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Lung Nodule Growth Rate: An Important Factor in Assessing Risk of Cancer

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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.

So we expect a cancer to grow, but there’s a lot of variability in the rate of an individual cancer’s growth. We know that different histologies (cancer subtype under a microscope) have different growth characteristics: SCLC has a typical VDT of 30 days, while NSCLC has an average VDT of 100 days. But on one end of the spectrum for NSCLC, a poorly differentiated adenocarcinoma or squamous cell carcinoma may have a VDT in the range of SCLC, while a well-differentiated cancer like many bronchioloalveolar carcinoma (BAC) tumors may have a VDT of more over a year. So by observing a nodule over time, we can learn a good bit about the probability of it being a cancer. For instance, nodules that grow incredibly quickly (VDT less than a week, for instance) are far more likely to be infection than cancer, and those that go for a year and a half or so without doubling are generally too slow-moving to be cancer. The common definition of stability is a lack of change over two years of observation, and then patients with a nodule being followed are generally felt to have a very low likelihood of cancer. However, I’ve seen a few cancers that didn’t have convincing growth until more than two years of follow-up had been completed (although a cancer that takes 3-4 years to double is likely to be much less life-threatening over the next several years than a more typical, faster growing lung cancer). And there’s always a rare very rapidly growing cancer that can grow remarkably during a period of observation. The key is weighing the risk of watching (which usually helps to clarify the risk that a nodule really is cancer or not) vs. the risk of jumping in and overtreating lots of nodules that aren’t cancer after all.

Among the key principles is that it’s not sufficient to just “eyeball” a nodule, but rather to have a radiologist carefully measure the nodule on a scan. And the level of detail required necessitates follow-up CT scanning rather than chest x-rays. Even with measuring nodule diameter on CT scans, very small nodules of just a few mm can differ in their apparent size just as a function of where the CT slices through the nodule (slice cuts may be every 3-5 mm for example). Imagine the difference between cutting through an orange through the middle vs. toward one side. If you only see the cross-sectional size, different cuts can give a different sense of the same nodules.

As I suggested in the discussion above about how tumor histology correlates with VDT, there have been studies that have looked at different kinds of tumors and their typical doubling times. For instance, ground glass opacities typically have the slowest VDT, with solid nodules a faster VDT, and “semi-solid nodules” in between the two (abstract here). In this study, the median VDT for pure GGOs was 813 days (as in, more than two full years), underscoring the point that some of the most indolent cancers, predominantly BACs, can grow remarkably slowly but still be a cancer (see prior post here about some of the issues with the most indolent BAC tumors).

Finally, there’s a website that includes a doubling time calculator, in which you input the dates of your CT scan studies and the size of the nodule. The calculator is here (and there’s also some more information on imaging of lung cancer).

The key points, though, are that cancers should grow over time of being observed on CT, and while there is a lot of variability in how quickly lung cancers grow, the fastest and slowest moving are less likely to be cancer than the ones that double over something in the range of a month to a year or so. The ones with convincing but not extremely rapid growth are the most suspicious for cancer.


14 Responses to Lung Nodule Growth Rate: An Important Factor in Assessing Risk of Cancer

  • dabarger says:

    Thanks Dr. West for this series of posts concerning nodules. I had a ct scan in Sept of this year that revealed, among other things, new multiple poorly defined nodules throughout both lung fields which were not noted 2 months earlier in July. A repeat scan in Oct. showed no change. Your information has helped me to understand the kind of changes my med. onc. may be looking for with the repeat scans. Thanks again for making this information available in way that “layman” such as myself can understand!! :)

    David Barger
    Asheville NC
    Diagnosed Dec. 06, stage 3b nsclc
    Completed carbo/taxol/radiation May 07
    Bronch/Med and left side VATS biopsies in July 07-
    No evidence of active disease at that time
    New multiple nodules

  • lesliebilbrey says:

    my husband is a 4.5 year survivor of nsclc stage 3a with recent recurrence in cervical nodes…whee should I lokk for new and promising treatments?

  • Dr. West says:

    Leslie,

    I’m sorry about his recurrence…that’s a remarkably long time to go after treatment, and it suggests that if it is truly the same cancer (are you sure it’s not a new primary cancer?), it must be remarkably slow-growing to recur this late.

    Our treatments for recurrent lung cancer are really the same as the ones I’ve described for stage IV NSCLC, and after a period as long as 4.5 years, it would generally be approached the same as first line treatment. So I think the posts I’ve written on advanced NSCLC, including clinical trials, should apply. Check on the subject archives to find both core concepts and a large number of additional posts in the stage IV section of the subject listings.

