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We determined the trends in incidence of skin basal cell carcinoma (BCC) using a primary care population-based cohort study in the UK. 11,113 adults with a BCC diagnosis were identified from a total of 7.22 million person-years of data between 1996 and 2003 from the Health Improvement Network database. From a random subsample of BCC cases identified from the database, 93% were confirmed by hospital letter and/or pathology report. The incidence of BCC was 153.9 per 100,000 person-years (95% CI 151.1, 156.8) and was slightly higher in men as compared to women (Incidence Rate Ratio 1.10, 95% CI 1.06, 1.14). There was a 3% increase year on year across the study period (IRR 1.03, 95% CI 1.01, 1.04), with the largest increase in incidence seen in the 30–39 year age groups, although this did not reach statistical significance. Our study indicates 53,000 new cases of BCC are estimated every year in the UK and figures are continuing to rise on a yearly basis. Incidence rates are highest for men and in particular in the older age categories. These findings are consistent with those reported for various other populations. We have also found an increase in incidence in ages 30–39, which may suggest a cohort effect of increasing ultraviolet exposure in successive younger generations. This may have a huge public and service impact in future years in countries such as the UK, with predominantly fair-skinned population, with high leisure exposure to ultraviolet light. Our findings underline the need for more elaborate preventive measures. © 2007 Wiley-Liss, Inc.
The incidence of skin cancer is increasing worldwide1, 2, 3, 4; up to 10% annually.5 Skin cancer is an increasing health problem placing a heavy burden on dermatologists and general practitioners (GP).
Basal cell carcinoma (BCC) accounts for about 75% of all skin cancers, and along with squamous cell carcinoma and a few rarer types of skin cancer, is often referred to as non-melanoma skin cancer. BCC is the commonest cancer overall in white people.6, 7, 8 Although the prevalence of metastasis and mortality is very low9, 10 BCCs may grow aggressively causing extensive tissue destruction.11
Over 30,000 new cases are reported each year in the UK. This figure is likely to be a gross underestimate owing to Regional Cancer Registries12 in the UK adopting different practices for registration of skin cancer, some registering only the first of each skin cancer type with others not registering BCCs at all. The situation is further complicated by the fact that some BCCs may be treated by destructive methods such as cryotherapy, with no resultant histology. Details of BCCs treated in this way may not reach the cancer registries, especially if they are treated in primary care.
A sustained rise in the incidence of BCC has been documented using a validated register in South Wales.13 In the US, the incidence of BCC has doubled approximately every 14 years3 and similar changes have occurred in Australia.14 Worryingly, the incidence of BCC appears to be increasing in younger people.15 Studies in persons younger than 40 years have often been too small2, 3, 4, 16, 17, 18 to assess trends across time. A recent study in the US19 has shown a disproportionate increase in BCC in young women, and another study from the Netherlands20 predicts the number of BCC cases to increase by 78% by 2015, with the largest increase in ages 15–64 years. Because of the absence of similar and complete data over time in the UK, we used a large database from primary care [The Health Improvement Network (THIN) database] to estimate age and sex specific incidence of BCC from 1996 to 2003 over time and in different age groups.
Material and methods
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- Material and methods
Most people (95%) are registered with a GP for primary health care in the UK. Under the UK healthcare system, comprehensive records of every patient's medical history are maintained within primary care, and these are captured in the THIN database.21
THIN is a database of anonymised clinical records for over 4 million patients in the UK; previous assessment of the completeness and accuracy of data recording has been shown to be of sufficient quality for use in medical research.22
We extracted the records of all adults with a first recorded diagnosis of BCC between January 1, 1996 and December 31, 2003 from the THIN databases. To preserve data quality only practices using Vision software as a method of recording diagnoses were selected. We excluded individuals with Gorlin's syndrome (or basal cell naevus syndrome), organoid naevi or other genetic syndromes. From a random subsample of forty BCC cases identified from the database, 93% were confirmed as BCCs by hospital letter and/or pathology report. The remaining cases were either confirmed as a squamous cell carcinoma (1 case) or not confirmable because of death (1 case) or documentation being unavailable (1 case).
The study had ethical approval from Nottingham Ethics Committee (04/Q2403/140) and Queen's Medical Centre Medical Research and Development committee, Nottingham, UK.
The primary outcome measures were incidence rates across years and across age groups. The secondary outcomes were trends in age specific incidence rates over time. Annual incidence rates for BCCs were estimated from the THIN database between January 1, 1996 and December 31, 2003. Incidence rates were estimated with the numerator based on the number of persons with a first occurrence of a BCC for each year between these dates. The denominator was obtained using the specific yearly mid point value from the total number of persons in our database. Age specific incidence rates between 1996 and 2003, inclusive, were calculated for a priori specified age bands (18–29, 30–39, 40–49, 50–64, 65–79, 80+ years). Incidence rates are presented as incidence per 100,000 person-years. European and World Age-Standardised incidence Rates (EASRs and WASRs, respectively) were calculated using the direct standardisation method23 to allow for direct comparison of incidence rates with other populations.
