As is fitting for Lung Cancer Awareness Month, we should become more aware of the concept of the solitary pulmonary nodule, or SPN, which is how lung cancer appears in the small proportion of (relatively) luckier people who have their lung cancer detected incidentally or in screening. Technically, it’s defined as a spherically-shaped lesion that measures up to 3 cm (larger than that is considered a mass) and is entirely surrounded by lung tissue. There are two main ways that they are detected: an incidental finding on a scan done pre-operatively or for some other reason, or as part of a screening study. Specifically talking about solitary nodules (not nodules spread throughout the lungs), these aren’t all cancer, and they can range from being old scar tissue to infection, inflammation, a primary lung cancer, potentially spread of another cancer to the lungs, or some other cause. As our CT scans become more and more detailed, and as CT scanners and scans are more widely available, we are seeing more and more SPNs. The more you look, the more you find.
SPNs can be managed in three basic ways. First, you can continue to watch them on repeat films over time. You can also do a biopsy, sticking a needle in and taking a sample to try to determine what it is under a microscope. Or you could just do lung surgery and take out the whole thing to find out what it is. Surgically removing a nodule is a great approach if it’s cancer, but there are significant risks associated with lung surgery, and we don’t want to do surgery for non-cancerous causes of lung nodules.
The features of the nodules found depend on whether we’re talking about SPNs found incidentally on a scan for another cause or as part of a screening study. The ones found incidentally tend to be larger, have faster doubling times (grow faster), and are more likely to actually be cancer than ones detected in screening studies.
How common are SPNs? The studies are so different in who is included and how they’re done that it’s hard to make any general statements. Populations that live in areas with many lung infections (like the Southwest and Ohio River Valley) include many, many people with lots of nodules, but few that represent cancer. Populations enriched for long-term smokers are at high risk for lung nodules, and they are more likely to actually be cancer, as you’d expect. But the studies have shown that anywhere from 8% to about 50% of the scans, or people getting scans, have SPNs, so that’s quite a huge range. Moreover, once a nodule is detected, we know they aren’t all cancer, and the rate of these actually turning out to be malignant has been reported to be anywhere from about 1% to 12%. With that much variability in these reports, it’s no wonder that the concept of screening for cancer vs. chasing down many anxiety-producing but non-cancerous nodules remains controversial.
Of course, not all lung nodules are created equal, and some look more likely to be benign while others are much more suspicious for cancer. I’ll turn next to some of the factors that make us think cancer is more or less likely for a particular SPN in question.
posted by Dr. West @ 11:21 pm link to this post
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November 10th, 2007 at 11:15 am
OK, so it sounds to me like it’s time for a large clincal trial to investigate SPNs, and do it now so that we can get some results in the next 15 years without some sort of controversy.
Since there are so many people in the country that have these SPNs, it will be easy to find candidates for such a study/trial.
Based on some pre-determined responsible guidelines, if an individual has any suspicious SPNs, one arm can undergo the “watchful waiting” process, another arm can have needle biopsy or some sort of minimally invasive biopsy, and perhaps another arm can undergo some sort of multidirectional radiotherapy to cut out the suspicious SPNs.
Follow the individuals in the study for 5-7 years and let’s see what the survival statistics that the 3 arms produce in order to determine the best way of dealing with SPNs going forward. Perhaps such a study will allow us to gain a better understanding on which SPNs are more likely to become maligancies as time goes on.
Who knows, we may even find that many more of these nodules than we thought are indeed cancerous, but that certain individual’s immune systems or genetic profiles are better at keeping these cancers in check and thus slower moving.
We could learn why certain individuals are able to keep these cancers in check better than others, and design treatment plans to make cancerous SPNs into slow growing SPNs that will not affect a person’s life span.
I’m sure I am over-simplifying, but let’s start thinking outside of the box a bit. We haven’t made that much progress in lung cancer survival the past 30 years. I am afraid that everyone keeps thinking “inside the box” for a magic chemical compound that is going to erradicate lung cancer (or any cancer for that matter) once it is at it’s latest stages.
Jim
November 10th, 2007 at 4:03 pm
Perhaps, but we’d run into problems if/when people assigned to watching a nodule decided to go somewhere outside of the trial to get a biopsy or surgery, or if there were a few deaths after surgery for things that turned out to be scar and not cancer. Not to mention the people who just ended up with pain, infections, or on long-term oxygen after surgery that was in the end not really needed.
