Demographic and Clinical Characteristics of the Study Population
The demographic and clinical characteristics of 214 consecutive TNBC patients undergoing radiation therapy at our center are summarized in Table 1. At diagnosis, 19.6% were<50 years old; the majority presented with right-sided cancers (53.3%). Most patients were T-stage T1 (tumor size ≤20mm; 51.9%), followed by T2 (tumor size 20–50 mm; 39.2%) and T3 (tumor size >50 mm; 6.1%). The majority were lymph node negative (N0; 62.1%), followed by N1 (22.0%) and N2 (9.3%). Less than half the patients (46.3%) were treated with IMRT; two-thirds of the patients received hypofractionated doses (66.5%). Mastectomy was less common (21.5%) than breast conservation surgery (78.5%).
For the whole group, mean DFS was 106.4 (SD 48.7) months; OS 109.4 (SD 52.1) months. Chemotherapy (neoadjuvant, adjuvant) was not a significant factor for DFS (p=0.244) nor for OS (p=0.962). The effect of tumor size on survival was examined in the patient cohort (Table 2 and Figure 1). Patients with T2 were significantly younger than T1 patients (p=0.010). More patients were treated with hypofractionated protocols in the T1 and T2 groups (Both p=0.0001). Survival analysis showed that both DFS (p<0.0001) and OS (p=0.0004) (Figure 1) differed significantly according to tumor size with shortest survival times for T3/T4 patients.
The effect of nodal status on survival was examined in the patient cohort (Table 3). Patients with nodal status N2/N3 were significantly younger than N0 patients (p=0.014). While more patients were treated with hypofractionated protocols in the N0 group (p=0.0001), fewer patients received hypofractionated doses in the N2/N3 group (p=0.0413). Survival analysis showed that both DFS (p<0.0001) and OS (p=0.012) (Figure 1) differed significantly according to nodal status with poorer survival times for N1 and N2/N3 patients than lymph node-negative patients.