Adjuvant Radiation Therapy Extends Survival in TNBC

Sean Szeja, MD

Adjuvant radiation therapy was shown to improve overall survival (OS) and disease-specific survival (DSS) following lumpectomy for elderly women with early stage triple-negative breast cancer (TNBC), according to a retrospective study reported at the 2015 Breast Cancer Symposium.

After 23 months of follow-up, the OS rate for those who received lumpectomy plus radiotherapy was 98.2% versus 85.6% for those who had lumpectomy alone. Breast cancer—related deaths, DSS, were also more common in the lumpectomy-only group (6%) compared with the cohort who also had radiation (1%). The DSS rate at 23 months was 99% with radiation therapy versus 94% with lumpectomy alone (P = .003).

When other factors were considered, such as age, tumor size, and other treatment descriptions, the use of adjuvant radiation was associated with an overall 6-fold decrease in death from any cause, as well as death from breast cancer.

“When clinicians treat elderly patients with early-stage, triple-negative breast cancer, they can use these findings to make a more refined decision—with more information—to weigh the risks and benefits of radiation after lumpectomy,” explained lead author Sean Szeja, MD, radiation oncologist, University of Texas Medical Branch in Galveston, in an interview at the 2015 Breast Cancer Symposium. “The benefit from radiation is very substantial, and strong consideration should be given.”

In the study, which was conducted using the SEER database, 974 women were identified who were diagnosed with TNBC from 2010-2011 aged ≥70 years treated with lumpectomy for their local, stage T1-2 TNBC with no lymph node involvement. Of the total, 68% of the women (n = 662) received adjuvant radiation therapy and 312 patients received lumpectomy alone.

OS and DSS were calculated using Kaplan-Meier curves and long-rank tests. Cox multivariate regression was performed to calculate hazard ratios and control for confounding variables including neoadjuvant chemotherapy, number of lymph nodes sampled, age, laterality, grade, T stage, extent of surgery, existence of other cancers.

Across the full population, the utilization of radiation therapy resulted in an 85% reduction in the risk of death (HR, 0.15; P <.001) and an 86% improvement in the risk of death specifically from breast cancer (HR, 0.14; P = .01).

However, findings in each subgroup were less clear than what was seen across the full population of the study. The benefit in OS and DSS with radiation appeared to be nullified in patients with T2 versus T1 tumors (HR, 2.32 P = .03). Additionally, the HR for DSS was 80.45 for radiation and lumpectomy versus lumpectomy alone for those with grade IV disease.

Szeja acknowledged that whether to treat elderly patients with radiotherapy can be a complex decision, due to their age, weight, comorbidities, as well as social factors such as family support. “In addition to these other factors, the life expectancy of the patient is important, too.”

He said that in elderly patients with early-stage TNBC, researchers found that radiation as use was fairly widespread—approximately 68% of the time. While clinicians may have previously been recommended to hold off on radiation for this population, these findings suggest that the option should be considered more strongly, he added.

“This study suggests that adjuvant radiation therapy may benefit some elderly patients with breast cancer, but a prospective study will be needed to guide treatment decisions,” noted ASCO Expert Harold J. Burstein, MD, PhD, FASCO, in a statement accompanying release of the study. “When selecting treatments for elderly patients, we need to be particularly careful about weighing the benefits and risks.”

Given the retrospective nature of the study and the potential for selection bias, a prospective study will be needed to confirm the benefit seen with radiation.

Szeja S, Hatch SS. Outcomes associated with adjuvant radiation after lumpectomy for elderly women with T1-2N0M0 triple-negative breast cancer: SEER analysis. Presented at: 2015 Breast Cancer Symposium; September 25-27; San Francisco, CA. Abstract 39.