SAN FRANCISCO—Women who survive breast cancer may be at an increased risk of thyroid cancer during their lifetimes—requiring continued surveillance, researchers suggested at the 2016 ASCO Cancer Survivorship Symposium.
In a study that followed outcomes among Korean women, 32 cases of thyroid cancer occurred among 5,514 women who survived breast cancer—about three times the number of thyroid cancer that would have been expected in the general population.
“Our study would suggest that a prolonged follow-up examination for a second primary cancer is needed to provide earlier detection and effective cancer prevention strategies,” said Hong Kyu Jung, MD, a fellow in breast surgery at Soonchunhyang University, Seoul Hospital, Republic of Korea.
The study only looked at second primary cancers other than breast cancer—the most common second primary in women who have had a first breast cancer diagnosis.
Aside from thyroid cancer and breast cancer, Jung suggested the risk of another second primary in breast cancer survivors is about the same as the risk in the general population. In his poster presentation, he told OT he reassures his patients who have undergone successful breast cancer surgery they should not worry about a second primary aside from thyroid cancer. He also said women who are receiving tamoxifen should also undergo regular checks for endometrial cancer.
In his study that followed women who underwent breast cancer surgery from January 1989 through January 2014 at three Korean institutions, there were 99 cases of a second primary cancer—and 48 of those cases were thyroid cancer.
The research team estimated the expected number of thyroid cases in the general population would have been about 13 cases, so the survivors of breast cancer had about a 2.5 times risk of developing thyroid cancer, a significant difference [Standardized incidence ratio (SIR) 2.47 (95% CI 1.69=3.48)].
There were six cases of endometrial cancer reported among the women who survived breast cancer. In the general population, less than one case of that disease would have been expected. That translates to more than an eightfold risk of endometrial cancer in this group, also a significant finding [SIR 8.36 (95% CI 3.05-18.20)].
However, Jung noted most of the women who developed endometrial cancer after surgery were on tamoxifen or other hormonal therapy—and the relationship between tamoxifen and subsequent endometrial cancer has been well-documented.
Ten patients were diagnosed with stomach cancer as a second primary, but that was not statistically different than the expected incidence in the general population of Korean women.
In conducting the study, Jung and his colleagues reviewed the medical records of patients diagnosed with invasive breast cancer—excluding patients who were diagnosed with ductal carcinoma in situ—at three branch hospitals of Soonchunhyang University in Seoul, Cheonan, and Bucheon. Other than second breast cancer diagnoses, the research team also excluded patients who developed cancers within two months of the original breast cancer diagnosis. About 10 percent of the women who developed a second primary experienced that cancer 10 years or longer after the original breast cancer diagnosis.
About 16 percent of the patients in the study were ages 30-39 years, and 8 percent of the patients were older than 70 years. About 27 percent of the patients were ages 50-59 years, Jung reported. Of the women who did develop second cancers in the study, 77 had received chemotherapy, 68 had been taking hormonal therapy, and 44 had undergone radiation therapy.
Surveillance & Treatment
In commenting on the study, Debra Friedman, MD, co leader of the Cancer Health Outcomes and Control Research Program at Vanderbilt-Ingram Cancer Center, Nashville, Tenn., told OT, “The data from this presentation is intriguing and appropriately raises the question of surveillance for second primary neoplasms for breast cancer survivors. However, this is not a simple question, nor can a guideline for surveillance with imaging be easily recommended.”
Friedman, who is also Associate Pprofessor of Pediatrics (Pediatric Hematology and Oncology) and the E. Bronson Ingram Professor of Pediatric Oncology, added, “These data encapsulate what has been reported in childhood cancer survivors over the past several decades. With progressive increases in survival, adverse long-term health conditions, including subsequent neoplasms, have been a focus of investigation. In fact, this has led to follow-up guidelines and changes in therapy to maintain efficacy and decrease risk for long-term morbidity and mortality.
“The data presented here about breast cancer survivors are not yet in and of themselves adequate to establish imaging screening guidelines. However, this, together with what we know about risk of other adverse health outcomes in cancer survivors, supports the need for all breast cancer survivors to be followed clinically for assessment of long-term effects of treatment and not simply relapse, and to receive survivorship care plans, which educate them on risks and provide advice on screening guidelines as they evolve,” she said.
“Furthermore,” Friedman said, “providers caring for these survivors should also receive such plans and education as they may be unaware of risk. Such follow-up may be performed in a variety of health care settings, but dedicated cancer survivorship programs should be promoted as an optimal option.”
Ed Susman is a contributing writer.