Small Cell Lung Cancer (SCLC): Causes, Symptoms, and Treatment

Small cell lung cancer (SCLC) is a highly malignant tumor process, often characterized by rapid growth and widespread metastases. It is typically found in the hilar or central location of the lung, often involving the larger airways.

Causes of Small Cell Lung Cancer

SCLC is characterized by the uncontrolled growth of epithelial cells lining the bronchi. The tumor cells, often small with well-defined margins, organize themselves into groups or masses. The pathogenetic event triggering the onset of SCLC is usually a mutation of the genes that stimulate cell growth and inhibit apoptosis, a process of programmed cell death. Tumor suppressors, which prevent the growth of cancer cells, also play a significant role in the progression of this type of tumor. However, before becoming neoplastic, respiratory epithelial cells need prolonged exposure to carcinogens and to accumulate multiple genetic aberrations.

Risk Factors

The onset of SCLC is closely related to cigarette smoking, and it is rarely found in individuals who have never smoked. The risk varies based on the intensity and duration of this habit and may decrease after quitting the habit, but can never be comparable to that of someone who has never smoked. Other risk factors include exposure to certain substances at the workplace, air contamination, certain diseases of the respiratory tree, a positive family history of this form of cancer, and previous treatment of radiotherapy.

Symptoms

Due to its highly malignant nature, SCLC is extremely aggressive and spreads very quickly. Symptoms are caused by local invasion of the tumor, involvement of adjacent organs, and metastases. In several cases, SCLC is asymptomatic in its early stages or causes nonspecific manifestations. The most common symptoms include persistent cough, difficulty breathing, chest pain, weight loss, and/or loss of appetite. Paraneoplastic syndromes, characterized by symptoms that occur in areas distant from a tumor or its metastases, are also common in patients with SCLC.

Diagnosis

The diagnostic process for SCLC begins with an accurate medical history and a complete physical examination. Further evaluation is usually done with computed tomography (CT) or PET-CT. The diagnosis requires cytopathological confirmation via percutaneous biopsy, bronchoscopy, or thoracoscopic surgery and subsequent histological examination.

Staging

Small Cell Lung Cancer is typically classified into two main stages based on the extent of tumor spread:

• Limited Stage
  In this stage, the cancer is confined to one side of the chest and may involve nearby lymph nodes. The disease is restricted enough to be treated within a single radiation therapy field. Early diagnosis at this stage allows for more aggressive treatment approaches, combining chemotherapy and radiotherapy, with the goal of achieving remission.
• Extensive Stage
  In the advanced or extensive stage, the cancer has spread beyond the original area, affecting the opposite lung, distant lymph nodes, or other organs such as the brain, liver, or bones. At this stage, the disease is considered metastatic and treatment focuses mainly on systemic therapies, such as chemotherapy and immunotherapy, to control symptoms and prolong survival.

Treatment

At any stage, SCLC is initially sensitive to treatment, but responses are often short-lived. The most effective approach in prolonging survival and improving the quality of life of patients involves the use of radiotherapy and/or chemotherapy. Surgery is indicated only in selected cases and is performed very rarely. Biological therapies based on drugs that have a precise molecular target are still being studied.

Prognosis

The prognosis for SCLC is unfortunately poor. The median survival time for limited small cell tumor disease is 20 months, with a 5-year survival rate of 20%. Patients with SCLC with widespread disease have a particularly poor prognosis, with a 5-year survival rate of less than 1%.