«Health and Safety Executive The burden of occupational cancer in Great Britain Melanoma Prepared by the Health and Safety Laboratory, the Institute ...»
Health and Safety
The burden of occupational cancer
in Great Britain
Prepared by the Health and Safety Laboratory,
the Institute of Occupational Medicine and
Imperial College London
for the Health and Safety Executive 2012
Health and Safety
The burden of occupational cancer
in Great Britain
Health and Safety Laboratory
Harpur Hill, Buxton
Derbyshire SK17 9JN
John Cherrie, Martie Van Tongeren
Institute of Occupational Medicine Research Avenue North Riccarton Edinburgh EH14 4AP Léa Fortunato, Sally Hutchings, Lesley Rushton Department of Epidemiology and Biostatistics Imperial College London Norfolk Place London W2 1PG The aim of this project was to produce an updated estimate of the current burden of cancer for Great Britain resulting from occupational exposure to carcinogenic agents or exposure circumstances. The primary measure of the burden of cancer was the attributable fraction (AF) being the proportion of cases that would not have occurred in the absence of exposure; and the AF was used to estimate the number of attributable deaths and registrations. The study involved obtaining data on the risk of the cancer due to the exposure of interest, taking into account confounding factors and overlapping exposures, as well as the proportion of the target population exposed over the relevant exposure period. Only carcinogenic agents, or exposure circumstances, classified by the International Agency for Research on Cancer (IARC) as definite (Group 1) or probable (Group 2A) human carcinogens were considered. Here, we present estimates for melanoma that have been derived using incidence data for calendar year 2004, and mortality data for calendar year 2005.
The estimated total (male and female) AF for melanoma of the eye related to overall occupational exposure is 1.56% (95%Confidence Interval (CI)= 0.30-3.62), which equates to 1 (95%CI= 0-3) death and 6 (95%CI= 1-15) registrations, all of which were attributable to occupational exposure to ultraviolet radiation from welding.
This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.
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ACKNOWLEDGEMENTSFunding was obtained from the Health and Safety Executive (HSE). Andrew Darnton from the HSE was responsible for the work on mesothelioma. The contributions to the project and advice received from many other HSE and Health and Safety Laboratory staff is gratefully acknowledged. Two workshops were held during the project bringing together experts from the UK and around the world. We would like to thank all those who participated and have continued to give advice and comment on the project. We would also like to thank Helen Pedersen and Gareth Evans for their help in editing and formatting the reports.
The aim of this project was to produce an updated estimate of the current burden of cancer for Great Britain resulting from occupational exposure to carcinogenic agents or exposure circumstances. The primary measure of the burden of cancer used in this project was the attributable fraction i.e. the proportion of cases that would not have occurred in the absence of exposure; this was then used to estimate the attributable numbers. This involved obtaining data on the risk of the disease due to the exposure of interest, taking into account confounding factors and overlapping exposures, and the proportion of the target population exposed over the period in which relevant exposure occurred. Estimation was carried out for carcinogenic agents or exposure circumstances classified by the International Agency for Research on Cancer (IARC) as definite (Group 1) or probable (Group 2A) human carcinogens. Here, we present estimates for melanoma that have been derived using incidence data for calendar year 2004, and mortality data for calendar year 2005.
Solar radiation has been classified by the IARC as a definite human carcinogen for melanoma skin cancer. However, the risk for malignant melanoma of the skin caused by occupational exposure to solar radiation is uncertain due to difficulties in classifying solar exposure as occupational or recreational. Both positive and negative associations have been found giving no overall increase in risk. The attributable fraction and numbers of deaths and registrations due to occupationally related solar radiation has therefore not been estimated for melanoma of the skin.
Ultraviolet radiation from artificial sources has been classified by IARC as a probable human carcinogen for melanoma, particularly of the eye. Evidence of high intensity exposure in welding is particularly strong. Due to assumptions made about cancer latency and working age range, only cancers in ages 25+ in 2005/2004 could be attributable to occupation. For Great Britain in 2005, there were 39 total deaths in men aged 25+ and 44 in women aged 25+ from melanoma of the eye; in 2004 there were 198 total registrations for melanoma of the eye in men aged 25+ and 185 in women aged 25+.
The estimated total (male and female) attributable fraction for melanoma of the eye is 1.56% (95%Confidence Interval (CI)=0.30-3.62), which equates to 1 (95%CI=0-3) death and 6 (95%CI=1-15) registrations, all of which were attributable to occupational exposure to ultraviolet radiation from welding.
1 INCIDENCE AND TRENDSThe cells that become cancerous in melanoma are called ‘melanocytes’ (Cancer Research UK 2008). They are mainly found between the dermis and epidermis, but are also found in many other places, including the hair and the lining of internal organs, such as the eye. The melanocytes produce a dark-coloured pigment called melanin, which is responsible for the colouring of the skin.
The pigment helps to protect the body from the ultraviolet (UV) light of the sun, which can cause burns.
1.1 MELANOMA OF THE SKIN
Melanoma of the skin, also called cutaneous melanoma or malignant melanoma (ICD-10 C43; ICDaccounted for 160,000 new cases, and 41,000 deaths, worldwide in 2002 (Parkin et al.
2005). There were slightly more cases in women than men, however, there were more deaths in men. This type of tumour is particularly common in white populations living in sunny climates.
High incidence rates are found in Australia, New Zealand, North America and Northern Europe.
