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SUNBURN AND MELANOMA
1184
been based on skin-test reactivity, the relation between this response and immunity to infection is unknown. At the very least the current vaccine trials will yield some important clues, and will also provide a basis for future trials of molecularly defined vaccines.
SUNBURN AND MELANOMA
SQUAMOUS cell and basal cell cancers are a late result of the cumulative effects of prolonged exposure to ultraviolet (UV) irradiation. The role of sunlight in the production of malignant melariomas, however, has been more debatable. A new report by the Royal College of Physicians1 should help to increase public awareness of the dangers of sunburn, and in particular its role in the development of cutaneous melanoma. Lentigo malignant melanoma, the most benign form, usually starts as a brown stain on the face of an elderly person, and resembles squamous cell and basal cell cancers in that it seems to be the result of a lifetime’s exposure to sunlight. A link between sunlight and the more dangerous superficial spreading melanoma (SSM) and nodular melanoma (NM) is more controversial, since these tumours tend to arise in much younger people, often on parts of the body that are usually covered. They are much commoner in Caucasians who live in sunny countries, but the fact that the frequency of S SM and NM per unit area of skin is higher on the trunk than the face suggests that there is no direct relation to the total cumulative dose of radiation received. It seems more likely that the damage is caused not by chronic low-dose exposure, but by intermittent high-intensity irradiation which causes sunburn. The induction period between the sunburn and the development of the malignancy may be quite short (a few months or years). The sunburn hypothesis would explain why the incidence of malignant melanoma in Caucasians has been rising steadily by about 5% per annum in most developed countries for the last 30 or 40 years. This increase has accompanied various changes in lifestyle which have resulted in more and more pallid people exposing their skin to short bursts of strong sunshine. Malignant melanoma, unlike squamous cell and basal cell cancer, is more common in people of higher socioeconomic status.’ The difference is unlikely to relate to occupational exposure, such as irradiation from fluorescent lamps in offices,s since the same gradient in melanoma incidence is seen in both spouses.2-4 Unlike squamous cell and basal cell cancers, melanoma is commoner in indoor than outdoor workers, but the socioeconomic incidence gradient is the same in both groups. Malignant melanoma is therefore one of the few diseases in which poverty is protective. Case-control studies have shown that repeated sunburn is associated with an increased risk of subsequent melanoma, and other studies have shown that melanoma is much more common in
fair-skinned people who burn easily and tan poorly.’-9 Melanoma is more common in Scandinavia than in other European countries. to If sunburn predisposes to melanoma, it is possible that a carefully controlled course of low-dose UV irradiation before exposure to holiday sunshine would be prophylactic. The RCP report does not comment on this possibility, but puts its faith in the use of regular use of topical sunscreens with a sun-protection factor of at least 6 (ie, one that will increase the minimal erythema dose and hence the exposure time six-fold). The report is guarded about the use of commercial UV-A sunbeds, which produce a pleasing tan with little or no erythema. Malignant melanoma has developed in a few patients shortly after use of such beds, although a cause-and-effect relation is far from proven. There is some evidence that prolonged exposure to UV-A irradiation can accelerate cutaneous ageing changes, and, in mice at least, UV-A rays can cause squamous cell cancer." The report states "Fair skinned subjects who burn easily and tan with difficulty cannot be reassured that sunbeds are ’safe’ and they should be warned that as LTV-A irradiation leads to very little visible inflammation, damage may be done to the skin without the customary redness and peeling seen with natural sunlight." The report provides a useful seven-point check-list of the clinical features that might suggest a diagnosis of malignant melanoma (presence of itch or altered sensation, diameter of 1 cm or greater, increasing size, presence of an irregular or geographic border, variations in density of pigment within the lesion, inflammation, and bleeding or crusting). Any lesion scoring three or less is said to have a 90% chance of being a non-melanoma, whereas any lesion scoring five or more has a 95 % chance of being a melanoma. The check-list has been widely reported in the press, and, although such publicity might cause transient alarm in some nonmelanoma patients, its effect in accelerating the treatment of some people with melanoma cannot be doubted. A similar one-week publicity campaign in Scotland in 19851z was followed by a pronounced increase in dermatologists’ workload, but as a result many melanomas were treated at an earlier stage. After the Scottish campaign, the proportion of melanomas treated in the good prognosis "thin" stage ( < 1 5 mm measured vertically from the epidermal granular layer to the deepest melanoma cell) increased from 38% to 62%. There was a corresponding decrease from 34% to 15% in the poor prognosis "thick" (>3-5 mm) tumours.l1 Before the publicity campaign, the delay between the patient becoming aware of the lesion and receiving treatment had been more than a year in 34% of cases; this delay was not due to failure of recognition by the doctors, but to public ignorance. Similar improvements in the prognosis of malignant melanoma have followed improved public education about sinister skin lesions in other countries. Thus the RCP report may well improve the melanoma mortality rate in the short term-but will it reduce the acreage of red skin this summer? .
