In this prospective observational study, ALND based on BLL attempted to resect potentially metastatic tissues level by level to minimize the extent and morbidity of ALND. Staged tracing (injection of 0.1 ml MB into the SLNs) was utilized to reveal the breast lymphatic system in the axilla basin. The median number of BLL was four, ranging from three to six. A horizontal line 1.0 cm away from the superior blue-stained BLN and a vertical line 1.0 cm away from the medial blue-stained ABLN formed BLL 2nd, 3rd, 4th. The skip metastasis rate was zero when an en bloc resection was performed upwards towards the BLL that contained the first confirmed negative blue-stained ABLN. As described in a previous study, a horizontal line 1.5 cm away from the superior blue-stained ABLN and a vertical line 1.5 cm away from the medial blue-stained ABLN formed BLL 1st, which was proposed to be removed en bloc in breast cancer patients with negative SLN to reduce the number of false-negative events from SLNB. In the present study, through resecting the lymph nodes level by level for breast cancer patients with node-positive axilla, the surgical approach of ALND based on BLL was valuable in reducing the BCRL rate without reducing cancer control.
Depending on the various criteria of BCRL and the extent of axillary dissection, a pooled estimation of the arm lymphedema rate is 16.6% (95% CI 13.6–20.2). The risk factors of BCRL can be affected by two aspects: demographic and lifestyle, and breast cancer-related variables, including radiotherapy to the axilla, number of nodes involved and removed, and taxane-based chemotherapy. In addition, a hypothesis was proposed that the transection of lymphatic vessels that drain the arm during their course through the axilla during complete ALND was associated with BCRL. Thompson et al. and Nos et al. have previously described a new technique, axillary reverse mapping (ARM), to identify and preserve arm lymph nodes, which reduced the number of arm lymphedema events. A refined ARM technique was proposed in our institution to identify the arm lymphatic system and eliminate postoperative arm lymphedema.[16, 17] An intact pathway for lymphatic arm drainage is adjacent to the axillary vein and is usually located above the second intercostobrachial nerve. Hence, a horizontal line in this study was designed as the upper landmark during ALND surgery based on BLL to protect the arm lymphatic system. In addition, according to the direction of the lymphatic drainage, the medial and superior blue-stained ABLNs were selected as the landmark.
Over the past few years, axillary management has changed greatly. With effective multidisciplinary treatment, the theory of breast cancer surgery leans towards “less is more”. After the publication of the ACOSOG-Z0011 and AMAROS trials, varieties of patterns of care for axillary surgery were present, particularly for cT1 − 2N0M0 patients with positive SLNs, which aimed to decrease the treatment-related morbidity without reducing cancer control. For breast cancer patients with cN + axilla, NCT was often performed and targeted axillary dissection was done to identify the patients who might not require ALND. The omission of complete ALND in these studies was associated with much lower rates of lymphedema. However, clinically node-positive patients who undergo ALND and patients who are not eligible based on the Z0011 criteria also need de-escalate surgical areas for ALND. Approximately 25% of the patients who undergo SLNB have positive nodes, and these patients undergo ALND and remain at risk for arm lymphedema.
As is well-known, metastasis from breast cancer does not involve the breast regional lymph nodes as a unit but rather progresses from the primary tumor to the first-line draining nodes and, in turn, sequentially to the second and third echelon nodes. Based on the biological and anatomical rationale of SLNB, the approach of ALND based on BLL was proposed in our institution to balance the demand of preventing axillary recurrence and the wish of avoiding treatment-related morbidity, particularly arm lymphedema. Classifying the ABLNs according to lymphatic drainage is a feasible and dynamic way to limit axillary surgical dissection. In the present study, to dispel ‘skip’ metastasis, nonstained ABLNs were sent for pathological examination separately by resecting serial tissue every 0.5 centimeter away from the horizontal line and vertical line along the marginal blue-stained ABLN (Fig. 2). In cases of skip metastasis, additional involved nodes were found within the area 1.0 cm away from the marginal blue-stained ABLNs (Table 3). Therefore, a horizontal line 1.0 cm away from the superior blue-stained ABLN and a vertical line 1.0 cm away from the medial blue-stained ABLN formed the BLL 2nd, 3rd, 4th. The skip metastasis rate was zero when ‘en bloc’ resection was performed upwards towards the breast lymphatic level that contained the first confirmed negative blue-stained ABLN (Fig. 3f), which could limit the extent of axillary dissection and reduce the number of BCRL events.
Considering that NCT could influence the structure of the breast lymphatic and lead to an incomplete lymphatic pathway, patients who underwent NCT were excluded from the study. The pilot phase of the randomized controlled trial comparing ALND based on BLL and standard ALND revealed a satisfactory outcome. Axillary recurrence rates for patients randomized to ALND based on BLL were equivalent to axillary recurrence rates for patients randomized to standard ALND. Further randomized controlled trial was needed to confirm its effect.