Rapid increases in incidence and mortality are being observed in both males and females in many countries, including countries where rates are typically low, such as Japan. Survival from melanoma is relatively high in developed areas (81% in Europe). In contrast, survival is lower in developing countries (typically around 40%); this is partly due to late diagnosis, and the majority of tumours being acral melanoma (located on the soles of the feet), which have a poorer prognosis than other melanoma types.
There are four main types of cutaneous melanoma: superficial spreading melanoma, nodular melanoma, lentigo maligna melanoma and acral lentiginous melanoma (Cancer Research UK 2008). Superficial spreading melanoma is the most common, accounting for about 70% of cases.
This type of melanoma tends to grow outwards initially, then downward into the deeper layers of the skin. Approximately 25% of UK melanomas are nodular; these develop quickly and grow down into the skin, usually on infrequently exposed parts of the body. Lentigo maligna melanoma appears in areas of skin that get a lot of sun exposure and is largely restricted to the head and neck, especially the face. Acral lentiginous melanoma, by definition, is found on the skin of the palms of the hands and more commonly on the soles of the feet. Melanoma of the skin arises in different anatomic sites in men and women. The trunk (back, abdomen and chest) is the most common in men, accounting for 38%. Melanoma is most commonly found on the legs (including the hips and thighs) in women, accounting for 42%.
Sun exposure is the main cause of cutaneous melanoma, or more specifically solar UV radiation (Gruber and, Armstrong 2006). Benign acquired nevi (those that develop after 6 months of age) and atypical nevi are also well-established risk factors for melanoma of the skin. Nevi are most likely to be associated with superficial spreading melanoma rather than other types. Congenital nevi (those present immediately at birth) are categorised by size, which corresponds to the malignant potential, thus cutaneous melanoma arising in small congenital nevi is rare.
In the UK and Ireland in the 1990s, melanoma of the skin accounted for 1 in 50 diagnosed cases of cancer and 1 in 100 cancer deaths (Gavin and Walsh 2005). Overall, the age-standardised incidence rates were 7.7 and 9.7 per 100,000 in males and females, respectively. Although there was a higher incidence rate for females, the mortality rates were similar. The age-standardised mortality rate was
2.5 per 100,000 in males and 2.0 per 100,000 in females.
Currently cutaneous melanoma is the seventh most common cancer in the UK; sixth in women and tenth in men. In Great Britain, the numbers diagnosed have been steadily increasing from approximately 5,500 cases each year to in excess of 8,500 (Table 1). Nearly 2,000 people die from the condition each year (Table 2). Long-term trends in the incidence and mortality were studied based on notifications of cancer cases and deaths in England, Wales and Scotland over the past tenyears. On average 2,427 males and 3,189 females were diagnosed with cutaneous melanoma in England, giving an average annual incidence of around 10.0 per 100,000 males and 12.6 per 100,000 females. The crude rate for both males and females appears to be steadily increasing for both males and females in all three countries. On average 900 males and 800 females died from cutaneous melanoma in Great Britain. The crude rate for both males and females appears to be stable at around 28 for males and 23 for females in England and Wales and 3 for males and 2 for females, in Scotland.
Cutaneous melanoma risk generally increases with age but the condition is disproportionately higher in younger people, with almost one third of cases occurring in people under 50 years of age (Cancer Research UK 2008). Melanoma of the skin is the most common cancer in young adults (aged 15-34) and is twice as common in young women as in young men. In 2004, incidence rates peaked in men and women aged 55-59, which was followed by a steady decline. Mortality rates peaked in men aged 70-74, whereas, mortality rates for women peaked much later at over 85 years of age.
Cutaneous melanoma survival rates have been improving over the past 25 years and are now amongst the highest for any cancer (Cancer Research UK 2008). For patients diagnosed with this cancer in 2000-2001 in England and Wales, the population-based five-year relative survival rate is very high for both males (78%) and females (91%), with rates being consistently higher in females.
Generally, the five-year relative survival rate varies between 20% and 90% depending on the stage of disease, thickness of the tumour and age at diagnosis. Patients with advanced stage cutaneous melanoma have a significantly lower five-year survival rate than patients diagnosed in the early stages (Stage 1: 90%, Stage 2: 80%, Stage 3: 40-50% and Stage 4: 20-30%). Survival rates decline slightly both with tumour thickness and age. The five-year survival rate decreases from around 90% for the thinnest tumours (1.5mm) to around 50% for the thickest (3.5mm). Patients diagnosed who are under 40 years of age have a five-year survival rate of about 76% for men and 90% for women but for patients aged over 80 years this decreases to 44% in men and 61% in women. In 2004, cancer mortality to incidence ratios for melanoma of the skin (C43) were 0.25 for men and
0.16 for women (ONS 2006).
1.2 MELANOMA OF THE EYE
Melanoma of the eye, also called ocular or intraocular melanoma can develop in one of several places. Uveal melanoma is the most common type of ocular melanoma, meaning it occurs in the uveal tract, which includes the choroid, ciliary body and iris (Cancerbackup 2007). Melanoma can also occur in the thin lining over the white part of the eye (the conjunctiva) or on the eyelid, but this is very rare.
There are three main types of ocular melanoma; spindle cell, epithelioid cell and mixed cell (Gruber and Armstrong 2006). Iris melanomas are more likely to be spindle cell, as opposed to choroidal or ciliary body melanomas. Although rare, this disease begins to appear in teenage years and increases in incidence from early 20s to late 40s for both men and women. Thereafter it increases at a greater rate in men to a peak at 80 years of age. Currently it is uncertain whether solar UV radiation is a causal factor, although there is compelling evidence for artificial UV radiation being a cause.