Transcript lecture15hs
BIOE 301 Lung Cancer Warning: I have determined that cigarette smoke is dangerous to your health. Lung Cancer: 2005 • 174,470 new cases in US, 2006 – accounts for 13% of new cancer cases • 162,460 deaths in US, 2006 – and 29% of all cancer deaths each year in US • Signs and Symptoms – symptoms of lung cancer can take many years to develop which often leads to diagnosis at an advanced stage of this disease. • • • • • Increase in volume of sputum Wheezing Change in color of sputum Blood in sputum Repeated episodes of pneumonia or bronchitis Lung Cancer • Risk Factors: #1 Tobacco Use. -90% of lung cancer cases in men and 78% of lung cancer cases in women are caused by smoking tobacco. -Smokers vs. Non-smokers A smokers risk for developing lung cancer is 20 to 30 times greater than a non smoker Second Hand Smoke -Second hand (passive) tobacco smoke is carcinogenic and may increase the lung cancer risk by 20%. Radon Exposure -Radon is an invisible gas that occurs naturally in rock and soil. About 10% of lung cancer cases are due to excessive radon exposure. Asbestos Exposure Asbestos is a fibrous mineral used in many industries. Exposure increases ones risk of developing lung cancer by 3-4 times. 100 4500 90 Per capita cigarette consumption 4000 80 3500 70 3000 60 Male lung cancer death rate 2500 50 Male lung cancer death rate 2000 40 Female lung cancer death rate 1500 30 1000 20 500 10 Year 2000 1995 1990 1985 1980 1975 1970 1965 1960 1955 1950 1945 1940 1935 1930 1925 1920 1915 1910 0 1905 0 Age-Adjusted Lung Cancer Death Rates* 5000 1900 Per Capita Cigarette Consumption Tobacco Use in the US, 1900-2000 *Age-adjusted to 2000 US standard population. Source: Death rates: US Mortality Public Use Tapes, 1960-2000, US Mortality Volumes, 1930-1959, National Center for Health Statistics, Centers for Disease Control and Prevention, 2002. Cigarette consumption: US Department of Agriculture, 1900-2000. Geographical Incidence of Lung Cancer: 2004 www.cdc.gov Incidence & Mortality Lung Cancer Around the World • Incidence: – Lung cancer is the most common cancer worldwide, accounting for 1.2 million new cases annually – Lung cancer accounts for 17.8% of all cancer deaths – Half of all cases (49.9%) occur in the developing world – The estimated numbers of lung cancer cases – worldwide has increased by 51% since 1985 – Highest incidence in: • North America • Europe (esp. Eastern Europe) • Mortality: – Most common cause of death from cancer, with 1.18 million deaths worldwide Lung Cancer Around the World American Cancer Society Cancer Atlas Cancer Risks for Boys http://www.cancer.org/downloads/AA/CancerAtlas03.pdf Cancer Risks for Girls http://www.cancer.org/downloads/AA/CancerAtlas04.pdf Lung Cancer Around the World http://www.cancer.org/downloads/AA/CancerAtlas13.pdf World Wide Incidence of Lung Cancer: Men vs. Women Incidence: Male v. Female A little Background: The Lungs Initiation of Cellular Changes Injurious inhalant Normal Epithelium Carcinogen Squamous Metaplasia Persistent Squamous Metaplasia Increasingly severe atypia Cancer in situ Invasive Carcinoma Progression of tissue changes leading to cancer Normal epithelium of the bronchi Cellular Changes: •Thickening of the epithelium =hyperplasia •Loss of the ciliated columnar cells which are replaced by a squamous epithelium •Proliferation of basal cells = dysplasia •Development of abnormal cell structure and abnormal nuclei Cross-section: normal lung Cross-section: normal lung Cross-section: cancerous lung Surfaceview: view: Surface normallung lung normal Surface view: cancerous lung Lung Cancer Screening Your CONFIDENTIAL Test Results have arrived…. Your CONFIDENTIAL Test Results • You can open now, or you can wait and learn more… Possible Outcome Cancer Diagnosis Automatic 100% on Exam 2 True Positive: You have cancer and the test correctly identified your condition. You will receive treatment. Lose 10 points on Exam 2 False Negative: You have cancer, but the test did not identify your condition. You will not receive treatment. Lose 1 point on Exam 2 False Positive: You do not have cancer, but the test says you do. You will undergo unnecessary, painful tests. No effect on Exam 2 score True Negative: You do not have cancer and the test correctly