Sunday, April 7, 2019

Non-Small Cell Lung Cancer Treatment (PDQ®) 1/5 —Health Professional Version - National Cancer Institute

Non-Small Cell Lung Cancer Treatment (PDQ®)—Health Professional Version - National Cancer Institute

National Cancer Institute

Non-Small Cell Lung Cancer Treatment (PDQ®)–Health Professional Version

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General Information About Non-Small Cell Lung Cancer (NSCLC)

NSCLC is any type of epithelial lung cancer other than small cell lung cancer (SCLC). The most common types of NSCLC are squamous cell carcinoma, large cell carcinoma, and adenocarcinoma, but there are several other types that occur less frequently, and all types can occur in unusual histologic variants. Although NSCLCs are associated with cigarette smoke, adenocarcinomas may be found in patients who have never smoked. As a class, NSCLCs are relatively insensitive to chemotherapy and radiation therapy compared with SCLC. Patients with resectable disease may be cured by surgery or surgery followed by chemotherapy. Local control can be achieved with radiation therapy in a large number of patients with unresectable disease, but cure is seen only in a small number of patients. Patients with locally advanced unresectable disease may achieve long-term survival with radiation therapy combined with chemotherapy. Patients with advanced metastatic disease may achieve improved survival and palliation of symptoms with chemotherapy, targeted agents, and other supportive measures.

Incidence and Mortality

Estimated new cases and deaths from lung cancer (NSCLC and SCLC combined) in the United States in 2019:[1]
  • New cases: 228,150.
  • Deaths: 142,670.
Lung cancer is the leading cause of cancer-related mortality in the United States.[1] The 5-year relative survival rate from 1995 to 2001 for patients with lung cancer was 15.7%. The 5-year relative survival rate for patients with local-stage (49%), regional-stage (16%), and distant-stage (2%) disease varies markedly, depending on the stage at diagnosis.[2]

Anatomy

NSCLC arises from the epithelial cells of the lung of the central bronchi to terminal alveoli. The histological type of NSCLC correlates with site of origin, reflecting the variation in respiratory tract epithelium of the bronchi to alveoli. Squamous cell carcinoma usually starts near a central bronchus. Adenocarcinoma and bronchioloalveolar carcinoma usually originate in peripheral lung tissue.
ENLARGERespiratory anatomy; drawing shows right lung with upper, middle, and lower lobes; left lung with upper and lower lobes; and the trachea, bronchi, lymph nodes, and diaphragm. Inset shows bronchioles, alveoli, artery, and vein.
Anatomy of the respiratory system.

Pathogenesis

Smoking-related lung carcinogenesis is a multistep process. Squamous cell carcinoma and adenocarcinoma have defined premalignant precursor lesions. Before becoming invasive, lung epithelium may undergo morphological changes that include the following:
  • Hyperplasia.
  • Metaplasia.
  • Dysplasia.
  • Carcinoma in situ.
Dysplasia and carcinoma in situ are considered the principal premalignant lesions because they are more likely to progress to invasive cancer and less likely to spontaneously regress.
In addition, after resection of a lung cancer, there is a 1% to 2% risk per patient per year that a second lung cancer will occur.[3]

Pathology

NSCLC is a heterogeneous aggregate of histologies. The most common histologies include the following:
  • Epidermoid or squamous cell carcinoma.
  • Adenocarcinoma.
  • Large cell carcinoma.
These histologies are often classified together because approaches to diagnosis, staging, prognosis, and treatment are similar.

