The presented data show that AI is very effective in preventing axillary recurrences. A rate of 1–3% axillary recurrences in clinically lymph node-negative early stage breast cancer patients can be achieved, thus defining radiotherapy as an alternative to ALND [20
]. After ANS with less than 5 resected axillary lymph nodes or limited ALND, radiotherapy as adjuvant treatment in cases where ALND is not completed is an excellent treatment option. The outcome with tangential whole breast radiotherapy and additional AI on early stage breast cancer with clinically negative lymph nodes also provides a firm basis for this being a possible alternative treatment option. If we focus on the impact of tangential whole breast radiotherapy only in early stage breast cancer with clinically negative axillary lymph nodes, several studies prove a low incidence of axillary recurrences compared to either SLND, ALND, or no axillary treatment at all. Furthermore, recent studies show that knowledge of further nodal status beyond SLN biopsy (SNB) does not significantly influence the decision for adjuvant systemic treatment, which is mostly based on tumor characteristics and SNB status alone [26
]. The morbidity seen after ALND implies a risk of lymph edema and decreased arm and shoulder function in 5–35% of patients. Its severity depended on the extent of the dissection [4
]. Only in limited axillary surgery morbidity seems to be as low as in AI [30
]. Uncommon side effects of AI include brachial plexopathy and radiation pneumonitis, and with technology in the field of radiooncology emerges rapidly providing favorable dose distributions and precise dose application, the rate of severe side effects is still declining [8
]. The American College of Surgeons Oncology Group Z0011 trial excluded patients with 3 or more involved axillary lymph nodes and randomized patients with SLN metastases to undergo ALND or no further axillary treatment after positive SLND. ALND was defined as anatomic level I and II dissection with at least 10 nodes removed [6
]. Standard whole breast tangential radiotherapy unavoidably includes a large part of level I and II due to technical reasons, whereas in full AI, levels I–III are intentionally and completely included. Referring to the data of Veronesi et al. [18
], 4–7% of patients with negative SLN harbor occult metastases in the remaining axillary nodes, again emphasizing the effect of radiotherapy on local nodal control. In both treatment cohorts in the study by Wernicke et al. [7
] with 265 node-negative patients receiving either full ALND or SLND only and each treated with adjuvant whole breast tangential radiotherapy, the incidence of axillary recurrence was 0% after 10 years of follow-up. The study of Wong et al. [8
] investigated adjuvant radiotherapy with whole breast tangential fields without ALND, SLND, or AI in 92 patients. This retrospective study, applying radiation techniques available in the period of 1988–1993, used conventional tangential fields encompassing the lower echelon axillary nodes, mostly of level I. In these studies, the effect of preventing local recurrence was reached by destroying occult tumor foci by inadvertent coverage of a large portion of the axilla. 2 studies investigated the dosage coverage of level I and II axillary lymph nodes with standard tangential field radiotherapy. One showed that the 95% isodose encompassed only an average of 55% of axillary level I-II lymph nodes. The other study reported a mean total dose in the volume of interest of lower than 40 Gy in all but 1 (1/15) patient. The authors concluded that significant modifications in treatment planning for complete coverage of levels I-II are necessary as the therapeutic dose is not delivered adequately [32
]. One should not dismiss the results of these studies, as the inadequate dosage coverage is explained by the purpose of the standard tangential field technique that was implemented to simply irradiate the breast tissue. Dose delivery to the level I-II anatomical lymph node region is a mere ‘side effect’ of the treatment. In full AI, all 3 lymph node areas are in the treatment fields with adequate target doses, hence the good results in axillary local control with tangential whole breast radiotherapy and additional AI in early stage breast cancer with clinically negative lymph nodes have a strong (fig. ). Today, in the field of radiation oncology technology, numerous innovations in dose application and delivery are becoming available, such as three-dimensional computed tomography (3D-CT) planning with state of the art beam calculation algorithm including image fusion modalities to better define the target. The knowledge of anatomical boundaries of regional lymph nodes in treatment positioning is established to optimize conformal radiotherapy [34
]. Furthermore, intensity modulated radiotherapy (IMRT), image-guided radiotherapy (IGRT), and volumetric modulated arc therapy (VMAT) upgrade the quality and precision of treatment delivery in radiotherapy. Hence, it has become possible to irradiate breast tissue and specific lymph node regions precisely at once, and this shift in technology will affect future study results.
Fig. 1 Example for involvement of axillary lymph node regions in tangential breast radiotherapy: yellow = level I axillary lymph nodes, light blue = level II, purple = level III. Isodoses are given in each picture of the left column. On the left side, 1 coronal (more ...)
In summary, irradiation of axillary lymph nodes is highly effective in controlling microscopic disease with equal efficacy and less morbidity than surgical procedures. Most recent data suggest that radiotherapy might have an impact on the prevention of further metastatic disease, which has never been shown for any surgical procedure. Thus, it can be hypothesized that, provided lymph node treatment impacts on outcome, radiotherapy may be the better treatment compared to surgery. Furthermore, improved dose coverage of level I-II lymph node areas in tangential breast radiotherapy may even further lower the rate of axillary recurrences in patients with positive SNL without ALND and clinically negative lymph nodes in early stage breast cancer.