Breast cancer survivor banks on tumor vaccine
Pat Pangburn was chairman of the Texas Racing Commission in 1993 when she entered a race more difficult to win than the Kentucky Derby—an all-out sprint against breast cancer. She is still running the race today, and hopes an experimental vaccine she is receiving in San Antonio will help keep her cancer in remission.
Researchers at the Health Science Center and the Cancer Therapy & Research Center (CTRC) are conducting a Phase 3 clinical trial of the Theratope® vaccine made by Biomira Inc. Pangburn receives a shot in her thigh every month to stimulate her immunity against breast cancer cells. The clinical trial is designed for patients who have undergone first-line chemotherapy for metastatic disease—stubborn cancers that have returned even after surgery, chemotherapy and other therapies.
Pangburn, who lives in Irving, heads to an airport once a month for the hourlong flight to San Antonio. She is one of the first 950 patients worldwide to receive the vaccine. Five of those patients are in San Antonio, where Dr. Peter M. Ravdin, professor of medicine at UTHSC and medical oncologist with the CTRC, enrolls them in the clinical trial. He is the local principal investigator.
"I might as well have a degree in breast cancer," Pangburn says. Her persistence in seeking information on the Internet led her to Dr. Ravdin and the Health Science Center/CTRC trial. The two institutions are partners in the San Antonio Cancer Institute, one of only two Comprehensive Cancer Centers in Texas as designated by the National Cancer Institute.
Her education began after a routine mammography. Two weeks after the initial reading, the radiologist called and asked her to come in for another session. She underwent a surgical biopsy that revealed cancer in both breasts, but not in the lymph nodes. She was diagnosed with stage one, or early, breast cancer. She chose the most aggressive surgical treatment — bilateral mastectomy — and six months later underwent breast reconstruction.
"Mastectomy was supposed to take care of it," Pangburn says. "I had every favorable prognostic indicator. I was disease-free for seven years, but then it came back. That’s why people are scared of cancer—because of its unpredictability."
Her nadir came the week after Thanksgiving 1999, when a chest x-ray revealed a small tumor on her left lung. Both patient and doctor hoped it was not a metastasis, because tumors that spread from the original site tend to be incredibly aggressive. "But it had identical pathology to my original tumor. I had it removed, and the doctors said it was nowhere else in my body. Still, the nature of metastatic disease is it keeps on coming back."
She received her first injection of the vaccine last August. "We are treating her with vaccine to try to extend her remission," Dr. Ravdin says. "We started a year ago with our first patient. This type of immunity-based therapy may soon become a prime weapon, along with surgery, chemotherapy, hormone therapy and radiation therapy, in our arsenal against cancer."
Dr. Ravdin, who joined the UTHSC faculty in 1987, is one of the country’s leading medical oncologists. He was an invited participant in the Consensus Development Conference on Adjuvant Therapy for Breast Cancer, held Nov. 1-3 at the National Institutes of Health. The group discussed topics such as selection of post-operative therapies, side effects and promising new research directions.
Pangburn believes women must take an active role in their own care. "I want to encourage any woman with breast cancer to actively seek out a clinical trial in which she can help herself and other women, because that’s the only way we are going to get a cure." Fewer than 5 percent of women eligible to participate in such trials actually do so, she says. "We need to say to our private oncologists, ‘I want to be in a clinical trial.’ "
The Theratope® vaccine consists of an antigen that reacts with the surface of breast cancer cells. An antigen is any substance capable of inducing a specific immune response. Researchers theorize that the vaccine teaches the body’s own immune cells to recognize the surface of the cancerous invaders and to attack them.
The vaccine was tested in Phase 1 and 2 clinical trials that showed promising results and few side effects, mostly irritation at the site of the injections. It remains to be seen whether the vaccine can significantly extend the lives of patients. Participants in the Phase 3 trial are divided into two treatment groups, one receiving the vaccine along with a general immune cell stimulant and the other receiving the immune cell stimulant alone.
Pangburn raised and raced horses in the 1980s in the Dallas suburb of Southlake. Then her race really began. She has survived surgeries on her breast and lung, has endured front-line chemotherapy after surgery and has received endocrine therapy. At the time of her last screening exam, she was disease-free. But the specter of recurrence is ever present. That is why a vaccine, if it works, would be so important.
"I live from scan to scan," she says. "I hope others after me won’t have to."