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Epidemiology of Hypopharyngeal and Oropharyngeal Cancers in Japan

Motoi Nishi

Motoi Nishi, Department of Fundamental Health Sciences, Health Sciences University of Hokkaido, Tobetsu, Hokkaido, Japan

Conflict-of-interest statement: The author(s) declare(s) that there is no conflict of interest regarding the publication of this paper.

Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http: //creativecommons.org/licenses/by-nc/4.0/

Correspondence to: Motoi Nishi, Department of Fundamental Health Sciences, Health Sciences University of Hokkaido, 1757 Tobetsu, Hokkaido, 061-0293 Japan.
Email: motoi@hoku-iryo-u.ac.jp
Telephone: +81-(0)133-23-1211
Fax: +81-(0)133-23-1669

Received: December 21, 2017
Revised: February 3, 2018
Accepted: February 6, 2018
Published online: March 23, 2018

ABSTRACT

BACKGROUND: Both hypopharyngeal cancer and oropharyngeal cancer are rare malignancies. However, it is reported that the incidences of these cancers have increased in Japan. It is known that smoking and drinking are risk factors for both cancers. Recently, human papillomavirus (HPV) is regarded as a risk factor for oropharyngeal cancer. In this article the changes in the mortality rates of these cancers are described from the viewpoint of descriptive epidemiology.

METHODS: The numbers of deaths due to the 2 cancers from 1979 to 2016 were obtained from the vital statistics of Japan. The numbers of persons in each of the years were obtained from the census and vital statistics of Japan.

RESULTS: For males, the ratio of the numbers of deaths from hypopharyngeal cancer/oropharyngeal cancer has been almost constant, at about 2. The crude mortality rate of hypopharyngeal cancer for males has been increasing. The rate in 2016 was about 9 times that in 1979. The male/female ratio has been increasing as well, which is due to the large increase for males and the small increase for females. The crude mortality rate of oropharyngeal cancer for males has been increasing. The rate in 2016 was more than 10 times that in 1979. In the group 50-59 years of age, the crude mortality rate of hypopharyngeal cancer for males has been almost constant. However, in the groups aged 70 years and older, it has been rapidly increasing. The changes in the crude mortality rates of oropharyngeal cancer were similar to those of hypopharyngeal cancer. In the group aged 50-59 years, the crude mortality rate remained stable. However, in the groups 70 years of age and older, it has been rapidly increasing. The age-adjusted mortality rate of hypopharyngeal cancer for males has been increasing, and there has been no clear sign of a decrease. The age-adjusted mortality rate of oropharyngeal cancer for males has been increasing as well, and there has been no sign of a decrease. While the smoking rate has been decreasing since 1966, the number of cigarettes per smoker per day was increasing during the period from 1960 to 2000. The percentage of heavy drinkers among the population remained almost stable.

CONCLUSIONS: For males, since the age-adjusted mortality rates of the 2 cancers have been increasing, it is certain that their incidences have been increasing. Their incidences may largely increase in older age groups. The contribution of the number of cigarettes per smoker to the pathogenesis of these 2 cancers may be larger than that of the smoking rate. The influence of HPV on oropharyngeal cancer was not apparent in the data for mortality rates.

Key words: Descriptive epidemiology; Hypopharyngeal cancer; Mortality; Oropharyngeal cancer, Vital statistics

© 2017 The Author(s). Published by ACT Publishing Group Ltd. All rights reserved.

Nishi M. Epidemiology of Hypopharyngeal and Oropharyngeal Cancers in Japan. Journal of Tumor 2018; 6(1): 504-509 Available from: URL: http://www.ghrnet.org/index.php/jt/article/view/2233

INTRODUCTION

Both hypopharyngeal cancer and oropharyngeal cancer are rare malignancies. In Japan in 2015, the former accounted for 0.41% of the total deaths due to cancer, and the latter 0.25%. Though their precise etiologies remain unknown, it is almost certain that tobacco and alcohol raise their risks[1] and there is interaction between the cumulative exposures to smoking and alcohol and the risk of cancers of the upper aerodigestive tract[2]. In the Netherlands, the incidence of oropharyngeal cancer increased between 1989 and 20063). In Scotland, its incidence continues to rise[4]. Recently, based on the data of the cancer registry in Osaka, Japan, it is reported that the incidences of both hypopharyngeal and oropharyngeal cancers increased[5], especially for males[6]. In this article, the changes in the mortality rates of these cancers and related matters are described from the viewpoint of descriptive epidemiology.

