Epidemiologic panorama of colorectal cancer in Mexico, 1980-1993

Epidemiologic Panorama of Colorectal Cancer in Mexico, 1980-1993 Vfctor Tovar-Guzm~in, M.Sc.,* Mario Flores-Aldana, M.Sc.,* Jorge Salmer6n-Castro, Ph.D.,-~ Eduardo C~sar Lazcano-Ponce, Ph.D.* From the Center for Public Health Research, National Institute of Public Health, Cuernavaca, Morelos, Mexico, and tEpidemiology and Health Services Research Unit, Mexican Social Security Institute, Siglo XXI National Medical Center, Mexico City, Mexico INTRODUCTION: Colorectal cancer is the third cause of cancer-related death in the world, with 468,000 estimated deaths in 1993. In some countries mortality rates have started to decline, and survival rates have increased. In this study performed in Mexico, information is presented on the increase in mortality from this form of cancer, especially in more economically developed areas. METHODS: The mortality trend for colorectal cancer was evaluated and standardized by five-year age groups in the period 1980 to 1993. Also, the standardized mortality ratio was calculated for Mexico's 32 states, as was the possible association between mortality and indicators of rurality level and fertility rates in the different regions of Mexico. RESULTS: In the period studied, 18,962 deaths were officially reported. The average age of death was 66 years. The mortality rate among women (1.8) was significantly higher than among men (1.55 per 100,000 inhabitants). Mortality from colorectal cancer grew by 100 percent in both genders (/3 = 0.089; P < 0.001), especially in the age group 34 and younger, in the 45 to 49 age group, and in the older than 75 age group (P < 0.05). The standardized mortality ratio was greater in the states in the north of Mexico. Finally, an inverse correlation was observed throughout Mexico between the rurality index (r = -0.60; P < 0.001) and the fertility rates (r = -0.43; P < 0.05) and mortality from colorectal cancer. CONCLUSIONS: In this study, there is evidence that mortality from this cancer is higher in geographic areas with greater socioeconomic development, similar to regional patterns observed in other countries. In Mexico, the coming years will see a serious epidemic in mortality from this disease; therefore, immediate attention must be given to identifying the profile of high-risk subjects and implementing early cancer detection measures. [Key words: Colorectal cancer; Trend; Mortality; Standardized mortality ratio]

a n d that the survival rate has i n c r e a s e d b y 49 p e r c e n t in patients w i t h d i a g n o s e d t u m o r s at the e n d o f the 1970s a n d 56 p e r c e n t in t h o s e d i a g n o s e d in the 1980s. 4 In Mexico, c a n c e r in g e n e r a l is a m a j o r p u b l i c h e a l t h p r o b l e m . It is the s e c o n d c a u s e o f m o r t a l i t y after c a r d i o v a s c u l a r diseases, w i t h a rate a r o u n d 51.6 p e r 100,000 inhabitants, a m o u n t i n g for 46,423 d e a t h s in 1994. 5 T h r o u g h o u t Mexico, 2,361 n e w cases of c o l o r e c t a l c a n c e r a n d a total o f 1,809 d e a t h s w e r e r e p o r t e d in 1993. This a c c o u n t s for 4 p e r c e n t o f all c a n c e r d e a t h s in the country, w i t h a specific mortality rate for colorectal c a n c e r o f 2.48 p e r 100,000 inhabitants. 5 T h e o b j e c t i v e of this s t u d y w a s to calculate the s t a n d a r d i z e d colorectal c a n c e r m o r t a l i t y t r e n d in fivey e a r age g r o u p s , b a s e d o n official statistics for the p e r i o d 1980 to 1993 a n d the s t a n d a r d i z e d m o r t a l i t y ratio (SMR) for colorectal c a n c e r in the s a m e p e r i o d in the 32 states of Mexico. In addition, t h e p o s s i b l e a s s o c i a t i o n b e t w e e n s t a n d a r d i z e d m o r t a l i t y rates a n d the s o c i o e c o n o m i c level a n d fertility rates o f the different r e g i o n s o f M e x i c o w a s calculated. MATERIALS