1. Mackie RM, Elwood JM, Hawk JLM. Links between exposure to ultraviolet radiation and skin cancer. A report of the Royal College of Physicians. J R Coll Physicians Lond 1987, 21: 1-6. 2. Cooke KR, Skegg DCG, Fraser J. Socio-economic status, indoor and outdoor work and malignant melanoma. Int J Cancer 1984; 34: 57-62. 3. Lee JAH, Strickland D. Malignant melanoma, social status and outdoor work. Br J Cancer 1980; 41: 757-63. 4. Williams RR, Horn J. Association of cancer sites with tobacco and alcohol consumption and socio-economic status of patients. J Nat Cancer Inst 1977; 58: 525-35. 5. Beral V, Evans S, Shaw H, Milton G. Malignant melanoma and exposure to fluorescent lighting at work. Lancet 1982; ii: 290-93. 6. Whitehead M. The health divide: inequalities in health in the 1980s. London: Health Education Council, 1987
7. Mackie
RM, Aitchison TG. Severe sunburn and subsequent risk of primary malignant melanoma in Scotland. Br J Cancer 1982; 46: 955. 8. Beral V, Evans S, Shaw H, Milton G. Cutaneous factors related to the risk of malignant melanoma. Br J Dermatol 1983, 109: 165-72. 9. Spinilli JJ, Elwood JM, Gallagher RP, Hill GB. Pigmentation and skin reaction to sun as risk factors for cutaneous melanoma. Western Canada melanoma study. Br Med J 1984; 288: 99-102. 10. Waterhouse J, Muir C, Correa P, Powell J, Cancer Incidence in five continents, vol III. Lyon: International Agency for Research on Cancer 1976: 508-11, 542-43 11. Strickland PT. Photocarcinogenesis by near-ultraviolet (UV-A) radiation m Sencar mice. J Invest Dermatol 1986; 87: 272-75. 12. Doherty VR, Mackie RM. Reasons for poor prognosis in British patients with cutaneous malignant melanoma. Br Med J 1986; 292: 987-89. cutaneous
been based on skin-test reactivity, the relation between this response and immunity to infection is unknown. At the very least the current vaccine trials will yield some important clues, and will also provide a basis for future trials of molecularly defined vaccines.
SUNBURN AND MELANOMA
SQUAMOUS cell and basal cell cancers are a late result of the cumulative effects of prolonged exposure to ultraviolet (UV) irradiation. The role of sunlight in the production of malignant melariomas, however, has been more debatable. A new report by the Royal College of Physicians1 should help to increase public awareness of the dangers of sunburn, and in particular its role in the development of cutaneous melanoma. Lentigo malignant melanoma, the most benign form, usually starts as a brown stain on the face of an elderly person, and resembles squamous cell and basal cell cancers in that it seems to be the result of a lifetime’s exposure to sunlight. A link between sunlight and the more dangerous superficial spreading melanoma (SSM) and nodular melanoma (NM) is more controversial, since these tumours tend to arise in much younger people, often on parts of the body that are usually covered. They are much commoner in Caucasians who live in sunny countries, but the fact that the frequency of S SM and NM per unit area of skin is higher on the trunk than the face suggests that there is no direct relation to the total cumulative dose of radiation received. It seems more likely that the damage is caused not by chronic low-dose exposure, but by intermittent high-intensity irradiation which causes sunburn. The induction period between the sunburn and the development of the malignancy may be quite short (a few months or years). The sunburn hypothesis would explain why the incidence of malignant melanoma in Caucasians has been rising steadily by about 5% per annum in most developed countries for the last 30 or 40 years. This increase has accompanied various changes in lifestyle which have resulted in more and more pallid people exposing their skin to short bursts of strong sunshine. Malignant melanoma, unlike squamous cell and basal cell cancer, is more common in people of higher socioeconomic status.’ The difference is unlikely to relate to occupational exposure, such as irradiation from fluorescent lamps in offices,s since the same gradient in melanoma incidence is seen in both spouses.2-4 Unlike squamous cell and basal cell cancers, melanoma is commoner in indoor than outdoor workers, but the socioeconomic incidence gradient is the same in both groups. Malignant melanoma is therefore one of the few diseases in which poverty is protective. Case-control studies have shown that repeated sunburn is associated with an increased risk of subsequent melanoma, and other studies have shown that melanoma is much more common in