Materials and Methods

In Japan, the ICD9 was used from 1979 to 1994, and the ICD10 has been used since 1995. The codes for hypopharyngeal cancer are 148 in the ICD 9 and C13 in the ICD10. Those for oropharyngeal cancer are 146 and C10, respectively. The numbers of deaths due to the 2 cancers in 5-year age categories were obtained from the vital statistics of Japan for the period from 1979 through 2016. The numbers of persons in 5-year age categories in each of the years were obtained from the census and the vital statistics of Japan. To calculate the age-adjusted mortality rates from 1979 to 2016, the model population in Japan in 1985 (0-4, 5-9, 10-14, etc. to 80-84 and 85 years of age or older) was employed. For the statistical test of the correlation coefficient (Pearson), t-distribution was employed.

RESULTS

1. Numbers of deaths due to hypopharyngeal and oropharyngeal cancers (Table 1)

(1) Hypopharyngeal cancer. The numbers of deaths from hypopharyngeal cancer have been increasing for both sexes. That for males in 2016 was about 10 times that in 1979. That for females increased as well, but not so drastically.

(2) Oropharyngeal cancer. The numbers of deaths of oropharyngeal cancer have been increasing for both sexes. That for males in 2016 was more than 11 times that in 1979, whereas that for females increased modestly.

(3) Ratio of hypopharyngeal cancer/oropharyngeal cancer. For males, the ratio of the numbers of deaths from hypopharyngeal cancer/oropharyngeal cancer has been almost constant, at about 2.

Table 1 Number of deaths due to hypopharyngeal and oropharyngeal cancers.
Year Hypopharyngeal cancerOropharyngeal cancerRatio (Hypo/Oro)
malefemalemalefemalemalefemale
19791497374232.01 3.17
19801835566202.77 2.75
198118855105191.79 2.89
198218581100181.85 4.50
198320876109211.91 3.62
198423878112172.13 4.59
198523463135251.73 2.52
198630265152221.99 2.95
198731580165441.91 1.82
198834674195371.77 2.00
198936662205261.79 2.38
199039673191332.07 2.21
199147994242301.98 3.13
199245981240241.91 3.38
1993519118248332.09 3.58
199455884303321.84 2.63
199561192298332.05 2.79
1996636110328321.94 3.44
1997740104351442.11 2.36
1998764103385511.98 2.02
1999788103450521.75 1.98
2000830110442641.88 1.72
2001904107486561.86 1.91
2002901122503731.79 1.67
20031024114534801.92 1.43
20041063110586871.81 1.26
20051085133655911.66 1.46
200611061315981091.85 1.20
20071181112722981.64 1.14
200811891477271171.64 1.26
200912351267181281.72 0.98
201013111037431331.76 0.77
201112591216971121.81 1.08
201214111277071142.00 1.11
201313511257401351.83 0.93
201413731388551401.61 0.99
201514151237801621.81 0.76
201614401498891451.62 1.03

2. Crude mortality rates of hypopharyngeal and oropharyngeal cancers (Table 2)

(1) Hypopharyngeal cancer. The crude mortality rate of hypopharyngeal cancer for males has been increasing. The rate in 2016 was about 9 times that in 1979. The male/female ratio has been increasing as well, which is due to the large increase for males and the small increase for females.

(2) Oropharyngeal cancer. The crude mortality rate of oropharyngeal cancer for males has been increasing. The rate in 2016 was more than 10 times that in 1979. The male/female ratio was around 5-6.

