Radiotherapy in Breast Cancer Patients With Isolated Regional Recurrence After Mastectomy: A Joint Analysis of 144 Cases From Two Institutions

Abstract

<h3>Purpose/Objective(s)</h3> To analyze the prognosis and locoregional failure patterns of patients with isolated regional recurrence (RR) after mastectomy and investigate the effect of radiotherapy (RT) and optimal radiation target volumes. <h3>Materials/Methods</h3> A total of 144 patients with first isolated RR after mastectomy treated in two institutions between 2001 and 2018 were retrospectively analyzed. All had not received postmastectomy RT. 100 (69.4%) had supraclavicular fossa (SC) recurrence, 54 (37.5%) had axilla recurrence, and 7(4.9%) had internal mammary region (IM) recurrence. After RR, 93 (63.6%) patients received local plus systemic therapy, 10 (6.9%) received local therapy, and 40 (27.8%) received systemic therapy alone. Among the 103 patients who received local therapy, 27 (26.2%) received surgery plus RT, 60 (58.3%) received RT and 16 (15.5%) received surgery alone. Of the 87 patients who received RT, 14 (16.1%) received involved-field RT, and 73 (83.9%) received additional prophylactic RT to the initially uninvolved locoregional sites. The median dose to the recurrent tumor or tumor bed after surgery was 60 Gy. Of the 73 patients who received prophylactic RT, the median dose was 50 Gy, to chest wall (CW) in 67/87 (77.0%), to SC in 24/28 (85.7%), to axilla in 6/53 (11.3%), and to IM in 3/81 (3.7%). Post-recurrence progression-free survival (PFS) and overall survival (OS) rates were calculated by Kaplan-Meier method and the differences were compared with Log-rank test. Competing risk model was used to estimate the subsequent locoregional recurrence (sLRR) rates, and the differences were compared with Gray test. Multivariate analysis was performed using Cox logistic and Fine–Gray regression. <h3>Results</h3> With a median follow-up of 82.5 months (range, 5.0-205.0) after RR, the 5-year sLRR, PFS and OS rates for the entire group were 42.1%, 22.9% and 62.6%. Local plus systemic therapy was an independent favorable prognostic factor for sLRR and PFS. Surgery plus RT was an independent favorable prognostic factor for sLRR. The most common sLRR sites were initially involved nodal regions, followed by CW, and then initially uninvolved nodal regions. Surgery plus RT significantly reduced the risk of recurrence within the initially involved nodal regions (<i>P</i><0.001). Patients with CW irradiation showed 5-year subsequent CW recurrence rate of 12.1% compared to 14.8% (<i>P</i> = 0.206) for those without. Subsequent SC recurrence rate was numerally lower in patients with prophylactic SC irradiation than those without (9.9% vs. 23.8%, <i>P</i> = 0.206). The incidences of initially uninvolved axillary and IM recurrence were below 10% regardless of prophylactic RT. <h3>Conclusion</h3> Patients with isolated RR after mastectomy have an optimistic OS but a high risk of sLRR after RR in the contemporary era. Comprehensive locoregional treatment including surgery and RT combined with systemic therapy is recommended. The CW, axillary and IM regions should not be routinely included in the radiation target volume.