Neoadjuvant Therapy Reduces Risk of Secondary Primary Cancer in Early-Stage Breast Cancer

Neoadjuvant radiation therapy in patients with early-stage breast cancer significantly lowers the risk of developing secondary primary tumors at any site, new findings suggest.

In a study published in Breast Cancer Research, investigators sought to evaluate the long-term overall and disease-free survival rates of neoadjuvant radiotherapy compared with adjuvant radiotherapy.

The investigators used the Surveillance, Epidemiology, and End Results (SEER) database to create an analytical dataset of 250,195 women with early-stage breast cancer who received radiotherapy prior to surgery.

Disease-free survival was defined as time to diagnosis of secondary primary tumor at any location, according to the report.

Study participants diagnosed between 1973 and 2011 with carcinoma in situ or localized breast cancer without prior cancer elsewhere were divided into 2 groups: those who received neoadjuvant radiotherapy and those who received adjuvant radiotherapy.

The results of the study showed that the higher-risk for second primary cancer diagnosis among the ER-positive patients after neoadjuvant radiotherapy was significantly lower compared with adjuvant radiotherapy.

Patients who underwent a partial mastectomy have a slightly lower higher-risk of second primary tumor diagnosis if treated earlier. Patients with carcinoma in situ who underwent breast-conserving surgery had significantly higher incidences of second primary tumors compared with patients with stage T1 tumors.

Additionally, the probability of cancer-free survival in the largest cohort of ER-positive patients treated with partial mastectomy was 12% higher after neoadjuvant radiotherapy versus adjuvant radiotherapy.

A limitation of the analysis was its retrospective nature with all applicable biases, absent systemic treatment data, and no information on selection criteria for neoadjuvant radiotherapy, according to the authors.

“Our results suggest that [radiotherapy] before surgery reduces the incidence of second primary tumors without decreasing overall survival rates,” the authors concluded. “A reduced second cancer risk attributable to radiation-induced antitumor immunity could explain the significantly higher incidences of second primary tumors in patients with carcinoma in situ but not in patients with T2 or T3 tumors compared with patients with stage T1 tumors treated with partial mastectomy.

“These findings are worthy of a prospective clinical trial to improve local control while decreasing the risk of distant metastases and to identify the potential contribution of neoadjuvant versus adjuvant radiation-induced immunity.”

Breast cancer is the most common type of cancer among women, accounting for approximately 41,000 deaths in the United States in 2015.