A 10-year follow-up of treatment outcomes in patients with early stage breast cancer and clinically negative axillary nodes treated with tangential breast irradiation following sentinel lymph node dissection or axillary clearance

Abstract

We compare long-term outcomes in patients with node negative early stage breast cancer treated with breast radiotherapy (RT) without the axillary RT field after sentinel lymph node dissection (SLND) or axillary lymph node dissection (ALND). We hypothesize that though tangential RT was delivered to the breast tissue, it at least partially sterilized occult axillary nodal metastases thus providing low nodal failure rates. Between 1995 and 2001, 265 patients with AJCC stages I-II breast cancer were treated with lumpectomy and either SLND (cohort SLND) or SLND and ALND (cohort ALND). Median follow-up was 9.9 years (range 8.3-15.3 years). RT was administered to the whole breast to the median dose of 48.2 Gy (range 46.0-50.4 Gy) plus boost without axillary RT. Chi-square tests were employed in comparing outcomes of two groups for axillary and supraclavicular failure rates, ipsilateral in-breast tumor recurrence (IBTR), distant metastases (DM), and chronic complications. Progression-free survival (PFS) was compared using log-rank test. There were 136/265 (51%) and 129/265 (49%) patients in the SLND and ALND cohorts, respectively. The median number of axillary lymph nodes assessed was 2 (range 1-5) in cohort SLND and 18 (range 7-36) in cohort ALND (P < 0.0001). Incidence of AFR and SFR in both cohorts was 0%. The rates of IBTR and DM in both cohorts were not significantly different. Median PFS in the SLND cohort is 14.6 years and 10-year PFS is 88.2%. Median PFS in the ALND group is 15.0 years and 10-year PFS is 85.7%. At a 10-year follow-up chronic lymphedema occurred in 5/108 (4.6%) and 40/115 (34.8%) in cohorts SLND and ALND, respectively (P = 0.0001). This study provides mature evidence that patients with negative nodes, treated with tangential breast RT and SLND alone, experience low AFR or SFR. Our findings, while awaiting mature long-term data from NSABP B-32, support that in patients with negative axillary nodal status such treatment provides excellent long-term cure rates while avoiding morbidities associated with ALND or addition of axillary RT field.

Fig. 1

A relationship between local breast tangent radiation field and regional lymph nodes as depicted in the lateral beam’s eye view with a tangential portal. The superior border of the radiation portal is set below the heads of the clavicles (navy). Level I (blue), level II (purple), and level III (dark green) are partially covered by the 90% isodose area covering the breast tissue (orange). (Color figure online)

Fig. 2

A relationship between local breast tangent radiation fields and regional lymph nodes as depicted in the axial view on a CT slice. a Level I (blue) and level II (purple) ALN are included in the 90% isodose area covering the breast tissue (orange). b A small portion of the 90% isodose area covers all three echelons of ALN (level III is in dark green). (Color figure online)

Fig. 3

Progression-free survival for the cohort stratified by the type surgery addressing ALN status: sentinel lymph node sampling alone (SLND) and sentinel lymph node sampling followed by the full axillary lymph node dissection (ALND)