National Heart, Lung, and Blood Institute
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Principal investigator and lead author of the paper, Richard Childs, M.D., of NHLBI's Hematology Branch said, "Considering that there are no current treatments that benefit patients who have not responded to conventional therapy, we are very encouraged by the early high response rate in our first group of patients treated, with a few patients remaining completely free of cancer more than two years from the initiation of therapy." According to Childs, the overall response rate of greater than 50 percent in patients with treatment-resistant disease is remarkable, considering that current first-line therapy is effective in less than 20 percent of cases. Three patients (16 percent) had total regression of all metastases and seven (38 percent) showed partial regression of disease.
Although tumor regressions, described by the authors as "dramatic," occurred in a number of patients, Childs cautioned that significant, but rarely fatal, complications were associated with the procedure. "It should therefore remain an investigational approach to treating kidney cancer at this point in time," he said.
Advanced renal cell carcinoma is usually fatal in less than a year. Although highly resistant to chemotherapy treatment, renal cell carcinoma is unusual among solid tumors in that it is susceptible to attack from the body's own immune system. The use of drugs designed to boost immune cells, such as interleukin-2 and interferon-alpha, has provided benefit to some patients, although many do not to respond to such therapy. Since potent immune-mediated anticancer effects have been observed against
blood-borne cancers such as leukemia and lymphoma following conventional allogeneic stem cell transplantation, a pilot trial was initiated by investigators from the NHLBI in collaboration with scientists from The National Cancer Institute (NCI) and the NIH Warren Grant Magnuson Clinical Center to explore similar beneficial antitumor effects in patients with treatment-resistant kidney cancer.
The treatment approach used in this study was based on prior laboratory research which showed that immune cells taken from a healthy donor are capable of generating powerful antitumor effects against a number of different solid tumors. Between February 1998 and August 1999, researchers enrolled 19 patients with widespread metastatic kidney cancer who did not respond to prior therapy. To make the procedure safer, a modified transplant regimen was developed which used low-intensity conditioning to spare patients the multiple toxicities associated with conventional high-dose allogeneic transplantation. A combination of two immunosuppressive drugs, cyclophosphamide and fludarabine, was given with the intent to knock out the patient's immune system to allow the foreign donor immune cells to take hold. Blood stem cells and lymphocytes from a tissue-matched sibling donor were then infused. The drug cyclosporine was administered to prevent rejection of the donor cells and graft vs. host disease, a potentially life-threatening complication that occurs when donor immune cells attack the patient's normal tissues.
Once the transplant had taken place, patients were rapidly tapered off cyclosporine to enable the donor immune cells to become more effective and to increase the chances of generating an antitumor effect. Patients who failed to completely replace their immune system with donor cells or who had tumor growth following the procedure received additional infusions of donor lymphocyte cells to enhance antitumor reaction.
Response to treatment was defined as complete if all measurable tumor disappeared and partial if measurable lesions decreased in size by at least 50 percent for at least 30 days. Regression was seen in multiple sites, including lymph nodes, adrenal glands, liver, bones, and lung. A unique pattern of cancer regression was observed, characterized by delayed tumor regressions that did not occur until a median of four months following transplantation. In some cases tumor regression was markedly delayed, occurring greater than seven months following the procedure in two patients. Tumor regressions did not occur until the patient's immune system had been completely replaced by the donor's cells, and, in most cases, followed the withdrawal of cyclosporine. The researchers noted that, interestingly, six of 10 patients who ultimately had a response to the therapy had initial evidence of tumor growth in the first few months after transplantation.
The procedure was not without complications. Acute graft vs. host disease, usually mild to moderate in severity, was the major toxicity, occurring in 53 percent of the patients. Two patients died due to transplant-related complications, one from graft vs. host disease and one from a complication of bacterial sepsis.
Two patients who showed a response to the therapy have since developed progressive disease. Although follow-up was relatively short, there was a trend toward a survival advantage in those patients who had tumor shrinkage following the procedure. According to W. Marston Linehan, M.D., of the Urologic Oncology Branch of the NCI, "We hope to expand the number of patients who can enroll in our clinical trial. The ultimate objective is to test this therapy in a large, randomized controlled trial to determine the true efficacy of this treatment."
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Information on clinical research conducted by NHLBI's Hematology Branch can be found at http://www.nhlbi.nih.gov/index.htm.