up to a tenfold increase in toxicity for the tumour.
- Advantage: the tumour disappears more rapidly
- Isolate perfusion procedure is aplicable to the following organs or body parts:
- Thorax (lungs, thoracic wall and head)
- Extremities (arm, leg)
To remove excessive amounts of chemotherapy agents from the systemic circulation, the patient undergoes blood chemofiltration after each isolated perfusion phase. The blood chemofiltration helps to minimize side effects in cancer patients.