WEBVTT 1 00:00:00.660 --> 00:00:01.710 Hi, all. 2 00:00:01.710 --> 00:00:05.880 In today's lecture, we'll begin discussing lung cancer. 3 00:00:05.880 --> 00:00:08.040 This will be the first in a series of lectures 4 00:00:08.040 --> 00:00:10.980 and in this lecture, we'll cover lung function 5 00:00:10.980 --> 00:00:14.340 and global trends in incidence and mortality. 6 00:00:14.340 --> 00:00:15.750 So the goals of this lecture 7 00:00:15.750 --> 00:00:18.390 are to describe basic lung anatomy and function, 8 00:00:18.390 --> 00:00:20.970 to summarize global lung cancer cases and deaths, 9 00:00:20.970 --> 00:00:24.210 to describe global patterns of lung cancer mortality, 10 00:00:24.210 --> 00:00:27.540 to describe US lung cancer mortality in men and women, 11 00:00:27.540 --> 00:00:29.850 and to describe longitudinal patterns 12 00:00:29.850 --> 00:00:32.250 of lung cancer mortality and cigarette smoking 13 00:00:32.250 --> 00:00:34.470 and the relationship between the two. 14 00:00:34.470 --> 00:00:37.590 So to begin with, this figure from your textbook 15 00:00:37.590 --> 00:00:40.800 presents the anatomy of the human lung. 16 00:00:40.800 --> 00:00:42.690 And human lungs are paired organs 17 00:00:42.690 --> 00:00:44.460 that perform the essential function 18 00:00:44.460 --> 00:00:46.710 of exchanging carbon dioxide in the blood 19 00:00:46.710 --> 00:00:50.040 for oxygen in the air that's breathed in. 20 00:00:50.040 --> 00:00:51.990 The left lung is divided into two lobes, 21 00:00:51.990 --> 00:00:54.990 while the right lobe is divided into three lobes. 22 00:00:54.990 --> 00:00:58.530 And human lungs contain 1500 miles of airways 23 00:00:58.530 --> 00:01:01.440 and 300 to 500 million alveoli, 24 00:01:01.440 --> 00:01:03.720 which are like tiny air sacks 25 00:01:03.720 --> 00:01:06.960 where carbon dioxide is exchanged for oxygen. 26 00:01:06.960 --> 00:01:09.810 And we see a depiction of alveoli 27 00:01:09.810 --> 00:01:11.660 on the right side of the screen here. 28 00:01:12.720 --> 00:01:16.470 Lungs have a large surface area 29 00:01:16.470 --> 00:01:20.430 and a volume between six to four to six liters. 30 00:01:20.430 --> 00:01:22.611 Humans breathe 11,000 liters 31 00:01:22.611 --> 00:01:26.223 containing 2.3 liters of oxygen every day. 32 00:01:27.240 --> 00:01:29.610 The exchange of gases occurs in the respiratory zone, 33 00:01:29.610 --> 00:01:33.510 which consists of respiratory bronchioles, alveolar ducts, 34 00:01:33.510 --> 00:01:35.700 and the alveoli, which, again, 35 00:01:35.700 --> 00:01:39.213 we see in this small right figure here. 36 00:01:40.950 --> 00:01:43.560 There's two different types of cells 37 00:01:43.560 --> 00:01:47.820 in the lining of the alveoli 38 00:01:47.820 --> 00:01:51.480 and this is important because these are the types of cells 39 00:01:51.480 --> 00:01:54.630 that can become cancerous. 40 00:01:54.630 --> 00:01:58.113 So in one year, 41 00:01:59.370 --> 00:02:04.080 over 1.82 million new cases of lung cancer were diagnosed, 42 00:02:04.080 --> 00:02:09.080 and this was 1.24 million in men and 583,000 in women. 43 00:02:10.260 --> 00:02:14.613 This was an overall increase of 13.2% since 2008. 44 00:02:15.570 --> 00:02:18.180 This figure shows that the highest rates of lung cancer 45 00:02:18.180 --> 00:02:20.240 occur in North America, Europe, and China 46 00:02:20.240 --> 00:02:23.250 in this, which is the darker blue color. 47 00:02:23.250 --> 00:02:24.720 And the highest rates of lung cancer 48 00:02:24.720 --> 00:02:26.640 occur in nations with the highest prevalence rates 49 00:02:26.640 --> 00:02:30.090 of chronic smoking, like countries in North America 50 00:02:30.090 --> 00:02:33.213 and Europe, as well as East Asia, like China. 