Risk Factors

Increasing age is the most important risk factor for most cancers. Other risk factors for lung cancer include the following:
  • History of or current tobacco use: cigarettes, pipes, and cigars.[4]
  • Exposure to cancer-causing substances in secondhand smoke.[5,6]
  • Occupational exposure to asbestos, arsenic, chromium, beryllium, nickel, and other agents.[7]
  • Radiation exposure from any of the following:
    • Radiation therapy to the breast or chest.[8]
    • Radon exposure in the home or workplace.[9]
    • Medical imaging tests, such as computed tomography (CT) scans.[10]
    • Atomic bomb radiation.[11]
  • Living in an area with air pollution.[12-14]
  • Family history of lung cancer.[15]
  • Human immunodeficiency virus infection.[16]
  • Beta carotene supplements in heavy smokers.[17,18]
The single most important risk factor for the development of lung cancer is smoking. For smokers, the risk for lung cancer is on average tenfold higher than in lifetime nonsmokers (defined as a person who has smoked <100 cigarettes in his or her lifetime). The risk increases with the quantity of cigarettes, duration of smoking, and starting age.
Smoking cessation results in a decrease in precancerous lesions and a reduction in the risk of developing lung cancer. Former smokers continue to have an elevated risk of lung cancer for years after quitting. Asbestos exposure may exert a synergistic effect of cigarette smoking on the lung cancer risk.[19]

Prevention

A significant number of patients cured of their smoking-related lung cancer may develop a second malignancy. In the Lung Cancer Study Group trial of 907 patients with stage T1, N0 resected tumors, the rate was 1.8% per year for nonpulmonary second cancers and 1.6% per year for new lung cancers.[20] Other studies have reported even higher risks of second tumors in long-term survivors, including rates of 10% for second lung cancers and 20% for all second cancers.[21]
Because of the persistent risk of developing second lung cancers in former smokers, various chemoprevention strategies have been evaluated in randomized control trials. None of the phase III trials using the agents beta carotene, retinol, 13-cis-retinoic acid, [alpha]-tocopherol, N-acetylcysteine, or acetylsalicylic acid has demonstrated beneficial, reproducible results.[18,22-25][Level of evidence: 1iiA] Chemoprevention of second primary cancers of the upper aerodigestive tract is undergoing clinical evaluation in patients with early-stage lung cancer.
(Refer to the PDQ summary on Lung Cancer Prevention for more information.)

Screening

In patients considered at high risk for developing lung cancer, the only screening modality for early detection that has been shown to alter mortality is low-dose helical CT scanning.[26] Studies of lung cancer screening with chest radiography and sputum cytology have failed to demonstrate that screening lowers lung cancer mortality rates.
(Refer to the Screening by low-dose helical computed tomography subsection in the PDQ summary on Lung Cancer Screening for more information.)

Clinical Features

Lung cancer may present with symptoms or be found incidentally on chest imaging. Symptoms and signs may result from the location of the primary local invasion or compression of adjacent thoracic structures, distant metastases, or paraneoplastic phenomena. The most common symptoms at presentation are worsening cough or chest pain. Other presenting symptoms include the following:
  • Hemoptysis.
  • Malaise.
  • Weight loss.
  • Dyspnea.
  • Hoarseness.
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. Symptoms from distant metastases may also be present and include neurological defect or personality change from brain metastases or pain from bone metastases. Infrequently, patients may present with symptoms and signs of paraneoplastic diseases such as hypertrophic osteoarthropathy with digital clubbing or hypercalcemia from parathyroid hormone-related protein. Physical examination may identify enlarged supraclavicular lymphadenopathy, pleural effusion or lobar collapse, unresolved pneumonia, or signs of associated disease such as chronic obstructive pulmonary disease or pulmonary fibrosis.

Diagnosis

Investigations of patients with suspected NSCLC focus on confirming the diagnosis and determining the extent of the disease. Treatment options for patients are determined by histology, stage, and general health and comorbidities of the patient.
The procedures used to determine the presence of cancer include the following:
  • History.
  • Physical examination.
  • Routine laboratory evaluations.
  • Chest x-ray.
  • Chest CT scan with infusion of contrast material.
  • Biopsy.
Before a patient begins lung cancer treatment, an experienced lung cancer pathologist must review the pathologic material. This is critical because SCLC, which responds well to chemotherapy and is generally not treated surgically, can be confused on microscopic examination with NSCLC.[27] Immunohistochemistry and electron microscopy are invaluable techniques for diagnosis and subclassification, but most lung tumors can be classified by light microscopic criteria.
(Refer to the Staging Evaluation section of this summary for more information on tests and procedures used for staging.)

