Nomogram predicting survival as a selection criterion for postmastectomy radiotherapy in patients with T1 to T2 breast cancer with 1 to 3 positive lymph nodes

Abstract

BACKGROUND:The role of postmastectomy radiotherapy (PMRT) in women with pT1-T2N1 breast cancer is controversial. The authors developed a nomogram that was predictive for overall survival (OS) and identified patients who derived no benefit from PMRT. METHODS: The authors retrospectively evaluated 4869 patients with pT1-T2N1 breast cancer who were treated with mastectomy between 2000 and 2014 in 11 Chinese hospitals. Rates of locoregional recurrence and distant metastasis were calculated using competing risk analysis, and disease-free survival and OS rates were calculated using the Kaplan-Meier method. Based on the risk factors identified from Cox regression analysis in 3298 unirradiated patients, a nomogram predicting OS was developed. The benefit of PMRT was evaluated in different risk groups stratified by the nomogram model. RESULTS: After a median follow-up of 65.9 months, the 5-year OS, disease-free survival, locoregional recurrence, and distant metastasis rates were 93.3%, 84.3%, 5.2%, and 8.3%, respectively. A total of 1571 patients (32.3%) underwent PMRT. On multivariable analyses, PMRT was found to increase OS significantly (hazard ratio, 0.61; P = .002). An OS prediction nomogram evaluated the effect of age; tumor location; tumor size; positive lymph node ratio; estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 status; and treatment with trastuzumab. Based on nomogram scores, the entire patient cohort was classified into 3 risk groups. PMRT significantly improved the OS of patients in the intermediate-risk (P < .001) and high-risk groups (P = .004), but not in the low-risk group (P = .728). CONCLUSIONS: The authors developed a nomogram that is predictive of OS among women with pT1-T2N1 breast cancer after mastectomy. This nomogram may help to select a subgroup of patients with a good prognosis who will not benefit from PMRT.

A Prognostic Risk Stratification Model to Identify Potential Population Benefiting From Postmastectomy Radiotherapy in T1–2 Breast Cancer With 1–3 Positive Axillary Lymph Nodes

“…Although a multi-center study in China had established the first risk stratification nomogram for T1-2 breast cancer with 1-3 positive lymph nodes, it only included the Chinese population. Due to differences of race and other factors, the model applied in other races may have great limitations ( 43 ).…”

Practical Model to Optimize the Strategy of Adjuvant Postmastectomy Radiotherapy in T1-2N1 Breast Cancer With Modern Systemic Therapy

“…A practical reference risk stratifying system appears to be essential to identify patients who would benefit most from PMRT at the present time. A number of risk factors that have been identified by nomograms combining different risk factors have been developed as well ( 18 , 19 ). The most representative risk factors identified were patient age, number of positive lymph nodes, histological grade, and lympho-vascular invasion ( 20 ).…”

Influence of age as a continuous variable on the prognosis of patients with pT1-2N1 breast cancer

“…A multivariable Cox proportional hazards regression model with penalized splines (P-splines) was used to examine the relationship between age and all outcomes [16]. The multivariable analyses was adjusted for potential confounders, including treatment era (1997-2007 vs. 2008-2018), tumor location (inner quadrant vs. others), pathological T stage (pT2 vs. pT1), tumor grade (G3 vs. G1-2), lymphovascular invasion (LVI) (yes vs. no), hormone receptors (negative vs. positive), positive lymph node ratio (≤ 10% vs. 10%-20% vs. > 20%), PMRT (yes vs. no), chemotherapy (yes vs. no), J o u r n a l P r e -p r o o f and human epidermal growth factor receptor 2 (HER2) status stratified by treatment (positive without trastuzumab vs. negative & positive with trastuzumab) [17][18][19]. The multivariable analysis was performed using Cox logistic regression, and the effect of PMRT vs. no PMRT in different ages was expressed using hazard ratio (HR) curves [20].…”