Download Changing socioeconomic correlates for cancers of the upper

Annals of Oncology 12: 327-330. 2001.
© 2001 Kluwer Academic Publishers. Printed in the Netherlands.
Original article
Changing socioeconomic correlates for cancers of the upper digestive tract^
i—
C. Bosetti,1 S. Franceschi,2 E. Negri,1 R.Talamini, 3 F.Tomei 4 & C. LaVecchia 1 ' 5
yfstituto di Ricerche Farmacologiche®Mario Negri, Milan, Itajyjj2 International Agency for Research on Cancer, Lyon, France; Centro di
Riferimento Oncologico, Aviano (Pordenone); *Cattedra di Medicina del Lavoro, Universita La Sapienza', Rome; Istituto di Statistica Medica e
Biometria, Universita degli Studi di Milano, Milan, Italy
Summary
Cancers of the upper digestive tract have long
I Background:
Be
been associated with low socio-economic levels. It has however
been suggested that in recent times the social gradient for these
cancers is leveling off.
Patients and methods: Data from three case-control studies
on oral, pharyngeal and oesophageal cancer conducted in
Northern Italy during the periods 1984-1992 and 1992-1997
were combined and re-analyzed. Cases were subjects admitted
to the major teaching and general hospitals in the areas under
study with incident, histologically confirmed cancer of the oral
cavity and pharynx (n = 1126) and oesophagus (n - 714). Controls were subjects admitted to the same hospitals for a wide
spectrum of acute, non-neoplastic conditions, not related to
smoking or alcohol consumption (n - 4642).
Results; In the 1980s a significant association was observed
with low education and social class level. The multivariate
odds ratios for oral, pharyngeal and oesophageal cancers
combined was 1.78 for the lowest versus the highest educational level, and 1.75 for the lowest versus the highest social
class. No consistent pattern of risk was observed with any of
the socio-economic indicators considered in the studies conducted in the 1990s.
Conclusions: The present study indicates that the socioeconomic correlates of cancers of the upper digestive tract
have changed over the last few years in Italy, with a disappearance of the social gradient.^
Key words: case-control studies, oesophageal cancer, oral
pharyngeal cancer, risk factors, socio-economic factors
Introduction
Patients and methods
Cancers of the oral cavity, pharynx and oesophagus
have long been associated with low socio-economic
levels, as shown by low education and social class indicators [1-5]. This pattern of risk is partly, but not
completely, accounted for by the higher tobacco and
alcohol consumption and poorer diet in lowest social
classes [6].
In a case-control study on upper digestive tract neoplasms conducted in the 1980s in northern Italy [4] the
relative risk (RR) was around 5 for the lowest versus the
highest level of education for oral and pharyngeal cancer, and around 3 for oesophagus. Corresponding values
for the two highest versus the two lowest social classes
were around 2 for both sites.
It has, however, been suggested, on the basis of
descriptive data, that in France the incidence for oesophageal cancer has decreased in the last 20 years in those
social groups which bore the highest risk in the past, with
a consequent leveling off or disappearance of the social
gradient in oesophageal cancer risk [7].
We have therefore systematically re-considered the
socio-economic correlates of cancers of the upper digestive tract, using data from three case-control studies
conducted in Italy in the 1980s and in the 1990s.
Data of the present analysis derive from three case-control studies of
upper digestive tract neoplasms conducted in the provinces of Milan
and Pordenone in northern Italy between 1984 and 1997, whose general
design has been described in detail [8-11]. Briefly, the first study [8, 9]
was conducted between 1984 and 1992, and included 528 (449 men. 79
women) oral and pharyngeal cancer cases, 410 (343 men, 67 women)
squamous oesophageal cancer cases, and 2408 (1816 men, 592 women)
controls under age 75. The second one [10] was conducted between
1992 and 1997 on 598 (512 men, 86 women) oral and pharyngeal cancer
cases, and 1491 (1008 men, 483 women) controls younger than 78. The
third one [11] was conducted in the same period on 304 (275 men, 29
women) squamous-cell oesophageal cancer cases and 743 (593 men,
150 women) controls under age 78. In all the studies, cases were
subjects admitted to the major teaching and general hospitals in
the areas under study with incident, histologically confirmed cancer.