fair-skinned people who burn easily and tan poorly.’-9 Melanoma is more common in Scandinavia than in other European countries. to If sunburn predisposes to melanoma, it is possible that a carefully controlled course of low-dose UV irradiation before exposure to holiday sunshine would be prophylactic. The RCP report does not comment on this possibility, but puts its faith in the use of regular use of topical sunscreens with a sun-protection factor of at least 6 (ie, one that will increase the minimal erythema dose and hence the exposure time six-fold). The report is guarded about the use of commercial UV-A sunbeds, which produce a pleasing tan with little or no erythema. Malignant melanoma has developed in a few patients shortly after use of such beds, although a cause-and-effect relation is far from proven. There is some evidence that prolonged exposure to UV-A irradiation can accelerate cutaneous ageing changes, and, in mice at least, UV-A rays can cause squamous cell cancer." The report states "Fair skinned subjects who burn easily and tan with difficulty cannot be reassured that sunbeds are ’safe’ and they should be warned that as LTV-A irradiation leads to very little visible inflammation, damage may be done to the skin without the customary redness and peeling seen with natural sunlight." The report provides a useful seven-point check-list of the clinical features that might suggest a diagnosis of malignant melanoma (presence of itch or altered sensation, diameter of 1 cm or greater, increasing size, presence of an irregular or geographic border, variations in density of pigment within the lesion, inflammation, and bleeding or crusting). Any lesion scoring three or less is said to have a 90% chance of being a non-melanoma, whereas any lesion scoring five or more has a 95 % chance of being a melanoma. The check-list has been widely reported in the press, and, although such publicity might cause transient alarm in some nonmelanoma patients, its effect in accelerating the treatment of some people with melanoma cannot be doubted. A similar one-week publicity campaign in Scotland in 19851z was followed by a pronounced increase in dermatologists’ workload, but as a result many melanomas were treated at an earlier stage. After the Scottish campaign, the proportion of melanomas treated in the good prognosis "thin" stage ( < 1 5 mm measured vertically from the epidermal granular layer to the deepest melanoma cell) increased from 38% to 62%. There was a corresponding decrease from 34% to 15% in the poor prognosis "thick" (>3-5 mm) tumours.l1 Before the publicity campaign, the delay between the patient becoming aware of the lesion and receiving treatment had been more than a year in 34% of cases; this delay was not due to failure of recognition by the doctors, but to public ignorance. Similar improvements in the prognosis of malignant melanoma have followed improved public education about sinister skin lesions in other countries. Thus the RCP report may well improve the melanoma mortality rate in the short term-but will it reduce the acreage of red skin this summer? .
1. Mackie RM, Elwood JM, Hawk JLM. Links between exposure to ultraviolet radiation and skin cancer. A report of the Royal College of Physicians. J R Coll Physicians Lond 1987, 21: 1-6. 2. Cooke KR, Skegg DCG, Fraser J. Socio-economic status, indoor and outdoor work and malignant melanoma. Int J Cancer 1984; 34: 57-62. 3. Lee JAH, Strickland D. Malignant melanoma, social status and outdoor work. Br J Cancer 1980; 41: 757-63. 4. Williams RR, Horn J. Association of cancer sites with tobacco and alcohol consumption and socio-economic status of patients. J Nat Cancer Inst 1977; 58: 525-35. 5. Beral V, Evans S, Shaw H, Milton G. Malignant melanoma and exposure to fluorescent lighting at work. Lancet 1982; ii: 290-93. 6. Whitehead M. The health divide: inequalities in health in the 1980s. London: Health Education Council, 1987
7. Mackie
RM, Aitchison TG. Severe sunburn and subsequent risk of primary malignant melanoma in Scotland. Br J Cancer 1982; 46: 955. 8. Beral V, Evans S, Shaw H, Milton G. Cutaneous factors related to the risk of malignant melanoma. Br J Dermatol 1983, 109: 165-72. 9. Spinilli JJ, Elwood JM, Gallagher RP, Hill GB. Pigmentation and skin reaction to sun as risk factors for cutaneous melanoma. Western Canada melanoma study. Br Med J 1984; 288: 99-102. 10. Waterhouse J, Muir C, Correa P, Powell J, Cancer Incidence in five continents, vol III. Lyon: International Agency for Research on Cancer 1976: 508-11, 542-43 11. Strickland PT. Photocarcinogenesis by near-ultraviolet (UV-A) radiation m Sencar mice. J Invest Dermatol 1986; 87: 272-75. 12. Doherty VR, Mackie RM. Reasons for poor prognosis in British patients with cutaneous malignant melanoma. Br Med J 1986; 292: 987-89. cutaneous