The lungs are an important part of the respiratory system and are located above the diaphragm and behind the rib cage. These spongy two organs are not the same size, the right lung is divided into three sections, which are called lobes. At the same time, the left lung has two segments and lobes. As we all know that our heart is located on the left side of the chest, the size of the left lung is smaller.
When we breathe through our mouth or nose, air enters our lungs through the windpipe. The trachea exits into small tubes called bronchi, which further divide into smaller tubes called bronchioles when they enter the lungs. At the end of the bronchioles are small air sacs called alveoli. These cells absorb oxygen into the bloodstream from the air we breathe and expel carbon dioxide as we breathe out. The main job of the lungs is to take in oxygen and expel carbon dioxide.
The lungs are surrounded by a thin layer called the pleura that acts as cushioning and helps the lungs move back and forth during breathing.
The diaphragm is a dome-shaped muscle that separates the abdomen and chest. When we breathe, the diaphragm pushes air in and out of the lungs.
Lung cancers usually begin in the cells of the bronchi, bronchioles, or alveoli. It is broadly classified into two types – non-small cell lung cancer and small cell lung cancer, based on their subtle appearance.
Non-Small Cell Lung Cancer
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Non-small cell lung cancer is the most common form of cancer, occurring in about 85% of people.
There are three main subtypes of non-small cell lung cancer, which include:
- Adenocarcinoma
- Squamous cell carcinoma
- Large cell carcinoma
Adenocarcinoma – Adenocarcinoma has emerged as the most common type of lung cancer, mostly in Asia and the Western world. While there have not been large-scale epidemiological studies with respect to the incidence of different types of lung cancer in India, single-center reports from tertiary cancer centers indicate adenocarcinoma as the subtype most prevalent in India, its The latter is squamous cell carcinoma.
Although this form of lung cancer is seen in former and current smokers, with the recently increasing incidence, it is more commonly seen in smokers and women as well.
Squamous cell carcinoma – Squamous cell carcinomas begin in flat cells called squamous cells that line the passageways of the lungs. This cancer is associated with smoking and usually occurs in the central part of the bronchi near the main airways of the lungs.
Large Cell Carcinoma – Large cell carcinomas can arise in any part of the lungs. This form of cancer is aggressive and can be difficult to treat. Large cell neuroendocrine carcinoma is a rapidly growing subtype of large cell carcinoma and closely resembles small cell lung cancer.
Other subtypes: Some other, less common types of NSCNC include sarcomatoid carcinoma and adenosquamous carcinoma.
Small Cell Lung Cancer
Cancer that is found in people who smoke heavily and that can spread to other parts of the body is called small cell lung cancer.
There are three subtypes of SCLC, and these subtypes are named on the basis of the type of cells present in cancer and how the cancer cells are viewed under a microscope:
- Oat cell type
- Intermediate type
- Combined Small Cell
Difference between non-small cell lung cancer and small cell lung cancer
Cause: History of smoking in the past or present is a factor in both non-small cell lung cancer and small cell lung cancer. However, small cell lung cancer is more strongly linked to smoking than non-small cell lung cancer.
Size: Microscopically, small cell lung cancer is made up of smaller cells than non-small cell lung cancer.
Growth and spread: SCLC spreads to other parts of the body much faster than NSCLC. Most small cell lung cancers are discovered only when they have rapidly spread to other parts of the body.
Stage: The development of non-small cell lung cancer is divided into four stages.
Stage 1 – Cancer cells do not affect lymph nodes and are confined to the lungs.
Stage 2 – In this stage, nearby lymph nodes are affected.
Stage 3 – Also called locally advanced disease, stage 3 is when cancer has spread to the lymph nodes in the center of the chest or above the collarbone.
Stage 4- This stage is advanced, where cancer cells affect the lungs, surrounding pleura, pleural fluid, and other distant organs such as bone, kidney, or brain.
Small cell lung cancer progresses in two stages:-
Limited stage: In this stage, cancer usually grows in one lung without affecting the lymph nodes on only one side of the chest. Doctors use aggressive treatments, including radiation, combined with chemotherapy to treat cancer at a limited stage.
Extensive stage: Cancer that has spread beyond the lungs to lymph nodes, other parts of the body, including the other lungs or bone marrow, is classified as widespread. stage SCLC. Chemotherapy is the preferred treatment option in this stage of SCLC.
Treatment Options
Chemotherapy is an essential treatment option, regardless of the stage of small cell lung cancer. Radiation therapy may be used in addition to chemotherapy, depending on the stage of cancer.
Surgery or a combination of chemotherapy and radiation therapy may be recommended in the limited stage of SCLC. Typically, etoposide plus cisplatin are medical drugs used to treat limited-stage SCLC.
In cases of extensive-stage SCLC, surgery is used when there is no extensive spread. Radiation is used to reduce the size of the tumor. Chemotherapy, possibly in conjunction with immunotherapy medication, is usually used as an initial treatment procedure in people in fairly good health. A common combination of chemo drugs used is etoposide and cisplatin/carboplatin. Immunotherapy drugs such as atezolizumab may also be used along with chemotherapy drugs for initial treatment. While this can help shrink cancer significantly in most patients, unfortunately, cancer will recur at some point in cases of widespread SCLC.
Surgery is the treatment option for stage I and II NSCLC, with chemotherapy or radiation therapy depending on the post-operative biopsy report. For patients who are medically disabled or who refuse surgery, SBRT (Stereotactic body radiotherapy) may be an option.
In stage 3 NSCLC, cancer has spread to lymph nodes, which are near another lung or in the neck. Therefore, surgery is not a better option because cancer has spread to other important parts of the chest. For people in fairly good health, chemoradiation may be the initial treatment. If the cancer is under control after chemoradiation, the immunotherapy drug durvalumab may be recommended for up to one year to further stabilize the condition. For people who are not able to tolerate chemotherapy or radiation therapy, targeted therapy or immunotherapy may be used as an initial treatment. When it comes to stage 4 NSCLC, it is very important to understand the goals of treatment, as it is widespread in different parts of the body and very difficult to treat. Chemotherapy, radiation therapy, immunotherapy, targeted therapy, or surgery may be used to relieve symptoms even though the chances of a cure are low.
