WEBVTT 1 00:00:00.300 --> 00:00:03.060 Hi everyone, and welcome to today's lecture 2 00:00:03.060 --> 00:00:05.493 on the epidemiology of laryngeal cancer. 3 00:00:06.360 --> 00:00:08.850 In today's lecture, we have several goals. 4 00:00:08.850 --> 00:00:10.710 We're going to describe basic laryngeal 5 00:00:10.710 --> 00:00:12.063 anatomy and function. 6 00:00:13.110 --> 00:00:14.640 We'll describe the global pattern 7 00:00:14.640 --> 00:00:17.820 of laryngeal cancer mortality and incidence. 8 00:00:17.820 --> 00:00:20.190 We are going to review trends of laryngeal cancer 9 00:00:20.190 --> 00:00:24.990 in the US, describe synergisms of alcohol and tobacco, 10 00:00:24.990 --> 00:00:28.050 review studies of HPV and laryngeal cancer, 11 00:00:28.050 --> 00:00:31.740 and describe laryngeal cancer prevention and control. 12 00:00:31.740 --> 00:00:34.860 To begin with and to give a brief overview 13 00:00:34.860 --> 00:00:36.840 of the anatomy of the larynx, 14 00:00:36.840 --> 00:00:39.000 the larynx has three anatomic divisions, 15 00:00:39.000 --> 00:00:42.330 the supraglottis, the glottis, and the subglottis, 16 00:00:42.330 --> 00:00:43.503 which we can see here. 17 00:00:44.430 --> 00:00:46.920 The supraglottis consists of the epiglottis, 18 00:00:46.920 --> 00:00:49.470 the false vocal cords, the ventricles, 19 00:00:49.470 --> 00:00:52.980 and the aryepiglottic folds. 20 00:00:52.980 --> 00:00:55.440 The glottis includes the true vocal cords 21 00:00:55.440 --> 00:00:57.750 and the anterior commissure. 22 00:00:57.750 --> 00:00:59.880 And finally, the subglottis is located 23 00:00:59.880 --> 00:01:02.100 below the vocal chords and extends approximately 24 00:01:02.100 --> 00:01:04.563 five millimeters into the trachea. 25 00:01:08.340 --> 00:01:13.340 So looking at the male incidence of laryngeal cancer, 26 00:01:13.680 --> 00:01:16.680 we see the cancer of the larynx occurs over seven times 27 00:01:16.680 --> 00:01:19.530 more often in men than women. 28 00:01:19.530 --> 00:01:22.440 Globally in 2012, laryngeal cancer was diagnosed 29 00:01:22.440 --> 00:01:27.300 in 108 or 138,102 men 30 00:01:27.300 --> 00:01:32.300 compared to only 18,775 cases in women. 31 00:01:32.760 --> 00:01:37.230 It also caused 73,126 deaths in men 32 00:01:37.230 --> 00:01:40.980 compared to 10,115 deaths in women. 33 00:01:40.980 --> 00:01:44.790 Among men, cancer of the larynx comprised approximately 1.9% 34 00:01:44.790 --> 00:01:47.850 of all cancers and was responsible for 1.6% 35 00:01:47.850 --> 00:01:49.710 of all cancer deaths. 36 00:01:49.710 --> 00:01:51.600 Among women, the malignancy accounted 37 00:01:51.600 --> 00:01:55.710 for only 0.3% of all cancers and cancer deaths. 38 00:01:55.710 --> 00:02:00.140 Turning to look at the mortality, we see that the incidence 39 00:02:00.140 --> 00:02:02.460 of mortality rates of laryngeal cancer are highest 40 00:02:02.460 --> 00:02:05.370 in populations with the highest chronic or highest rates 41 00:02:05.370 --> 00:02:08.040 of chronic tobacco smoking and alcohol abuse. 