Table 2 Crude mortality rates of hypopharyngeal and oropharyngeal cancers (per million) .
Year Hypopharyngeal cancerOropharyngeal cancer
malefemaleratio (M/F)malefemaleratio (M/F)
19792.621.252.10 1.30.393.33
19803.20.933.44 1.150.343.38
19813.260.923.54 1.820.325.69
19823.191.352.36 1.720.35.73
19833.561.262.83 1.870.355.34
19844.051.283.16 1.90.286.79
19853.961.033.84 2.290.415.59
19865.081.064.79 2.560.367.11
19875.271.294.09 2.760.713.89
19885.771.194.85 3.250.65.42
19896.0816.08 3.410.428.12
19906.571.175.62 3.170.535.98
19917.931.55.29 40.488.33
19927.571.295.87 3.960.3810.42
19938.551.874.57 4.080.527.85
19949.171.336.89 4.980.519.76
199510.031.456.92 4.890.529.40
199610.411.736.02 5.370.510.74
199712.091.637.42 5.730.698.30
199812.461.617.74 6.280.87.85
199912.841.617.98 7.330.819.05
200013.51.727.85 7.1917.19
200114.681.668.84 7.890.879.07
200214.631.897.74 8.171.137.23
200316.621.779.39 8.671.246.99
200417.261.710.15 9.511.357.04
200517.612.068.55 10.631.417.54
200617.962.038.85 9.711.695.75
200719.21.7311.10 11.741.527.72
200819.362.288.49 11.841.816.54
200920.131.9510.32 11.711.995.88
201021.291.5913.39 12.072.055.89
201120.491.8710.96 11.341.736.55
201223.011.9711.68 11.531.766.55
201322.081.9411.38 12.092.095.78
201422.492.1410.51 14.012.176.46
201523.191.9112.14 12.782.525.07
201623.662.3210.20 14.612.266.46

3. Crude mortality rates of hypopharyngeal and oropharyngeal cancers in 5-year age categories

(1) Hypopharyngeal cancer (Figures 1 and 2). The crude mortality rates of hypopharyngeal cancer for males in 5-year age categories are shown in Figure 1 (50-69 years of age) and Figure 2 (70 years of age and older). In the group 50-59 years of age, the crude mortality rate has been almost constant. However, in the groups aged 70 years and older, it has been rapidly increasing.

Figure 1 Crude mortality rate of hypopharyngeal cancer (male, 50-69 yrs).

Figure 2 Crude mortality rate of hypopharyngeal cancer (male, 70- yrs).

(2) Oropharyngeal cancer (Figures 3 and 4). The changes in the crude mortality rates of oropharyngeal cancer were similar to those of hypopharyngeal cancer. In the group aged 50-59 years, the crude mortality rate remained stable. However, in the groups 70 years of age and older, it has been rapidly increasing. Using the data shown in Figures 1-4, correlation coefficients (year at death vs. crude mortality rate) were calculated (Table 3). For both cancers correlation coefficients increased as the age increased. Based on the data shown in Figures 1-4, the X coefficient and the Y intercept of a formula for each of the regression lines were calculated (Table 4). For both cancers, the X coefficient increased and the Y intercept decreased as age increased. That is, the slope of the regression lines became steeper.

Table 3 Correlation coefficients (year at death vs. crude mortality rate).
Age Hypopharyngeal cancerOropharyngeal cancer
50~540.527 0.786
55~590.750 0.784
60~640.879 0.901
65~690.954 0.956
70~740.965 0.940
75~790.964 0.945
80~840.974 0.933
85~0.949 0.851
All of them are significant (P<0.05)

Table 4 X coefficient and Y intercept of regression lines (year at death vs. crude mortality rate).
Age Hypopharyngeal cancerOropharyngeal cancer
X coefficientY interceptX coefficientY intercept
50~540.16 -299.7 0.14 -271.7
55~590.44 -851.9 0.32 -629.4
60~640.90 -1759.6 0.57 -1117.0
65~691.32 -2603.7 0.82 -1621.8
70~741.65 -3236.6 1.10 -2164.7
75~791.94 -3817.4 1.12 -2206.2
80~842.33 -4606.6 1.39 -2750.7
85~2.42 -4771.3 1.25 -2481.2

Figure 3 Crude mortality rate of oropharyngeal cancer (male, 50-69 yrs).