Molecular Features

The identification of mutations in lung cancer has led to the development of molecularly targeted therapy to improve the survival of subsets of patients with metastatic disease.[28] In particular, subsets of adenocarcinoma now can be defined by specific mutations in genes encoding components of the epidermal growth factor receptor (EGFR) and downstream mitogen-activated protein kinases (MAPK) and phosphatidylinositol 3-kinases (PI3K) signaling pathways. These mutations may define mechanisms of drug sensitivity and primary or acquired resistance to kinase inhibitors.
Other genetic abnormalities of potential relevance to treatment decisions include translocations involving the anaplastic lymphoma kinase (ALK)-tyrosine kinase receptor, which are sensitive to ALK inhibitors, and amplification of MET (mesenchymal epithelial transition factor), which encodes the hepatocyte growth factor receptor. MET amplification has been associated with secondary resistance to EGFR tyrosine kinase inhibitors.

Prognostic Factors

Multiple studies have attempted to identify the prognostic importance of a variety of clinicopathologic factors.[21,29-32] Factors that have correlated with adverse prognosis include the following:
  • Presence of pulmonary symptoms.
  • Large tumor size (>3 cm).
  • Nonsquamous histology.
  • Metastases to multiple lymph nodes within a TNM-defined nodal station.[33-43] (Refer to the Evaluation of Mediastinal Lymph Node Metastasis section of this summary for more information.)
  • Vascular invasion.[30,44-46]
For patients with inoperable disease, prognosis is adversely affected by poor performance status and weight loss of more than 10%. These patients have been excluded from clinical trials evaluating aggressive multimodality interventions.
In multiple retrospective analyses of clinical trial data, advanced age alone has not been shown to influence response or survival with therapy.[47]
(Refer to the separate treatment sections for each stage of NSCLC in this summary for more information about prognosis.)
Because treatment is not satisfactory for almost all patients with NSCLC, eligible patients should be considered for clinical trials. Information about ongoing clinical trials is available from the NCI website.

