Wafers offer new weapon in the war on brain tumors
Treats tumor without systemic toxicity
Malignant gliomas are one of the most deadly cancers left. And with 17,000 to 20,000 new brain tumor cases reported each year, the disease is on the rise. To date, the best medical science has achieved is to push the survival rate for brain tumor patients from time of diagnosis from four months 10 years ago to roughly 11½ months as the century draws to a close.
However, a new chemotherapy delivery system shows great promise in preliminary studies for increasing the survival rate without the systemic toxicity common to IV chemotherapy. "We know that 95% of brain tumors grow back within 20 mm of where they were resected," says Alan J. Hamilton, MD, head of the department of surgery and chief of the division of neurosurgery at the University of Arizona Health Sciences Center in Tucson. "Systemic chemotherapy wasn’t giving us a good outcome because of the brain/blood barrier which prevents the chemo ther apy agents from being delivered where they’re needed."
Hamilton says he is now seeing some promising results from Gliadel wafers (polifeprosan 20 with carmustine implant, by Rhone Poulenc Rorer Oncology in Collegeville, PA). Gliadel wafers contain chemotherapy agents sealed in a polymer that can be implanted directly into the resection cavity when the tumor is removed. "The wafers are a way of releasing the drug slowly directly into the operative bed. The polymer breaks up slowly, like a bar of soap dissolving in your shower. The drug is delivered over a period of four to six weeks, bypassing the blood/brain barrier."
Hamilton also say that because Gliadel is delivered directly into the brain, it doesn’t cause the systemic toxicity experienced by patients receiving the drug by IV. "The drug remains bound up in the brain tissues, which is right where you want it. It doesn’t do any good if the drug gets into the bloodstream — it only makes patients sick. With the wafers, patients don’t get nauseous, they don’t lose their hair, and they don’t have red blood cell counts that keep falling. "
Hamilton has conducted several studies of the efficacy of the Gliadel wafers. A double-blind, randomized, placebo-controlled study of 222 brain tumor patients who previously had failed standard treatment with surgery, radiation, and chemo therapy found that Gliadel patients with very malignant tumors had a 56% survival rate at six months vs. 30% in the placebo group.
A second, smaller, double-blind, randomized placebo-controlled study of 32 newly diagnosed patients implanted with Gliadel wafers at the time of initial tumor removal found that the median survival rate for patients in the Gliadel group was 58 weeks, compared with 40 weeks for the placebo group. "Our number of long-term survivors is increasing and suggests that treating patients upfront has a significant survival benefit and may make two- to three-year survival rates the norm," says Hamilton.
In fact, he has five patients who are alive and well five years after treatment with Gliadel wafers. "More important, they have a good quality of life. They are all working and report feeling well."
The implantation procedure itself has several benefits over traditional brain tumor removal surgery, notes Hamilton. "A computer guidance system is used to locate the tumor and make linear incisions. A smaller flap is used which leaves a better cosmetic result and also heals better with less wound leakage and lower infection rates."
Patients undergoing this type of tumor removal and wafer implantation go home within 48 hours and recover more quickly, he notes. "This means they can start radiation sooner, and I get a double-whammy because the Gliadel makes any cells left in the brain more sensitive to radiation."
The wafers must be handled with double gloves, cautions Hamilton. "The wafers have a lot of chemotherapy agent in them. We time the arrival of the wafers to the operating room for the moment the tumor is removed. They come frozen and individually wrapped in foil. The wafers can be refrozen within six hours. If we only use four of the wafers in a box of eight, the remaining four wafers can be returned to the pharmacy."
Of course, new therapies often come with a high price tag, and Gliadel wafers are no exception, he says. A box of eight wafers costs $9,600, without the added costs of surgery and related hospital costs. "We want to compare the cost-effectiveness of the Gliadel wafers to traditional IV chemotherapy. Most payers cover the $14,000 cost of a course of systemic IV chemotherapy, but we’re still working on a case-by-case basis to get reimbursement for the Gliadel wafers," he says. (For more on reimbursement issues, see story, below.)
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