Microscopic Vascular Invasion as a Predictor of Lung Cancer
Data taken from newer studies now suggests that microscopic vascular invasion (MVI), or the spread of individual cancer cells via the most minute blood vessels in the human body, may be a more significant tool than typical staging methods in determining how severe and extensive cancerous tumors could be expected to become.
The study, by Enrico Ruffini, MD and colleagues, shows that MVI may, in fact, be a better predictor of the nature of various cancers, most notably lung cancers, than the more commonly used TNM staging system, the one most widely accepted by many cancer agencies and oncologists, or cancer doctors.
According to Lung-Cancer.com, lung cancer – divided into two main types (small cell and non-small cell) – is staged using the TNM system, though the categories are quite different.
TNM, which grades cancers on: the extent of the tumor (T); the spread of cancer cells to nearby lymph nodes (N); and its spread to more distant sites in the body (M, for metastasis), is a staging system that evaluates cancer based on the extent of the original tumor, if known, and its advance within the body’s tissues.
Other cancer staging systems include: the summary staging system favored by the National Cancer Institute’s (NCI’s) Surveillance, Epidemiology, and End Results Program, or SEER; The Jewett staging system, used for prostate cancer; The Ann Arbor staging system used for lymphomas by both the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC); the International Federation of Gynecology and Obstetrics system, used to stage cancers of the cervix, ovaries, uterus, vagina, and vulva, and; the staging criteria of the Children’s Oncology Group, used to evaluate pediatric cancers.
The work of Dr. Ruffini’s group, however, shows that using MVI as an evaluation tool may be more accurate, and a better predictor of how severe and extensive a tumor may be. For example, in a study of 512 patients with non-small cell lung cancer (staged for pathology analysis as node negative T1a to T3, using the 2009 edition of the TNM), researchers discovered that one third, or 154 patients, experienced MVI which correlated to a great extent with lymph node involvement and greater tumor size.
In addition, five-year survival rates were less for patients who exhibited a 50-percent MVI, as compared to those without MVI (at 66 percent). The evaluations and conclusions were presented at the Chicago Multidisciplinary Symposium in Thoracic Oncology, December 9-11, 2010.
In fact, this survival rate was significant even among those evaluated for squamous cell carcinoma, a form of skin cancer, and even more decidedly negative in the case of adenocarcinoma, a cancer of epithelial tissues most commonly arising in the bronchial mucosal glands. In both cases, greater rates of MVI clearly signaled greater lymphocytic involvement and more extensive tumor spreads.
Austrian researchers concluded much the same thing in a 2009 study showing that, when microscopic and macroscopic invasion were differentiated, the former remained statistically significant as a tumor size-and-spread evaluator, whereas the latter was not an independent measure of value. Researchers concluded that MVI should be considered in prognostic models for renal cell carcinomas, a form of kidney cancer, though they were equally quick to point out that both (microscopic and macroscopic) were associated with poor cancer outcomes.
Ultimately, the Italian group agreed that the study might have been incorrectly evaluated, in terms of MVI, because of its retrospective design, long interval (January of 1998 to August of 2008), and analysis of overall survival rather than disease-free survival.
A new study evaluating MVI as a prospective measure of tumor spread and lymphocytic involvement is underway, using what Dr. Ruffini identified as the International Association for the Study of Lung Cancer database.