identified that you do not have cancer, Who Should be Screened? • According to the American Cancer Society, February 2006, no organization recommends screening for lung cancer in asymptomatic individuals. • WHY? Inadequate evidence to determine whether or not screening truly reduces mortality. Potential Risks of Screening • Knowing that you have cancer may not improve your health or help you live longer. • False Negative Results • False Positive Results • Side effects of screening process (exposure to radiation) Lung Cancer: Screening 2 Methods Available: • • Chest X-Ray Spiral CT What are X-Rays??? X-Rays are a type of electromagnetic radiation Shorter Wavelengths, Longer Wavelengths, Higher Energy Lower Energy Electromagnetic waves are made up of discrete particles called photons http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html How Are X-Rays Produced? X-Ray Tube •Electrons produced at cathode accelerate towards anode. •Electrons interact with Tungsten atoms producing X-rays via two modes of interaction: -Bremsstrahlung -Characteristic Radiation http://radiology.med.sc.edu/2prod&use.htm Anode Cathode electrons http://www.colorado.edu/physics/2000/xray/making_xrays.html How are X-Ray Images Produced? • X-Rays interact with the bone, tissues, and air in the body. • These interactions cause a decrease in X-Ray energy called “attenuation.” The amount of X-Ray attenuation is related to the density of the material. • Mass Attenuation Coefficients (μ/ρ) Dry Air 0.1541 cm2/g Lung Tissue 0.1695 cm2/g Bone 0.1855 cm2/g Values taken at X-Ray energy of 100keV: energy level typical of chest x-rays Source: http://physics.nist.gov/PhysRefData/XrayMassCoef/tab4.html Increasing attenuation How are Chest X-Ray Images Produced? tumor Patient http://radiology.med.sc.edu/2prod&use.htm Diagram of X-Ray Imaging Setup http://www.cancercouncil.com.au/editorial.asp?pageid=48 Image: Chest X-Ray Setup of the Chest X-Ray http://www.radiologyinfo.org/en/photocat/photos_pc.cfm?Image=philip21.jpg&pg=c hestrad Limitations of Chest X-Rays • Details of soft tissues are hard to resolve • Some structures (cancers) are too small to be detected. • Subject to human interpretation (and error). A New Kind of X-Ray: Low Dose CT (LDCT) http://www.cqch.org/images/ct_lg.jpg http://www.radiologyinfo.org/en/photocat/photos_pc.cfm?image=chest-ctlungs.jpg&&pg=chestct Limitations of LDCT Scans • Motion can lessen the quality of the image • Requires patient to hold their breath for 20 seconds. • Improved soft tissue detail over conventional X-Ray, but still not great. Is CT Screening Cost Effective? • Some scenarios…. 1) Annually screen 100,000, 60 yr. old smokers -1 QALY costs $116,300 2) Annually screen 100,000 60 yr. old smokers in the process of quitting. -1 QALY costs $558,600 3) Annually screen 100,000, 60 yr. old former smokers (quit in last 5 years) -1 QALY costs $2.3 million! How does a chest X-ray compare to a LDCT? • National Cancer Institute Randomized Controlled Trial: The Lung Screening Study • 3318 Participants • 30 pack-year history – 1 Pack a day for the last 30 years, 2 packs a day for last 15 years, 3 packs a day for last 7.5 years, etc... • Participants randomized to receive either a LDCT scan or a Chest X-Ray. Gohagan,J. Marcus,P. Fagerstrom,R. Pinsky,P. Kramer,B. and Prorok P. Baseline findings of a randomized feasability trial of lung cancer screening with spiral CT scan vs chest radiograph: the lung screening study of the National Cancer Institute. 2004. Chest.126:114-121. Study Results: CXR vs. LDCT CXR LDCT 1550 1586 # of positive screens 152 (9.8%) 325 (20.5%) # of people with positive screens that had an additional invasive procedure 15 (10%) 55 (17%) 7 (0.45% of total) 30 (1.9% of total) 145 (9%) 295 (19%) # of Participants # diagnosed with cancer # of false positives Ongoing Trials • National Cancer Institute: National Lung Screening Trial • 50,000 participants (former and heavy smokers) • 8 years long (scheduled to end in 2009) • Compare risks and benefits of standard chest x-ray to LDCT • Should Produce more definitive screening recommendations • Local Connection: MD Anderson is one of 30 hospitals participating in this trial. Your CONFIDENTIAL Test Results • Second Chance, do you want to choose to be screened?