A cancer has to grow faster than the tissue around it to become a tumor. Progressive growth is therefore a central feature of a cancer and a critical factor in distinguishing cancerous nodules from benign ones. There is a characteristic "volume doubling time" (VDT), the interval it takes for a nodule to double in volume. It's worth keeping in mind that because a nodule is generally spherical, an increase in the diameter by just 28% (such as a 2 mm increase from 7 to 9 mm) actually represents a doubling of the volume of a nodule.
As you might suspect, there are features of different spolitary pulmonary nodules (SPNs) that makes us more or less suspicious for cancer. The first is the size of the nodule. Looking at multiple series of SPNs, the likelihood of cancer among nodules that measured under 5 mm is generally in the 0-1% range. Nodules in the 5-10 mm range have been found to be cancer in up to about about 28% of cases, with most studies showing the risk of cancer in this range to be one in four or five.
PET scans are an important way to discriminate between metabolically active nodules, suggestive of cancer but sometimes representing inflammation or infection, and non-PET-avid lesions that are felt much likely to represent cancer. They are also a cornerstone of "clinical" staging by imaging and patient exam (vs. "pathologic" staging by surgery to clarify where cancer is or isn’t).
A substantial revision of the staging system was presented at the World Conference on Lung Cancer in Korea this week. This project involved multiple lung cancer experts from all over the world and from a variety of specialties over the last several years, who reviewed the data on approximately 100,000 lung cancer cases, both NSCLC and SCLC. They looked at various ways to break down this large database of cases in order to provide a more accurate prognosis for patients.
Staging in lung cancer, as well has two categories, clinical and pathologic. The clinical staging is based on what appears on scans like the CT and PET scan that are now pretty routine parts of the staging workup. Our scans are better than ever before, but some lymph nodes with cancer involvement are not enlarged and have no visible abnormalities, and no scan can pick up lesions that are only visible as a small collection of cancer cells under a microscope.
NOTE: ALL FIGURES CAN BE SEEN BY DOUBLE-CLICKING ON THEM, EVEN THOUGH NOT ALL APPEAR AS THUMBNAIL VIEWS PROPERLY.
One of the central ideas in management of advanced NSCLC is that many two-drug chemo combinations have been compared and show essentially superimposable results, as I described in a prior post.
I've been meaning to write on tumor markers detectable in the blood for the management of lung cancer. These are proteins that are produced by some tumors, and the idea is that the levels of the tumor markers in the blood can potentially be used to monitor the status of the disease.
I'm going to cover the general concepts of management of brain metastases, a subject that is still evolving because of our growing technology, particularly with stereotactic radiosurgery (SRS), commonly referred to as gamma knife. In many cases, our practice has moved a bit ahead of the data. We'll start with some general issues and then, over several posts, cover issues from surgery to radiation to medical therapy.