Related Summaries

Other PDQ summaries containing information related to lung cancer include the following:
References
  1. American Cancer Society: Cancer Facts and Figures 2019. Atlanta, Ga: American Cancer Society, 2019. Available online. Last accessed January 23, 2019.
  2. Ries L, Eisner M, Kosary C, et al., eds.: Cancer Statistics Review, 1975-2002. Bethesda, Md: National Cancer Institute, 2005. Available online. Last accessed November 30, 2017.
  3. Johnson BE: Second lung cancers in patients after treatment for an initial lung cancer. J Natl Cancer Inst 90 (18): 1335-45, 1998. [PUBMED Abstract]
  4. Alberg AJ, Ford JG, Samet JM, et al.: Epidemiology of lung cancer: ACCP evidence-based clinical practice guidelines (2nd edition). Chest 132 (3 Suppl): 29S-55S, 2007. [PUBMED Abstract]
  5. Tulunay OE, Hecht SS, Carmella SG, et al.: Urinary metabolites of a tobacco-specific lung carcinogen in nonsmoking hospitality workers. Cancer Epidemiol Biomarkers Prev 14 (5): 1283-6, 2005. [PUBMED Abstract]
  6. Anderson KE, Kliris J, Murphy L, et al.: Metabolites of a tobacco-specific lung carcinogen in nonsmoking casino patrons. Cancer Epidemiol Biomarkers Prev 12 (12): 1544-6, 2003. [PUBMED Abstract]
  7. Straif K, Benbrahim-Tallaa L, Baan R, et al.: A review of human carcinogens--part C: metals, arsenic, dusts, and fibres. Lancet Oncol 10 (5): 453-4, 2009. [PUBMED Abstract]
  8. Friedman DL, Whitton J, Leisenring W, et al.: Subsequent neoplasms in 5-year survivors of childhood cancer: the Childhood Cancer Survivor Study. J Natl Cancer Inst 102 (14): 1083-95, 2010. [PUBMED Abstract]
  9. Gray A, Read S, McGale P, et al.: Lung cancer deaths from indoor radon and the cost effectiveness and potential of policies to reduce them. BMJ 338: a3110, 2009. [PUBMED Abstract]
  10. Berrington de González A, Kim KP, Berg CD: Low-dose lung computed tomography screening before age 55: estimates of the mortality reduction required to outweigh the radiation-induced cancer risk. J Med Screen 15 (3): 153-8, 2008. [PUBMED Abstract]
  11. Shimizu Y, Kato H, Schull WJ: Studies of the mortality of A-bomb survivors. 9. Mortality, 1950-1985: Part 2. Cancer mortality based on the recently revised doses (DS86). Radiat Res 121 (2): 120-41, 1990. [PUBMED Abstract]
  12. Katanoda K, Sobue T, Satoh H, et al.: An association between long-term exposure to ambient air pollution and mortality from lung cancer and respiratory diseases in Japan. J Epidemiol 21 (2): 132-43, 2011. [PUBMED Abstract]
  13. Cao J, Yang C, Li J, et al.: Association between long-term exposure to outdoor air pollution and mortality in China: a cohort study. J Hazard Mater 186 (2-3): 1594-600, 2011. [PUBMED Abstract]
  14. Hales S, Blakely T, Woodward A: Air pollution and mortality in New Zealand: cohort study. J Epidemiol Community Health 66 (5): 468-73, 2012. [PUBMED Abstract]
  15. Lissowska J, Foretova L, Dabek J, et al.: Family history and lung cancer risk: international multicentre case-control study in Eastern and Central Europe and meta-analyses. Cancer Causes Control 21 (7): 1091-104, 2010. [PUBMED Abstract]
  16. Shiels MS, Cole SR, Kirk GD, et al.: A meta-analysis of the incidence of non-AIDS cancers in HIV-infected individuals. J Acquir Immune Defic Syndr 52 (5): 611-22, 2009. [PUBMED Abstract]
  17. The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. The Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group. N Engl J Med 330 (15): 1029-35, 1994. [PUBMED Abstract]
  18. Omenn GS, Goodman GE, Thornquist MD, et al.: Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J Med 334 (18): 1150-5, 1996. [PUBMED Abstract]
  19. Wingo PA, Ries LA, Giovino GA, et al.: Annual report to the nation on the status of cancer, 1973-1996, with a special section on lung cancer and tobacco smoking. J Natl Cancer Inst 91 (8): 675-90, 1999. [PUBMED Abstract]
  20. Thomas P, Rubinstein L: Cancer recurrence after resection: T1 N0 non-small cell lung cancer. Lung Cancer Study Group. Ann Thorac Surg 49 (2): 242-6; discussion 246-7, 1990. [PUBMED Abstract]
  21. Martini N, Bains MS, Burt ME, et al.: Incidence of local recurrence and second primary tumors in resected stage I lung cancer. J Thorac Cardiovasc Surg 109 (1): 120-9, 1995. [PUBMED Abstract]
  22. van Boxem AJ, Westerga J, Venmans BJ, et al.: Photodynamic therapy, Nd-YAG laser and electrocautery for treating early-stage intraluminal cancer: which to choose? Lung Cancer 31 (1): 31-6, 2001. [PUBMED Abstract]
  23. Blumberg J, Block G: The Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study in Finland. Nutr Rev 52 (7): 242-5, 1994. [PUBMED Abstract]
  24. Lippman SM, Lee JJ, Karp DD, et al.: Randomized phase III intergroup trial of isotretinoin to prevent second primary tumors in stage I non-small-cell lung cancer. J Natl Cancer Inst 93 (8): 605-18, 2001. [PUBMED Abstract]