AND

METHODS

A s t u d y o f the t r e n d s in m o r t a l i t y f r o m colorectal c a n c e r w a s p e r f o r m e d u s i n g i n f o r m a t i o n o n the m o r tality o f colorectal c a n c e r ( I n t e r n a t i o n a l Classification o f D i s e a s e s 153 a n d 154) 6 b y five-year a g e g r o u p s , g e n d e r , a n d state for the p e r i o d 1980 to 1993, w h i c h w a s o b t a i n e d from the official d e a t h r e c o r d s o f the M e x i c a n National Statistics, G e o g r a p h y a n d Informatics Institute. F o r m o r t a l i t y rate calculations, the d e n o m i n a t o r u s e d w a s the p o p u l a t i o n b y five-year a g e g r o u p s , g e n d e r , a n d state for e a c h y e a r of the p e r i o d studied, p r o j e c t e d b y the M e x i c a n National P o p u l a tion Council. T h e rurality level i n d i c a t o r u s e d w a s t h e i n d e x c a l c u l a t e d in 1990 b y t h e M e x i c a n National P o p u l a t i o n Council, w h i c h p r o v i d e d i n f o r m a t i o n o n r u r a l - u r b a n a r e a d e v e l o p m e n t in the 32 states. T h e

Tovar-Guzmfin V, Flores-Aldana M, Salmer6n-Castro J, Lazcano-Poncc EC. Epidemiologic panorama of eolorectal cancer in Mexico, 1980-1993. Dis Colon Rectum 1998;41: 225-231. C

olorectal c a n c e r is the third l e a d i n g c a u s e o f c a n c e r - r e l a t e d d e a t h s in the w o r l d , w i t h 468,000 e s t i m a t e d d e a t h s in 1993, m o s t o f t h e m in North A m e r i c a a n d E u r o p e . 1-3 Recent r e p o r t s s u g g e s t that c o l o r e c t a l c a n c e r m o r t a l i t y rates in s o m e c o u n t r i e s s u c h as the U n i t e d States h a v e b e g u n to fall since 1985 Address reprint requests to Dr. Lazcano-Ponce: Center for Public Health Research, National Institute of Public Health, Av. Universidad 655, Col. Sta. Marfa Ahuacatitl~_n, Cuemavaca, Morelos, C.P. 62508, Mdxico. 225

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fertility rates for 1990, by state, were obtained from the reports by Garda et a17 at the Mexican National Institute of Public Health. The SMR by age were calculated for the period 1980 to 1993. To evaluate the trend through time, a linear regression model was constructed, testing the hypothesis that the slope (/3) is other than zero. s In this analysis, the dependent variable used was the SMR from colorectal cancer and the independent variable was the year of occurrence. To evaluate the differences by state in the mortality rate from colorectal cancer the SMR was calculated, taking the specific national mortality rate as a reference and using the indirect rate-adjustment method. 9 When constructing this indicator, the numerator used was deaths from colorectal cancer reported in the period studied and the denominator was expected colorectal cancer deaths. The rates ratio was calculated for the five-year age groups in the period studied, taking the 45 to 49 year age group as a reference, because this age group is the one in which the increase in this disease begins. 1° The correlation coefficients between SMR by age from colorectal cancer in 1990 by state and the rurality index were calculated. The operations were repeated for fertility rates. Information was processed using the Quattro-Pro 4.0 spreadsheet (Borland International, Scotts Valley, CA) and the Stata statistics package 3.1 (Stata Corp., College Station, TX).

Dis Colon Rectum, February 1998 RESULTS

The number of deaths from colorectal cancer reported in Mexico in the period 1980 to 1993 was 18,962. The average age at the time of death was 66 years, and 53.5 percent of these cases were women. The standardized mortality rate by age from colorectal cancer in the period studied was significantly higher (P < 0.0001) for w o m e n than men (1.8 compared with 1.55 per 100,000 inhabitants, respectively). In the period 1980 to 1993, the overall colorectal cancer mortality rate (standardized by age) rose from 1.09 to 2.1 and from 1.58 to 2.84 per 100,000 inhabitants in men and women, respectively (test for trend, P < 0.0001; Table 1). There was large regional variability in colorectal cancer mortality in Mexico. The SMR was greater in the northern states of the country (Fig. 1). The state of Baja California (SMR, 1.69; 95 percent confidence interval, 1.55-1.83) had the highest risk compared with the states in the south (SMR, 0.5 and 95 percent confidence interval, 0.44-0.56 in Guerrero; SMR, 0.5 and 95 percent confidence interval, 0.31-0.70 in Quintana Roo; Table 2). In Mexico, mortality from colorectal cancer, standardized by age, rose by more than 100 percent in both genders in the period studied, as seen in Figure 2 (/3 = 0.089; P < 0.0001). With regard to age groups, an increasing trend in colorectal cancer mortality was

