Latest trends in cancer incidence among UK South Asians in Leicester

Abstract

Using cancer registry data, we show that although South Asians have lower rates of cancer than the rest of the population, this is changing with age and time. Younger South Asians, particularly children, are at increased risk. While generally cancer rates have fallen over the last decade, they are increasing among South Asians.

Cancer incidence rates in the UK have been reported to be much lower for South Asians (Indian, Pakistani and Bangladeshi) than the rest of the population (Winter et al, 1999). However, there has been little report on recent trends in cancer among South Asians in the UK. In order to explore recent cancer incidence trends, we used 1990–1999 cancer registry data for Leicester, UK, a city where 22% of residents classified themselves as South Asian in the 1991 census.

MATERIALS AND METHODS

Data were obtained from Trent Cancer Registry on all registrations of cancer diagnosed between 1 January 1990 and 31 December 1999, where the patient was a Leicester resident at diagnosis. Since routine ethnicity data were not available for all patients, individuals were classified as South Asian or non-South Asian based on forename and surname. Software was used to do this (Cummins et al, 1999), but accuracy was increased by visual inspection of the data. Deprivation is often a confounder in studies of ethnicity since they are closely related. There have been shown to be trends in incidence with deprivation for various cancer sites (Pollock and Vickers, 1997) so it was important to take account of deprivation in the analyses of cancer incidence. Therefore, the Townsend Index (Townsend et al, 1988) was used to assess the level of deprivation of the patient's area of residence. The local research ethics committee approved the study.

Data were analysed for all cancers combined (all ages) and then for five common cancer sites (patients age 30 years and over): colorectal, head and neck, breast, lung and prostate. Electoral ward level population estimates were obtained from the 1991 census (by sex, ethnicity and 5-year age bands) and aggregated by deprivation tertile in order to calculate incidence rates. Variation in incidence rates by ethnicity, deprivation tertile, age and year of diagnosis (and any interactions between them) was explored using Poisson regression, separately for men and women. Firstly, a model was fitted to estimate the incidence rate ratio (IRR) for South Asians compared with non-South Asians for each age group, adjusting for deprivation tertile, and an interaction between ethnicity and age group was fitted to explore differential trends with age (Table 1 ). An interaction between time period (1990–1994 and 1995–1999) and ethnicity was then included to compare changes in incidence over time between South Asians and non-South Asians (Table 2 ). Interactions with deprivation were also explored.

Table 1. Incidence rate ratios (95% Confidence Intervals) comparing South Asians with non-South Asians by sex, cancer site and age, adjusted for deprivation tertile.