  25. van Zandwijk N, Dalesio O, Pastorino U, et al.: EUROSCAN, a randomized trial of vitamin A and N-acetylcysteine in patients with head and neck cancer or lung cancer. For the EUropean Organization for Research and Treatment of Cancer Head and Neck and Lung Cancer Cooperative Groups. J Natl Cancer Inst 92 (12): 977-86, 2000. [PUBMED Abstract]
  26. Aberle DR, Adams AM, Berg CD, et al.: Reduced lung-cancer mortality with low-dose computed tomographic screening. N Engl J Med 365 (5): 395-409, 2011. [PUBMED Abstract]
  27. Travis WD, Colby TV, Corrin B, et al.: Histological typing of lung and pleural tumours. 3rd ed. Berlin: Springer-Verlag, 1999.
  28. Pao W, Girard N: New driver mutations in non-small-cell lung cancer. Lancet Oncol 12 (2): 175-80, 2011. [PUBMED Abstract]
  29. Albain KS, Crowley JJ, LeBlanc M, et al.: Survival determinants in extensive-stage non-small-cell lung cancer: the Southwest Oncology Group experience. J Clin Oncol 9 (9): 1618-26, 1991. [PUBMED Abstract]
  30. Macchiarini P, Fontanini G, Hardin MJ, et al.: Blood vessel invasion by tumor cells predicts recurrence in completely resected T1 N0 M0 non-small-cell lung cancer. J Thorac Cardiovasc Surg 106 (1): 80-9, 1993. [PUBMED Abstract]
  31. Ichinose Y, Yano T, Asoh H, et al.: Prognostic factors obtained by a pathologic examination in completely resected non-small-cell lung cancer. An analysis in each pathologic stage. J Thorac Cardiovasc Surg 110 (3): 601-5, 1995. [PUBMED Abstract]
  32. Fontanini G, Bigini D, Vignati S, et al.: Microvessel count predicts metastatic disease and survival in non-small cell lung cancer. J Pathol 177 (1): 57-63, 1995. [PUBMED Abstract]
  33. Sayar A, Turna A, Kiliçgün A, et al.: Prognostic significance of surgical-pathologic multiple-station N1 disease in non-small cell carcinoma of the lung. Eur J Cardiothorac Surg 25 (3): 434-8, 2004. [PUBMED Abstract]
  34. Osaki T, Nagashima A, Yoshimatsu T, et al.: Survival and characteristics of lymph node involvement in patients with N1 non-small cell lung cancer. Lung Cancer 43 (2): 151-7, 2004. [PUBMED Abstract]
  35. Ichinose Y, Kato H, Koike T, et al.: Overall survival and local recurrence of 406 completely resected stage IIIa-N2 non-small cell lung cancer patients: questionnaire survey of the Japan Clinical Oncology Group to plan for clinical trials. Lung Cancer 34 (1): 29-36, 2001. [PUBMED Abstract]
  36. Tanaka F, Yanagihara K, Otake Y, et al.: Prognostic factors in patients with resected pathologic (p-) T1-2N1M0 non-small cell lung cancer (NSCLC). Eur J Cardiothorac Surg 19 (5): 555-61, 2001. [PUBMED Abstract]
  37. Asamura H, Suzuki K, Kondo H, et al.: Where is the boundary between N1 and N2 stations in lung cancer? Ann Thorac Surg 70 (6): 1839-45; discussion 1845-6, 2000. [PUBMED Abstract]
  38. Riquet M, Manac'h D, Le Pimpec-Barthes F, et al.: Prognostic significance of surgical-pathologic N1 disease in non-small cell carcinoma of the lung. Ann Thorac Surg 67 (6): 1572-6, 1999. [PUBMED Abstract]
  39. van Velzen E, Snijder RJ, Brutel de la Rivière A, et al.: Lymph node type as a prognostic factor for survival in T2 N1 M0 non-small cell lung carcinoma. Ann Thorac Surg 63 (5): 1436-40, 1997. [PUBMED Abstract]
  40. Vansteenkiste JF, De Leyn PR, Deneffe GJ, et al.: Survival and prognostic factors in resected N2 non-small cell lung cancer: a study of 140 cases. Leuven Lung Cancer Group. Ann Thorac Surg 63 (5): 1441-50, 1997. [PUBMED Abstract]
  41. Izbicki JR, Passlick B, Karg O, et al.: Impact of radical systematic mediastinal lymphadenectomy on tumor staging in lung cancer. Ann Thorac Surg 59 (1): 209-14, 1995. [PUBMED Abstract]
  42. Martini N, Burt ME, Bains MS, et al.: Survival after resection of stage II non-small cell lung cancer. Ann Thorac Surg 54 (3): 460-5; discussion 466, 1992. [PUBMED Abstract]
  43. Naruke T, Goya T, Tsuchiya R, et al.: Prognosis and survival in resected lung carcinoma based on the new international staging system. J Thorac Cardiovasc Surg 96 (3): 440-7, 1988. [PUBMED Abstract]
  44. Thomas P, Doddoli C, Thirion X, et al.: Stage I non-small cell lung cancer: a pragmatic approach to prognosis after complete resection. Ann Thorac Surg 73 (4): 1065-70, 2002. [PUBMED Abstract]
  45. Macchiarini P, Fontanini G, Hardin MJ, et al.: Relation of neovascularisation to metastasis of non-small-cell lung cancer. Lancet 340 (8812): 145-6, 1992. [PUBMED Abstract]
  46. Khan OA, Fitzgerald JJ, Field ML, et al.: Histological determinants of survival in completely resected T1-2N1M0 nonsmall cell cancer of the lung. Ann Thorac Surg 77 (4): 1173-8, 2004. [PUBMED Abstract]
  47. Earle CC, Tsai JS, Gelber RD, et al.: Effectiveness of chemotherapy for advanced lung cancer in the elderly: instrumental variable and propensity analysis. J Clin Oncol 19 (4): 1064-70, 2001. [PUBMED Abstract]

