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ONCOLOGY: LUNG CANCER
A Comprehensive Overview of Lung Cancer An interview with Theresa Lowry Lehnen (PhD), Clinical Nurse Practitioner and Associate Lecturer South East Technological University
survival rate nearly 100%) after complete resection,” Theresa adds. Lung cancer is divided into two broad histologic classes: smallcell lung carcinomas (SCLC) and non-small cell lung carcinomas (NSCLC), which grow and spread differently. Theresa continues, “About 1 in 7 of all lung cancers is the small cell type. Smoking is the major risk factor for small cell lung cancer. SCLCs are the most dedifferentiated cancers and tend to be central mediastinal tumours. SCLCs comprise 10%–15% of all lung cancers. They are extremely aggressive, disseminating rapidly into submucosal lymphatic vessels and regional lymph nodes, and are almost always present without bronchial invasion.
Lung cancer is the 5th most common cancer in Ireland, with almost 2,700 people being diagnosed each year. It affects both women and men, usually over the age of 50. Lung cancer can be treated with surgery, drug therapies and radiotherapy, depending on the type and where it is found. Lung cancer is a highly invasive, rapidly metastasising and prevalent cancer accounting for approximately 12.4% of all cancers globally. It is one of the most frequently diagnosed cancers, and the leading cause of cancer-related deaths worldwide. There are an estimated 2 million new cases and 1·76 million related deaths annually. 70% of patients diagnosed with lung cancer present with advanced stage disease. We spoke with Theresa Lowry Lehnen, PhD, Clinical Nurse Practitioner and Associate Lecturer South East Technological University to gain a better insight into the overview of this condition. “The pathophysiology of lung cancer is complex and incompletely understood, she told us. “It is theorised that repeated exposure to carcinogens, such as cigarette smoke leads to dysplasia of lung epithelium. If the exposure continues, it leads to genetic mutations and affects protein synthesis. This, in turn, disrupts the cell cycle and promotes carcinogenesis.
“The most common genetic mutations responsible for lung cancer development are MYC, BCL2, and p53 for small cell lung cancer and EGFR, KRAS, and p16 for non-small cell lung cancer. Approximately 90% of lung cancer cases are caused by smoking and the use of tobacco products. Lung diseases such as idiopathic pulmonary fibrosis increase the risk of lung cancer independent of smoking. “Other factors such as radon gas, asbestos, air pollution, and chronic infections can also contribute to lung carcinogenesis. Multiple inherited and acquired mechanisms of susceptibility to lung cancer have been proposed. Highly heterogeneous, lung cancer can occur in many different sites in the bronchial tree, presenting variable signs and symptoms depending on its anatomic location.” Squamous cell lung cancers represent 25%–30% of all lung cancers and tend to arise in the main bronchi and advance to the carina. Adenocarcinomas account for approximately 40% of all lung cancers and consist of tumours arising in peripheral bronchi. Bronchioloalveolar cancers (BAC), now reclassified into adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA), develop in the alveoli and spread through the interalveolar connections. “Both AIS and MIA have good disease-free survival rates (5-year
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“Small cell carcinoma is composed of round, oval, or angulated cells, with a small amount of cytoplasm, and are about the size of a resting lymphocyte. No distinct nucleoli are seen and they usually stain positive with chromogranin or synaptophysin. SCLCs are extensively necrotic. The WHO previously classified SCLC into three cell subtypes: oat cell, intermediate cell, and combined cell (SCLC with NSCLC component, squamous, or adenocarcinoma). “However, studies have shown that such classification does not have much clinical significance or prognostic value. Regardless of stage, the current prognosis for patients with SCLC is poor despite improvements in diagnosis and therapy during the past three decades. Without treatment, SCLC has the most aggressive clinical course of any type of pulmonary tumour, with median survival from diagnosis of only 2 to 4 months. About 10% of the total population of SCLC patients remains free of disease during the 2 years from the start of therapy, which is the time period during which most relapses occur.” Even these patients, however, are at risk of dying from lung cancer, she explains. “The overall survival rate at 5 years is 5% to 10%. An important prognostic factor for SCLC is the extent of disease. Patients with limited disease (LD) have a better prognosis than patients with extensive disease
(ED). For patients with LD, median survival of 16 to 24 months and 5-year survival rates of 14% with current forms of treatment have been reported. “Patients diagnosed with LD who smoke should be encouraged to stop smoking before undergoing combined-modality therapy because continued smoking may compromise survival. Improved long-term survival in patients with LD has been shown with combined-modality therapy. Non-small cell lung carcinomas is any type of epithelial lung cancer other than small cell lung cancer. Most lung cancers are NSCLC and there are four main types; squamous cell carcinoma (25%), large cell carcinoma (10%), adenocarcinoma (40%), and not otherwise specified (NOS).” Presentation There are no specific signs and symptoms for lung cancer. Theresa adds, “Most patients already have advanced disease at the time of presentation. Lung cancer symptoms occur due to local effects of the tumour, such as cough due to bronchial compression by the tumour due to distant metastasis, strokelike symptoms secondary to brain metastasis, paraneoplastic syndrome, and kidney stones due to persistent hypercalcemia.” Symptoms can include, difficulty breathing; a cough that does not go away or a change in a long-term cough; repeated chest infections that won’t go away, even after antibiotics; feeling more tired than usual; hoarse voice; coughing up blood-stained phlegm; pain in the chest, especially when coughing or breathing in; loss of appetite / weight loss; swelling around the face and neck and difficulty in swallowing. Staging The tumour, node, metastasis (TNM) staging system for lung cancer is an internationally accepted system used to characterise the extent of disease. The TNM system combines features of the tumour into disease stage groups that correlate with survival and are linked to recommendations for treatment. T describes the size of the tumour and any spread of cancer into nearby tissue. N