Heated Intraperitoneal Chemotherapy
Heated intraperitoneal chemotherapy, also known as HIPEC, is a recently developed strategy for using chemotherapy to treat peritoneal mesothelioma more effectively. Instead of delivering chemotherapy drugs to the patient intravenously, which is how the therapy is traditionally given, HIPEC involves injecting heated drugs directly into the abdominal cavity to kill cancer cells and shrink tumors.
HIPEC is often used as part of a multimodal approach to treating mesothelioma, with surgery done first to remove as much of the tumors as possible. Traditionally, chemotherapy has not worked very well for treating peritoneal mesothelioma, but HIPEC has improved survival rates among patients and has proven to be one of the most effective ways to treat this type of cancer.
What is HIPEC?
HIPEC stands for hyperthermic or heated intraperitoneal chemotherapy. Chemotherapy is usually one of the most effective treatments for cancer. It involves administering one or more drugs that targets and kills fast-growing and fast-dividing cells, like cancer cells. For many patients it is effective at shrinking tumors and in some cases achieving remission. The usual way to administer the drugs is intravenously. This means the drugs go into the bloodstream and move throughout the body. The treatment is not specific to cancer cells and results in damage to many healthy cells as well.
HIPEC is more directed and specific than this traditional way of administering chemotherapy drugs. Instead of simply putting the drugs into bloodstream where they can then reach any part of the body, the drugs are injected directly into the abdomen to target peritoneal tumors. The drugs are heated first and the abdominal cavity is essentially bathed in the chemotherapy drugs.
HIPEC begins with cytoreductive surgery, which means using surgery to remove as much of the tumors as possible. This is an important step because the chemotherapy drugs cannot penetrate to the center of tumors. The bulk of the tumors must be removed first for the chemotherapy step to be effective. Once most of the tumor tissue is removed, the bath of chemotherapy drugs can circulate and kill the remaining cancerous cells. In some cases the tumors are too numerous to all be removed by surgery, in which case the chemotherapy may not be as effective.
The second phase of the treatment is the heated chemotherapy bath. Even if the surgery resulted in the removal of all visible tumors, there are likely still cancer cells remaining in the abdomen. The goal of the second step of the procedure is to eliminate whatever remains. To do this, catheters are inserted into the abdomen. These are connected to a special machine that heats up a solution of chemotherapy drugs and pumps it through the catheters and into the abdominal cavity.
The temperature of the bath in the abdomen is monitored carefully to keep the solution at 105 degrees or a little higher. This is important because cancer cells start to die in temperatures of 105, but healthy cells can tolerate temperatures up to about 110. The machine pumps in the solution, while outflow catheters send the solution back to the machine after it has circulated through the abdomen. This procedure goes on for a prescribed amount of time, typically a couple of hours.
Chemotherapy Drugs Used
There are many options for which chemotherapy drugs are used in HIPEC, but research has found that using a combination of two drugs is more effective at extending life expectancy than using just one. Studies have also been done to determine which drugs are most effective. Some of the most common chemotherapy drugs have been used effectively in HIPEC procedures: cisplatin, carboplatin, pemetrexed, gemcitabine, and doxorubicin. Researchers continue to study the best combinations for survival of patients.
Patients undergoing HIPEC can expect to remain in the hospital for about a week. Complete recovery from HIPEC can take a few months. This includes recovering from surgery including allowing incisions to heal and making sure there are no infections. The chemotherapy drugs, however, will cause the most side effects, particularly fatigue. It can take several months to fully recover from the fatigue and to be back to normal energy levels.
How HIPEC Affects Survival Rates
HIPEC has had a significant effect on the survival of patients with peritoneal mesothelioma. In some cases, patients live five or more years after the procedure, which is a drastic improvement on survival times in patients who undergo more traditional treatments. One of the largest studies of HIPEC looked at over 400 patients and found that the median survival time was between four and five years. One patient in the study was still alive 19 years later and was considered to be cured.
Patients Eligible for HIPEC
Not all patients with peritoneal mesothelioma will be eligible for this treatment, but many are. First, it is important that the patient be healthy enough for surgery. Without surgery as the first step, HIPEC is not effective. Another disqualifying factor is extensive spread of the cancer. If the tumors have spread outside of the abdominal cavity, the procedure will have little effect on the patient’s survival. Patients who are healthy enough with no serious comorbid conditions like heart disease, and whose cancer has not spread too far, are excellent candidates and should benefit from HIPEC treatment.
Benefits and Risks
The most important benefit of undergoing HIPEC for patients with peritoneal mesothelioma is improved survival time. Most patients will have an extended life expectancy after being treated this way. There are other benefits too, as compared to traditional chemotherapy. HIPEC causes fewer and less severe side effects and it allows for a safer delivery method for more powerful and concentrated chemotherapy drugs, which helps improve survival times. HIPEC also improves quality of life for patients. Once the side effects have dissipated, patients experience reduced symptoms of the cancer, especially pain.
There are always risks and potential complications associated with surgery and chemotherapy. About 15 percent of patients will experience intraabdominal complications like fistulas, gastrointestinal leaks, or abscesses. Fifteen percent will experience abdominal wall morbidity complications, which include infections at the incision sites. Also possible are systemic complications caused by the chemotherapy drugs: infections, pulmonary problems, and suppression of bone marrow. Of course, there is also always the risk that the cancer will return at some point after the procedure.
HIPEC and Pleural Mesothelioma
HIPEC has long been used only for the treatment of peritoneal mesothelioma, but some specialists are adapting the technique for pleural mesothelioma. The practice, called heated intrapleural chemotherapy, is controversial, and while some studies have found that life expectancy can be extended, others have found that when the procedure is used in the chest cavity it is no safer than intravenous chemotherapy. This is because there are a lot of blood vessels in the chest cavity and they absorb the chemotherapy drugs from the heated bath, spreading them throughout the body, just as happens with intravenous chemotherapy. Still, some specialists have found success using the procedure and have been able to extend patient survival by years.
Research into improving HIPEC, including using a similar technique for treating pleural mesothelioma, is expected to continue. Experts and researchers should be able to advance the treatment strategy even more, helping more patients to live longer after a mesothelioma diagnosis.
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