Cellular Classification of NSCLC

Malignant non-small cell epithelial tumors of the lung are classified by the World Health Organization (WHO)/International Association for the Study of Lung Cancer (IASLC). There are three main subtypes of non-small cell lung cancer (NSCLC), including the following:
  • Squamous cell carcinoma (25% of lung cancers).
  • Adenocarcinoma (40% of lung cancers).
  • Large cell carcinoma (10% of lung cancers).
There are numerous additional subtypes of decreasing frequency.[1]

WHO/IASLC Histologic Classification of NSCLC

  1. Squamous cell carcinoma.
    1. Papillary.
    2. Clear cell.
    3. Small cell.
    4. Basaloid.
  2. Adenocarcinoma.
    1. Acinar.
    2. Papillary.
    3. Bronchioloalveolar carcinoma.
      1. Nonmucinous.
      2. Mucinous.
      3. Mixed mucinous and nonmucinous or indeterminate cell type.
    4. Solid adenocarcinoma with mucin.
    5. Adenocarcinoma with mixed subtypes.
    6. Variants.
      1. Well-differentiated fetal adenocarcinoma.
      2. Mucinous (colloid) adenocarcinoma.
      3. Mucinous cystadenocarcinoma.
      4. Signet ring adenocarcinoma.
      5. Clear cell adenocarcinoma.
  3. Large cell carcinoma.
    1. Variants.
      1. Large cell neuroendocrine carcinoma (LCNEC).
      2. Combined LCNEC.
      3. Basaloid carcinoma.
      4. Lymphoepithelioma-like carcinoma.
      5. Clear cell carcinoma.
      6. Large cell carcinoma with rhabdoid phenotype.
  4. Adenosquamous carcinoma.
  5. Carcinomas with pleomorphic, sarcomatoid, or sarcomatous elements.
    1. Carcinomas with spindle and/or giant cells.
    2. Spindle cell carcinoma.
    3. Giant cell carcinoma.
    4. Carcinosarcoma.
    5. Pulmonary blastoma.
  6. Carcinoid tumor.
    1. Typical carcinoid.
    2. Atypical carcinoid.
  7. Carcinomas of salivary gland type.
    1. Mucoepidermoid carcinoma.
    2. Adenoid cystic carcinoma.
    3. Others.
  8. Unclassified carcinoma.

