Bones are the third most common location where cancer cells spread and metastasize. Bone metastases occur when cancer cells gain access to the blood stream, reach the bone marrow, begin to multiply and then grow new blood vessels to obtain oxygen and food-which in turn causes the cancer cells to grow more and spread. Some bone metastases become painful because the tumor eats away at the bone, creating holes that make the bone thin and weak. As the bones are replaced with tumor, nerve endings in and around the bone send pain signals to the brain. If left untreated, bone metastases can eventually cause the bone to fracture–seriously affecting a patient’s quality of life. In treating cancer patients with painful bone metastases, interventional radiologists may use one of the two different thermal ablation techniques–radiofrequency ablation and cryoablation. This form of therapy is aimed at desensitizing the bone by killing the nerve endings in the vicinity of the metastasis. They can also treat painful vertebral metastases or fractures with vertebroplasty.
- Bone pain affects 70 percent of patients with bone metastases
- Bone fracture
- Spinal cord compression
Bone Cancer Diagnosis
There are a number of tests that can help in the diagnosis of cancer, including blood tests, physical examination and a variety of imaging techniques including X-rays (e.g., chest X-rays and mammograms); computed tomography (CT); magnetic resonance (MR) and ultrasound. Usually, however, the final diagnosis cannot be made until a biopsy is performed. In a biopsy, a sample of tissue from the tumor or other abnormality is obtained and examined by a pathologist. By examining the biopsy sample, pathologists and other experts also can determine what kind of cancer is present and whether it is likely to be fast or slow growing. This information is important in deciding the best type of treatment. Open surgery is sometimes performed to obtain a tissue sample for biopsy. But in most cases, tissue samples can be obtained without open surgery with interventional radiology techniques.
Bone Cancer Treatments
As vascular experts, interventional radiologists are uniquely skilled in using the vascular system to deliver targeted treatments via catheter throughout the body. In treating cancer patients, interventional radiologists can attack the cancer tumor from inside the body without medicating or affecting other parts of the body.
Radiofrequency ablation (RFA) offers a nonsurgical, localized treatment that kills the target tissue with heat, while sparing the healthy tissue. Because of the localized nature of this treatment, RFA does not have any systemic side effects. Radiofrequency ablation can be performed without affecting the patient’s overall health and most people can resume their usual activities in a few days.
In this procedure, the interventional radiologist uses imaging to guide a small needle through the skin into the tumor. From the tip of the needle, radiofrequency energy is transmitted into the target tissue, where it produces heat and kills the tumor. Although the dead tumor tissue shrinks, the bone that is already eaten away will not grow back.
Preliminary studies have demonstrated that RFA significantly reduced bone pain from metastatic disease in over 90 percent of patients who had failed or were not suitable candidates for conventional therapy. In these studies, there were only few patients who suffered any side effects or complications. Therefore, RFA was demonstrated to be safe and effective in selected patients. A multicenter clinical trial is underway to further investigate the role of RFA in management of painful bone metastases. A direct comparison of RFA and radiation therapy may be warranted in the future.
- May be performed under conscious sedation or general anesthesia
- Is well tolerated. Most patients can resume their normal routines the next day and may feel tired only for a few days.
- Can be repeated if necessary
- May be combined with other treatment options
- Can relieve pain and suffering for many cancer patients
Cryoablation is similar to RFA in that the energy is delivered directly into the tumor by a probe that is inserted through the skin. But rather than killing the tumor with heat, cryoablation uses an extremely cold gas to freeze it. This technique has been used for many years by surgeons in the operating room, but in the last few years, the needles have become small enough to be used by interventional radiologists through a small nick in the skin, without the need for an operation. The “ice ball” that is created around the needle grows in size and destroys the frozen tumor cells.
The spine is one of the most common sites of metastasis. Vertebral bodies involved by the tumor may become painful and may eventually fracture. Surgical intervention with reconstruction of the spinal column is indicated only if the tumor causes compression of the spinal cord or instability of the spine. Vertebroplasty is an outpatient procedure performed using conscious sedation. An interventional radiologist inserts a needle through a small incision in the back, directing it under fluoroscopy (continuous, moving X-ray imaging) into the fractured vertebra. The physician then injects a medical-grade bone cement into the vertebra. The cement hardens within about 15 minutes and stabilizes the fracture. This treatment reduces pain, prevents further collapse of the vertebra, and restores mobility. Vertebroplasty dramatically improves back pain within hours of the procedure, provides long-term pain relief and has a low complication rate, as demonstrated in multiple studies.
