OVERVIEW

What is small cell lung cancer?

Small cell lung cancer (SCLC) is a type of lung cancer. Due to significant differences in treatment and prognosis compared to other types of lung cancer, all lung cancers other than SCLC are collectively referred to as non-small cell lung cancer (NSCLC).

This disease is more common in elderly males. It originates from neuroendocrine cells, is highly malignant, progresses rapidly, and is prone to metastasis.

Common symptoms include cough, bloody sputum, and chest pain. Although it is initially sensitive to radiotherapy and chemotherapy, it quickly develops resistance, leading to a relatively poor prognosis^[1].

Is small cell lung cancer common?

It is relatively common.

Lung cancer is the most prevalent malignant tumor in China, with approximately 787,000 new cases and 631,000 deaths annually^[2]. SCLC accounts for 10%–15% of all lung cancer cases^[3], meaning that out of every 100 lung cancer patients, 10–15 have SCLC.

What are the types of small cell lung cancer?

Based on the cytological features of tumor tissue, SCLC can be classified into the following types:

• Oat cell type: Most oat cell-type cancer cells are round or rhomboid, resembling "oats." They often occur in large bronchi, grow along the bronchial submucosa, form narrow, tail-like extensions, and quickly penetrate the bronchial wall to grow outward^[4].

• Intermediate cell type: In addition to infiltrating the bronchi, they often invade the mucosal surface, manifesting as bronchial lumens being enveloped, with nodules or polypoid growths inside the lumen, possibly accompanied by atelectasis^[4].

• Combined oat cell type: Exhibits characteristics of both the above types^[4].

Based on the location of the lesion, SCLC is divided into the following two stages:

• Limited stage: Confined to one hemithorax^[5].

• Extensive stage: Classified as extensive stage if the cancer spreads to the contralateral lung, metastasizes to contralateral lymph nodes, or undergoes hematogenous dissemination^[5].

SYMPTOMS

What are the common early symptoms of small cell lung cancer?

Patients may have no obvious symptoms in the early stages, but as the disease progresses, the following symptoms may occur:

• Cough: About 70% of small cell lung cancer patients experience coughing (approximately 70 out of 100 patients). Cough is the most common clinical symptom^[5].
• Bloody sputum: About 58% of small cell lung cancer patients have bloody sputum (approximately 58 out of 100 patients), which is the most diagnostically significant symptom^[5].
• Chest pain: About 39% of small cell lung cancer patients experience chest pain (approximately 39 out of 100 patients). Mild chest pain is very common in the early stages, often presenting as irregular dull pain (similar to pain after being struck by a heavy object)^[5].
• Fever: About 32% of small cell lung cancer patients develop fever (approximately 32 out of 100 patients). Low to moderate fever is most common, usually not exceeding 38.5°C, but high fever may occur if infection is present^[5].
• Shortness of breath or dyspnea: About 13% of small cell lung cancer patients experience shortness of breath (approximately 13 out of 100 patients). Due to tumor compression, malignant pleural effusion caused by pleural metastasis, or rare cases of pneumothorax, patients may develop dyspnea or shortness of breath^[5].

What are the symptoms when small cell lung cancer invades surrounding tissues?

Clinical manifestations caused by small cell lung cancer invading adjacent tissues or organs:

• Hoarseness: Involvement of the recurrent laryngeal nerve can lead to vocal cord paralysis, resulting in hoarseness^[5].
• Difficulty swallowing: Tumor invasion or compression of the esophagus can cause dysphagia^[5].
• Weight loss and fatigue: Advanced patients may experience loss of appetite, lethargy, and subsequently develop weight loss and fatigue^[5].
• Superior vena cava syndrome: Often caused by tumor or metastatic lymph nodes compressing or invading the superior vena cava, or by cancer thrombus blocking venous return^[5].
• Diaphragmatic paralysis: If the tumor invades the phrenic nerve, it may manifest as persistent hiccups, chest tightness, or breathlessness^[5].
• Horner syndrome: Pancoast tumors can compress the cervical sympathetic nerve^[5], leading to miosis (pupil constriction), ptosis (drooping of the upper and sometimes lower eyelids), slight elevation of the lower eyelid, narrowing of the palpebral fissure, and enophthalmos (sunken eyeball) due to denervation of orbital smooth muscles.

What are the symptoms of small cell lung cancer metastasis?

Symptoms of small cell lung cancer metastasis:

• Brain metastasis: Depending on the size, number, and location of metastatic lesions, symptoms may include headache, vomiting, dizziness, double vision, unsteady gait, limb weakness, seizures with loss of consciousness, and sometimes mental status changes or visual disturbances^[5].
• Bone metastasis: Commonly affects the ribs, spine, pelvis, or long bones, often causing severe localized pain and tenderness^[5].
• Liver metastasis: May lead to loss of appetite, upper abdominal distension, jaundice, etc.^[5].
• Adrenal metastasis: Can cause poor appetite, diarrhea, skin hyperpigmentation, loss of axillary hair, and hypotension.