Figure 4 Crude mortality rate of oropharyngeal cancer (male, 70- yrs).

4. Age-adjusted mortality rates of hypopharyngeal and oropharyngeal cancers (Table 5)

For males, the age-adjusted mortality rate of hypopharyngeal cancer has been increasing. In 2012 it reached 12.2 per million, and there has been no clear sign of a decrease. The ratio of males/females has also been increasing. This is because the age-adjusted mortality rate for females has remained almost constant.

For males, the age-adjusted mortality rate of oropharyngeal cancer has been increasing as well, and in 2016 it reached 7.66. There has been no sign of a decrease.

Table 5 Age-adjusted mortality rates of hypopharyngeal and oropharyngeal cancers (per million).
Year Hypopharyngeal cancerOropharyngeal cancer
malefemaleratio (M/F)malefemaleratio (M/F)
19793.351.322.54 1.640.414.00
19804.010.964.18 1.550.344.56
19814.010.934.31 2.220.326.94
19823.91.342.91 2.050.297.07
19834.141.213.42 2.160.346.35
19844.721.213.90 2.170.268.35
19854.530.934.87 2.540.376.86
19865.590.955.88 2.790.319.00
19875.631.134.98 2.880.64.80
19885.9915.99 3.330.56.66
19896.090.87.61 3.360.359.60
19906.360.936.84 3.10.417.56
19917.441.196.25 3.780.389.95
19926.9416.94 3.640.2713.48
19937.711.395.55 3.650.389.61
19948.010.938.61 4.310.3611.97
19958.511.038.26 4.130.3511.80
19968.621.217.12 4.440.3313.45
19979.721.049.35 4.630.479.85
19989.791.039.50 4.930.529.48
19999.830.9810.03 5.610.5111.00
200010.03110.03 5.380.638.54
200110.641.0410.23 5.690.5310.74
200210.251.168.84 5.80.698.41
200311.441.0111.33 60.78.57
200411.461.0211.24 6.380.718.99
200511.381.159.90 6.920.729.61
200611.440.9911.56 6.220.96.91
200711.760.9412.51 7.270.838.76
200811.581.169.98 7.280.937.83
200911.661.0810.80 6.91.046.63
201012.10.8114.94 7.051.066.65
201111.560.9112.70 6.510.857.66
201212.20.9612.71 6.390.877.34
201311.640.9312.52 6.321.016.26
201411.531.0211.30 7.341.047.06
201511.380.8912.79 6.531.115.88
201611.621.0111.50 7.6617.66

5. Number of cigarettes consumed per smoker per day

The Ministry of Health, Labor and Welfare reports the annual amounts of cigarettes sold (http://www.health-net.or.jp/tobacco/product/pd070000.html). Using these data, the numbers of persons (20 years of age or older) and the smoking rates, the annual number of cigarettes consumed per smoker per day was calculated (Table 6). It has been increasing.

Table 6 Number of cigarettes consumed per smoker per day.
YearSmoking rate (%) Population (≥20 yrs.)Number of smokersNumber of cigarettessold (100 million)Number of cigarettes (per smoker per day)
malefemalemalefemalemalefemaletotal
196081142686446829178889217602194085044258452641227.613.0
196582.315.72995134232305549246499545071971297219261714.4915.8
197077.515.63346304336012633259338585617971315518292221.3219.3
197576.215.13686021839464148280874865959086340465722898.4223.3
198070.214.43899583941783867273750796016877333919563039.7424.9
198564.613.7412588004416830026653185605105732704242303225.4
199060.514.3436553874669594326411509667752033089029322026.7
199558.815.2463948964954468627280199753079234810991334726.3
200053.513.7482765085155105625827932706249532890426324527.0

6. Percentage of heavy drinkers

Using the number of heavy drinkers (drinking 150 mL/day or more alcohol) in the report by Tanaka[7] and the numbers of persons (20 years old or older), the annual percentage of heavy drinkers was calculated (Table 7). Since 1970, it has been almost constant.

