Researchers at MD Anderson’s Cancer Center recently announced the results of its Phase II clinical trial. The researchers found that the combination of bevacizumab and atezolizumab decreased clinical trial participants’ malignant peritoneal mesothelioma (MPeM) by an average of forty percent. In most of the patients, the disease was at an advanced stage of malignancy, yet the drugs were well-tolerated.
According to Science Daily, MPeM strikes about three hundred to five hundred Americans each year. The clinical trial is investigating bevacizumab and atezolizumab for the treatment of MPeM as well as other advanced cancers.
The drug combination also proved to be effective for patients who were intolerant (refractory) to prior chemotherapy. There are only a few treatment options for this rare cancer which forms in the lining of the abdomen. Symptoms are often not detected until the disease has progressed at which time there are virtually no treatment options. If the patient does not receive treatment, life expectancy is approximately one year.
The objective responses occurred in spite of the presence of PD-L1 which is a protein that controls immune responses. PD-L1 is usually found in normal cells and in even higher amounts in some malignant cells. The study was recently published in Cancer Discovery.
MPeM vs. Peural Mesothelioma
The majority of studies for the two drugs have centered on pleural mesothelioma (cancer of the lining of the lung) usually excluding patients with MPeM. Treatment strategies include:
- cytoreductive surgery- to remove as much tissue as possible
- hypothermic intraoperative peritoneal perfusion (with chemotherapy) –
targets abdominal cancers that have spread into the abdomen, and
- early postoperative intraperitoneal chemotherapy.
Treatment for MPeM is similar to that of peural mesothelioma even though the diseases differ in many regards. MPeM is extremely rare, is minimally associated with exposure to asbestos, occurs at a younger age, and affects women more often.
Platinum chemotherapy is recommended for both types of mesotheliomas. However, after MPeM has progressed there are no FDA approved treatments for it in advanced stages.
Progression-Free and Overall Survival
There were twenty patients assigned to the MPeM group with a median age of sixty-three. Women comprised sixty percent of the group. Seventy-five percent had no exposure to asbestos. Eighty percent of the participants were white while ten percent were Hispanic. Five percent were black and five percent other.
Atezolizumab is an immune checkpoint inhibitor targeting PD-L1 while bevacizumab inhibits vascular endothelial growth factor (a protein that stimulates the formation of blood vessels) thus slowing the growth of new blood vessels.
Patients who received standard doses of chemotherapy prior to participating in the Phase 2 clinical trial began their next therapy at eight months. This compares to patients receiving bevacizumab and atezolizumab with a median response duration of twelve months.
At the one-year mark, progression-free survival was sixty-one percent. The overall survival rate at one year was eighty-five percent. The most consistent adverse events were anemia and hypertension.
A New Treatment Option
Associate Professor Kanwal Raghav, M.D. led the study. Dr. Raghav stated that the outcome of the study far surpassed outcomes from conventional treatments. This is an indication that clinical trials are valuable in prolonging patient survival with an emphasis on rare cancers.
Dr. Raghav added that future trials should include a greater number of participants to validate the Phase 2 results and also to determine if the combination could improve surgical outcomes.