How Breast Cancer Spreads
Posted 8/16/2012
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It has been a while since I posted a scientific paper, so it seems time to offer this to those of you interested in more geek-y writing. The question of how breast cancer spreads beyond the breast and becomes systemic/ metastatic/Stage IV disease is clearly vitally important and, as of yet, imperfectly understood. We all know about the prognostic importance of positive axillary lymph nodes (meaning, the presence of cancer cells in one or more of those nodes), but that is only one of the possible ways for breast cancer cells to escape. Although the presence or absence of positive lymph nodes is important and directs treatment decisions, it is surely not the "who will live and who will die" statement. I frequently try to reassure women who are waiting for a final pathology report that this is one important factor, but most surely not the only one. I have known many women who had many positive lymph nodes (I can think of a few who had 15-20) who have been fine for years after treatment.
A related comment about axillary node dissections: Full dissections used to be the standard of care before the development of sentinel node dissection. Now, the full dissection is used only when the sentinel node is positive or, as sometimes happens, it is known before surgery that there are positive lymph nodes. Many women have wondered why some have 8 nodes removed while others have 12 or more. Here is the non-medical answer (I am certain that a surgeon would cringe at my language): surgeons take a circumscribed area of tissue. We have different numbers of nodes in that specific "chunk," and the surgeon does not know in advance how many will be there.
This is an abstract from a forthcoming Clinical Experiences paper about the varying ways that breast cancer cells can leave the breast and spread throughout the body. Since it is virtually impossible to know with certainty whether or not this has happened, most women are treated with some kind of systemic therapy (chemo or hormone) to try to eradicate any cells that may be on the move. Here is the abstract and then a link:
Lymphatics, lymph nodes and the immune system: barriers and gateways for cancer spread
Robert L. Ferris • Michael T. Lotze • Stanley P. L. Leong • David S. B. Hoon • Donald L. Morton
Abstract: Metastasis to the regional lymph node is the most important prognostic indicator for the outcomes of patients with sold cancer. In general, it is well recognized that cancer development is genetically determined with progression from the microenvironment of the primary tumor site, oftentimes via the SLN gateway, to the distant sites. In about 20 % of the time, the cancer cells may spread directly through the blood vascular system to the distant sites. Thus, in general, cancer progression is consistent with Hellman's spectrum theory in that development of nodal and systemic metastasis from a localized cancer growth is a progressive process. Cancer proliferation within the tumor microenvironment may give rise to increased tumor heterogeneity, which is further complicated by its continuous change through its evolution within the host in a Darwinian sense. It is crucial to understand the molecular process of lymphangiogenesis and hemangiogenesis in the tumor microenvironment with respect to the initial steps of cancer cells entering into the lymphatic and vascular systems so that rational therapy can be developed to curb the process of specific routes of metastasis. This chapter elucidates the role of lymphatics, nodal metastasis and antitumor immunity. We present novel immune targets in nodal metastases, the importance of the lymph node as a pre-metastatic niche, and immune-related proteins as biomarkers of metastasis.
Note: This abstract has been published online before the release of the whole article. Here is a link that you can follow later if you choose to read more when it becomes available:
http://www.ncbi.nlm.nih.gov/pubmed/22851005
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