Biopsies of the internal mammary sentinel nodes may improve patients' chances of survival

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At the moment the axillary lymph nodes under the armpits are routinely checked to see whether breast cancer has metastasised to them. If metastases are found there then patients usually receive radiotherapy and/or chemotherapy to mop up the straying cancer cells. The status of the internal mammary (IM) lymph nodes is known to be an important prognostic factor as well, since women with IM metastases usually do less well. The sentinel node (SN) is the first lymph node to which cancer cells metastasise from the breast tumour, and the internal mammary sentinel node (IM-SN) can be identified via a scan once a radioactive tracer has been injected into the patient.

Dr van der Ent said: "While performing routine axillary SN scans, which we have been doing since 1997, we frequently detected IM-SNs as well, which represented lymph drainage from the breast tumour to the IM lymph nodes. We know that the concept of the SN biopsy is valid in predicting whether there are metastases in the axillary nodes, so why then ignore the presence of IM-SNs, visible during the same scan? So, since 1997 we have been performing routine IM-SN biopsies whenever the scans detect them."

The IM-SN biopsy is more difficult to perform than an axillary SN biopsy, but complications are rare and not usually serious (in 7% of cases slight damage to the membrane round the lungs is caused, but this is treated by simple vacuum drainage for 12 hours). The biopsy involves a small cut (2-2.5 cms) over the area adjacent to the breast bone, through which the radioactive IM-SN is removed surgically. IM-SN biopsy is successful in 65% of cases.

Dr van der Ent and his colleagues have performed axillary and IM-SN biopsies on 470 patients so far, and have found metastases in 20-25% of breast cancer patients. In a small proportion of the patients (5%) the biopsies revealed no metastases in the axillary lymph nodes, but only metastases in the IM-SNs. This means that if no IM-SN biopsy had been performed, these few patients might then have had less appropriate treatment, with no adjuvant chemotherapy, because the doctors would have presumed there were no metastases at all.

Dr van der Ent said: "Our results show metastatic tumour involvement in the IM nodes in 20-25% of breast cancer patients. These findings are associated with poor prognosis, as we know from investigations in the 1950s and 1960s when the same percentage (25%) of IM metastases was found, using extensive and mutilating surgical procedures. Thus, IM-SN biopsy, while using a minimally invasive technique, provides important additional prognostic information."

Once patients have been identified as having IM-SN metastases, they are given additional radiotherapy and chemotherapy. Adjuvant chemotherapy is usually given to patients with metastases in their axillary nodes, but only exceptionally to patients with no axillary node metastases. Dr van der Ent said: "The small group of axillary node negative, but IM node-positive patients in our series, who were recognised thanks only to IM-SN biopsy, also have a need for adjuvant chemotherapy. Therefore the results from these biopsies caused significant changes to the treatment given to our patients."

Dr van der Ent concluded: "It is not yet possible to prove any survival benefit from IM-SN biopsy, simply because we have not been performing the biopsy for very long and the patient groups are too small. However, we believe that IM-SN biopsy, by improving nodal staging, recognises high-risk patients. By incorporating the diagnostic information of IM-SN biopsy in future trials, we could develop more individualised treatment protocols, which in turn might lead to a survival advantage."

MW Communications