They also wonder how long lung cancer takes to develop, or when it first started.
Thegrowth rate of lung canceris not just a math question.
It could affect treatment decisions in a new and evolving era of care.
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Even two lung cancers of the same jot down and stage may behave quite differently at the molecular level.
Not every cancer grows at the same rate.
Each care decision is made based on multiple factors.
The timing between diagnosis and start of treatment can affect outcomes.
In some cases, starting treatment right away may not be the right choice.
It’s possible to have a better outcome if you wait a month for test results instead.
That’s especially true if there’s a specific gene mutation that can be treated withtargeted therapy.
It’s important to understand lung cancer growth rates, but it’s not the only thing to know.
Factors such as the pop in of lung cancer also contribute to how cancer will grow and spread.
How Fast Lung Cancer Grows
Proliferationdescribes how fast lung cancer cells grow.
Doubling time is the amount of time it takes atumorto double in size.
Unfortunately, there are limits to the math and models used to estimate cancer growth.
This means estimates of the true growth rate may be far too high or too low.
In other words, there is no simple formula.
The Science of Lung Cancer Cell Growth
A cancer cell no longer works like a normal cell.
A normal lung cell becomes a cancer cell after a series of mutations in genes that control cell growth.
The genetic changes don’t usually all happen at once.
They add up as the cells divide into the billions over a period of time.
This process sometimes takes decades.
Even then, lung cancer still may be missed by a chest X-ray.
Cancer growth estimates are based on exponential growth.
In real life, however, not all cells divide at the same rate and at the same time.
Different types of cancer have different “growth fractions.”
Some cancers, such as childhood leukemias, have a very high growth fraction.
This means a large number of cells are dividing at a specific time.
Other cancers, like breast cancer, have a low growth fraction.
Tumors are not just copies of the cells involved in out-of-control growth.
There may be new mutations that change the tumor.
Researchers use both growth rate and doubling time to help estimate how fast a tumor will grow.
To understand how lung cancer grows, it’s crucial that you know how cancer cells work.
As we’ve seen, though, there are limits to the models used to estimate doubling time.
One study compared the doubling time of breast cancer with that of non-small cell lung cancer (NSCLC).
It found that the volume doubling time for lung cancer was 134 days.
This was significantly faster than breast cancer, which was 252 days.
On average, lung cancers double in size in four to five months.
After the scans, the patients had surgery to remove the tumors.
The study found that the average doubling time was 191 days.
Non-small cell tumors grew significantly slower than small cell lung tumors.
In a third of patients with these tumors, the cancer spread to distant parts of the body.
A different study also looked at the doubling time of CT-detected lung cancer.
Researchers put the tumors in three categories:
They then compared these doubling times with subtypes.
They found that 86.7% of patients in the slow-growing group hadlungadenocarcinomaor a subtype formerly calledbronchioloalveolarcarcinoma.
Only 20% of patients with these subtypes were in the rapid doubling group.
In contrast, 60% of patients in the rapid doubling group hadsquamous cell carcinoma of the lung.
Only 3.3% of patients in the slow doubling group had this subtype.
Squamous cell carcinoma of the lung tends to have a more rapid doubling time than lung adenocarcinoma.
Studies have also looked at the doubling time of adenocarcinomas that areEGFR positive.
Most people who have lung cancer with this mutation have little or no history of smoking.
These studies have had mixed findings, with some showing a longer doubling time and others not.
Doubling time with small cell lung cancer has not been as well studied as that of NSCLC.
It does appear to be both rapid and dependent on stage.
A 2012 study looked at initial CT image scans in people with small cell lung cancer.
The average doubling time was 70 days for the primary tumor, and 51.1 days for affected lymph nodes.
The doubling time was much faster with extensive stage disease than it was in limited stage disease.
Extensive stage disease had a doubling time of 24 days while limited stage was 97.6 days.
Other factors play a role, too, such as history of smoking.
One study looked at the predicted survival times of people with inoperable lung cancer.
It found that doubling time could be used to predict survival times.
