Sentinel Node Mapping for Breast Cancer: Current Situation

2. Clinical Scenarios and Current Indications

Currently, the sentinel node biopsy procedure is recognized as the standard treatment for stages I and II. In these stages, this approach has a positive node rate similar to those observed after lymphadenectomy, a significant decrease in morbidity and similar nodal relapse rates at 5 years. No significant differences on disease-free survival, overall survival, and local control of disease were seen in case of negative sentinel node [5]. The indications and recommendations of the sentinel node biopsy are summarized in Table 1.

(i) Pregnancy is no contraindication for sentinel node biopsy, but only for blue dye, and it has been demonstrated that the dose to the foetus from this procedure is negligible [6].

(ii) The evidence regarding the safety of sentinel node biopsy is mainly based on studies including T1 and small T2 tumours only. However, in patients with larger tumours (T3-T4), the false negative rate has been similar and no increased axillary recurrence has been reported [6, 7].

(iii) Multifocal breast cancer is defined as separate foci of ductal carcinoma more than 2 cm apart within the same quadrant, while multicentric breast cancer indicates the presence of separate independent foci of carcinoma in different quadrants. The prevalence of axillary metastases and false negative results is higher in multifocal or multicentric tumours. However, the reported axillary recurrence rates are acceptable also in patients with multifocal or multicentric tumours [6–9].

(iv) DCIS does not metastasize to regional lymph nodes. However, invasion is missed in up to 40% of patients in the preoperative diagnosis. Therefore, sentinel node biopsy is recommended in patients undergoing mastectomy. In patients with breast conservation, sentinel lymph node biopsy can be performed as a second operation if invasion is detected in the surgical specimen [6, 10].

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(v) Palpable axillary nodes may be tumour negative in up to 40% of the patients. Preoperative axillary ultrasound with fine needle aspiration cytology or core needle biopsy from the suspicious nodes is a widely accepted policy. In many units, sentinel node biopsy is performed also in patients with palpable nodes if negative in the preoperative diagnosis [6].

(vi) Internal mammary sentinel node detection rate is significantly affected by the depth of radiopharmaceutical injection. It is generally recognized that mapping of inner mammary chain requires deep injection (peritumoural or intratumoural) of radiotracer. With this approach, internal mammary chain sentinel nodes have been detected in about 30% of patients with breast cancer, of which about 60%–90% could be harvested during surgery and 11%–27% of them will have metastases. However, the significance of internal mammary sentinel node biopsy is under debate. There is evidence that mapping it leads to stage migration and modification of treatment planning with respect to radiotherapy and systemic therapy, but more evidence is necessary to support that it will improve the outcome of treatment and survival [11, 12].

A second sentinel node biopsy may be performed in patients with a local recurrence after breast conservation and negative axillary sentinel node biopsy. The success rate may be lower when compared with a primary sentinel node biopsy. Furthermore, extra axillary sentinel nodes are visualized more frequently. Sentinel node biopsy can be performed in patients undergoing breast surgery due to a local recurrence after breast conservation in DCIS. Furthermore, plastic surgery with breast augmentation or reduction does not contraindicate the procedure. In prior excisional biopsy the lymph drainage is probably changed in patients who have undergone previous breast surgery (oncologic and nononcologic). Extra-axillary drainage is identified more frequently in reoperative sentinel node biopsy than in former sentinel node biopsy. However, there are evidences that sentinel node biopsy performed in the area of previous breast biopsy do not affect the accuracy of the procedure [6, 13].

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(vii) Before neoadjuvant chemotherapy, sentinel node biopsy gives a more precise axillary staging, with more information about the nodal spread. But it may delay the beginning of the therapy, and two surgeries can be necessary. After neoadjuvant chemotherapy, the sentinel node biopsy may lead to an underestimation of the initial stage. On the other hand, axillary nodal status after neoadjuvant therapy is also a highly significant prognostic factor. Pathologic complete response in the axilla can be achieved in up to 40% of the patients. These patients avoid axillary lymph node dissection and associated morbidity. Available data show that there are no significant differences in the success rate of sentinel node biopsy according to clinical tumour size or clinical nodal status, and that the false-negative rate is not affected by tumour response to chemotherapy [14, 15].

Despite this, the current controversy in this scenario lies on the question of axillary lymph node dissection after a positive sentinel node biopsy, mainly stimulated by the recent publication of the ACOSOG-Z0011 data [16].


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About the Author: Tung Chi