What are the symptoms of advanced small cell lung cancer?

Paraneoplastic syndrome: Some patients may develop various non-metastatic systemic symptoms due to neuroendocrine substances produced by the tumor, such as heat intolerance and exophthalmos (seen in hyperthyroidism) or central obesity and moon face (seen in Cushing syndrome)^[5].

CAUSES

What are the common causes of small cell lung cancer?

The exact causes of small cell lung cancer remain unclear, but the following risk factors have been identified:

• Smoking: Long-term heavy smoking is the most significant risk factor. The more one smokes, the earlier the habit starts, and the longer it continues, the higher the risk of developing the disease^[1].

• Air pollution: This includes both outdoor environmental pollution and indoor air pollution. Industrial exhaust, smog, dust, and other pollutants can increase the incidence of small cell lung cancer. Indoor pollution caused by smoking, coal burning, and cooking fumes is also a significant contributing factor^[1].

• Occupational exposure: Long-term exposure to substances such as arsenic, cadmium, chromium, nickel, asbestos, coal tar processing, radon, and ionizing radiation increases the risk of the disease^[1].

• Genetic predisposition: Individuals with a family history of lung cancer (especially first-degree relatives) may have a higher risk^[1].

Is small cell lung cancer hereditary?

It may be hereditary.

Many studies suggest that the development of this disease is closely related to changes in cellular genetic material and the tumor microenvironment. Research in China indicates that women with a family history have a higher risk than men^[5].

DIAGNOSIS

Under what circumstances should patients with small cell lung cancer seek medical attention at the hospital?

Patients who experience persistent coughing, blood in sputum, mild chest pain, or other symptoms should seek medical attention promptly for relevant examinations to achieve early detection and treatment.

High-risk groups, such as long-term smokers, those who started smoking at an early age, heavy smokers, individuals with environmental or occupational exposure, or those with a family history, should undergo annual physical examinations.

What tests are needed if small cell lung cancer is suspected?

The diagnosis of small cell lung cancer involves two main steps: locating the lesion in the lungs and determining the tumor stage. Diagnostic methods are selected based on the principle of starting with simple and non-invasive procedures before moving to more complex and invasive ones^[5]:

1. Medical history and physical examination: Most early-stage patients show no obvious symptoms, but some may exhibit extrapulmonary signs such as clubbing of fingers or gynecomastia in males^[5].
2. Imaging tests:
   • Chest X-ray: One of the most common methods for detecting this disease. However, its low resolution limits its effectiveness in early-stage detection^[1].
   • CT scan: Offers higher resolution and can detect small lung lesions and areas difficult to visualize on standard chest X-rays^[1].
   • Magnetic resonance imaging (MRI): Less sensitive than CT in detecting small lung lesions but may be considered for patients allergic to iodine who cannot undergo contrast-enhanced CT scans^[1].
   • Ultrasound: Plays a significant role in staging small cell lung cancer and is an important auxiliary method for evaluating supraclavicular lymph nodes and pleural effusion^[1].
3. Histopathological examination:
   • Sputum cytology: A key diagnostic method for lung cancer. To improve detection rates, deep airway sputum samples must be collected and sent for testing at least three times^[1].
   • Bronchoscopy: Allows visualization of tracheal and bronchial lesions, precise localization, and collection of pathological evidence^[1].
   • Endobronchial ultrasound-guided needle aspiration (EBUS-TBNA): Performed via bronchoscopy under ultrasound guidance to conduct fine-needle aspiration biopsy of lymph nodes for pathological diagnosis and staging. This method is minimally invasive^[1].
   • Mediastinoscopy: Conducted under general anesthesia, this procedure involves direct tissue sampling via incision, offering high diagnostic accuracy and ample tissue yield^[1].

TREATMENT

Which department should small cell lung cancer patients visit first when going to the hospital?

Respiratory Medicine, Oncology, or Thoracic Surgery.

For patients requiring chemotherapy or targeted therapy, they can seek treatment in the Respiratory Medicine or Oncology department.

For patients requiring surgical intervention, it is recommended to visit the Thoracic Surgery department.

Can small cell lung cancer be cured?

Due to its high malignancy and rapid growth, small cell lung cancer is highly sensitive to radiotherapy and chemotherapy in the early stages but quickly develops resistance, generally resulting in a poor prognosis^[1]. However, standardized chemotherapy and radiotherapy can slow tumor growth and metastasis, prolong survival time, and improve quality of life.

How is small cell lung cancer treated?

1. Surgical Treatment: Mediastinoscopy or other mediastinal examinations are used to determine whether mediastinal metastasis has occurred. The preferred surgical approach is lobectomy combined with mediastinal lymph node dissection. After complete resection, patients without lymph node metastasis undergo routine chemotherapy, while those with lymph node metastasis receive both chemotherapy and mediastinal radiotherapy postoperatively^[5].