Overall, it’s thought that current models aren’t able to accurately answer this question.
Since metastases are the reason for most cancer deaths, it’s an important question.
The answer is that it depends.
The speed that cancer spreads may be tied closely with the pop in of lung cancer.
While there are differences, it’s important to note that almost any lung cancer can potentially spread.
An exception is stage 0 lung cancer or noninvasivecarcinoma in situ.
Almost any stage or size lung cancer has the potential to spread.
Small cell lung cancer can spread very early.
Even very tiny small cell lung cancers may spread to the brain or other organs.
In fact, brain-related symptoms are often the first sign of the disease.
Squamous cell carcinomas of the lung, however, may be quite large before they spread.
Lung adenocarcinomas appear to be somewhere in the middle.
It was once thought that a tumor had to reach a certain size before it could spread.
Researchers also believed it would spread to lymph nodes first, then onward from there.
We now know this isn’t the case.
Instead, tumors may have specific mutations that help them spread.
The speed can also depend on how the cells travel through the body.
First, the cancer cells need to “escape.”
Normal cells have molecules that hold them together.
Different mutations in cancer cells can make it easier or harder to for them to break loose.
Then they have to travel through either the blood, lymphatic system, or airways.
It takes longer for cancer to spread through the lymphatic system.
The bloodstream, however, can “seed” cancer cells in other parts of the body much faster.
Sometimes this can happen long before the tumor is found.
Tumor cells in the bloodstream are common even in very early-stage NSCLC.
Most of the cancer cells die when they arrive in a new location.
For growth to occur, the cells need a blood supply, calledangiogenesis.
They also need a change in the environment so the immune system doesn’t attack them.
To do this, they need to communicate with normal cells nearby.
It could be that some lung cancer cells develop mutations that let them do these things more easily.
This means it is important to find ways to prevent cells from setting up in other body sites.
In early stage breast cancer, for example,bisphosphonatescan lower the risk of recurrence.
These drugs appear to work by changing the microenvironment of bone.
The newly arriving cancer cells can’t set up a home base and instead die off.
Different cancers may spread at different rates.
They can’t predict what will happen with individual people, though.
When Does Lung Cancer Begin?
Many patients want to know when their cancer first began.
You may wonder if a stressful time in your life or specific chemical exposure “caused” your cancer.
There isn’t a good answer to this question.
A 2017 study suggested that it takes along time for a lung cancer to develop, perhaps decades.
This may be especially true for lung adenocarcinomas.
When Can Lung Cancer First Be Detected?
Lung cancer is most treatable in the early stages.
Unfortunately, most people have an advanced-stage tumor when they are diagnosed.
A chest CT, though, may find tumors as small as 6 mm, sometimes 4 mm.
The difference is clear.
Can Better Detection Mean a Cure?
With better screening, some people want to know if smaller tumors can be cured.
In 2017, researchers created a simulation model to help answer this question.
They found that in males, the most aggressive NSCLCs would need to be diagnosed 10 mm in size.
In females, the diagnosis would need to be made at 15 mm.
Without screening, the average size of a lung tumor at diagnosis is 33 mm.
Summary
The rate that lung cancer spreads is different for every patient.
Doubling time can provide important information, but it isn’t the only thing that can predict growth rate.
Different subtypes of lung cancer may grow at different rates.
Growth rates can also depend on factors like genetic mutations and history of smoking.
Some cancers may also be better at spreading to distant parts of the body.
Lung cancer can be caught early on a CT scan.
If you’re in a high risk group, talk to your doctor about lung cancer screening.
A Word From Verywell
Today, genomic testing is often done before newly diagnosed patients begin treatment.
Outcomes, or how a person does with the disease, are what is most important.
Starting treatment right away before knowing the best treatment options can sometimes do more harm than good.
Cancer treatment is changing rapidly, and many new treatment options are available.
This is why it’s important to find a doctor you trust.
Another way to learn about your disease is to connect with thelung cancer communityand get support while facing uncertainty.
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