Research Highlights from the San Antonio Breast Cancer Symposium 2018

The 41st San Antonio Breast Cancer Symposium, held Dec. 4-8, drew more than 7,500 attendees from more than 90 countries. The Symposium offered the latest clinical, translational, and basic research, providing a forum for interaction and communication among researchers, health professionals, and those with a special interest in breast cancer.

“Breast cancer is the most common cancer in women and the second [leading] cause of cancer-related death, the first one being lung cancer, and advances in the field are many and keep coming faster,” said Carlos L. Arteaga, MD, one of the three cochairs of the Symposium, in an interview with Medscape to preview this year’s Symposium.

Here are brief summaries of some of the studies presented at the five-day meeting:

In the phase III clinical trial KATHERINE, investigators tested whether treating breast cancer patients at higher risk for recurrence after they had received neoadjuvant (presurgery) therapy (based on the finding of persisting invasive breast cancer at surgery) with trastuzumab emtansine (T-DM1, Kadcyla) instead of the standard therapy of trastuzumab (Herceptin) would reduce the risk of recurrence.

The trial met its primary endpoint of invasive disease-free survival (IDFS): Substituting T-DM1, Kadcyla for adjuvant trastuzumab in patients who had residual disease after neoadjuvant chemotherapy plus trastuzumab reduced the risk of developing an invasive recurrence of HER2-positive early-stage breast cancer by 50 percent.

IDFS events (events of disease recurrence or death without recurrence) occurred in 12.2 percent of patients in the T-DM1 arm, compared with 22.2 percent in the trastuzumab arm. The side effects from T-DM1 in this study were comparable to those seen in patients with metastatic disease who are being treated with this therapeutic. T-DM1 is currently approved by the U.S. Food and Drug Administration to treat patients with metastatic HER2-positive breast cancer following previous treatment with trastuzumab and a taxane type of chemotherapy.

Data from the randomized, phase III GEICAM/CIBOMA clinical trial showed that patients with early-stage triple-negative breast cancer did not benefit from treatment with the chemotherapy agent capecitabine, if it was given after they completed surgery and standard chemotherapy. After a median follow-up of 7.3 years, five-year disease-free survival was 79.6 percent among the 448 patients who were randomly assigned to receive capecitabine and 76.8 percent among the 428 patients randomly assigned to observation.

A poster session at the 2018 San Antonio Breast Cancer Symposium. Photo by ©MedMeetingImages/Todd Buchanan 2018

In subgroup analyses, however, among patients with nonbasal-like disease, those who received capecitabine were 49 percent less likely to experience a disease event and 52 percent less likely to die compared with those in the observation arm.

A meta-analysis of data from 52 clinical trials showed that among patients who had a pathological complete response (pCR) after neoadjuvant chemotherapy, those who received adjuvant chemotherapy had similar clinical outcomes compared with those who did not receive adjuvant chemotherapy.

A pCR was defined as the lack of all signs of invasive cancer in the breast tissue and lymph nodes removed during surgery after treatment with chemotherapy. The investigators suggest that the data from this study support treatment escalation/de-escalation strategies in the adjuvant setting based on initial neoadjuvant response.

Data from the randomized, phase III TAM-01 clinical trial showed that compared with placebo, treatment with a low dose of tamoxifen (5 mg per day) halved the risk of disease recurrence and new disease for women who had been treated with surgery following a diagnosis of breast intraepithelial neoplasia, which include ductal carcinoma in situ (DCIS), lobular carcinoma in situ (LCIS), and atypical ductal hyperplasia (ADH). After a median follow-up of 5.1 years, 5.5 percent of patients in the low-dose tamoxifen arm and 11.3 percent of patients in the placebo arm had disease recurrence or new disease.

Serious adverse events were comparable in the low-dose tamoxifen arm and the placebo arm. Further, there were no significant differences between the two arms in reporting of menopausal symptoms such as hot flashes, vaginal dryness, and pain during intercourse. The investigators note that the risk reduction from low-dose tamoxifen is comparable to that of the standard dose (20 mg per day) tested in NSABP B-24 and NSABP-P1 trials, and that it occurred alongside a significant reduction in serious adverse events.

Virginia Kaklamani, MD, DSc

Symposium cochair Virginia Kaklamani, MD, said, “To me, in my clinic, this is extremely important because now I can give tamoxifen safely at a lower dose and achieve the same outcomes.”

Results of the Energy Balance and Breast Cancer Aspects-II (EBBA-II) trial indicated that women who underwent a supervised program of cardiovascular exercise during adjuvant breast cancer treatment experienced better cardiovascular function than those who were not part of the exercise program.

Participants in the exercise arm received a detailed training program based on their VO2 max (maximal oxygen uptake, a common measure of cardiovascular fitness) at baseline. Under guidance, the group worked out twice a week for 60 minutes each time, in a combination of aerobic exercise, stretching, and weight training. The researchers found that among the patients who were receiving chemotherapy, those in the exercise arm had returned to their pre-surgery cardiovascular strength by the 12-month follow-up, whereas those in the control group continued to experience reduced cardiovascular function.

Kent Osborne, MD

Commenting on studies that addressed patients’ quality of life during and after treatment, Symposium cochair Kent Osborne, MD, noted that it is time to put old ideas, such as that patients undergoing chemotherapy are bound to feel sick and incapacitated, to rest. Exercise and diet have very prominent effects on the quality of life and reduction in the side effects of chemotherapy and improvement in the outcomes from the cancer, he emphasized. “Doctors need to start encompassing (exercise and diet) in their treatment plans.”

In a randomized, double-blind, placebo-controlled clinical trial, investigators tested whether oxybutynin, an anticholinergic agent commonly used to treat urinary incontinence, could lower hot flashes in breast cancer survivors taking tamoxifen or an aromatase inhibitor and those who could not take hormone replacement. Besides impacting quality of life, hot flashes are also associated with discontinuation of breast cancer treatment, which could increase the risk of breast cancer recurrence and death.

The study showed that patients who took oxybutynin experienced decreases in their hot flashes scores compared with those who took placebo. Women who took oxybutynin also reported improvement in work, social activities, leisure activities, sleep, and overall quality of life.