A critical reappraisal of false negative sentinel lymph node biopsy in melanoma.

Lymphatic mapping and sentinel lymph node biopsy (SLNB) have completely changed the clinical management of cutaneous melanoma. This procedure has been accepted worldwide as a recognized method for nodal staging. SLNB is able to accurately determine nodal basin status, providing the most useful prognostic information. However, SLNB is not a perfect diagnostic test. Several large-scale studies have reported a relatively high false-negative rate (5.6-21%), correctly defined as the proportion of false-negative results with respect to the total number of "actual" positive lymph nodes. The main purpose of this review is to address the technical issues that nuclear physicians, surgeons, and pathologists should carefully consider to improve the accuracy of SLNB by minimizing its false-negative rate. In particular, SPECT/CT imaging has demonstrated to be able to identify a greater number of sentinel lymph nodes (SLNs) than those found by planar lymphoscintigraphy. Furthermore, a unique definition in the international guidelines is missing for the operational identification of SLNs, which may be partly responsible for this relatively high false-negative rate of SLNB. Therefore, it is recommended for the scientific community to agree on the radioactive counting rate threshold so that the surgeon can be better radioguided to detect all the lymph nodes which are most likely to harbor metastases. Another possible source of error may be linked to the examination of the harvested SLNs by conventional histopathological methods. A more careful and extensive SLN analysis (e.g. molecular analysis by RT-PCR) is able to find more positive nodes, so that the false-negative rate is reduced. Older age at diagnosis, deeper lesions, histologic ulceration, head-neck anatomical location of primary lesions are the clinical factors associated with false-negative SLNBs in melanoma patients. There is still much controversy about the clinical significance of a false-negative SLNB on the prognosis of melanoma patients. Indeed, most studies have failed to show that there is worse melanoma-specific survival for false-negative compared to true-positive SLNB patients.

Sentinel lymph node mapping in breast cancer: a critical reappraisal of the internal mammary chain issue.

Although, like the axilla, the internal mammary nodes (IMNs) are a first-echelon nodal drainage site in breast cancer, the importance of their treatment has long been debated. Seminal randomized trials have failed to demonstrate a survival benefit from surgical IMN dissection, and several retrospective studies have shown that IMNs are rarely the first site of recurrence. However, the recent widespread adoption of sentinel lymph node (SLN) biopsy has stimulated a critical reappraisal of such early results. Furthermore, the higher proportion of screening-detected cancers, improved imaging and techniques (i.e., lymphoscintigraphy for radioguided SLN biopsy) make it possible to visualize lymphatic drainage to the IMNs. The virtually systematic application of adjuvant systemic and/or loco-regional radiotherapy encourages re-examination of the significance of IMN metastases. Moreover, randomized trials testing the value of postmastectomy irradiation and a meta-analysis of 78 randomized trials have provided high levels of evidence that local-regional tumor control is associated with long-term survival improvements. This benefit was limited to trials that used systemic chemotherapy, which was not routinely administered in the earlier studies. However, the contribution from IMN treatment is unclear. Lymphoscintigraphic studies have shown that a significant proportion of breast cancers have primary drainage to the IMNs, including approximately 30% of medial tumors and 15% of lateral tumors. In the few studies where IMN biopsy was performed, 20% of sentinel IMNs were metastatic. The risk of IMN involvement is higher in patients with medial tumors and positive axillary nodes. IMN metastasis has prognostic significance, as recognized by its inclusion in the American Joint Committee on Cancer staging criteria, and seems to have similar prognostic importance as axillary nodal involvement. Although routine IMN evaluation might be indicated, it has not been routinely performed, perhaps because IMN drainage with lymphoscintigraphy is more difficult to demonstrate than axillary drainage. This difference is due to technical reasons and not the absence of lymphatics to the IMN. Recent anatomical studies have confirmed a model of breast lymphatic drainage that comprises superficial, deep and perforating systems. The superficial system drains to the axilla, usually to a lymph node posterior to the pectoralis minor muscle. The deep system drains to the axilla and also anastomoses with the perforating system which drains to the IMNs. The perforating system does not connect with the superficial system. The prevalence of IMN drainage tends to reflect the method of lymphoscintigraphy, where peritumoral (deep lymphatic system) injections have a much higher likelihood of IMN drainage than subareolar or subdermal (superficial lymphatic system) injections. The fused SPECT/CT images represent a further technical solution to increase the identification of IMNs and consequently can significantly reduce the false negative rate of sentinel lymph node biopsy. Before mature results from current and future randomized trials assessing the benefit of IMN irradiation become available, lymphoscintigraphy and IMNs biopsy may be used to guide decisions regarding systemic and local-regional treatment. However, even in patients with visualized primary IMN drainage, the potential benefit of treatment should be balanced against the risk of added morbidity.

Radionuclide therapy and integrated protocols for bone metastases.

Bone metastases are responsible for most of the morbidity and mortality associated with solid malignant tumors, occurring in about 65-70% of the patients with advanced breast or prostate cancer. The pathophysiology of skeletal metastasis is a complex process that involves several biologic process leading to cellular invasion, adhesions and stimulation of osteoclasts and osteoblasts with the mediation of several factors including cytokines, serine proteases and tumor-derived factors. The clinical management of pain from bone metastasis, which is mostly due to indirect stimulation of sensory nerve endings by cytokines and other biologically-active compounds released locally in response to the presence of tumor cells in the bone marrow, includes several options that can be used either alone or in varying combinations, such as analgesic drugs, chemo- or hormonal therapy, bisphosponates, external beam radiation therapy, and surgery. Bone-seeking radiopharmaceuticals play an important role in the treatment of pain caused by multiple blastic or mixed-type skeletal lesions; they have in general a favorable toxicity profile and a high rate of overall clinical benefit, although they may differ in terms of duration of pain palliation and suitability for repeat treatments. The palliative effect can be attributed to the radiation targeted to the bone marrow space, and the overall average response ranges between about 45-80%, with complete response in 10-30% of the cases. In selected clinical conditions, radionuclide therapy can also constitute an effective systemic treatment beyond bone pain palliation, and a synergistic anti-tumour effect can be expected by the combination with other agents, such as chemotherapy or bisphosphonates. This review summarizes the current experience with bone-seeking radiopharmaceuticals used for bone pain palliation, focusing on indications, patients' selection, efficacy and toxicity. Finally, the available data on combination therapies showing encouraging results as to potential anti-tumor efficacy are also reviewed.