2. Chemotherapy: The current standard regimen for small cell lung cancer involves the use of etoposide and cisplatin, which has been shown to significantly improve survival compared to untreated patients^[5].

   For first-time chemotherapy, doctors often prescribe a dual-drug regimen containing platinum-based drugs (e.g., cisplatin, carboplatin, nedaplatin) combined with another chemotherapy agent for patients in good physical condition (assessed using a clinical scoring system).

   Different chemotherapy drugs act through distinct mechanisms. Studies confirm that combining drugs with different mechanisms can attack cancer cells more effectively.

   If disease progression occurs during or after chemotherapy, another chemotherapy drug or targeted therapy is required. Options for subsequent treatments include taxanes, pemetrexed, gemcitabine, etc., each with pros and cons. Doctors will tailor the next treatment plan based on the patient's condition.

3. Radiotherapy: Used for localized lesions or cases where surgery is anatomically impractical or contraindicated. Combining radiotherapy with chemotherapy can enhance efficacy. For patients with widespread metastasis, adding radiotherapy after systemic chemotherapy can improve tumor control and prolong survival. Among all lung cancer types, small cell lung cancer is the most radiosensitive, requiring lower radiation doses^[1].

4. Targeted Therapy: Offers high specificity, efficacy, and fewer side effects. Common drugs include nivolumab and pembrolizumab, which effectively alleviate symptoms and extend survival^[1].

What are the side effects of chemotherapy drugs for small cell lung cancer?

Chemotherapy kills cancer cells but also damages normal cells, leading to side effects.

Hair loss is a commonly associated side effect, but not all chemotherapy drugs cause it, and side effects vary. If your doctor says hair loss won’t occur, don’t be surprised.

The most common side effect of many chemotherapy drugs is reduced white blood cell counts. Blood tests before and after chemotherapy are mandatory. Patients with severe leukopenia may need "white blood cell boosters" (growth factors), and some may require delayed or paused treatment.

Other common side effects include nausea, vomiting, loss of appetite, fatigue, thrombocytopenia, anemia, and allergic reactions to chemotherapy drugs.

How is small cell lung cancer monitored?

After treatment, patients should track whether symptoms like cough, chest pain, or weight loss improve and watch for new symptoms. Seek immediate medical attention if headaches, vomiting, jaundice, etc., occur.

Follow-up examinations are required as per the doctor’s instructions. The frequency varies by individual case. Imaging tests like CT or contrast-enhanced CT are typically used to assess disease progression.

DIET & LIFESTYLE

What should small cell lung cancer patients pay attention to in their diet?

• Focus on increasing nutrition. It is recommended to consume protein-rich foods such as meat, eggs, and milk to enhance nutrition and avoid malnutrition and physical decline.
• Eat fresh vegetables and fruits, especially carrots, broccoli, and kale.
• If the patient experiences bone marrow suppression or decreased platelets during chemotherapy, avoid overly hard foods to prevent gum bleeding and similar issues.

What should small cell lung cancer patients pay attention to in daily life?

• Quit smoking: Smoking is closely related to this disease, so patients are advised to quit as much as possible.
• Exercise: Under a doctor's guidance, choose suitable exercises and gradually increase intensity to avoid overexertion.
• Stay positive: The disease and its treatment may negatively impact the patient. Small cell lung cancer patients are prone to tension and anxiety. Talking to family or friends can help relieve emotions, and seeking professional psychological help when necessary is recommended.

PREVENTION

Can Small Cell Lung Cancer Be Prevented? How?

Since the cause of small cell lung cancer is unknown, it cannot be completely prevented. However, the risk of developing the disease can be reduced by avoiding risk factors.

• Long-term heavy smoking is the most important risk factor for this disease^[1], so quitting smoking can effectively lower the likelihood of developing it.
• When cooking, use a range hood as much as possible, avoid areas with industrial exhaust emissions, and wear a mask in smoggy weather.
• People who are frequently exposed to substances such as arsenic, cadmium, chromium, nickel, asbestos, chemicals produced during coal processing, radon, and ionizing radiation are more susceptible to the disease^[1]. Therefore, those at risk should take protective measures and undergo regular health checkups.

Who Are the Key Groups for Small Cell Lung Cancer Screening?

Evidence from domestic and international studies shows that screening high-risk groups (such as smokers, those frequently exposed to secondhand smoke, individuals with a history of chronic obstructive pulmonary disease, those long-term exposed to hazardous substances like asbestos, radon, and nickel, and those with a family history of lung cancer) using low-dose spiral CT can lead to early detection of lung cancer, improve prognosis, and reduce mortality rates. The incidence of lung cancer remains relatively low before the age of 44, rises rapidly after 45, peaks between 80 and 84, and then declines^[6].