Controls were subjects admitted to the same hospitals as the cases for a
wide spectrum of acute, non-neoplastic conditions, not related to
smoking or alcohol consumption (including acute surgical conditions,
orthopaedic and non-alcohol related traumas, skin, eye. ear or nose
and miscellaneous disorders).
Similar structured questionnaires were used by trained interviewers
in all study centers, and administered to both cases and controls during
their hospital stay. The questionnaires included information on sociodemographic characteristics, including education and occupation;
general life-style habits, such as tobacco smoking and alcohol drinking;
a food frequency questionnaire; personal medical history and family
history of cancer. The questionnaires were tested for reproducibility
and reliability [12].
328
Table I. Distribution of 528 oral and pharyngeal cancer cases, 410 oesophageal cancer cases and 2408 controls, according to education and social
class, and corresponding odds ratios" (OR) and 95% confidence intervals (CI). Northern Italy, 1984-1992.
Number of subjects
Educationc (years)
>\2
7-11
<7
OR (95% CI)
Oral cavity and
pharynx
Oesophagus
Controls
27
92
408
45
69
294
402
660
1336
lb
1.32(0.82-2.14)
2.24(1.44-3.49)
X2 trend (/'-value)
Social class
1-2
3
4-5
Farmers
Other or unknown
Oral cavity and
pharynx
21.18 (<0.0001)
13
113
293
96
13
lb
2.12(1.13-4.00)
2.56(1.38-4.74)
4.92 (2.47-9.78)
1.74(0.74-4.13)
216
764
1159
147
122
23
114
220
27
26
X2 trendd (P-value)
23.92 ( < 0.0001)
Oesophagus
lb
0.90(0.59-1.37)
1.60(1.10-2.31)
12.05 ( < 0.001)
lb
1.35(0.81-2.22)
1.46(0.90-2.38)
1.47(0.75-2.87)
1.45(0.75-2.80)
2.15(0.14)
All
lb
1.08(0.78-1.51)
1.78(1.32-2.40)
24.48 ( < 0.0001)
lb
1.56(1.03-2.35)
1.75(1.17-2.62)
2.61 (1.60-4.24)
1.65(0.95-2.87)
15.19(<0.0001)
" Estimates from unconditional logistic regression models, including terms for age, sex, study center, alcohol and tobacco consumption.
b
Reference category.
c
The sum does not add up to the total because of some missing values.
d
Other or unknown excluded.
Table 2. Distribution of 598 oral and pharyngeal cancer cases and 1491 controls, 304 oesophageal cancer cases and 743 controls, according to
education and social class, and corresponding odds ratios" (OR) and 95% confidence intervals (CI). Northern Italy, 1992-1997.
Number of subjects
Education0 (years)
£12
7-11
<7
OR (95% CI)
Oral cavity and
pharynx
Controls
Oesophagus
Controls
Oral cavity and
pharynx
53
130
410
194
400
896
22
65
216
98
189
454
lb
0.66(0.42-1.03)
0.79(0.52-1.20)
X2 trend (f-value)
Social class
1-2
3
4-5
Farmers
Other or unknown
0.10(0.75)
23
113
373
59
30
82
406
747
147
109
9
74
181
31
9
59
206
370
75
33
X2 trendd (P-value)
lb
0.66(0.37-1.19)
0.84(0.48-1.48)
0.69(0.36-1.35)
0.73(0.35-1.51)
0.02 (0.88)
(Desophagus
b
.31 (0.70-2.45)
.61 (0.90-2.87)
:>.99 (0.08)
b
.53 (0.67-3.50)
.59(0.71-3.55)
.59 (0.64^.00)
.96 (0.60-6.42)
().63 (0.43)
All
lb
0.83(0.57-1.19)
1.01(0.72-1.43)
0.61 (0.44)
lb
0.88(0.54-1.53)
1.06(0.67-1.70)
0.96(0.55-1.66)
1.00(0.54-1.86)
0.59 (0.44)
" Estimates from unconditional logistic regression models, including terms for age, sex, study center, alcohol and tobacco consumption.
b
Reference category.
c
The sum does not add up to the total because of some missing values.
d
Other or unknown excluded.
