Assessing sentinel nodes is highly valuable in the early period of cancer, facilitating accurate staging and dictating the correct treatment pathway. What are the imaging techniques used in nuclear medicine to detect the sentinel nodes associated with breast cancer and what are the benefits of SPECT/CT?


INTRODUCTION The evaluation of the sentinel node by nuclear medicine and subsequent removal by surgical intervention has applications in several different forms of cancer (penile, breast, multiple myeloma)1


. Assessing sentinel nodes is highly valuable in the early period of


cancer, facilitating accurate staging and dictating the correct treatment pathway. This review will focus on the imaging techniques used in nuclear medicine to detect the sentinel nodes associated with breast cancer, detailing the benefits of single photon emission computed tomography/computed tomography (SPECT/CT) in aiding surgery.


CANCER Statistics show that rates of morbidity and mortality are reducing for the majority of cancers2


In the United States, the incidence of breast cancer is high, with 1 in 8 females affected. In the United Kingdom, the incidence of breast cancer is slightly lower, with 1 in 9 females affected; despite improvements in mortality rates only lung cancer is responsible for more deaths3


. Although large numbers of patients survive the disease, it is clear that breast cancer still constitutes a great challenge in both diagnosis and treatment.


THE SENTINEL NODE The lymph nodes local to, and on the drainage pathway of, the primary tumour are a common site for initial metastasis4


31 2011


IMAGING & ONCOLOGY


. It had been accepted that the removal of all lymph


nodes surrounding the primary tumour (the axilla in breast cancer) could be potentially curative, but it has since been discovered that spread of this nature is more akin to the advanced stages of disease and is not necessarily the case in the early disease, prompting a reconsideration of treatment strategies. Lymph nodes have been found to be disease free in 60 per cent of early breast cancer sufferers. Breast cancer treatment has seen a dramatic change, where lumpectomy can replace mastectomy, and SLNB has replaced total axillary lymph node dissection (ALND) unless lymph nodes are proven to be cancerous.


ALND was typically associated with high morbidity (painful lymphoedema, reduced arm motion and parasthesia) but SLNB may reduce these complications, thus improving the patient experience. There are also associated cost-saving benefits to long-term care if morbidity is reduced. Correct identification and evaluation of the sentinel node is, therefore, highly valuable.


Predictable lymphatic drainage was first identified in a 1977 study of penile cancer5


Lymphatic drainage was said to be predictable, involving a chain of lymph nodes (Figure 1)6


. Early detection, raised public awareness, better screening programmes, and


improved technology and treatment regimes, are all contributing factors. Breast cancer is a good example, where sentinel lymph node biopsy (SLNB) and SPECT/CT have enhanced the patient experience through an improved technique to allow reduced morbidity.


Cancer rates per annum have stabilised but detection rates can vary with the introduction of new diagnostic tools and variation in population sizes2


. Survival rates


have also improved in the prevalent population (those with cancer), but increased life expectancy raises the possibility of both disease recurrence and complications related to any treatment of the cancer. Therefore, consideration of the long-term effects of treatment is important to both the patient and those involved in their care. However, treatment strategies are not the same for every patient and are highly dependent on accurate staging of the cancer, where the presence or absence of secondary disease (lymph nodes local to the primary tumour or distant metastases) could determine whether the treatment was conservative or aggressive.


. where the first node in this chain, the sentinel node, indicates the spread of


disease. A disease-free node indicates that the lymphatic system is clear of disease, but anatomical variation of lymphatic drainage can be a complicating factor and care must be taken to accurately determine the sentinel node(s)6


. On occasion, there can be more than one sentinel node, depending on the lymphatic drainage pathway.


morbidity and operating times


speCt/Ct is reduCing


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