Table 7 Number and percetage of heavy drinkers.
YearNumberPercentage*
196510300001.8
197014000002.2
197517050002.5
198019050002.5
198520230002.5
199020580002.4
199523160002.6
199922700002.4
*Percentage within population aged 20 yrs or older.

DISCUSSION

According to a study in Japan whose subjects were 722 patients with hypopharyngeal cancer, the overall 5-year survival rate has been improving from 34% (1993-1997), to 39% (1998-2002), 54% (2003-2007) and 60% (2008-2012)[8].

In a study of 38 patients with oropharyngeal cancer who were newly diagnosed from 1978 to 1985, the overall 5-year survival rate was 34%[9]. In another study of 95 patients with oropharyngeal cancer who were newly diagnosed from 1971 to 1990, the overall 5-year survival rate was 42%[10]. According to a study in Japan whose subjects were 523 patients with oropharyngeal cancer who were newly diagnosed from 2005 to 2007, the overall 5-year survival rate was 69.9%[11].

Thus, in Japan, the prognoses for the present 2 cancers have been improving. Since their age-adjusted mortality rates have been increasing, it is also certain that their incidences have been increasing.

Since the percentage of heavy drinkers has been almost stable, smoking may have a large contribution to the increase in the age-adjusted mortality rates of the 2 cancers. In Japan, after World War 2, the age-adjusted mortality rate of lung cancer for males increased, but after 1995, it has been decreasing[12]. On the other hand, the peak of the smoking rate was recorded in 1966[12]. Thus, there is a time lag of 30 years between the peak of the age-adjusted mortality rate of lung cancer and that of the smoking rate. However, the age-adjusted mortality rates of the present 2 cancers have not yet begun to decrease. Consequently, it is possible that the latent periods of the 2 cancers are longer than that of lung cancer.

The smoking rate has been decreasing, but the number of cigarettes per smoker has been increasing. However, the number of cigarettes per smoker is not involved in calculating the smoking rate. It is also possible, therefore, that the contribution of the number of cigarettes per smoker to the pathogenesis of these 2 cancers may be larger than that of the smoking rate.

For males, in the groups aged 70 years and older, rapid increases in the crude mortality rates were observed for the present 2 cancers. The increases as a whole are mainly due to the increases in these age groups. It is difficult to explain why the increase in the crude mortality rate is rapid in older age groups. The life expectancy of Japanese people is becoming longer. For example, for males in 1955 it was 63.60 years, and then rose to 74.78 in 1985 and 80.75 in 2015. As a result, the number of aged persons is increasing. It is possible that among them there are not a few who have smoked heavily since their youth, and their risk for the present 2 cancers would thus be high.

Recently, it was reported that the incidence of oropharyngeal cancer whose pathogenesis is human papillomavirus (HPV) is increasing in the USA, northern Europe, and Japan[13-16]. HPV was detected in about 50% of 157 oropharyngeal squamous cell carcinoma patients according to a recent multicenter study in Japan[16]. In the US, the incidence increased significantly among persons aged 40-59 years[13]. However, as far as the present results are concerned, the crude mortality for persons 50-59 years of age was almost stable. It is mainly oropharyngeal cancer in which HPV is involved in the pathogenesis. For males, however, the ratio of the numbers from deaths of hypopharyngeal cancer/oropharyngeal cancer has been almost constant. These results might be explained by the fact that the prognosis for oropharyngeal cancer due to HPV is good[17]. At present, the influence of HPV on oropharyngeal cancer is not apparent in the data on mortality.

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Peer Reviewer: Sherif Abdelwahab

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