3017 - Nomogram Guided Stratified Postmastectomy Radiotherapy in HER-2 Positive Breast Cancer Underwent Neoadjuvant Therapy: A SEER Population-Based Study

03:00pm - 04:00pm PT

Hall F

Screen: 13

POSTER

Presenter(s)

Yanqun Zhang, - The First Affiliated Hospital of Bengbu Medical University, Bengbu, Anhui Province

Y. Zhang, L. X. Xie, L. Y. Bian, and Y. C. Zhou; Department of Radiation Oncology, The First Affiliated Hospital of Bengbu Medical University, Bengbu, China

Purpose/Objective(s):

The role of Postmastectomy Radiotherapy (PMRT) following neoadjuvant therapy (NAT) in Human Epidermal Growth Factor Receptor-2 (HER-2) positive breast cancer remains controversy. This study aimed to establish a nomogram for guiding the clinical decision in breast cancer patients treated with NAT and mastectomy.

Materials/Methods:

We conducted a retrospective analysis of 1,866 HER-2 positive patients with cT1-4N1-3M0 breast cancer who received NAT and mastectomy from Surveillance, Epidemiology, and End Results (SEER) database between 2010 to 2017. Initial univariate and multivariate assessments were performed on 564 patients who did not undergo PMRT to identify independent factors influencing breast cancer-specific survival (BCSS). These identified factors were then employed to construct the nomogram. Subsequently, the clinical outcomes of 1,302 patients who received PMRT were evaluated based on this nomogram.

Results:

The entire cohort presented a follow-up duration of 69 months (range from 3 to 131 months), with a 5-year BCSS rate of 86.4%. The nomogram incorporated six risk factors derived from multivariable analysis of the training set, which included age, PR status, cT stage, cN stage, pN stage, and response to NAT. In the training cohort, the concordance index (C-index) of the nomogram for predicting BCSS was 0.83 [95% confidence intervals (95% CI): 0.79-0.87]. Patients were then categorized into low-risk, intermediate-risk, and high-risk groups based on nomogram scores and cut-off values (142 and 167) determined by X-tile. Significant differences in BCSS were observed among these groups (P < 0.05). Moreover, compared to non-PMR patients, PMRT notably improved BCSS in the high-risk subgroup (P = 0.025), whereas no difference was found in low and intermediate-risk subgroups (P > 0.05).

Conclusion:

The developed nomogram can estimate the individualized BCSS for HER-2 positive breast cancer undergo NAT and mastectomy, and help identify high-risk patients who are more likely to benefit from PMRT.