Q6：What are the CT manifestations of SCLC?A6：90-95% of SCLCs are central type lung cancers, which often encircle or squeeze the main bronchus or lobar bronchus, often leading to a lobe or whole lung atelectasis. Central type SCLC can directly invade and metastasize to regional lymph nodes (92% in the mediastinum and 84% in the hilum) or spread along lymphatic vessels within the lung. Mediastinal masses often involve at least one hilar, although primary tumors and mediastinal lymph node enlargement may sometimes be seen together, but in cases of fused mediastinal lymph node enlargement, no primary tumor can be found. Mediastinal structures such as trachea, esophagus, heart and blood vessels including SVC can be surrounded by the tumor. Intratumoral calcification is seen in 23% of patients. Of course, in addition to large bronchi, a small number of SCLCs (less than 5%) can also occur incidentally in relatively small bronchi, mainly as isolated pulmonary nodules (SPN) or masses without lymph node enlargement. Surgical resection of SCLC in general is very rare. However, on resected pathology, the tumor often presents as a well-defined, peripheral 2- to 4-cm nodule or mass with necrosis within the lung. On MDCT, these peripheral lung tumors have typical lobulation and burr, imaging manifestations indicating invasion into blood vessels, lymphatics, or alveoli, and a peri-tumor ground glass-like density (GGO), the latter indicating local edema and hemorrhage or, more rarely, intra-alveolar tumor invasion. Uncommon manifestations of primary SCLC include solidity, airspace density, and carcinomatous lymphangitis, which appears as a thickening of the lobular septa or in a nodular pattern. In addition, at least one lobar atelectasis and post-obstructive pneumonia may be present. Pleural fluid, pleural thickening, and/or nodules and masses suggest pleural metastases. Pericardial effusion and/or pericardial thickening suggest pericardial involvement. Contralateral pulmonary nodules or masses suggest pulmonary metastases, while extrathoracic metastases may involve the bones (19%-38%), liver (17%-34%), adrenal glands (10%-17%), and brain (up to 14%).CT is routinely used to assess the outcome of treatment and the patient’s residual or recurrent tumors after treatment.Q7: Is MRI helpful in the diagnosis of SCLC?A7: Chest MRI cannot be routinely used to assess MRI can also be used to identify intracranial metastases, which is superior to FDG PET and FDG PET-CT, because the brain parenchyma can be extensively taken up by FDG which can hinder the display of metastases in the latter two. Of course, for bone metastases, patients who cannot do FDG PET-CT can switch to 99mTc bone imaging or abdominal CT. q8: How does FDG PET-CT help in staging SCLC? It plays an extremely important role in staging and restaging of SCLC, guiding treatment and suggesting prognosis. SCLC can be almost identified on FDG PET due to its high metabolic activity. FDG PET combined with conventional imaging can lead to overstaging of 19% of patients with limited SCLC to diffuse SCLC and understaging of 8% of patients with diffuse SCLC to limited SCLC. PET is inferior to CT and MRI in detecting brain metastases, but it is more sensitive and specific than conventional imaging. The new FDG PET performance led to a change in initial clinical treatment in 27% of patients, while the change in total disease stage led to a revision of the total treatment plan in 32% of patients. In addition, improved detection of intrathoracic lesions led to revision of the radiographic field in 68% of patients. few studies have used FDG PET for post-treatment restaging, showing that 20%-57% of patients were found to have more lesions, while 14%-38% of patients were found to have fewer lesions than a single CT examination. Because FDG PET provides functional information, it can be used to assess treatment outcomes and evaluate residual and/or recurrent tumors. FDG PET can also be used to assess prognosis. High SUVmax values are associated with a worse prognosis for patients. SUVmax values were negatively correlated with patient survival, as were pre-treatment SUVmax values and survival time. Interestingly, however, no correlation was found between SUVmax values and tumor stage in primary lung cancer. Q9: How long do patients with SCLC live? A9: Due to the aggressive nature of SCLC, patients have a median survival time of only 2 to 4 months without treatment after diagnosis. Typical SCLC is effective against chemotherapy and is 60% to 70% effective against first-line combination chemotherapeutic agents. Although patients are effective with this first treatment, most