Not that I don’t appreciate you making suggestions, Jim. But it’s hard to come up with a really great, feasible plan that thousands of people would really buy into and that will answer the important questions. You’re right that we’re slow in our progress, but in truth these are hard questions to answer ethically and with maximum safety.
-Dr. West
November 10th, 2007 at 10:58 pm
This is why I qualified the study to have a pre-determined responsible guidelines about what is a suspicious SPN. From your latest Onctalk post today, I see that there is already some criteria of what a suspcious SPN may look like as gained from the latest I-ELCAP work (that so many doctors are quick to dismiss.)
If it is expected that anywhere from 20%-70% of the general population have at least 1 of these SPNs, I think that a there could still be plenty of people available to reach a statistical significant study.
A study such as this is really meant to be a preemptive study, and a study to help determine which SPNs are likely to become malignant. If a subject sought treatment outside of the study because they were afraid they have a malignany SPN(s), the new doctor would still subscribe to the currently recommended “watchful waiting” process.
I understand that needle biopsies and bronchoscopies are dandgerous diagnostic examinations. But some of the complication statistics of these procedures are likely biased due to the fact that they are being performed on some patients that are already very ill. But anyway, perhaps that arm is eliminated and another diagnostic process replaces it (like maybe one of these blood protein or antibody tests or the breath test.) And only after a positive result would then further more invasive diagnositic procedures be tried on that arm.
I have a strong suspicion that the more that these SPNs are investigated, the more we are going to find out that they are all not as benign as we currently think, but I think that we will find that some subjects are better equipped immune wise or genetically wise to keep these SPNs better in check than others. And there must be some reason for that, which may be the way to boost survival rates - from the front end of the disease rather than the back end.
Again, I know colon cancer is a very different cancer, but they do not leave any polyps behind during a colonscopy, and 5 year survivals have jumped considerably. I am sure that many of these polyps, and perhaps even the great majority of these polyps, are benign - but they are removed anyway. In lung cancer, we are not doing anything with these suspicious masses at all, until it is too late.
We need to start studying this current “watchful waiting” group better or we will never find a way to catch lung cancer earlier.
Jim
November 12th, 2007 at 10:41 pm
Jim,
I understand where you’re coming from, but I think it’s worth pointing out that the vast majority of polyps are pre-cancerous and will progress to become colon cancer in several years, while the nodules in the lung that aren’t cancer are far more likely to just be scar tissue or some other benign cause that will never become cancer. The other issue is that colonoscopy, while not the most pleasant test, doesn’t require surgery to open up the chest. Taking out polyps during a colonscopy is far less risky than going into the chest to look around and take what you find. I just don’t see anything like this really happening on any meaningfully large scale, and I know that I’d discourage patients with minimally suspicious nodules from having lung surgery largely in the name of getting more complete answers.
-Dr. West
November 12th, 2007 at 11:51 pm
Leaving aside for a moment the question of whether solitary pulmonary nodules (which is the way I started this adventure) can transform over time, aren’t there three other factors that are also used to evaluate the likelihood that a nodule is malignant? These include (as I recall) smoking history, age, and (newest of all) PET scan results. I know, Dr. West, that you said you were going to talk about doubling time later, but I’m talking about things you do even before watchful waiting.–Neil
April 14th, 2008 at 10:27 am
I am a 37 yr old female with a noncalcified 3 mm nodule in the upper right lobe. I was a twenty pack year smoker and this nodule was not present on a previous chest ct two years ago. What is the best plan for me start with. I am extremely concerned.
April 14th, 2008 at 4:40 pm
we generally have patients with small nodules followed with repeat CT scans to look for any change in growth, with a repeat scan typically recommended to be done 3-6 months later. If it has grown, that will typically merit a biopsy, a PET scan, and/or even possibly removing it surgically. However, the most common first step for a small nodule is to see if it grows over time.
-Dr. West
April 15th, 2008 at 6:45 am
Dr West,
Would it be safe to say that most non calcified lung lesions in an already diagnosed lung cancer (spn on initial diagnosis) patient are probably more of the same disease. Or do you see non calcified lesions that are benign?
Mary Ann