Environmental factors, such as smoking and severe sunburn, were more important than genetic factors in establishing risk for melanoma in older patients, according to the findings of an observational case-control study.
The study also found that melanoma risk factors in older patients (aged 60 and older) were different than those already established for a younger population. Other risk factors cited included prolonged occupational sun exposure, blond or red hair, and a personal (but not family) history of nonmelanoma skin cancer, noncutaneous neoplasia, or melanocytic nevi.
"The most striking differences in melanoma incidence and mortality occur in the elderly," wrote Dr. Eduardo Nagore of the department of dermatology at the Instituto Valenciano de Oncología, Valenica, Spain, and his colleagues. In the United States, for example, the melanoma mortality rate in older patients increased 157% from 1969 to 1999, with a nearly fivefold increase in incidence in older men.
Thicker melanomas were found to be associated with agingbearing in mind that Breslow thickness is the most accurate prognostic tool in cutaneous melanoma; lentigo malignant melanomas and acral lentiginous melanomas are more prevalent in this age group; and aging itself, independent of Breslow thickness, ulceration, and node metastases, is an independent prognostic factor.
For the current study, the investigators selected consecutive melanoma patients who visited the institute in Valenica for the first time or for a control visit. To be included, they had to be aged 60 years or older and have a diagnosis of melanoma that had been histopathologically confirmed. The final sample after deaths and loss to follow-up was 160 patients (54% men, median age 68 years). There were 318 controlstwo age- and sex-matched controls for each melanoma case, except for one, a 96-year-old man (J. Eur. Acad. Dermatol. Venereol. 2009 June 26 [doi:10.1111/j.1468-3083.2009.03353.x]).
The data for both cases and controls were derived from an interview and a physical examination by two dermatologists. Details of the following were obtained: intermittent sun exposure, such as during sunbathing or sports; occupational sun exposurechronic exposure from an outdoor job such as gardening, farming, or sailingand the duration in years; the lifetime number of episodes of severe and light sunburns; smoking history; personal history of noncutaneous neoplasias and nonmelanoma skin cancer; family history; phototype; and hair and eye color.
In the physical examination, the investigators recorded number of melano-cytic nevi of more than 2 mm in diameter and the presence of solar lentigines and actinic keratoses.
The results of univariate comparisons between the cases and the controls showed that a higher proportion of melanoma patients had blue or green eyes, blond or red hair and a low phototype, and a history of sunburns. A higher percentage of melanoma patients also reported having had many years of occupational sun exposure and having smoked, and there was a higher prevalence of solar lentigines, actinic keratoses, and melanocytic nevi, and of a personal history of nonmelanoma skin cancer and other noncancerous neoplasias, the authors reported. However, not all of these factors showed significance in multivariate analyses.
"Chronic sun exposure and smoking seem to be a risk factor of developing melanoma in the elderly in contrast to the entire population," wrote the authors, who also put the number of lifetime severe sunburns in this category. "On the other hand, broadly demonstrated melanoma risk factors such as low phototype, fair eye color, and family history of melanoma have not shown significance in patients" aged 60 or older.
In addition to chronic sun exposure and smoking, lifetime severe sunburns, blond or red hair, the number of melanocytic nevi, and personal history were statistically significant in the multivariate analyses, whereas solar lentigines and actinic keratoses and intermittent sun exposure were not.
The authors emphasized the importance of these findings in the context of a progressively aging population. However, they cited their use of self-reported data, selection bias, and small sample size as limitations of the study and said that further studies are needed.
None of the authors disclosed any conflicts of interest.