Lung Cancer During Pregnancy

While rare, the incidence may be increasing

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On very rare occasions, lung cancer can occur during pregnancy. When it does, it is usually diagnosed in the advanced stages of the disease and is more difficult to treat given the risks to both the mother and baby.

Lung adenocarcinoma, a type of non-small cell lung cancer, is responsible for the majority of lung cancer cases in pregnant women. This is the type found most often in young people and never smokers with the disease.

As rare as lung cancer is in pregnant women, studies suggest that the rate may soon increase due to changes in lifestyle and smoking habits.

Characteristics

It is estimated that one of every 1,000 women will get some form of cancer while pregnant. Of the many forms, lung cancer is one of the least likely causes. The first case was documented back in 1953, and, as of 2016, there have only been an additional 70 cases reported in the medical literature.

A 2016 review in the Journal of Advanced Research looked into these cases and found certain commonalities:

  • Average age: The average age at diagnosis was 36.
  • Trimester: The diagnosis was usually made closer toward the beginning of the third trimester (an average of 27.3 weeks of gestation).
  • Cancer type: Non-small cell lung cancer was the cause in 82% of cases.
  • Cancer stage: 97% were stage 3 or stage 4 at the time of diagnosis, suggesting that lung cancer may be more aggressive during pregnancy.
  • Delivery status: 82% of the women gave birth to normal newborns.

Are Rates Increasing?

Other cancers, such as breast cancer, cervical cancer, lymphoma, and leukemia, are more commonly seen during pregnancy than lung cancer. With that said, experts speculate that the rates of lung cancer in pregnant women are likely to increase for two key reasons:

  • Rates of smoking among women in the United States are approaching those of men (13.6% versus 17.6%, respectively).
  • Women are delaying pregnancy compared to generations past, rising from 21.4 years in 1970 to 26.8 years in 2017.

The combination of high smoking rates and older age suggests that the incidence of lung cancer are likely to increase in pregnant women⁠—although it is unclear by how much. Today, only around 1.7% of lung cancers are in people under 45.

Causes

The reasons for these findings are not entirely clear, but it believed that immune suppression plays a central role.

According to a 2019 study in the Frontier in Immunology, lung cancer can blunt the body's immune defenses during pregnancy as evidenced by increases in a protein called programmed death-ligand 1 (PD-L1).

PD-L1 is found on cancer cells and can bind to defensive white blood cells, called T-cells, and neutralize them. Without T-cells to defend the body, tumors can grow unchecked and at far greater speeds. When this occurs during pregnancy, as it often does, a tumor can be far more aggressive and dangerous.

PD-L1 cancer cells are more common with solid adenocarcinoma tumors—the type that is mainly seen in pregnant women with lung cancer—than other subtypes and are associated with poorer outcomes.

Diagnosis

Diagnosing lung cancer in pregnant women can be challenging in that lung adenocarcinomas tend to develop in the periphery of the lungs and only cause symptoms when they are quite large.

Even if symptoms develop, such as shortness of breath and fatigue⁠, they are easily mistaken for symptoms of pregnancy. This is especially true if the doctor doesn't query the woman about her past smoking habits.

It is for this reason that lung cancer is usually not recognized in pregnant women until advanced stages when there may be wheezing, swollen cervical (neck) lymph nodes, hemoptysis (coughing up blood), and unexplained weight loss.

If lung cancer is suspected, a doctor can use the following tests to help diagnose the disease during pregnancy:

  • Chest X-rays and computed tomography (CT) scans, both of which use ionizing radiation to create images, can be used safely if a lead apron is worn to protect the baby from radiation.
  • Sputum cytology involves the coughing up of phlegm and may expose cancer cells under the microscope.

If any of these initial tests suggest cancer, a biopsy (such as fine needle aspiration) would be performed to collect a sample of cells for examination in the lab. This can provide a definitive diagnosis of cancer.

Bronchoscopy, sometimes used to diagnose lung cancer from within the airways, is contraindicated during pregnancy due to the use of anesthesia.

There are no blood tests that can help diagnose lung cancer.

Molecular Profiling

There is a greater incidence of so-called "actionable gene mutations" in women with lung cancer. These mutations—like EGRF mutations or BRAF mutations—cause physical changes in a cancer cell. These changes create specific receptors on the surface of the cell onto which a targeted drug can latch.

These mutations can be identified with a battery of genetic tests called molecular profiling. Women diagnosed with lung cancer during pregnancy will usually undergo molecular profiling to see if they are candidates for newer targeted therapies.

Treatment

If you are pregnant and have been diagnosed with lung cancer, it is important to find an oncologist experienced in dealing with pregnancy. The cancer specialist would also work collaboratively with an obstetrician specializing in high-risk pregnancies.

Together, these doctors can help you weigh the risks of continuing the pregnancy (including premature delivery) and exposing your baby to cancer treatments.

The treatment options during pregnancy are not as extensive as those for non-pregnant women. They include:

  • Surgery: Surgery for lung cancer offers the best chance for a cure for women with early-stage lung cancer (stage 1, stage 2, and stage 3A). It requires extensive preoperative imaging, such as magnetic resonance imaging (MRI) scans, and a surgical oncologist familiar with the nuances of maternal physiology.
  • Chemotherapy: Chemotherapy is not associated with a birth defect during the second or third trimester. Chemotherapy may increase the risk of intrauterine growth restriction (IUGR) and low birth weight.
  • Targeted therapies: In the past, targeted therapies were avoided during pregnancy, but recent studies have reported that there was no significant evidence of harm in fetuses exposed to Tarceva (erlotinib), Iressa (gefitinib), or Xalkori (crizotinib).

Radiation therapy is contraindicated during pregnancy. Immunotherapy drugs like Opdivo (nivolumab) and Keytruda (pembrolizumab) are also avoided due to the risk of fetal harm, although they may be used after the delivery.

A Word From Verywell

Lung cancer during pregnancy is still uncommon but is likely to increase due to high smoking rates in women and older maternal age. If you are or are planning to become pregnant, let your doctor know if you've ever been a smoker and how many pack-years you smoked. (Pack-years is the number of packs of cigarettes smoked per day times the number of years you've smoked.)

By knowing your smoking history from the start, your doctor will be aware of your risk and better able to spot the early signs of lung cancer while it is still highly treatable.

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