Education was classified according to the number of years at school,
and categorized into three groups corresponding approximately to
primary, secondary and higher education. Social classes were defined
according to the head of household's occupation, with a classification
derived from that used by the British Registrar General [13], and
reclassified in three categories, corresponding to the Registrar General's
social classes 1 and 2 (professional, managerial and intermediate),
social class 3 (skilled occupation), and social classes 4 and 5 (partly
skilled and unskilled occupations). Farmers and subjects with other or
unknown occupation were included in two further categories.
Odds ratios (OR), and the corresponding 95% confidence intervals
(CI), were estimated using unconditional multiple logistic regression
models [14], including terms for age, sex, study center, alcohol and
tobacco consumption.
Results
Table 1 gives the distribution of oral, pharyngeal and
oesophageal cancer cases and controls collected in the
1980s, according to education and social class.
329
For both social-economic indicators a significant in- consumption [18, 19] are included. The changed social
verse association was observed: the OR for both cancers pattern over the last few years indicates, therefore, that
combined was 1.8 (95% CI: 1.3-2.4) for the lowest versus the differential exposure in the main risk factors for the
the highest educational level, and 1.8 (95% CI: 1.2-2.6) upper digestive tract neoplasms has tended to decline
for subjects in social class 4 and 5, versus those in social (i.e., from 38.8% to 28% current smokers, respectively,
class 1 and 2. The OR was 2.6 for farmers. The associa- in the two studies, and from 13% to 9% heavy alcohol
tion with low social-economic indicators was, however, drinkers), following a general decrease in alcohol and
stronger for oral and pharyngeal, than for oesophageal tobacco consumption in Italy, mostly in men [20-22],
and a more widespread availability of a more affluent and
cancer.
Table 2 gives comparable data for the studies con- varied diet.
ducted in the 1990s. No consistent pattern of risk was
observed with any of the socio-economic indicators
considered, the OR being 1.0 (95% CI: 0.7-1.4) for the Acknowledgements
lowest versus the highest educational level, and 1.1 (95%
CI: 0.7-1.7) for subjects in social class 4 and 5, com- This work was conducted with the support of the Italian
pared with those in the highest class. Likewise, the OR Association for Cancer Research, Milan. The authors
for farmers was close to unity. The ORs were apparently, thank Mrs M. P. Bonifacino for editorial assistance.
but not significantly, above unity for oesophageal cancer,
but the estimates were unstable, since only nine cases
were in the highest social class category.
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Discussion
The present study indicates that the social correlates of
cancers of the upper digestive tract have changed over
the last few years, with a disappearance of the social
gradient previously reported. A similar pattern has been
observed for oesophageal cancer in the department of
Calvados, France [7], and has been partly attributed to
the changed histological types, with a recent rise in
adenocarcinomas [15, 16]. The present data, however,
indicate that the changes in social correlates are observed
also for oesophageal squamous-cell cancers. This pattern
is also reflected in the descriptive epidemiology of cancers
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The studies included in the present analysis are
hospital-based and have some of the related limitations
[14]. Since the study designs were similar, however, these
can hardly account for such large differences in results
between studies as those observed with reference to the
social class indicators considered. Moreover the characteristics of the controls were similar in the two studies in
terms of education (56% in the lower educational level
for the first study and 59% for the second one) and social
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Received 16 August 2000; accepted 13 November 2000.
Correspondence to:
Dr C. Bosetti
Istituto di Ricerche Farmacologiche 'Mario Negri'
Via Eritrea 62
20157 Milan
Italy
^
E-mail :)[email protected]