Basal cell carcinoma is the most common form of skin cancer, with nearly one million new cases diagnosed each year in the United States. A diet that contains even a small protective factor may have great public health impact, the researchers said.
"Our study indicates that coffee consumption may be an important option to help prevent basal cell carcinoma," said lead researcher Fengju Song, a postdoctoral fellow in the department of dermatology at Brigham and Women's Hospital and Harvard Medical School in Boston.
"The amount of caffeine consumption was inversely associated with risk," Song said, meaning the more coffee consumed, the lower the risk of skin cancer.
The study could not prove cause-and-effect, however, and at this point the finding remains an association only.
Decaffeinated coffee was not associated with a decreased risk of basal cell carcinoma, and the researchers said any protective effect would likely be because of caffeine, a stimulant.
Other types of skin cancer
The study authors also expressed surprise that coffee did not reduce the risk of two other types of skin cancer, squamous cell carcinoma and the less common but potentially deadly melanoma.
Earlier experiments in mice found caffeine helped reduce the development of squamous cell carcinoma by eliminating cells damaged by ultraviolet radiation, but that effect was not seen in the current study.
The results were scheduled for presentation at an American Association for Cancer Research International Conference in Boston.
For the study, Song's team collected data on nearly 113,000 adults – almost 73,000 women who took part in the US Nurses' Health Study and almost 40,000 men who were part of the Health Professionals Follow-Up Study.
Over more than 20 years of follow-up, more than 25,000 cases of skin cancer were diagnosed among the men and women in the studies. Of these, about 23,000 were basal cell carcinoma, about 2,000 were squamous cell cancer and 741 were melanoma.
The researchers found that women who drank more than three cups of coffee a day had a 20% lower risk of developing basal cell carcinoma compared with women who drank less than one cup of coffee in a month.
For men, the risk was 9% lower for those who drank three cups of java daily compared with those who drank less than one cup a month, Song's group noted.
The risk for women who drank the most coffee was lowered 18%; for men who downed the most coffee, the risk was reduced 13%, Song's team found.
Additional studies exploring the mechanism behind this association are needed, Song said. People who spend a lot of time in the sun are more likely than others to develop skin cancer, but coffee's role in prevention is still not understood.
Dr. Robert S. Kirsner, professor and vice chairman of dermatology and cutaneous surgery at the University of Miami Miller School of Medicine, said the findings "could open a new avenue of developing chemo-prevention for non-melanoma skin cancer."
However, Kirsner doesn't advise starting to drink coffee solely to prevent skin cancer.
Although basal cell carcinoma is rarely fatal, there may be consequences of treatment, including disfigurement, especially if it is ignored, he said.
Because it is so common, the cost of treating basal cell carcinomas is "huge", he added. Prevention would affect overall health funding.
"Also, some evidence suggests that having one type of skin cancer makes other cancers more likely," Kirsner said. "The obvious ones are other skin cancers, but also non-skin cancers, for example, lymphoma or testicular cancer.
The question is, is this just by chance, or is it a shared risk factor, or is it something basal cell carcinoma induces that makes it more likely for those cancers to develop?" he said.
"Preventing a basal cell carcinoma may have other benefits than just preventing that cancer," Kirsner added.
Research presented at meetings should be considered preliminary until published in a peer-reviewed medical journal.
(HealthDay, Steven Reinberg, October 2011)