Squamous cell carcinoma

Most squamous cell carcinomas of the lung are located centrally, in the larger bronchi of the lung. Squamous cell carcinomas are linked more strongly with smoking than other forms of NSCLC. The incidence of squamous cell carcinoma of the lung has been decreasing in recent years.

Adenocarcinoma

Adenocarcinoma is now the most common histologic subtype in many countries, and subclassification of adenocarcinoma is important. One of the biggest problems with lung adenocarcinomas is the frequent histologic heterogeneity. In fact, mixtures of adenocarcinoma histologic subtypes are more common than tumors consisting purely of a single pattern of acinar, papillary, bronchioloalveolar, and solid adenocarcinoma with mucin formation.
Criteria for the diagnosis of bronchioloalveolar carcinoma have varied widely in the past. The current WHO/IASLC definition is much more restrictive than that previously used by many pathologists because it is limited to only noninvasive tumors.
If stromal, vascular, or pleural invasion are identified in an adenocarcinoma that has an extensive bronchioloalveolar carcinoma component, the classification would be an adenocarcinoma of mixed subtype with predominant bronchioloalveolar pattern and a focal acinar, solid, or papillary pattern, depending on which pattern is seen in the invasive component. However, the future of bronchioloalveolar carcinoma as a distinct clinical entity is unclear; a multidisciplinary expert panel representing the IASLC, the American Thoracic Society, and the European Respiratory Society proposed a major revision of the classification of adenocarcinomas in 2011 that entails a reclassification of what was called bronchioloalveolar carcinoma into newly defined histologic subgroups.
The following variants of adenocarcinoma are recognized in the WHO/IASLC classification:
  • Well-differentiated fetal adenocarcinoma.
  • Mucinous (colloid) adenocarcinoma.
  • Mucinous cystadenocarcinoma.
  • Signet ring adenocarcinoma.
  • Clear cell adenocarcinoma.

Large cell carcinoma

In addition to the general category of large cell carcinoma, several uncommon variants are recognized in the WHO/IASLC classification, including the following:
  • LCNEC.
  • Basaloid carcinoma.
  • Lymphoepithelioma-like carcinoma.
  • Clear cell carcinoma.
  • Large cell carcinoma with rhabdoid phenotype.
Basaloid carcinoma is also recognized as a variant of squamous cell carcinoma, and rarely, adenocarcinomas may have a basaloid pattern; however, in tumors without either of these features, they are regarded as a variant of large cell carcinoma.

Neuroendocrine tumors

LCNEC is recognized as a histologically high-grade non-small cell carcinoma. It has a very poor prognosis similar to that of small cell lung cancer (SCLC). Atypical carcinoid is recognized as an intermediate-grade neuroendocrine tumor with a prognosis that falls between typical carcinoid and high-grade SCLC and LCNEC.
Neuroendocrine differentiation can be demonstrated by immunohistochemistry or electron microscopy in 10% to 20% of common NSCLCs that do not have any neuroendocrine morphology. These tumors are not formally recognized within the WHO/IASLC classification scheme because the clinical and therapeutic significance of neuroendocrine differentiation in NSCLC is not firmly established. These tumors are referred to collectively as NSCLC with neuroendocrine differentiation.

Carcinomas with pleomorphic, sarcomatoid, or sarcomatous elements

This is a group of rare tumors. Spindle cell carcinomas and giant cell carcinomas comprise only 0.4% of all lung malignancies, and carcinosarcomas comprise only 0.1% of all lung malignancies. In addition, this group of tumors reflects a continuum in histologic heterogeneity as well as epithelial and mesenchymal differentiation. On the basis of clinical and molecular data, biphasic pulmonary blastoma is regarded as part of the spectrum of carcinomas with pleomorphic, sarcomatoid, or sarcomatous elements.

