Lung Cancer

"Lung cancer or bronchogenic carcinoma refers to tumors originating in the lung parenchyma or within the bronchi." Its mechanism is only partly known: "It is hypothesized 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."

Different drivers by type. StatPearls names MYC, BCL2 and p53 for SCLC and EGFR, KRAS and p16 for NSCLC. In SCLC, "Loss of RB1 removes a critical cell-cycle regulator, enabling uncontrolled cellular proliferation, while TP53 mutations disrupt apoptotic signaling." EGFR matters to the nurse because it guides targeted therapy — and "EGFR (epidermal growth factor receptor), the lung cancer oncogene, must not be confused with eGFR (estimated glomerular filtration rate), a measure of renal function."

[NSCLC] "NSCLC accounts for 85% of diagnosed lung cancer cases in the United States." "Adenocarcinoma is the most common type of lung cancer in this category and includes one-half of all lung cancer cases." "Large cell carcinoma is a subset of NSCLC that is a diagnosis of exclusion." "Patients who have stage I, II, or III NSCLC are treated with the intent to cure" — surgery, chemotherapy, radiation or a combination; "Lobectomy is generally accepted as an approach for surgical intervention on early-stage NSCLC."

[SCLC] "SCLC accounts for approximately 15% of bronchogenic carcinomas." It is "a highly aggressive, high-grade neuroendocrine tumor arising from pulmonary neuroendocrine cells within the bronchial epithelium, most often in the central bronchus." "The typical presentation is of a large hilar mass with bulky mediastinal lymphadenopathy." "SCLC is more responsive to chemotherapy and radiation therapy than other cell types of lung cancer. However, a cure is difficult to achieve because SCLC has a greater tendency to be widely disseminated by the time of diagnosis." Untreated, it has "a median survival from diagnosis of only 2 to 4 months."

Staging differs. "Staging is primarily done for NSCLC using the TNM classification." SCLC is usually grouped as limited or extensive because it spreads early: "At the time of diagnosis, approximately 30% of patients with SCLC have tumors confined to the hemithorax of origin, mediastinum, or supraclavicular lymph nodes. These patients have limited-stage disease (LD)."

"Most patients already have advanced disease at the time of presentation." In SCLC, "Symptoms are often not produced until late in the disease course and occur from complications, eg, lung collapse, postobstructive infection, or bleeding."

Local invasion. "Symptoms may result from local invasion or compression of adjacent thoracic structures, such as compression involving the esophagus causing dysphagia, compression involving the laryngeal nerves causing hoarseness, or compression involving the superior vena cava causing facial edema and distension of the superficial veins of the head and neck." A squamous tumor in the lung apex can cause "Pancoast syndrome, manifested by pain in the shoulder (but may also include the forearm, scapula, or fingers), Horner syndrome, atrophy of the hand muscles, or bony destruction."

SVC syndrome. The superior vena cava "is thin-walled, and the blood flowing in it is under low pressure," so enlarging nodes compress it; "The more rapid the onset, the more severe the symptoms because the collateral veins do not have time to distend to accommodate an increased blood flow." NCI: "Almost 95% of SVCS cases described in published modern series result from cancer," and it is "classically associated with SCLC" (StatPearls); another StatPearls chapter reports NSCLC, as a class, causes about half of cases.

Paraneoplastic syndromes. "SCLC is the most common solid tumor to cause paraneoplastic syndromes due to its neuroendocrine origin" — SIADH, ectopic ACTH (Cushing syndrome) and Lambert-Eaton myasthenic syndrome. Squamous NSCLC is the classic source of hypercalcemia: "Symptomatic hypercalcemia secondary to lung cancer may be due to secretion of the parathyroid hormone-related protein or due to extensive bony metastases." "Paraneoplastic syndromes may precede the cancer diagnosis by months."

Screening (USPSTF 2021, Grade B). "The USPSTF recommends annual screening for lung cancer with low-dose computed tomography (LDCT) in adults aged 50 to 80 years who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years." "One pack-year is the equivalent of smoking an average of 20 cigarettes—1 pack—per day for a year." Screening stops "once a person has not smoked for 15 years or develops a health problem that substantially limits life expectancy or the ability or willingness to have curative lung surgery." Chest x-ray and sputum cytology are "not recommended because they have not been found to be beneficial." "Screening does not prevent most lung cancer deaths; thus, smoking cessation remains essential."

Surgery for early NSCLC. "Lobectomy is generally accepted as an approach for surgical intervention on early-stage NSCLC." After lobectomy, "Epidural analgesia or paravertebral nerve blocks are preferred over systemic opioids to preserve respiratory function," and "Early mobilisation and chest physiotherapy begin from day 1 to prevent atelectasis and pneumonia."

Why a chest tube. After thoracic surgery a chest tube is placed "to prevent fluid or air accumulation and ensure proper lung reexpansion." "The water seal chamber functions as a 1-way valve, allowing air to exit but preventing reentry into the thoracic cavity." "Tidaling, the rise and fall of the water-seal chamber during respiration, indicates a patent chest tube influenced by negative pressure. The absence of tidaling may suggest tube occlusion." "Bubbling in the water-seal chamber typically indicates ongoing air leakage."