The role of postoperative radiotherapy after primary tumor resection in patients with de novo stage IV breast cancer

Aim This study was undertaken to investigate the role of postoperative radiotherapy (PORT) including post-breast conserving radiotherapy (PBCRT) and post-mastectomy radiotherapy (PMRT) in stage IV breast cancer patients who underwent planned primary tumor resection (PTR). Methods This study enrolled 112 patients diagnosed with de novo stage IV breast cancer who were treated with potentially curative PTR with or without PORT. The primary outcome was overall survival (OS), and the secondary outcomes were locoregional recurrence-free survival (LRRFS) and distant progression-free survival (DPFS). Results At a median follow-up of 48.9 months (range, 3.5-183.4 months), the median OS was 54.9 months (range, 5.3-185.9 months) with a 5 year OS rate of 59.6%. Lower clinical T stage, Luminal A or B type tumors and PBCRT were significantly predictive of longer OS. The 5 year LRRFS and DMFS rates were 79.0% and 34.3%, respectively. In multivariate analysis for LRRFS, the PBCRT arm demonstrated significant superiority compared to the No PORT arm. A comparison of patients who did and did not receive PORT showed that patients with disseminated metastasis more likely did not receive PORT and were excluded from the analysis. PBCRT arm demonstrated significantly superior LRRFS of 100% while PMRT and No PORT arm demonstrated 81.5% and 84.0%, respectively CONCLUSIONS: De novo stage IV breast cancer patients who received planned PTR showed favorable survival outcomes compared with historical cohorts. PTR may be predictive of a good prognosis, especially in patients with luminal A or B type tumors. PORT, especially PBCRT was predictive of LRRFS, suggesting that patients may benefit from this treatment.