Table 1. Colorectal Cancer Mortality Rates in Mexico, by Sex, 1980-1993 Male Deaths 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993

417 408 410 494 537 608 639 665 754 699 762 768 818 830

Female Rate* 1.09 1.07 1.06 1.27 1.39 1.56 1.63 1.69 1.91 1.78 1.94 1.95 2.08 2.10

Deaths 484 517 552 600 585 737 768 718 826 827 837 824 899 979

Total Rater

Deaths

Rates

1,58 1.67 1.75 1.89 1.82 2.27 2.35 2.18 2.47 2.47 2.49 2.42 2.63 2.84

901 925 962 1,094 1,122 1,345 1,407 1,383 1,580 1,526 1,599 1,592 1,717 1,809

1.35 1.37 1.40 1.58 1.61 1.92 1.99 1.95 2.21 2.13 2.22 2.20 2.36 2.48

Total 8,809 10,153 * Mortality rates are per 100,000 men. Test for trend, P < 0.0001. 1" Mortality rates are per 100,000 women. Test for trend, P < 0.0001. Mortality rates are per 100,000 inhabitants. Test for trend, P < 0.0001.

18,962

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COLORECTAL CANCER MORTALITY IN MEXICO

227

United States of America

N

Gulf of Mdxico

* SMR by 100,000 inhabitant •

%%

1.11to 1,7 (8)

[ ] 0.86to 1.10 (12) [ ] 0.5 to 0.85 (12)

o

250

500

Kil6meters

Figure 1. Standardized mortality ratio (SMR) of colorectal cancer in Mexico, 1980 to 1993. Table 2.

Standardized Mortality Ratio of Colorectal Cancer by States in Mexico, 1980-1993 State

SMR

Baja California Norte 1.69 Chihuahua 1.53 Baja California Sur 1.44 Coahuila 1.44 Sonora 1.35 Tamaulipas 1.28 Distrito Federal 1.20 Jalisco 1.11 Nuevo Lebn 1.11 Colima 1.09 Tabasco 1.00 Morelos 0.98 Michoac~.n 0.95 Hidalgo 0.94 Nayarit 0.92 Aguascalientes 0.90 SMR = standardized mortality ratio; 95%

95% CI

State

(1.55, 1.83) Sinaloa (1.43, 1 . 6 3 ) Guanajuato (1.14, 1.76) M~xico (1.33, 1.55) Yucat~.n (1.24, 1 . 4 6 ) Veracruz (1.19, 1.38) Chiapas (1.16, 1.24) Tlaxcala (1.06, 1.17) Puebla (1.04, 1 . 1 7 ) Quer6taro (0.88, 1 . 3 0 ) Zacatecas (0.88, 1.30) Durango (0.86, 1 . 0 9 ) Campeche (0.89, 1.02) San Luis Potos[ (0.85, 1.04) Oaxaca (0.79, 1.05) Guerrero (0.75, 1 . 0 6 ) Quintana Roo CI = 95% confidence interval.

o b s e r v e d in t h e 34 a n d y o u n g e r g r o u p (/3 = 0.003; P < 0.0001), the 45 to 49 y e a r g r o u p (/3 = 0.020; P = 0.05), a n d in the o l d e r t h a n 75 y e a r s g r o u p (/3 = 0.932; P < 0.05) as s e e n in T a b l e 3.

SMR

95% CI

0.89 0.88 0.86 0.86 0.85 0.84 0.84 0.82 0.80 0.76 0.76 0.76 0.75 0.60 0.50 0.50

(0.81, 0.97) (0.82, 0.94) (0.82, 0.90) (0.77, 0.96) (0.80, 0.89) (0.76, 0.90) (0.70, 0.98) (0.76, 0.88) (0.67, 0.92) (0.67, 0.86) (0.67, 0.86) (0.60, 0.92) (0.68, 0.83) (0.54, 0.65) (0.44, 0.56) (0.31, 0.70)

T h e r e w a s i n v e r s e c o r r e l a t i o n for 1990 ( r = 0,6; P < 0.001) b e t w e e n t h e SMR f r o m c o l o r e c t a l c a n c e r a n d t h e state s o c i a l class i n d e x . Similar c o r r e l a t i o n s w e r e f o u n d b e t w e e n c o l o r e c t a l m o r t a l i t y r a t e s in

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TOVAR-GUZlVIANE T A L

Dis Colon Rectum, February 1998

3 Women

Rate 100,000 inhabitants

2.I

Total Men

I

I

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 Year

(r2=0.94; 8=.0894; p