Chapter 085. Neoplasms of the Lung (Part 6)

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Diagnosis and Staging Screening Most patients with lung cancer present with advanced disease, raising the question of whether screening would detect these tumors at an earlier stage when they are theoretically more curable. The role of screening high-risk patients (for example current or former smokers 50 years of age) for early stage lung cancers is debated. Results from five randomized screening studies in the 1980s of chest xrays with or without cytologic analysis of sputum did not show any impact on lung cancer–specific mortality from screening high-risk patients, although earlier-stage cancers were detected in the screened groups. These studies have been...

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Chapter 085. Neoplasms of the Lung (Part 6) Diagnosis and Staging Screening Most patients with lung cancer present with advanced disease, raising the question of whether screening would detect these tumors at an earlier stage when they are theoretically more curable. The role of screening high-risk patients (for example current or former smokers >50 years of age) for early stage lung cancers is debated. Results from five randomized screening studies in the 1980s of chest x- rays with or without cytologic analysis of sputum did not show any impact on lung cancer–specific mortality from screening high-risk patients, although earlier-stage cancers were detected in the screened groups. These studies have been criticized for their design and statistical analyses, but they led to current recommendations not to use these tools to screen for lung cancer. However, low-dose, noncontrast, thin-slice, helical, or spiral CT has emerged as a possible new tool for lung cancer
screening. Spiral CT is a scan in which only the pulmonary parenchyma is examined, thus negating the use of intravenous contrast and the necessity of a physician being present at the exam. The scan can usually be done quickly (within one breath) and involves low doses of radiation. In a nonrandomized study of current and former smokers from the Early Lung Cancer Action Project (ELCAP), low-dose CT was shown to be more sensitive than chest x-ray for detecting lung nodules and lung cancer in early stages. Survival from date of diagnosis is also long (10-year survival predicted to be 92% in screening-detected stage I NSCLC patients). Other nonrandomized CT screening studies of asymptomatic current or former smokers also found that early lung cancer cases were diagnosed more often with CT screening than predicted by standard incidence data. However, no decline in the number of advanced lung cancer cases or deaths from lung cancer was noted in the screened group. Thus, spiral CT appears to diagnose more lung cancer without improving lung cancer mortality. Concerns include the influence of lead- time bias, length-time bias, and over-diagnosis (cancers so slow-growing that they are unlikely to cause the death of the patient). Over-diagnosis is a well-established problem in prostate cancer screening, but it is surprising that some lung cancers are not fatal. However, many of the small adenocarcinomas found as "ground glass" opacities on screening CT appear to have such long doubling times (>400 days) that they may never harm the patient. While CT screening will detect lung cancer in 1–4% of the patients screened over a 5-year period, it also detects a substantial number of false-positive lung lesions (ranging from 25 to 75% in
different series) that need follow-up and evaluation. The appropriate management of these small lesions is undefined. Unnecessary treatment of these patients may include thoracotomy and lung resection, thus adding to the cost, mortality, and morbidity of treatment. A large, randomized trial of CT screening for lung cancer (National Lung Cancer Screening Trial) involving ~55,000 individuals has completed accrual and will provide definitive data in the next several years on whether screening reduces lung cancer mortality. Until these results become available, routine CT screening for lung cancer cannot be recommended for any risk group. For those patients who want to be screened, physicians need to discuss the possible benefits and risks of such screening, including the risk of false- positive scans that could result in multiple follow-up CTs and possible biopsies for a malignancy that may not be life-threatening. Establishing a Diagnosis of Lung Cancer Once signs, symptoms, or screening studies suggest lung cancer, a tissue diagnosis must be established. Tumor tissue can be obtained by a bronchial or transbronchial biopsy during fiberoptic bronchoscopy; by node biopsy during mediastinoscopy; from the operative specimen at the time of definitive surgical resection; by percutaneous biopsy of an enlarged lymph node, soft tissue mass, lytic bone lesion, bone marrow, or pleural lesion; by fine-needle aspiration of thoracic or extrathoracic tumor masses using CT guidance; or from an adequate cell block obtained from a malignant pleural effusion. In most cases, the
pathologist should be able to make a definite diagnosis of epithelial malignancy and distinguish small cell from non-small cell lung cancer. Staging Patients with Lung Cancer Lung cancer staging consists of two parts: first, a determination of the location of tumor (anatomic staging) and, second, an assessment of a patient's ability to withstand various antitumor treatments (physiologic staging). In a patient with NSCLC, resectability (whether the tumor can be entirely removed by a standard surgical procedure such as a lobectomy or pneumonectomy), which depends on the anatomic stage of the tumor, and operability (whether the patient can tolerate such a surgical procedure), which depends on the cardiopulmonary function of the patient, are determined. Non-Small Cell Lung Cancer The TNM International Staging System should be used for cases of NSCLC, particularly in preparing patients for curative attempts with surgery or radiotherapy (Table 85-2). The various T (tumor size), N (regional node involvement), and M (presence or absence of distant metastasis) factors are combined to form different stage groups. At presentation, approximately one-third of patients have disease localized enough for a curative attempt with surgery or radiotherapy (patients with stage I or II disease and some with stage IIIA disease), one-third have distant metastatic disease (stage IV disease), and one-third have
local or regional disease that may or may not be amenable to a curative attempt (some patients with stage IIIA disease and others with stage IIIB disease) (see below). This staging system provides useful prognostic information.