		Age at diagnosis (years)
	All ages	0–14	15–29	30–49	50–74	75+	χ2 statistic (P-value) change in IRR for ethnicity by age
Males
All cancers	0.61	2.56	1.18	0.68	0.55	0.59	χ24=26.4
	(0.55, 0.68)	(1.33, 4.93)	(0.73, 1.92)	(0.51, 0.90)	(0.48, 0.64)	(0.47, 0.74)	(P=0.0001)
	NSA=401, NNSA=5535	NSA=19, NSA=17	NSA=22, NSA=66	NSA=59, NNSA=276	NSA=223, NNSA=3097	NSA=78, NNSA=2079
Colorectal	0.44			0.94	0.50	0.10	χ22=10.96
	(0.32, 0.61)			(0.43, 2.08)	(0.34, 0.73)	(0.02, 0.40)	(P=0.0042)
	NSA=38, NNSA=778			NSA=8, NNSA=30	NSA=28, NNSA=431	NSA=2, NNSA=317
Head and neck	1.53			1.08	1.28	3.64	χ22=6.8
	(1.09, 2.15)			(0.42, 2.76)	(0.83, 1.96)	(1.87, 7.09)	(P=0.033)
	NSA=43, NNSA=197			NSA=6, NNSA=17	NSA=26, NNSA=136	NSA=11, NNSA=44
Lung	0.40			0.53	0.40	0.37	χ22=0.41
	(0.31, 0.53)			(0.21, 1.37)	(0.29, 0.55)	(0.20, 0.67)	(P=0.81)
	NSA=55, NNSA=1187			NSA=5, NNSA=32	NSA=39, NNSA=724	NSA=11, NNSA=431
Prostate	0.52			-	0.47	0.60	χ21=0.45
	(0.37, 0.72)				(0.31, 0.72)	(0.36, 1.00)	(P=0.50)
	NSA=38, NNSA=856			NSA=0, NNSA=2	NSA=23, NNSA=429	NSA=15, NNSA=425
Person-years	PYSA=347 960	PYSA=107 300	PYSA=82 050	PYSA=105 820	PYSA=48 350	PYSA=4440
	PYNSA=1206 950	PYNSA=245 190	PYNSA=287 120	PYNSA=299 330	PYNSA=304 850	PYNSA=70 460
Females
All cancers	0.75	1.66	1.15	0.71	0.71	0.77	χ24=9.79
	(0.68, 0.82)	(0.89, 3.12)	(0.72, 1.83)	(0.58, 0.86)	(0.62, 0.81)	(0.60, 1.00)	(P=0.044)
	NSA=461, NNSA=5731	NSA=17, NNSA=23	NSA=24, NNSA=69	NSA=122, NNSA=567	NSA=238, NNSA=2741	NSA=60, NNSA=2331
Breast	0.61			0.45	0.71	0.65	χ22=4.79
	(0.50, 0.73)			(0.32, 0.63)	(0.56, 0.90)	(0.34, 1.27)	(P=0.091)
	NSA=121, NNSA=1477			NSA=36, NNSA=273	NSA=76, NNSA=768	NSA=9, NNSA=436
Colorectal	0.51			1.11	0.39	0.46	χ22=4.92
	(0.35, 0.75)			(0.54, 2.28)	(0.23, 0.68)	(0.21, 1.04)	(P=0.086)
	NSA=30, NNSA=776			NSA=10, NNSA=30	NSA=14, NNSA=333	NSA=6, NNSA=413
Head and neck	2.97			4.58	1.99	3.48	χ22=3.95
	(2.02, 4.37)			(2.46, 8.52)	(1.10, 3.60)	(1.23, 9.83)	(P=0.14)
	NSA=42, NNSA=121			NSA=24, NNSA=18	NSA=14, NNSA=64	NSA=4, NNSA=39
Lung	0.32			-	0.31	0.65	χ21=2.07
	(0.20, 0.50)			NSA=0, NNSA=30	(0.18, 0.53)	(0.29, 1.47)	(P=0.15)
	NSA=20, NNSA=637				NSA=14, NNSA=372	NSA=6, NNSA=235
Person-years	PYSA=355 200	PYSA=104 230	PYSA=93 260	PYSA=104 580	PYSA=48 220	PYSA=4910
	PYNSA=1311 820	PYNSA=231 940	PYNSA=303 080	PYNSA=301 120	PYNSA=335 280	PYNSA=140 400

Number of cancer cases and Person-years for South Asians: N_SA, PY_SA; Number of cancer cases and Person-years for non-South Asians N_NSA, PY_NSA.

Table 2. Incidence rate ratios (95% confidence intervals) comparing incidence rates for 1995–1999 with 1990–1994, by ethnicity, sex and cancer site adjusted for age and deprivation tertile.

	Ethnicity
	South Asians	Non-South Asians	χ2 statistic (P-value) for change in IRR between time periods by ethnicity
Males
All cancers	1.28	0.95	χ21=8.01 (P=0.0047)
	(1.05, 1.56)	(0.90, 1.00)
	N90–94=176, N95–99=225	N90–94=2834, N95–99=2701
Colorectal	1.24	1.03	χ21=0.31 (P=0.58)
	(0.65, 2.34)	(0.89, 1.18)
	N90–94=17, N95–99=21	N90–94=384, N95–99=394
Head and neck	0.95	0.88	χ21=0.06 (P=0.80)
	(0.52, 1.74)	(0.66, 1.16)
	N90–94=22, N95–99=21	N90–94=105, N95–99=92
Lung	1.39	0.81	χ21=3.82 (P=0.051)
	(0.81, 2.38)	(0.72, 0.91)
	N90–94=23, N95–99=32	N90–94=656, N95–99=531
Prostate	1.71	0.93	χ21=3.27 (P=0.071)
	(0.89, 3.31)	(0.82, 1.07)
	N90–94=14, N95–99=24	N90–94=443, N95–99=413
Females
All cancers	1.24	0.91	χ21=10.0 (P=0.0015)
	(1.03, 1.49)	(0.86, 0.96)
	N90–94=206, N95–99=255	N90–94=3000, N95–99=2731
Breast	1.37	0.81	χ21=7.70 (P=0.0055)
	(0.96, 1.97)	(0.73, 0.90)
	N90–94=70, N95–99=51	N90–94=816, N95–99=661
Colorectal	2.33	0.95	χ21=5.37 (P=0.020)
	(1.07, 5.09)	(0.83, 1.09)
	N90–94=9, N95–99=21	N90–94=398, N95–99=378
Head and neck	1.33	1.33	χ21=0.001 (P=0.99)
	(0.72, 2.46)	(0.93, 1.90)
	N90–94=18, N95–99=24	N90–94=52, N95–99=69
Lung	1.50	1.11	χ21=0.43 (P=0.51)
	(0.61, 3.67)	(0.94, 1.30)
	N90–94=8, N95–99=12	N90–94=304, N95–99=333