Multivariate Poisson regression models were constructed to estimate trends in adjusted incidence rate ratios (IRR) of BCC acquisition with 95 or 99% confidence intervals (CI) for primary or secondary outcomes, respectively, and included age, sex and year as potential covariates. All analyses were performed using STATA version 8.2.
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The THIN database cohort included 11,113 people with BCC, of which 42% had multiple recordings of BCCs between the years 1996 and 2003, inclusive. Their mean age was 70.5 years (standard deviation, SD 13 years) with a slightly higher proportion of men (51.4%). Women were significantly older than men by 1.1 years (t-test, p < 0.0001).
The incidence of BCC between 1996 and 2003 was 153.9 per 100,000 person-years (95% CI 151.1, 156.8) with incidence significantly increasing with age (p < 0.001). The incidence was significantly higher in males than females (IRR 1.102, 95% CI 1.062, 1.144) however there appeared to be an interaction between age and sex as seen from Table I.
Table I. Crude and Age-Standardised Incidence Rates of Skin BCC in UK, by Year and Age (The THIN Database 1996–2003)
|Cases (n)||Incidence/100,000 py||Cases (n)||Incidence/100,000 py||Cases (n)||Incidence/100,000 py|
|Age group (years)|
| Crude rate||5,400||143||5,713||166||11,113||154|
| WASR|| ||53|| ||69|| ||60|
| EASR|| ||78|| ||104|| ||89|
The European and World Age-Standardised incidence Rates (EASRs and WASRs) were overall 89 per 100,000 person-years (104 for men and 78 for women) and 60 per 100,000 person-years (69 men and 53 for women), respectively (Table I).
Using Poisson regression modelling, with adjustment for age and sex, we found that there was a significant 12% increase in incidence in 2003 as compared to 1996 (IRR 1.121, 95% CI 1.004, 1.251) (Fig. 1), which equated to a 3% annual increase (IRR 1.026, 95%CI 1.013, 1.040).
Age-specific incidence rates across the years were calculated using a priori specified age groups. There was a general increase in incidence for all age groups across the years; in particular, significant increases were seen for the 50–64 years (IRR 1.049, 99% CI 1.022, 1.076) and 65–79 years (IRR 1.033, 99% CI 1.014, 1.052). However, the largest average increase in incidence was for the 30–39 year age group (IRR 1.052, 99% CI 0.956, 1.156), although this failed to reach statistical significance at the 5% level (Fig. 2).
Figure 2. Age-specific annual incidence rates of skin BCC in UK. The THIN database 1996–2003. (NB: The scales on the Y-axis vary). [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]
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Our figures suggest that 53,000 new cases of BCC will be diagnosed in the UK population every year (based on EASRs). We have also shown a pattern of continued increase in incidence rates with age over time, which is in agreement with other European and World Age-Standardised incidence Rates from Europe (Registry. Trent Cancer Registry, Information request. Personal communication, 2006).24, 25, 26, 27, 28 Our main concern must be with our findings of increased rates over time in young people, not previously reported in the UK. Concern over rising rates in the young (and, in particular females) has been highlighted in a paper from the Netherlands.20 This increase in incidence of BCCs in the young could mean an exponential increase in its occurrence in the future elderly population. In particular a recent study indicated that the relative risk of a second BCC is greater at younger age and declines with advancing age.29 In addition a number of papers have reported BCCs in younger people to be more aggressive11, 30 resulting in further long term morbidity.11
We found that in age groups less than 50 years, women generally had higher incidence rate when compared to men, however these rates became comparable in the age group 50–54 years, thereafter the incidence rates were higher in men than women. This pattern is similar to that reported by the National Cancer Control Initiative 2003, Melbourne.31
Association between BCC development and recreational sun exposure during childhood and adolescence, as well as a strong relationship with family history of skin cancer has been shown.32, 33 Factors other than solar UV radiation exposure may be important in accounting for the risk of BCC.34
The escalating incidence rate of BCCs will increase the burden on GP, dermatologists, plastic surgeons and pathologists. This highlights the need for accurate evaluation of cancer incidence to adequately train the physicians and to plan preventative measures.
Although we have shown the incidence for BCC is increasing we are unable to say anything about the size, site or severity of the lesions and this must be considered a limitation of these data as more severe lesions will have an additional impact on health services. It is likely that a percentage of BCCs may have been treated in general practice by destructive methods, with no resultant histology, however this was a pragmatic study set out to look at trends in incidence to reflect the burden on the UK NHS. Finally although numbers were smaller for the subgroup analysis, they were still larger than in other studies that looked at the same subgroups. We believe this is the largest study to date, using a national primary care database, to look at trends in incidence of BCC across time and age groups confirming the findings from other smaller studies showing that the incidence of BCC is increasing, and in particular in the young. This highlights the need for prevention studies and methods to increase public awareness in the UK.