    -Dr. West

  • pattimarzano says:

    Hello Dr. West,
    In March 2007 I had a peripheral 1.4×1.7cm nodule. In June it was 1.8×1.8. When I had it biopsied in October it measured 3.0×2.2cm. I don’t understand a lot of this yet, but would you consider this fast growing? I believe my doctor, who is not an oncologist, but a Pulmonary Hypertension specialist said it is considered a tumor at 3.0×3.0cm.
    I am treating this myself at this point with diet and other nutritional options as I have no insurance and it seems none of the oncologists at University Hospital in Denver are interested in seeing me. I have PAH, RHF and Scleroderma, so agressive treatment is out and the diagnosis was severe squamus cell dysplasia and suggested another biopsy, but my PH doctor said no to that as my lung partially collapsed during the last biopsy.
    My pulmonary artery pressure is 98. What are your thoughts on this Dr. West?

  • Dr. West says:

    I don’t do any work on PAH or deal with pulmonary artery pressures, so I would defer to a pulmonologist on this.

    I do think that the growth rate of that nodule is concerning, and unfortunately I don’t think I could be very reassured by an ambiguous biopsy if it keeps growing. However, I really can’t put this into context of your other medical problems, and your PAH physician may very well be giving a very appropriate assessment of the priorities of what you’re dealing with. Your case sounds like one that really needs to be individualized, so I think it’s appropriate for me to defer to the docs who actually know you and your medical situation.

    -Dr. West

  • a white rabbit says:

    ..ok, following on growth rate as an indicator of cancer, how does shrinkage rate compare, what indications does it give ?

    ..i had a 2.8 cm discovered and opted for removal of the lobe, upper right lung, during surgery they found two more, in the same lung, one on the Hilar node, they did what they could and stitched me up, ( wish they’d asked, take out the lung was logical). The CT-scan showed 2 1.8 cm sites remaining. The follow up agressive chemo, cisplatin/gemzar , as of latest scans after 4 sessions shows nothing, even on max-Zoom, and my CEA has gone from 21 pre-op to a wobbly 5-6, down to 3.5 minmum after chemo..

    ..so if it grows quickly is a cause for worry, does it shrinking quickly constitute cause for joy ?..

    ..Richard

  • a white rabbit says:

    ..after thought..

    ..my hospital puts the CT-scan on disc for me, both the normal and the glow-in-the-dark versions, s’a great program. Spot the cancer cell, then do some creative but destructive visualisation has been one of my past-times these past few months..

  • Dr. West says:

    Significant shrinkage is always a cause for joy, or at least very strong encouragement. While we are often pleased to see at least stable disease (vs. a default alternative for growth if cancer has its way), shrinkage is especially welcome, particularly if dramatic.

    -Dr. West

  • pattimarzano says:

    Hi again Dr West,

    Are you familiar with this drug? It is a commonly used drug for PH. I’m going to talk to my doctor about this study and see if maybe I can get in it and maybe kill two birds with one stone.

    Hopkins Early Lung cancer Prevention Program
    LUNG CANCER CHEMOPREVENTION RESEARCH STUDY

    Active or Former Heavy Long Term Smokers needed To help in the testing of a drug for lung cancer prevention

    ILOPROST*

    Iloprost is an orally active compound which relaxes blood vessels and has anti-inflammatory properties

    Are you familiar with this?

  • Dr. West says:

    I’m aware of the drug, but it’s not one I’ve had a patient on since I was a resident in general medicine and occasionally taking care of patients with pulmonary hypertension. I’m not familiar with it being used in this setting, but it sounds like an interesting trial.

    -Dr. West

  • pattimarzano says:

    Dr West,
    My PH doctor called today and wants another needle biopsy. Originally she didn’t want to do it again due to the lung collapsing last time, but the oncologists she spoke to said we need to have a name for this beast and we’re going to do that after the first of the year. Thank you for your kindness in answering my posts. I also spoke to her about the Iloprost, and she said it was a study for prevention and not treatment or cure.

  • Julie2009 says:

    I am going to have my needle biopsy done on 9/1/11. The more I read what you wrote above – the more convinced I feel that I have BAC cancer. The sorry part is I have to get a PPO in January 2012 so I can have CyberKnife instead of VATS. Thank you so much for clarifying things for me.

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  • dawnbyers says:

    I have a question. My dad has a mass on his right lung and they did a X ray and found it then they did a Ct scan 3 days later and there was a difference in size. will there be a difference in size when it comes to X ray verses ct scan. He seen a pulmonalogist and a oncologist and they want to do a biopsy but they say his lungs are really bad. They did another ct scan of his brain and abdomen and a full body bone scan. What are these test for? They are also saying they cant treat the lung because he has a bad heart. Help me understand a little.

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