Why does "couple cancer" occur? Will contact with lung cancer patients be contagious?

Recently, a woman in Henan Province found out that she had lung cancer during a physical examination. After detailed questioning, the doctor learned that her husband had been a long-term smoker and had also been diagnosed with squamous cell lung cancer a few years ago. Why does "couple cancer" occur? Is lung cancer contagious? Who are the high-risk groups? How to prevent it? Let's learn together...

1. What is lung cancer?

Lung cancer is divided into two major histological types, small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). NSCLC accounts for about 85% of all lung cancers. The earlier lung cancer is detected and treated, the higher the survival rate.

Lung cancer is prone to metastasis, and common metastatic sites include the liver, brain, bones, pleura, lymph nodes, etc. Once metastasis occurs, it is considered to be in the late stage.

The latest global cancer burden data for 2020 released by the World Health Organization's International Agency for Research on Cancer (IARC) show:

In 2020, there were 2.2 million new cases of lung cancer, making it the second most common cancer in the world.

There were 9.96 million cancer deaths worldwide, of which 1.8 million were from lung cancer, ranking first in the number of cancer deaths.

In 2020, the number of cancer deaths in China was 3 million, and the number of deaths from lung cancer was as high as 710,000, accounting for 23.8% of the total cancer deaths.

Lung cancer is medically divided into four stages. Data show that after standardized treatment, the possibility of cure for patients with carcinoma in situ is nearly 100%; the 10-year survival rate for patients with stage I lung cancer is 88%; and the 5-year survival rate for patients with stage III/IV lung cancer is only about 15%.

2. Who are the high-risk groups for lung cancer?

The "Guidelines for Lung Cancer Screening, Early Diagnosis and Treatment in China 2021" states that people at high risk of lung cancer should meet one of the following conditions: 1. Smoking: Smoking pack-years ≥ 30 pack-years, including former smokers with a pack-year of ≥ 30 pack-years but less than 15 years of quitting smoking;

2. Passive smoking: living or working in the same room with a smoker for ≥ 20 years;

3. Suffering from chronic obstructive pulmonary disease (COPD);

4. Have a history of occupational exposure (to asbestos, radon, beryllium, chromium, cadmium, nickel, silicon, coal smoke and coal dust) for at least 1 year;

5. A first-degree relative (parents, children, and siblings) has been diagnosed with lung cancer.

Pack-years = number of packs smoked per day (20 cigarettes per pack) × number of years of smoking

The guidelines recommend lung cancer screening for people at high risk of lung cancer, and low-dose spiral CT (LDCT) screening is recommended.

The guidelines recommend screening age: 50-74 years old.

At present, the problem of secondhand smoke in my country is serious. The "Guidelines" emphasize that people who have been exposed to passive smoking for more than 20 years should also undergo lung cancer screening.

In clinical work, many young patients with early lung cancer were discovered through chest CT scans for physical examinations or other reasons. In 2021, a tertiary hospital added a chest CT scan to its employee physical examination program, and found four lung cancer cases in their 40s with no obvious symptoms, two of whom were women. Fortunately, both were in the early stages and had been cured by surgery.

The "Chinese Expert Consensus on Lung Cancer Screening and Management (2019)" has stricter age requirements and recommends that people over 40 years old start lung cancer screening.

If the smoking amount is 20 pack-years, which is what we used to call a smoking index of over 400, you should take the initiative to get screened.

3. Will it be contagious if I come into contact with patients with lung cancer?

Lung cancer is not an infectious disease. Infectious diseases must have three factors, namely, the source of infection, the route of transmission, and the susceptible population. These three conditions are indispensable. At present, many clinical medical studies have verified that cancer itself is not infectious, and cancer patients are not the source of infection. Therefore, you will not get cancer if you come into contact with lung cancer patients in your daily life.

The reason why cancer occurs among couples and brothers is that family members live together for a long time. If they have an unreasonable diet structure and bad living habits, the chance of co-occurrence of the disease may increase.

The woman in Henan was exposed to her husband's second-hand and third-hand smoke for a long time, which led to both her and her husband developing lung cancer.

4. If a family member has lung cancer, will it be inherited?

Genetic factors play a certain role in the occurrence and development of lung cancer.

If there is a cancer patient in the family, then under the stimulation of the same carcinogenic factors, the chances of the offspring getting cancer will generally be greater than others.

5. Some people have annual physical examinations but are not diagnosed with lung cancer at an early stage. What is the reason?

Early lung cancer has no obvious symptoms. In recent years, a small number of units have chosen chest CT scans during physical examinations, but the vast majority of units use chest X-rays or even chest radiography. Both chest X-rays and chest radiography are two-dimensional images with low resolution and high missed diagnosis rates. They are more likely to miss nodules within two centimeters or lesions on the diaphragm.

Compared with chest X-ray, chest CT is like cutting bread into slices and observing them one by one. It can clearly show the organs and structures and smaller lesions. It can detect tiny lesions of a few millimeters and poorly located tumors, which can make up for the deficiencies of ordinary chest X-rays.

6. Low-dose spiral CT is the best method for screening lung cancer, but is it necessary to do a CT scan once a year?

Screening for early lung cancer must distinguish between high-risk and low-risk groups.

For the high-risk groups for lung cancer mentioned above, it is recommended to undergo a low-dose CT screening once a year. The amount of radiation received is relatively safe.

Some units offer physical examinations including full-body CT scans to their employees as a "benefit", which is completed once a year. Some people even undergo repeated CT scans out of "cancer fear".

For low-risk people, they can undergo chest CT screening. If the result is negative and they maintain a healthy lifestyle, there is no need to have annual check-ups. Doctors recommend choosing the interval between CT scans based on different age groups.

When you have certain symptoms, such as coughing and expectoration, you go to the hospital for a physical examination and do CT or other imaging examinations. After reading the examination report, the doctor tells you that it may be lung cancer. However, whether you have lung cancer ultimately depends on the gold standard of pathological examination.