Adenoid cystic carcinoma, a tumor type that represents less than 1 percent of all breast carcinomas, generally is treated with surgery alone, either lumpectomy or mastectomy. Steven Chen, assistant professor of surgical oncology, wanted to find out if adding radiation therapy to surgery would improve outcomes for patients.
Chen's research was sparked by a patient whom he cared for two years ago. "I had seen a patient with this type of cancer, and wasn't sure what to do with her after surgery," Chen said. "I wondered if she was supposed to get radiation therapy."
Chen took the case to a meeting of other cancer specialists. All agreed that there was no solid evidence available about the value of radiation therapy for this type of tumor. Physicians do not like to give patients any radiation dose when it is not clear that it could be effective.
Published online this month in the Journal of Surgical Oncology, Chen's study identified 376 patients across the country diagnosed with adenoid cystic carcinoma of the breast in the Surveillance, Epidemiology, and End Results (SEER) registry maintained by the National Cancer Institute. All of the patients had undergone breast cancer surgery between 1988 and 2005. Among them, 129 (34 percent) also had received radiation therapy.
"We found that the women who got radiation treatment did better," Chen said. "Even after accounting for age, tumor stage and type of surgery, radiation therapy still cut the death rate by 56 percent overall."
Among women who had radiation therapy after lumpectomy, survival rates after five years for those undergoing surgery and radiation were 94 percent; survival rates were 82 percent for those having surgery alone. By 10 years, that gap had widened: 86 percent of those undergoing radiation were still alive, whereas only 67 percent of those having surgery alone were still alive.
Because of the relatively small number of patients in the study, results were limited to women with early-stage disease. And because so few of the women in the study had a mastectomy, the sample was too small to determine a benefit from radiation therapy for those patients.
Chen hopes the research gives cancer specialists helpful information in choosing therapeutic approaches for patients with this type of breast cancer.
"We hope surgical oncologists will see this study and start referring patients to radiation oncology more often," he said. "There are good reasons why a woman might choose not to have radiation therapy, but they won't have an opportunity to have that discussion if they don't get a referral."
Other authors on the study were Jodi M. Coates, Steve Martinez and Richard Bold, all members of the UC Davis Cancer Center's surgical oncology team.
UC Davis Cancer Center is the only National Cancer Institute-designated center serving the Central Valley and inland Northern California, a region of more than 6 million people. Its top specialists provide compassionate, comprehensive care for more than 9,000 adults and children every year, and offer patients access to more than 150 clinical trials at any given time. Its innovative research program includes more than 280 scientists at UC Davis and Lawrence Livermore National Laboratory. The unique partnership, the first between a major cancer center and national laboratory, has resulted in the discovery of new tools to diagnose and treat cancer. Through the Cancer Care Network, UC Davis is collaborating with a number of hospitals and clinical centers throughout the Central Valley and Northern California regions to offer the latest cancer-care services.