42 00:02:08.040 --> 00:02:10.320 In particular, male populations characterized 43 00:02:10.320 --> 00:02:14.280 by heavy smoking and drinking, such as in Cuba, Poland, 44 00:02:14.280 --> 00:02:16.650 Hungary, Romania, Turkey, Turkmenistan, 45 00:02:16.650 --> 00:02:20.610 Kazakhstan, Croatia, Russia, Spain, Italy, 46 00:02:20.610 --> 00:02:22.920 Portugal, and Brazil have incidence rates 47 00:02:22.920 --> 00:02:24.870 that are four to seven times higher 48 00:02:24.870 --> 00:02:28.860 than the average global rate of 1.9 per 100,000, 49 00:02:28.860 --> 00:02:31.440 and we see these countries highlighted 50 00:02:31.440 --> 00:02:34.353 in the darker blue color. 51 00:02:36.540 --> 00:02:41.540 In the US in 2020, the age-adjusted incidence 52 00:02:41.850 --> 00:02:45.510 of laryngeal cancer was two per 100,000 overall, 53 00:02:45.510 --> 00:02:48.450 with an incidence of 3.6 per 100,000 in men 54 00:02:48.450 --> 00:02:51.903 and 0.49 cases per 100,000 females. 55 00:02:53.190 --> 00:02:57.450 The mortality was one per 100,000 overall, 56 00:02:57.450 --> 00:03:02.450 1.9 per 100,000 men and 0.28 per 100,000 females. 57 00:03:04.050 --> 00:03:07.590 So as we've discussed before, the Surgeon General's 58 00:03:07.590 --> 00:03:09.930 1964 report, "Smoking and Health", 59 00:03:09.930 --> 00:03:13.110 touched upon lung cancer and laryngeal cancer. 60 00:03:13.110 --> 00:03:15.390 The report found that there was a 1.7-fold increase 61 00:03:15.390 --> 00:03:19.980 in all-cause mortality with a 10-fold increase 62 00:03:19.980 --> 00:03:22.530 in mortality for lung cancer and a 20-fold increase 63 00:03:22.530 --> 00:03:24.843 in mortality for heavy smokers. 64 00:03:26.610 --> 00:03:28.560 The key finding related to laryngeal cancer 65 00:03:28.560 --> 00:03:31.350 was that there was a 5-fold increase in mortality 66 00:03:31.350 --> 00:03:34.533 for people who smoked compared to those who don't smoke. 67 00:03:35.580 --> 00:03:39.600 So looking at the trend of incidence in the US 68 00:03:39.600 --> 00:03:43.410 over from 1980 to 2010, we see that the annual incidence 69 00:03:43.410 --> 00:03:46.020 of laryngeal cancer has declined by about 40% 70 00:03:46.020 --> 00:03:48.240 in the US since 1990. 71 00:03:48.240 --> 00:03:50.610 This trend has occurred concurrent with sharp declines 72 00:03:50.610 --> 00:03:53.640 in the prevalence of cigarette smoking in US men and women 73 00:03:53.640 --> 00:03:57.270 and during 1980 to 2011, the prevalence of smokers 74 00:03:57.270 --> 00:04:01.620 decreased by 40% in men, from 35% to 21%, 75 00:04:01.620 --> 00:04:06.090 and by 43% in women, from 30% to 17%. 76 00:04:06.090 --> 00:04:08.610 While the relative declines are similar by gender, 77 00:04:08.610 --> 00:04:11.670 the data continue to reflect a four to five-fold excess 78 00:04:11.670 --> 00:04:14.343 of incident cases in men compared to women. 79 00:04:17.610 --> 00:04:20.160 Looking at the age distribution of laryngeal cancer, 80 00:04:20.160 --> 00:04:23.190 we see that most cases, or 97% of cases, 81 00:04:23.190 --> 00:04:26.100 are diagnosed after the age of 45 years. 82 00:04:26.100 --> 00:04:29.850 The peak ages of onset are between 55 to 75 years 83 00:04:29.850 --> 00:04:33.510 during which about 58% of cases are diagnosed. 