patients experience relapse and even death within 2 years. Data from studies in the United States show that the 5-year survival rate for patients with limited-stage SCLC is about 10% to 15%, compared with 1% to 2% for patients with diffuse stage SCLC. The median survival time for patients with limited-stage SCLC is about 15 to 20 months, compared with 8 to 10 months for patients with diffuse stage SCLC, and their 2-year survival rate is about 10%. There are a number of prognostic factors that affect patient survival that have been identified. The most important negative characteristics of patients are diffuse SCLC, very poor behavioral status, weight loss and positive serum markers associated with major disease (the most important of which is lactate dehydrogenase). Favorable prognostic factors are young age, good behavioral status, normal serum creatinine and only single site metastasis in patients with diffuse SCLC.Q10: How should patients with SCLC be treated?A10: Typical treatment options for limited-stage SCLC are combination chemotherapy and early concurrent chest radiotherapy, whereas systemic chemotherapy is used for diffuse SCLC. Patients with limited-stage and diffuse SCLC who have completed chemotherapy are eligible for prophylactic head radiation therapy. Although the application and efficacy of new targeted therapeutic agents have been very hot in recent years, these agents such as growth factor receptor inhibitors, angiogenesis inhibitors and apoptosis promoters are still not approved for routine treatment in humans. Chemotherapy: Among several chemotherapy regimens currently in clinical use, the most commonly used is the combination of etoposide (Etoposide) and cisplatin (Cisplatin). This chemotherapy regimen produces a beneficial toxic effect for patients and also improves survival when used in combination with radiotherapy. Cisplatin is the best platinum drug for patients with limited-stage SCLC treated with concurrent radiotherapy. The efficiency of etoposide-cisplatin combination chemotherapy for patients with diffuse stage SCLC is 60% to 80%. The median survival time was about 8-12 months, while the 5-year survival rate was less than 5%, but there was little success in improving patient outcomes. Etoposide-carboplatin combination chemotherapy can be used as an alternative regimen for patients with diffuse SCLC with similar efficacy. Despite the high efficacy of first-line combination chemotherapy regimens, approximately 80% of limited-stage SCLC and indeed diffuse stage SCLC will develop recurrent or progressive disease. Additional chemotherapy is less than 15% effective in patients who develop relapses (recalcitrant or resistant lesions) within 3 months of first treatment. However, when the time interval between initial treatment and relapse is greater than 3 months (sensitive lesions), the effectiveness of additional chemotherapy is 15% to 60%. Topotecan is the only anti-tumor agent currently approved by the FDA for the treatment of recurrent SCLC. Chest radiotherapy: Chest radiotherapy is commonly used in patients with limited-stage SCLC treated with systemic chemotherapy. Studies have shown that this approach improves patient survival and reduces the intrathoracic failure rate from 75% to 90% (with single combination chemotherapy) to 30% to 60%. The greatest benefit in terms of patient survival was seen with the combination of thoracic radiotherapy + etoposide-cisplatin chemotherapy, and synchronous treatment was more effective than sequential treatment, and early combined with radiotherapy was better than late. Prophylactic head radiotherapy: Approximately 10-14% of SCLC patients have brain metastases at the time of diagnosis, and 50%-60% of patients develop brain metastases during disease progression. Prophylactic head radiotherapy reduces the prevalence of brain metastases by nearly 50%, and the 3-year survival rate increases from 15.3% to 20.7%. Although the pros and cons of prophylactic head radiotherapy need to be further investigated, it is currently recommended for patients with limited and diffuse stage SCLC who have good chemotherapy or radiotherapy results. Surgical procedures: As already mentioned in Q6, SCLC patients are largely excluded from surgical resection. Less than 5% of patients with stage I SCLC are often considered for surgical resection at the time of diagnosis, often with lobectomy and mediastinal lymph node dissection. Adjuvant etoposide-cisplatin combination chemotherapy is often administered to address the high rate of micrometastases. If hilar or mediastinal lymph nodes are positive at the time of surgery, adjuvant radiotherapy is feasible.