Drugs similar to chemicals in the body may help prevent a patient from suffering hair loss and other side effects of some cancer treatments but leave tumors completely unprotected, a researcher at Loyola University Medical Center, Chicago, and Edward Hines Jr. Veterans Affairs Hospital reported recently.
Laboratory studies indicate that synthetic prostaglandins, similar to substances released naturally by cells in response to injury, fail to interact with cancerous tissue, leaving tumors susceptible to the full impact of chemotherapy and radiation, Loyola scientist Dr. Wayne Hanson told colleagues at the 43rd Annual Meeting of the Radiation Research Society in San Jose, California
The finding represents a major step forward in the testing of prostaglandin medications, specifically misoprostol(Drug information on misoprostol) (Cytotec), to prevent side effects such as hair loss and mouth ulcers in patients undergoing cancer chemotherapy or radiation treatments, said Hanson, professor of radiation therapy and director of research in the joint Loyola-Hines radiotherapy department.
Working in conjunction with researchers at The University of Texas M.D. Anderson Cancer Center in Houston, Hanson and Dr. Luka Milas, head of the experimental radiotherapy department at M.D. Anderson, spent approximately 1½ years examining four types of rodent tumors with different characteristics.
Injecting the rodents with a prostaglandin solution prior to treatment of their tumors shielded the animals from hair loss and other damage to healthy cells, while leaving the tumors fully exposed to the radiation, Hanson said.
Protecting Against Stomatitis
Recent clinical trials of 70 patients undergoing radiation for head and neck cancers, conducted by Hanson and Dr. James Marks at Loyola and Hines, demonstrated that merely rinsing the mouth with a prostaglandin solution can protect healthy cells surrounding the tumors and reduce the development of mouth ulcers. All of the participating patients had first undergone surgery to remove most of their tumors.
"Patients in the study were asked to 'rinse and swish' their mouths with a solution in which we had dissolved a tablet of misoprostol and then to spit out the substance. Because we did not tell them to gargle, some of them developed sores at the back of their throats, although their mouths remained ulcer-free," Hanson said.
"Our early concern was that use of a prostaglandin medication would not only guard healthy tissue, but afford the tumor protection, as well. However, in our laboratory studies, we determined that this does not happen, although we do not know precisely why," Hanson said.
He hypothesized that the tumor presents a dramatically altered biologic environment in which prostaglandins are unable to interact with cells as they do in normal tissue.
Hanson, who began his prostaglandin research in the early 1980s, is now planning to coordinate a national study in which several hundred head-and-neck cancer patients will be asked to gargle and swallow a prostaglandin solution that is odorless and colorless before undergoing radiotherapy. The study will involve an estimated 50 institutions.
"One of the questions we are trying to answer is how large a dosage of prostaglandins is necessary to protect the patient adequately from harmful side effects of radiation or chemotherapy," Hanson said.
"We do know from our laboratory studies that when all of the cell receptors in healthy tissue are filled with prostaglandins, no further medication is necessary. We are also confident that an overdose of prostaglandins causes essentially no side effects, other than a bout of diarrhea, perhaps," he stated.
Hanson cautioned that the prostaglandin research is promising, but not necessarily a panacea for all side effects and all forms of cancer treatment.
"We do know prostaglandins protect from hair loss in laboratory studies and from a sore mouth in patient trials, but we do not know if they may be effective in preventing other side effects due to cancer treatments," Hanson said.
For example, prostaglandin medications are not effective with some chemotherapeutic drugs, including drugs containing platinum.
"Combining prostaglandins with these platinum drugs can actually make the side effects worse," Hanson said.
He emphasized that the use of prostaglandin medications in conjunction with cancer therapy remains experimental and is not currently available to patients.