51 00:02:34.530 --> 00:02:37.830 When we look at the depiction 52 00:02:37.830 --> 00:02:40.740 of the mortality rates from lung cancer, 53 00:02:40.740 --> 00:02:42.363 we see a similar pattern. 54 00:02:43.260 --> 00:02:47.400 Lung cancer caused 1.59 million deaths in 2012, 55 00:02:47.400 --> 00:02:50.880 which was more than double that of any other form of cancer. 56 00:02:50.880 --> 00:02:54.390 Nearly 90% of lung cancer patients die from the disease 57 00:02:54.390 --> 00:02:58.383 and most die within a few months of being diagnosed. 58 00:02:59.490 --> 00:03:01.110 In low and middle income countries, 59 00:03:01.110 --> 00:03:04.890 25 to 30% of all cancer deaths are due to lung cancer 60 00:03:04.890 --> 00:03:06.540 and more people die from lung cancer 61 00:03:06.540 --> 00:03:08.190 than breast cancer, prostate cancer, 62 00:03:08.190 --> 00:03:09.813 and colon cancer combined. 63 00:03:10.890 --> 00:03:14.490 Lung cancer was responsible for more than 25 million deaths 64 00:03:14.490 --> 00:03:16.230 in the 20th century, 65 00:03:16.230 --> 00:03:18.810 and it's estimated that 250 million people 66 00:03:18.810 --> 00:03:19.890 will die from lung cancer 67 00:03:19.890 --> 00:03:22.923 and other smoking-related cancers in the 21st century. 68 00:03:23.940 --> 00:03:28.940 In 2020, the updated lung cancer statistics are as follows. 69 00:03:29.310 --> 00:03:31.740 There was a age-standardized incidence rate 70 00:03:31.740 --> 00:03:35.580 of 22.4 per 100,000 people globally. 71 00:03:35.580 --> 00:03:40.580 We see that this is quite a bit more than the rate for women 72 00:03:41.790 --> 00:03:45.840 because men die or are diagnosed with lung cancer 73 00:03:45.840 --> 00:03:48.780 at much higher rates than women are. 74 00:03:48.780 --> 00:03:50.970 For mortality, we see a similar pattern. 75 00:03:50.970 --> 00:03:52.710 Men have a much higher mortality rate 76 00:03:52.710 --> 00:03:54.390 from lung cancer than women do, 77 00:03:54.390 --> 00:03:57.420 with 25.9 out of 100,000 men 78 00:03:57.420 --> 00:04:01.983 dying from lung cancer in 2020. 79 00:04:03.360 --> 00:04:06.390 Globally, tobacco smoke is responsible 80 00:04:06.390 --> 00:04:09.870 for approximately 87% of cases of lung cancer. 81 00:04:09.870 --> 00:04:11.730 The highest rates of lung cancer occur in nations 82 00:04:11.730 --> 00:04:14.130 with the highest prevalence rates of chronic smoking, 83 00:04:14.130 --> 00:04:15.300 as previously discussed, 84 00:04:15.300 --> 00:04:18.660 in North America, Europe, and East Asia, 85 00:04:18.660 --> 00:04:19.980 and lung cancer mortality rates 86 00:04:19.980 --> 00:04:23.253 are the consequence of many years of past smoking exposure. 87 00:04:24.150 --> 00:04:25.470 That's why it's such an issue 88 00:04:25.470 --> 00:04:28.470 that young people throughout the world are taking up smoking 89 00:04:29.400 --> 00:04:30.360 at such high rates. 90 00:04:30.360 --> 00:04:34.200 So up to 50% of the young people 91 00:04:34.200 --> 00:04:36.240 in countries like India, China, and Russia 92 00:04:36.240 --> 00:04:40.170 are picking up the habit of smoking. 93 00:04:40.170 --> 00:04:43.290 This will have devastating health consequences in the future 94 00:04:43.290 --> 00:04:45.780 in the form of lung cancer. 95 00:04:45.780 --> 00:04:48.450 Recent estimates for the 193 member nations 96 00:04:48.450 --> 00:04:49.890 of the World Health Organization 97 00:04:49.890 --> 00:04:52.803 suggests that one in three adults smoke globally. 98 00:04:54.554 --> 00:04:57.210 And we discussed last week 99 00:04:57.210 --> 00:04:59.100 that there's a rising prevalence of chronic smoking 100 00:04:59.100 --> 00:05:01.470 among women, which has made the rates 101 00:05:01.470 --> 00:05:05.163 of female lung cancer incidence and mortality increase. 