Is postmastectomy radiotherapy really needed in breast cancer patients with many positive axillary lymph nodes?
Background: Postmastectomy radiotherapy (PMRT) improves survival by eliminating potential occult lesions in the chest wall and lymphatic drainage area. Meta-analysis has shown that PMRT improves survival of patients with node-positive breast cancer (BC), but it is not clear if also patients with high number of positive axillary lymph nodes (PALN) benefit from PMRT. Our aim was to analyze the impact of the number of PALN on survival and distant metastasis occurrence in patients treated with PMRT.
Patients and methods: We reviewed medical records of 129 consecutive BC patients with PALN, treated at Institute of Oncology Ljubljana with PMRT between January 2003 and December 2004. We grouped patients according to the number of PALN twice, firstly according to TNM classification (N3 vs non-N3) and secondly as follows: group 1 (1-3 PALN); group 2 with (4-15 PALN) and group 3 with more than 15 PALN. All patients received adjuvant systemic therapy according to the clinical guidelines. Overall survival (OS), progression free survival (PFS), distant metastasis free survival (DMFS) and loco-regional free survival (LRFS) were analyzed.
Results: After the median follow-up time of 11.5 years, the Kaplan Meier survival analysis for patients grouped according to TNM PALN classification showed significant difference for PFS (6.5 years for N3 vs 9.0 years for non-N3, p=0.002) and DMFS (6.8 years for N3 vs 9.5 years for non-N3, p <0.001), but not for OS. The second grouping with the higher number of PALN showed significantly shorter OS (9.1 years; 9.9 years; 7.6 years; p= 0.027), shorter PFS (9.5 years; 8.6 years; 6.2 years; p= 0.014) and shorter DMFS (10.5 years; 9.0 years; 6.2 years; p < 0.001). In multivariate analysis more than 15 PALN were statistically significant for DMFS (HR 0.41, (CI 0.18 – 0.93).
Conclusions: Patients with higher number of PALN develop distant metastases significantly earlier and have shorter survival, though they receive the same loco-regional (LR) therapy. Due to probably already present microscopic metastatic disease at the time of adjuvant LR treatment, patients with many PALN might not benefit from PMRT. Clinically evident metastases develop and are treated with systemic therapy before local recurrence may occur. More studies with higher number of patients included are warranted to confirm our findings.