青少年黑色素瘤发病率增加

据4月16日在线发表于《儿科学》杂志的一项流行病学研究，自20世纪70年代以来，青少年中黑色素瘤的发病率一直以大约每年2%的速度增加，与成人相同。增加的原因尚不清楚，需要进行个体水平而非群体水平的研究以寻找产生这种趋势的原因。

近年来有研究证实，成人中黑色素瘤的发病人数有所增加，但无研究者对儿童期及青少年期的黑色素瘤进行评价。为此，国立癌症研究所癌症流行病学与遗传学科的Jeannette R. Wong等人分析了美国9大地区1973~2009年间的监测、流行病学与最终结果(SEER)数据库数据。他们查出了在20岁以下患者中诊断出的所有1,317例初发黑色素瘤。由于在非白人患者或种族不明患者中发生的恶性肿瘤极少，故分析中仅纳入了白人患者中发生的1,230例黑色素瘤。

分析结果显示，无论是男孩还是女孩，黑色素瘤的总体发病率都以平均2%/年的速度增加(Pediatrics 2013 April 16 [doi: 10.1542/peds.2012-2520])。女孩黑色素瘤的总体发病率大致为男孩的2倍(61% vs. 39%)，各年龄段的发病率相近(0~9岁，10~14岁，15~19岁)。发病率随年龄而增加。大多数黑色素瘤(77%)是在15~19岁的青少年中诊断出的，仅8%的黑色素瘤是在年龄≤9岁的儿童中诊断出的，其余15%是在10~14岁的儿童中诊断出的。局限性黑色素瘤的发病率远高于区域性(13%)或远处(2%)转移，或未分期的黑色素瘤(8%)。女孩中最常见的黑色素瘤发病部位是下肢和臀部，在整个研究期间，这些部位的黑色素瘤以3%/年的速度显著增加；而在男孩之中，黑色素瘤以面部和躯干部最多见，在整个研究期间以5%/年的速度增加。

究其原因，紫外线暴露似乎并不是导致黑色素瘤增加的主要因素。实际上，在紫外线暴露低的地域(比如康涅狄格州和华盛顿州)黑色素瘤的发病率略高于紫外线暴露高的地区(如夏威夷和加州)。然而，在整个研究期间，暴露于日光下的躯体部位的黑色素瘤发病率均有明显增加的趋势。该结果表明， 使用晒黑设备可能是发病率增加的一大原因，因为这类设备在低紫外线照射地区多得多。更多使用晒黑设备可能也是女孩黑色素瘤发病率比男孩高的原因。另外，也可能是由于近几年人们对黑色素瘤的警觉性增加，提高了儿童中黑色素瘤的检出率。

本研究的这些数据与既往相关研究一致。此前有研究者报道称澳大利亚、瑞典和英格兰儿科群体中黑色素瘤发病率增加。

尽管本研究纳入了30年以上有关黑色素瘤发病率的数据，但仍存在一定的局限性，例如未纳入个体水平户外紫外线暴露、晒黑设备使用以及黑色素瘤风险相关家庭因素方面的数据。

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By: MARY ANN MOON, Internal Medicine News Digital Network

Since the 1970s, the incidence of melanoma has been rising about 2% per year in adolescents, the same as it has in adults, according to an epidemiologic study published online April 16 in Pediatrics.

The reasons for this increase are not yet clear. Individual-level studies rather than population-level studies are needed to find the explanation for this trend, said Jeannette R. Wong of the division of cancer epidemiology and genetics at the National Cancer Institute, Rockville, Md., and her associates.、
 
Recent studies have documented the increase in adult melanoma cases and "illuminated likely contributing factors," but none have assessed childhood and adolescent melanoma, the researchers noted. They analyzed data from the Surveillance, Epidemiology, and End Results (SEER) database for nine U.S. geographic regions from 1973 through 2009. They identified all first melanomas diagnosed among patients aged 19 years and younger. 、

A total of 1,317 cases of melanoma were identified during the study period. Because few of the malignancies developed in nonwhite patients or in patients of unknown race/ethnicity, only the 1,230 cases that developed in white patients were included in the analysis.

The overall incidence of melanoma rose by an average of 2% per year for both boys and girls (Pediatrics 2013 April 16 [doi: 10.1542/peds.2012-2520]).

Melanoma was nearly twice as common in girls compared to boys overall (61% vs. 39%) with similar percentages within each age group (0-9 years, 10-14 years, and 15-19 years).

The incidence increased with age. The majority of melanomas – 77% – were diagnosed in adolescents aged 15-19 years. Only 8% of melanomas were diagnosed in children aged 9 years and younger, and 15% were diagnosed in those aged 10-14 years.

The incidence of localized melanoma was much higher (77%) than that of regional (13%), distant (2%), or unstaged disease (8%).

The most frequent melanoma sites in girls were the lower limbs and hips, on which melanomas increased by a significant annual percentage change of 3% over the study period. Among boys, melanomas were most common on the skin of the face and trunk, with annual percentage increase of 5% over the study period.

UVB exposure did not appear to be the primary factor contributing to the increase in melanoma, the researchers noted. In fact, melanoma rates were slightly higher in geographic areas that had low UVB exposure (such as Connecticut and Washington state) than in areas with high UVB exposure (such as Hawaii and California). "However, all significantly increasing trends for melanoma over our study period occurred in sun-exposed areas of the body," they said.

This finding suggests that tanning facilities may instead be a major source of the increase in incidence, because there are many more such facilities in low-UV regions, the researchers said.

Increased use of tanning facilities also may explain why the rate of melanoma is higher in girls than in boys, since girls are much more likely than boys to use such facilities, they added.

It is also possible that heightened awareness of melanoma in recent years has improved detection rates in the pediatric population, the researchers said.

These data are consistent with those of previous studies that have reported increasing rates of melanoma in the pediatric populations of Australia, Sweden, and England.

Although this study included more than 30 years of data on melanoma incidence, it was limited in that it did not include individual-level data on outdoor UV exposure, use of tanning facilities, or familial factors related to melanoma risk, the researchers said.