Chemotherapy for Mesothelioma
Chemotherapy Agents Used for Mesothelioma
There are many different chemotherapy agents available, and different ones are used for different types of cancers. For mesothelioma (whether it’s pleural, peritoneal or a more rare type like pericardial or testicular), the most commonly used chemotherapy regimen is pemetrexed (sometimes known by the brand name Alimta), combined with a platinum-based agent (cisplatin or carboplatin).
Since a 2003 clinical trial demonstrated a significant benefit to using pemetrexed along with cisplatin in patients with malignant pleural mesothelioma, this combination has been the standard chemotherapy regimen used in all types of mesothelioma. No other chemotherapy regimen has been shown to offer a survival benefit in mesothelioma patients. Cisplatin is usually preferred, but in those who experience significant side effects, carboplatin can be used instead.
Pemetrexed works by blocking enzymes that are needed for DNA replication. Without these enzymes, cancer cells are not able to divide. Platinum chemotherapy agents such as cisplatin and carboplatin work by reacting with and damaging the DNA inside of cancer cells. This damage ultimately leads to the death of the cell.
Cancer cells can sometimes develop resistance to particular chemotherapy agents. Using more than one chemotherapy agent at the same time helps to overcome this problem. When two different drugs are being used, then a particular cancer cell must become resistant to both of them in order to evade the treatment. Although using two drugs rather than one does help to reduce the likelihood of resistance, it doesn’t prevent it completely, and it’s still possible for a cancer to become resistant to treatment with multi-agent chemotherapy.
A 2016 study showed that, in those patients who experienced a clinical benefit from chemotherapy, overall survival improved from 6.5 months to 16.8 months. However, not all patients responded to the treatment. The likelihood of a response varied from 45 to 63 percent depending on the cell type of the cancer.
In most cases, chemotherapy is given in cycles. The patient comes to a cancer clinic to receive an infusion of the medications. It takes a few hours to receive a chemotherapy infusion. The body is then given a period of time to recover before the next infusion is given. Mesothelioma patients commonly receive two to four cycles of chemotherapy, spaced about three weeks apart. However, your treatment team may recommend a different protocol based on your specific situation.
Methods of Chemotherapy for Mesothelioma
Adjuvant chemotherapy is sometimes referred to as induction chemotherapy. Technically, this is not correct; induction chemotherapy actually refers to chemotherapy that’s given before radiation therapy, while adjuvant chemotherapy refers to chemotherapy that’s given before surgery. However, even some cancer researchers use the term “induction chemotherapy” to refer to chemotherapy given before surgery, so you may encounter this term in discussions of your medical care.
True adjuvant chemotherapy is given within three months after surgery. However, some oncologists recommend waiting to give chemotherapy after surgery until there is recurrence of the cancer. This is because there’s only one chemotherapy regimen that’s proven to be effective, and if it’s used as adjuvant chemotherapy, then there will be few additional therapeutic options left when the disease recurs. In addition, the surgical procedures used for mesothelioma are very invasive, and patients may not be healthy enough to receive chemotherapy soon after such a procedure.
Studies have shown that adjuvant and neoadjuvant chemotherapy are approximately equivalent in terms of their effectiveness. Oncologists may recommend different approaches in different patients based on factors such as the stage of the tumor and the patient’s overall medical condition.
Doing so increases the efficacy of the treatment and helps to reduce side effects by minimizing exposure of the rest of the body to the chemotherapy drugs. The medications are warmed before being infused in order to cause surface blood vessels to dilate and improve the ability of the chemotherapy to penetrate into the tissues.
For peritoneal mesothelioma, intraoperative chemotherapy has been part of the standard of care for years. This method is known as HIPEC, or hyperthermic intraperitoneal chemotherapy. It’s used during a surgical procedure known as cytoreductive surgery, or CRS, which involves the surgeon removing as much cancer tissue as possible from the abdomen. After the removal of tumor tissue is complete, a warmed solution of chemotherapy drugs is infused into the abdominal cavity. It’s left in place for a period of time and then washed out. This method is widely considered the gold standard of treatment for peritoneal mesothelioma, and five-year survival rates have been reported to be as high as 44 percent.
More recently, surgeons have begun using a similar method for pleural mesothelioma. The method is known as HITHOC, or hyperthermic intrathoracic chemotherapy. This is used during surgery to remove the cancer, which may be either extrapleural pneumonectomy (EPP) or pleurectomy/decortication (P/D). After the removal of tissue, a warmed solution of chemotherapy drugs is infused into the thoracic cavity. This is left in place for a period of time and then washed out. The available research shows that adding HITHOC to surgery extends survival by a few months, although more studies are needed to clarify how effective this treatment is.
These include patients in a more advanced stage, those who have a sarcomatoid cell type and those whose age and/or overall medical condition would not allow them to tolerate surgery.
When chemotherapy is not effective, the American Society of Clinical Oncology recommends that patients be encouraged to enroll in a clinical trial. This is because there are no effective second-line chemotherapy options available. If first-line chemotherapy has failed, then an experimental treatment may offer patients the best chance to extend life. It’s important to recognize that there are trade-offs to participating in a clinical trial; if this is an option that you’re interested in, you should discuss it with your treatment team to learn more about the potential risks and benefits of participation.
Palliative Chemotherapy for Mesothelioma
In palliative care, chemotherapy may be used to shrink particular tumors that are causing significant symptoms. For example, in a peritoneal mesothelioma patient, a particular tumor may be causing discomfort due to a blockage of the intestine. Chemotherapy can be used to attempt to shrink this tumor and relieve the symptoms. In this case, the goal is not to eliminate the cancer cells, but to make the patient more comfortable.
In palliative care, the risks of side effects from the chemotherapy must be weighed against the potential benefits of relieving symptoms that the cancer is causing. The ultimate goal is to improve the patient’s overall comfort, and chemotherapy may not be the best way to do so in all cases.
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