There are different ways to break down lung cancer into categories or types. First of all, they divide into small-cell lung cancer and non-small cell lung cancer. In other words, small-cell lung cancer goes in one category, and the remaining category contains anything that is not small-cell lung cancer.
In this article, we’re briefly going through the essentials of this type of cancer and what you need to know about its causes, symptoms, diagnosis, treatment, and prognosis.
What is small-cell lung cancer?
Small-cell lung cancer is also known as oat cell carcinoma. It is an aggressive type of lung cancer that spreads from an early phase of the disease. Small-cell lung cancer is often associated with neoplastic syndromes and other medical problems such as Eaton-lambert syndrome, hypercalcemia, etc.
Since small-cell lung cancer is so aggressive and easy to metastasize, these patients need to be assessed from an early phase of the disease to figure out the disease stage and what we can do about it.
What causes small-cell lung cancer?
The most common cause of small-cell lung cancer is chronic tobacco smoking. Along with squamous cell carcinoma, this type of lung cancer has a solid relationship with the habit of smoking. Actually, around 98% of patients with this type of cancer have an active or past smoking habit. That’s why part of the treatment of small-cell lung cancer should include smoking cessation to prevent the formation of new cancer cells.
Another cause of small-cell lung cancer is uranium and radon exposition. Actually, uranium miners have a higher incidence of lung cancer regardless of the type. Radon is an inert gas that results from the decay of uranium. It is a radioactive substance, and it is another cause of small-cell lung cancer.
Warning Signs and Early symptoms
Small cell lung cancer is more aggressive than other types, and most patients display symptoms. Only 5% of them remain without symptoms at the moment of diagnosis. The most common signs and symptoms include:
- Cough
- Shortness of breath
- Bone pain
- Neurologic problems
- Tiredness and fatigue
- Weight loss
These symptoms are usually reported in a period of around 8 weeks before the disease is diagnosed. They are more severe as the tumor keeps growing, spreads inside the thorax or to other areas.
When the tumor grows in the lungs without reaching other areas, it causes symptoms such as:
- Obstruction of the airflow
- Irritation of the airways
- Cough, often with hemoptysis (coughing up blood)
- Dyspnea
- Collapse of the airways in aggressive cases
- A higher predisposition to pulmonary infections
When the tumor spreads into the thoracic cavity, it causes additional symptoms:
- Hoarseness when the laryngeal nerve is compressed
- Paralysis of the breathing muscles on one side of the thorax when the phrenic nerve is compressed
- Difficulty to swallow (dysphagia) when the esophagus is compressed
- A characteristic breathing noise known as stridor when the major airways are compressed
- Swelling of mediastinal lymph nodes as noted in imaging studies
- Pressure or obstruction to the venous flow in the superior vena cava with swelling of the face and arms
When the tumor spreads outside of the thoracic cavity and to distant organs, it causes other symptoms:
- Nausea and vomiting
- Headache, confusion, increased sensitivity to light, and blurred vision in case of metastasis to the brain
- Slurred speech, extremity weakness, or sensory abnormalities in case of metastasis to the brain or the spinal cord
- Spinal cord compression with back pain and loss of neurologic function
- Bone pain in case of bone metastasis
- Abdominal pain and jaundice in case of liver metastasis
Diagnosis and workup
Since small cell lung cancer is so aggressive, screening for lung cancer is fundamental to identify the disease in an early phase. According to the U.S. Preventive Task Force, screening should be done with low-dose computed tomography, and it is only recommended in adults older than 55 years with a smoking history of 30 packs of cigarettes a year or more. Men who stop smoking should also get screened up to 15 years after quitting. After 15 years of no smoking, the risk is lower, and it is not necessary to screen for lung cancer.
But in the case of a patient with symptoms, they are received by a doctor, and a physical examination is made. The workup to diagnose small-cell lung cancer includes:
- A Complete Blood Count (CBC) with a peripheral smear
- Renal function tests and liver function tests
- Chest radiography
- CT scan of the abdomen and chest
- Magnetic resonance of the brain in case of neurologic symptoms
- Bone marrow aspiration in case of abnormalities in the CBC
After the tumor is located, a biopsy is fundamental to confirm a cancer diagnosis and say what type of cancer it is.
Treatment and prognosis
Small cell lung cancer is an aggressive type of cancer, and treatment should be initiated right away.
There are different modalities of treatment:
- Combination chemotherapy
- Radiotherapy
- Surgical resection
- Spinal cord decompression in case of a compression syndrome
Surgical resection of the tumor is only reserved for patients with no metastasis, and no lymph nodes were taken. The rest of the patients need chemotherapy and radiotherapy. It is also applied to patients with no metastasis after their surgery to destroy any cancer remnants in the lungs or elsewhere.
Radiation therapy is often reserved for the second or third cycle of chemotherapy, depending on how cancer responds to the treatment.
The prognosis of small-cell lung cancer depends on how disseminated cancer is at the moment of the diagnosis. Up to 70% of patients have disseminated disease at the moment of presentation, but not all of them have extensive and very severe metastasis.
Patients with extensive-stage disease respond well to the treatment and survive more than 7 months, but only a few survive for more than 5 years. In contrast, limited-stage disease responds very well to treatment. The survival of over 1 year is expected in 80% of patients, and 15% of them remain alive for more than 5 years.
These patients would have a poorer prognosis if they have a relapse of cancer, if their unintended weight loss is greater than 10%, if they have low sodium levels, and poor general health.
References:
Siddiqui, F., & Siddiqui, A. H. (2020). Cancer, lung. StatPearls [Internet].
Basumallik, N., & Agarwal, M. (2019). Cancer, lung small cell (oat cell). StatPearls [Internet].
Cooper, S., & Spiro, S. G. (2006). Small cell lung cancer: treatment review. Respirology, 11(3), 241-248.
Murray, N., & Turrisi III, A. T. (2006). A review of first-line treatment for small-cell lung cancer. Journal of Thoracic Oncology, 1(3), 270-278.