84 00:04:33.510 --> 00:04:36.240 Nevertheless, certain subtypes of laryngeal cancer 85 00:04:36.240 --> 00:04:38.340 are being diagnosed at earlier ages. 86 00:04:38.340 --> 00:04:41.220 For example, those related to HPV infection 87 00:04:41.220 --> 00:04:43.560 manifest on average about four years earlier 88 00:04:43.560 --> 00:04:45.963 than those associated with tobacco and alcohol. 89 00:04:49.560 --> 00:04:52.740 We also see a relationship between laryngeal cancer 90 00:04:52.740 --> 00:04:57.740 and smoking and this has been compared between, 91 00:04:59.310 --> 00:05:00.360 or comparisons have been drawn 92 00:05:00.360 --> 00:05:03.270 between filter and non-filter cigarettes. 93 00:05:03.270 --> 00:05:04.860 So we know that chronic cigarette smoking 94 00:05:04.860 --> 00:05:08.190 markedly increases the risk of developing laryngeal cancers, 95 00:05:08.190 --> 00:05:09.540 and among chronic smokers, 96 00:05:09.540 --> 00:05:11.820 there's a dose response relationship between the number 97 00:05:11.820 --> 00:05:13.200 of cigarettes smoked per day and the risk 98 00:05:13.200 --> 00:05:16.560 of developing laryngeal cancer and the dose response holds 99 00:05:16.560 --> 00:05:19.210 for smokers of both filter and non-filter cigarettes. 100 00:05:20.820 --> 00:05:23.130 We also see that chronic alcohol abuse 101 00:05:23.130 --> 00:05:26.670 markedly increases the risk of developing laryngeal cancer. 102 00:05:26.670 --> 00:05:29.280 Among regular drinkers, there is also a dose response 103 00:05:29.280 --> 00:05:32.520 relationship between grams of alcohol consumed per day 104 00:05:32.520 --> 00:05:34.720 and the risk of developing laryngeal cancer. 105 00:05:36.570 --> 00:05:40.590 Finally, we see that there's a synergistic relationship 106 00:05:40.590 --> 00:05:43.980 between chronic cigarette smoking and alcohol abuse 107 00:05:43.980 --> 00:05:46.440 and risk estimates approximate 108 00:05:46.440 --> 00:05:48.930 a multiplicative model of synergism, 109 00:05:48.930 --> 00:05:53.930 as we can see in this figure 110 00:05:54.780 --> 00:05:58.380 where people who are consuming more than four or more drinks 111 00:05:58.380 --> 00:06:02.220 per day and 30 or more cigarettes per day 112 00:06:02.220 --> 00:06:04.980 have a relative risk that is many times higher 113 00:06:04.980 --> 00:06:08.733 than any other condition on this graph. 114 00:06:10.980 --> 00:06:13.890 We also know that a subset of laryngeal cancers 115 00:06:13.890 --> 00:06:15.390 arise due to chronic infection 116 00:06:15.390 --> 00:06:19.883 by oncogenic strains of HPV, being HPV16 and HPV18. 117 00:06:20.850 --> 00:06:23.340 HPV-related cases tend to be diagnosed 118 00:06:23.340 --> 00:06:25.080 at younger ages than those with tumors 119 00:06:25.080 --> 00:06:27.603 arising from exposure to tobacco and alcohol. 120 00:06:29.340 --> 00:06:31.560 The key primary prevention steps 121 00:06:31.560 --> 00:06:34.290 for laryngeal cancer are to avoid smoking tobacco, 122 00:06:34.290 --> 00:06:36.390 avoid excess alcohol consumption, 123 00:06:36.390 --> 00:06:40.350 avoiding HPV infection, and being vaccinated by HPV, 124 00:06:40.350 --> 00:06:42.633 for HPV16 and HPV18. 125 00:06:43.980 --> 00:06:46.590 We'll discuss more about vaccination campaigns 126 00:06:46.590 --> 00:06:49.179 against the multiple strains of HPV 127 00:06:49.179 --> 00:06:53.013 in our lecture about cervical cancer later in the course.