Patients with a family history of melanoma were at significantly greater risk for developing melanoma and other skin cancers, especially on the trunk and extremities, an analysis of prospective cohorts suggests.
In a meta-analysis of three cohorts of white patients, individuals with a history of melanoma in a first-degree relative had a 74% higher risk of developing melanoma compared to those who reported no such family history (adjusted HR 1.74, 95% CI 1.45-2.09), reported Erin Wei, MD, of Harvard Medical School in Boston, and colleagues.

As described in the Journal of the American Academy of Dermatology, this increased risk was observed for melanoma lesions occurring on the trunk (HR 1.94, 95% CI 1.59-2.36) and extremities (HR 1.83, 95% CI 1.57-2.14).

Risk of squamous cell carcinoma (SCC) was also 22% higher in patients with a family history of melanoma (HR 1.22, 95% CI 1.07-1.40), though this applied only to SCCs on the extremities, the study authors pointed out.

Similarly, patients with a family history of melanoma had a 27% greater risk of developing basal cell carcinoma (BCC) compared to those with no family history of melanoma (HR 1.27, 95% CI 1.12-1.44).

“This study tells us that anyone with a first-degree family member with melanoma is at increased risk for all skin cancers,” Wei told MedPage Today in an email. “We should both educate individuals who have melanomas to educate their family members about sun safety behaviors and routine skin checks, and educate those with first-degree relatives with melanoma to participate in routine skin cancer screenings.”

The group examined data on 216,115 participants from the Nurses’ Health Study, the Nurse’s Health Study II, and the Health Professionals Follow-up Study — who were prospectively followed for over 20 years — to estimate the association between family history versus personal history of melanoma and other skin cancers.

In all three studies, participants were asked to provide information about the melanoma and skin cancer history of first-degree relatives, namely parents and siblings, at repeated interludes over time. Over the long-term follow-up, a total of 1,688 cases of melanoma, 2,905 cases of SCC, and 30,613 cases of BCC were documented.

“Having a family history of melanoma was significantly associated with an increased risk of melanoma in all three cohorts,” the investigators observed. “The associations were not materially changed in the multivariable-adjusted models.”

They noted that while the association between truncal melanoma and family history of melanoma was seen in both men and women, upper and lower extremity melanomas had a strong familial association in women (HR 1.90, 95% CI 1.39-2.62).

“These findings are in agreement with the fact that in the general population, melanomas are more commonly found on the trunk for men and lower extremities in women, and suggest a significant environmental component to melanoma development in our cohorts,” the authors noted.

Wei’s group did try to determine how much of the observed association between family and personal history of melanoma might be explained by distinct ultraviolet (UV)-related factors. After controlling for intrinsic UV-related factors — including hair color, childhood reaction to the sun, a history of childhood tanning, and mole count — they observed a greater change in the risk of developing melanoma in those with a family history of melanoma compared to any change caused by extrinsic UV-related factors such as number of sunburns, average sun exposure, and ambient UV flux.

“This suggests that intrinsic UV-related factors explain a higher proportion of the association between family history of melanoma and risk of melanoma than the extrinsic variables,” they noted.

However, when they analyzed the association between family history of melanoma and the risk of SCC or BCC, the same observation did not hold true in that the proportions explained by intrinsic UV-related factors were exactly the same as those explained by extrinsic-related factors.

“Familial risk for melanoma may be at least in part due to shared sun protective habits between family members, as one of the most important extrinsic factors, UVR [UV radiation] is a key factor in initiation of DNA damage and development of skin cancer in all skin types,” the authors wrote, and suggested that UVR-induced suppression of the immune system may also contribute to the development of skin cancer.

One might think that having a close family member who’s already diagnosed with melanoma might encourage other family members to pay particular attention to sun-protective behaviors but this apparently is not always the case, Wei’s team noted, as at least one study found that only about one-third of patients with a family history of melanoma indeed did avoid the sun as recommended.

Limitations of the study included the fact that all data was self-reported and subject to detection bias.

[Source: MedPage Today]