102 00:05:08.520 --> 00:05:10.710 In the US, cancer of the lung 103 00:05:10.710 --> 00:05:13.560 is the most common cause of cancer-related deaths 104 00:05:13.560 --> 00:05:15.930 among men and women. 105 00:05:15.930 --> 00:05:17.790 The dominant risk factor for lung cancer 106 00:05:17.790 --> 00:05:18.963 is cigarette smoking, 107 00:05:20.250 --> 00:05:23.310 and as we mentioned in a previous lecture, 108 00:05:23.310 --> 00:05:25.570 the early epidemiologic studies 109 00:05:26.490 --> 00:05:31.380 by some British and a United States-based epidemiologist 110 00:05:31.380 --> 00:05:33.180 demonstrated the etiologic link 111 00:05:33.180 --> 00:05:35.610 between cigarette smoking and cancer of the lung. 112 00:05:35.610 --> 00:05:40.240 You'll remember discussing Hill's criteria of causality 113 00:05:41.160 --> 00:05:43.623 and the web of causality. 114 00:05:44.490 --> 00:05:47.070 Cigarette smoking and tobacco use 115 00:05:47.070 --> 00:05:50.640 was really one of the first key linkages 116 00:05:50.640 --> 00:05:55.640 that was elucidated between cancer and a strong risk factor. 117 00:05:59.160 --> 00:06:01.980 Finally, this graph depicts 118 00:06:01.980 --> 00:06:06.980 the increasing odds ratio for lung cancer by amount smoked. 119 00:06:08.040 --> 00:06:11.070 So as we can see on the far right, 120 00:06:11.070 --> 00:06:15.880 men who smoke 41 or more cigarettes per day 121 00:06:17.580 --> 00:06:21.600 have more or have approximately 50 times the chances 122 00:06:21.600 --> 00:06:22.760 of developing lung cancer 123 00:06:22.760 --> 00:06:26.460 or being diagnosed for lung cancer than men who do not. 124 00:06:26.460 --> 00:06:31.393 Similarly, women who smoke 41 or more cigarettes per day 125 00:06:32.310 --> 00:06:34.920 have approximately 30 times the chances 126 00:06:34.920 --> 00:06:37.200 of being diagnosed with lung cancer 127 00:06:37.200 --> 00:06:42.200 than women who do not smoke that many cigarettes per day. 128 00:06:43.380 --> 00:06:44.340 And I will, some of you 129 00:06:44.340 --> 00:06:46.470 may have taken other epidemiology classes before 130 00:06:46.470 --> 00:06:48.810 and be familiar with the idea of an odds ratio. 131 00:06:48.810 --> 00:06:53.810 Essentially, that's showing the likelihood 132 00:06:54.090 --> 00:06:56.280 that one is going to develop a condition 133 00:06:56.280 --> 00:06:59.190 given that they fulfill a certain trait 134 00:06:59.190 --> 00:07:01.440 or characteristic or fit into a specific group. 135 00:07:01.440 --> 00:07:02.643 So in this case, 136 00:07:04.590 --> 00:07:08.340 all the blue bars are showing the odds ratio of women 137 00:07:08.340 --> 00:07:11.340 or the times more likely that a woman 138 00:07:11.340 --> 00:07:13.980 who smokes a certain number of cigarettes per day 139 00:07:13.980 --> 00:07:17.280 is of being diagnosed with lung cancer 140 00:07:17.280 --> 00:07:20.220 than someone who has never smoked a cigarette 141 00:07:20.220 --> 00:07:22.170 or who has smoked zero cigarettes per day. 142 00:07:22.170 --> 00:07:26.580 So this might be a complicated concept 143 00:07:26.580 --> 00:07:29.070 or a confusing concept for some people 144 00:07:29.070 --> 00:07:30.450 that haven't taken an epidemiology 145 00:07:30.450 --> 00:07:33.090 or biostatistic class before. 146 00:07:33.090 --> 00:07:34.890 So if it is, I encourage you to reach out. 147 00:07:34.890 --> 00:07:37.200 I'm more than happy to discuss 148 00:07:37.200 --> 00:07:41.700 some of the epidemiology terms 149 00:07:41.700 --> 00:07:43.770 that might be used in some of the studies 150 00:07:43.770 --> 00:07:45.603 and chapters of your textbook.