Thoracic surgeon Dr. Shanda Blackmon at the Mayo Clinic in Rochester, Minnesota, believes there is a place for cryotherapy in the future multidisciplinary treatment of pleural mesothelioma.
She wants to show it with this groundbreaking clinical trial.
“We think [cryotherapy] could play an important role in treatment,” Blackmon told Asbestos.com. “So far, things look promising, but you can’t say anything specific without more numbers. Right now, it’s a little like telling a story.”
Cryotherapy involves destroying cancer cells, or any abnormal tissues, by freezing them with controlled nitrogen vapors. It is often used for external tumors and applied directly with a spraying device.
It also is used internally with a tube called a cryoprobe for several types of cancers and precancerous conditions. Cryotherapy is being used selectively with prostate cancer and liver cancer and still being researched for use with cancers of the colon, breast and kidneys.
Cryotherapy as a Surgical Adjuvant for Mesothelioma
In this mesothelioma clinical trial, cryotherapy is being tested and measured as a surgical adjuvant.
The hope is that it will spark an immunological response, allowing the patient’s own immune system to better recognize and attack the tumor cells and reduce the extent of surgery.
Mesothelioma is a rare and aggressive cancer that spreads quickly once it takes hold, going unrecognized by the immune system.
The Mayo Clinic in Rochester is the only location for the trial.
Cryotherapy is done two weeks before major surgery, during a staging pleuroscopy — an otherwise minimally invasive procedure used to better measure the extent of disease.
The trial is expected to continue through 2018 and possibly beyond.
“Based on what we’ve seen so far, it doesn’t cause any harm. It’s not dangerous. And there is evidence that it’s doing something. Now, how much? We don’t have enough patients yet to measure that,” Blackmon said. “We are optimistic.”
Several Clinical Trials Available
The Mayo Clinic, a leader in both laboratory and clinical research, has several clinical trials open for patients with mesothelioma, including:
- An evaluation of the Surgery for Mesothelioma After Radiation Therapy (SMART) approach. Instead of the typical multidisciplinary protocol that includes radiation after surgery, this trial will use the opposite approach, measuring how much high-dose radiation shrinks tumor size and decreases spread before aggressive surgery.
- The immunotherapy combination of nivolumab (Opdivo) and ipilimumab (Yervoy) against a chemotherapy combination of pemetrexed and cisplatin will be measured in a trial for patients with unresectable disease.
- The intrapleural measles virus therapy is being tested for immunological response, potential side effects and best dosage levels for mesothelioma patients. The belief is that this vaccine strain also will kill some cancer cells directly.
- A first-line systemic study of an arginine degrading enzyme (ADI-PEG 20) used to restrict an amino acid thought necessary for mesothelioma cells to survive. The study includes a subset of patients who have not started either chemotherapy or radiation treatment.
Need for More Clinical Trial Participation
The Mayo Clinic treats an estimated 100 patients with mesothelioma each year, but only 15 to 20 percent are candidates for aggressive surgery.
Recruiting enough patients for a mesothelioma clinical trial is often difficult because of the rarity of the cancer.
Doctors diagnose less than 3,000 cases of mesothelioma each year in the U.S., and the majority of those are not diagnosed until the later stages.
Only a small percentage are surgical candidates.
The cryotherapy trial was restricted originally to patients undergoing a pleurectomy and decortication, but has been expanded to include those having an extrapleural pneumonectomy.
Although this is the only active cryotherapy clinical trial in the country for mesothelioma, a different version of the procedure — cryoablation — is used regularly at the Pacific Mesothelioma Center in Los Angeles.
Cryotherapy also can be used as a palliative treatment to help control the growth of tumors. It is less toxic to healthy tissue when tumors are more closely targeted.
The clinical trial procedure at the Mayo Clinic involves two or three applications of a spray on specific tumor sites within a minute.
If effective, it should allow the surgeon to preserve more of the lung involved.
“Without bigger numbers [of patients], it’s going to be difficult to make any definitive conclusions,” Blackmon said. “But we’re keeping this trial open because we think it could play an important role.”