Molecular features

The identification of mutations in lung cancer has led to the development of molecularly targeted therapy to improve the survival of subsets of patients with metastatic disease.[2] In particular, subsets of adenocarcinoma now can be defined by specific mutations in genes encoding components of the epidermal growth factor receptor (EGFR) and downstream mitogen-activated protein kinases (MAPK) and phosphatidylinositol 3-kinases (PI3K) signaling pathways. These mutations may define mechanisms of drug sensitivity and primary or acquired resistance to kinase inhibitors. Other mutations of potential relevance to treatment decisions include:
  • Kirsten rat sarcoma viral oncogene (KRAS).
  • Anaplastic lymphoma kinase receptor (ALK).
  • Human epidermal growth factor receptor 2 (HER2).
  • V-raf murine sarcoma viral oncogene homolog B1 (BRAF).
  • PI3K catalytic protein alpha (PI3KCA).
  • AKT1.
  • MAPK kinase 1 (MAP2K1 or MEK1).
  • MET, which encodes the hepatocyte growth factor receptor (HGFR).
These mutations are mutually exclusive, except for those involving PI3KCA and BRAFmutations, EGFR mutations, or ALK translocations.[3,4]
EGFR and ALK mutations predominate in adenocarcinomas that develop in nonsmokers, and KRAS and BRAF mutations are more common in smokers or former smokers. EGFRmutations strongly predict the improved response rate and progression-free survival of EGFR inhibitors. In a set of 2,142 lung adenocarcinoma specimens from patients treated at Memorial Sloan Kettering Cancer Center, EGFR exon 19 deletions and L858R were found in 15% of tumors from former smokers (181 of 1,218; 95% confidence interval [CI], 13–17), 6% from current smokers (20 of 344; 95% CI, 4–9), and 52% from never-smokers (302 of 580; 95% CI, 48–56; P < .001 for ever- vs. never-smokers).[5]
Fusions of ALK with EML4 genes form translocation products that occur in ranges from 3% to 7% in unselected NSCLC and are responsive to pharmacological inhibition of ALK by agents such as crizotinib. Sensitizing fusions of ALK with other genes have also been reported. Other mutations that occur in less than 5% of NSCLC tumors include:
  • HER2, present in 2% of tumors.
  • PI3KCA, present in 2% of tumors.
  • AKT1, present in 1% of tumors.
  • BRAF mutations, present in 1% to 3% of tumors.
BRAF mutations are mutually exclusive of EGFR and KRAS mutations. Somatic mutations in MAP2K1 (also known as MEK) have been identified in 1% of NSCLC. MET oncogene encodes hepatocyte growth factor receptor. Amplification of this gene has been associated with secondary resistance to EGFR tyrosine kinase inhibitors.
References
  1. Travis WD, Colby TV, Corrin B, et al.: Histological typing of lung and pleural tumours. 3rd ed. Berlin: Springer-Verlag, 1999.
  2. Pao W, Girard N: New driver mutations in non-small-cell lung cancer. Lancet Oncol 12 (2): 175-80, 2011. [PUBMED Abstract]
  3. Tiseo M, Gelsomino F, Boggiani D, et al.: EGFR and EML4-ALK gene mutations in NSCLC: a case report of erlotinib-resistant patient with both concomitant mutations. Lung Cancer 71 (2): 241-3, 2011. [PUBMED Abstract]
  4. Villaruz LC, Socinski MA, Abberbock S, et al.: Clinicopathologic features and outcomes of patients with lung adenocarcinomas harboring BRAF mutations in the Lung Cancer Mutation Consortium. Cancer 121 (3): 448-56, 2015. [PUBMED Abstract]
  5. D'Angelo SP, Pietanza MC, Johnson ML, et al.: Incidence of EGFR exon 19 deletions and L858R in tumor specimens from men and cigarette smokers with lung adenocarcinomas. J Clin Oncol 29 (15): 2066-70, 2011. [PUBMED Abstract]
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