High-Dose Chemotherapy for Breast Cancer: Clinical Trials Overview
Up until the mid-1990s, very few randomized clinical trials of high-dose chemotherapy for breast cancer had been done. In response to this, in the mid- to late-1990s, multiple clinical trials were begun around the world to compare the effectiveness of high-dose chemotherapy and blood cell transplant with a standard treatment for various stages of breast cancer.
These clinical trials included five trials sponsored by the National Cancer Institute and designated as "high-priority" studies. These five trials have now closed to further enrollment. One of the trials closed without results due to low enrollment. Two others (SWOG 9623 and EST 2190) are still treating and following patients who were at high risk of developing recurrent disease after initial treatment. [Note: Results from EST 2190 were published in the July 3, 2003, issue of the New England Journal of Medicine; see the journal abstract.)
A fourth high-priority trial (CALBG 9082), led by William Peters, M.D., Ph.D., of the Barbara Ann Karmanos Cancer Institute in Detroit, also treated patients with high-risk breast cancer. Final results are expected by 2003, but the researchers presented preliminary findings at the 1999 meeting of the American Society of Clinical Oncology.
Peters' study enrolled 783 patients with stage II or III breast cancer and more than 10 positive lymph nodes. Early results showed no difference in survival between patients who received high-dose therapy and patients who received intermediate-dose therapy.
The study compared patients who receive high doses of cyclophosphamide, cisplatin and BCNU, followed by transplants, with patients who receive intermediate doses of the same drugs without transplants. Although early results show no difference in survival, the patients will be followed for several more years before the trial is formally concluded.
The fifth high-priority trial (EPBT01) was led by Edward Stadtmauer, M.D., at the University of Pennsylvania Cancer Center, and enrolled 553 patients who had metastatic (spreading to other organs) breast cancer. All patients received four to six rounds of standard chemotherapy. The patients whose disease responded were then randomized; 89 received the standard chemotherapy and 110 the high-dose chemotherapy plus transplant.
After following patients for an average of three years, the researchers reported no significant difference in overall survival times: 32 percent of the high-dose group and 38 percent of the conventional chemotherapy group were alive at three years post-treatment. There also was no difference in the time it took for the disease to worsen: about nine months post-treatment for each group. In addition, infection, vomiting, diarrhea and other side effects were much more common in the high-dose group.
While enrollment in this study was smaller than originally planned, the authors stated that there were still enough patients to detect even a small (six month) survival-time advantage. They concluded that they did not recommend high-dose chemotherapy for patients with metastatic breast cancer. The results from this study were published in the April 13, 2000, issue of the New England Journal of Medicine.
Although not designated a NCI high-priority clinical trial, another study, led by Gabriel Hortobagyi, M.D., at the University of Texas M.D. Anderson Cancer Center, reached a similar conclusion for patients with high-risk breast cancer as defined by multiple positive lymph nodes. The results, published in the February 2, 2000, issue of the Journal of the National Cancer Institute found no significant difference in survival between the high-dose chemotherapy group and the standard dose chemotherapy group.
The three-year survival rate for the group receiving high-dose chemotherapy was 58 percent, compared to 77 percent for the standard chemotherapy group. Relapse-free survival rates were 48 percent and 62 percent, respectively.
However, this study included only 78 patients, a number "too small to detect even moderate differences" in survival times. The authors concluded that "high-dose chemotherapy [for high-risk breast cancer] is not indicated outside of a clinical trial."