New Cancer Treatments on the Horizon
Interventional radiology is playing a role in developing new techniques that may improve cancer treatment in the future, including the use of magnetic particles to draw cancer-killing agents into tumors; and the delivery of genetic material, called gene therapy, to fight or prevent cancers. These techniques are still investigational, but they offer new hope in the war against cancer.
Interventional radiologists are currently investigating a new technique in which magnets are used to pull chemotherapy drugs into tumors. Microscopic magnetic particles are attached to the cancer-killing drugs and infused through a catheter into the blood vessel that feeds the tumor. A rare earth magnet is positioned over the patient’s body directly above the site of the tumor. The magnet pulls the drug-carrying particles out of the blood vessel so that they lodge in the tumor. Although the technique is still experimental, early research is promising. Physicians are hopeful that it will bolster the effects of chemotherapy while avoiding some of the drugs’ side effects, such as hair loss and nausea.
In recent years, scientists have gained a new understanding about genes—the basic biological units of heredity—and the role they play in disease. This knowledge has set the stage for medical science to alter patients’ genetic material to fight or prevent cancer. Although the science of gene therapy is still in the early, experimental stages, researchers are hoping that in the future the therapy can be used to:
- alter the cells of a patient’s natural immune system with cancer-fighting genes and returning them to the body, where they could more forcefully attack the cancer;
- remove cancer cells from the body and alter them genetically so that the patient’s own immune system will mount a strong defense against them. In this technique, the altered cancer cells would act as a cancer vaccine;
- replace a faulty gene responsible for the growth of cancer with a “good” gene;
- inject a tumor with genes that will make it more susceptible to chemotherapy or other cancer-fighting agents; and
- make bone marrow and other organs resistant to chemotherapy, so that the drugs will destroy tumors without damaging healthy tissue.
One of the challenges of gene therapy is finding safe and effective ways to deliver genes or genetically altered cells to the site of the tumor. Interventional radiologists, with their special expertise in using X-rays and other imaging techniques to guide catheters and other tools through the body are expected to play an important role in this new technology.
Treatments for Cancer Complications
There are also a number of interventional radiology techniques that are used to treat the complications of cancer, including pain, bleeding, obstruction of vital organs, blood clots and infection. Although these treatments do not cure cancer, they can make patients more comfortable, extend life by treating serious complications and improve the quality of life for cancer patients.
Control of pain is one of the most important aspects of cancer care. Pain not only affects patients’ quality of life and ability to function, it may also lower their tolerance for needed cancer treatments.
In many cancer patients, pain results from the spread of the tumor into surrounding nerves and other tissues. For example, patients with cancer of the pancreas or stomach, sometimes experience pain from the spread of the tumor into a network of nerves and blood vessels in the abdomen called the celiac plexus. To treat the pain, interventional radiologists insert catheters or needles into the affected area and administer alcohol or other agents that destroy the nerves causing the pain.
A particularly painful complication of cancer is when the disease spreads (metastasizes) to bones. In a technique called transcatheter embolization, interventional radiologists inject tiny particles, the size of grains of sand, through a catheter and into the artery that supplies blood to the tumor. The particles cause clotting that decreases the tumor’s blood supply, reducing pain and decreasing the likelihood of bone fracture.
If a cancer spreads to the blood vessels it may cause hemorrhage or bleeding. An interventional radiology technique called transcatheter embolization can be used to clot the affected blood vessels and stop the bleeding.
Treating Organ Obstruction and Infection
Cancers can obstruct the normal flow of urine or bile, causing these fluids to build up in the body. If left untreated, these conditions are not only painful but may also result in organ failure or infection. Under X-ray guidance, catheters can be inserted to drain the collection of fluids. Often, a small device called a stent is inserted into the organ to bypass the obstruction and allow fluids to drain internally.
Treating Blood Clots
One common side effect of cancer or cancer treatments is the development of blood clots, or emboli, that can be life-threatening if they travel to the brain, lungs or heart. There are two interventional radiology procedures that can reduce the risks posed by blood clots:
- Intra-arterial thrombolysis. In this technique, the interventional radiologist guides a catheter through the blood vessels and to the site of a blood clot. Clot-busting drugs are infused through the catheter to break up the clot.
- Filter placement. This technique is most often used when a blood clot is detected in the blood vessels of the leg (a condition called deep vein thrombosis). The interventional radiologist guides a small filter into the blood vessel that receives blood from the lower body (the vena cava) and carries it to the heart. If the blood clot dislodges from the vein in the leg, the filter will trap it before it can reach the heart.
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