Number of cancer cases for 1990–1994: N_90–94; Number of cancer cases for 1995–1999 N_95–99. Person-years assumed same for 1990–1999.

RESULTS

Out of 12 128 cancer cases identified, 862 were classified as occurring in South Asians (7%). South Asians (median age 61.5 years) were younger than non-South Asians (median age 71.9 years).

Overall cancer rates adjusted for age and deprivation differences were lower for South Asians than non-South Asians (males: IRR=0.61 95% confidence interval (CI) (0.55, 0.68); females IRR=0.75 (0.68, 0.82)). However, this pattern changed significantly with age (Table 1). Although older South Asians had much lower rates of cancer than the rest of the population, younger South Asians were at increased risk compared with non-South Asians.

South Asians had significantly lower rates of colorectal, lung, breast and prostate cancer, but a higher rate of head and neck cancer. For colorectal cancer, trends with age were similar to all cancers combined, with increasing IRRs among younger age groups, although for women this was not formally significant. For men, head and neck cancer showed the opposite pattern, with a decrease in risk among younger South Asians. There was little evidence of a pattern with age for lung, prostate, breast or female head and neck cancer.

Time trends for all cancers combined (Table 2) were different for South Asians compared with the rest of the population. Adjusted incidence rates increased over time for South Asians (men: +28%; women: +24%), but decreased for non-South Asians (men: −5%; women: −9%). For men, time trends differed by deprivation tertile. South Asians from the most deprived tertile had much higher increases in cancer risk (IRR=1.93 (1.41, 2.65)) than those from the least deprived tertile (IRR=1.08 (0.83, 1.39)). For non-South Asian men, the time trend with deprivation was less steep with those from the most deprived tertile having little change in risk (IRR=1.02 (0.93, 1.11)) while those from the least deprived tertile had a decrease in risk (IRR=0.92 (0.84, 1.01)). For women, changes over time were similar for all deprivation tertiles.

For individual cancer sites, time trends were different for men and women. For men, lung and prostate cancer were seen to be increasing among South Asians and decreasing among the rest of the population. For lung cancer, this pattern changed with deprivation tertile among non-South Asians, with those from the least deprived tertile having little change in incidence over time, while those from the most deprived tertile showed a decrease in incidence. The incidence of colorectal and head and neck cancer showed little change over time for all men.

South Asian women showed increasing rates of colorectal and breast cancer over time, while the rates decreased among the rest of the population. Lung and head and neck cancer incidence increased over time for all women with no differences by ethnicity.

DISCUSSION

These findings in Leicester confirm that overall South Asians have lower rates of cancer than the rest of the population (Winter et al, 1999). However, they show that this is changing with age and time. While older South Asians have a much lower risk of cancer, those from younger age groups, particularly children, have a higher risk. Most importantly, over the last 10 years, cancer rates have increased among South Asians while they have fallen among the rest of the population.

Incidence of head and neck cancers among South Asians often receives attention because these cancers are relatively more common among South Asians than the rest of the population. Here we have shown that for men this pattern is changing with rates among younger age groups approaching those of the rest of the population. Furthermore, Bhopal and Rankin (1996) have highlighted the need to look at absolute numbers of cancer cases. In Leicester, lung cancer is the most common cancer for both South Asian and non-South Asian men, and numbers of colorectal, breast and prostate cancer among South Asians are rapidly increasing.

Cancer incidence appears to be increasing quite rapidly among South Asians. This suggests that health promotion programmes should target the whole population and that any tendency to regard South Asians as ‘low-risk’ populations for cancer needs to be rethought.