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By almost every measure, an analysis of four European studies found that women can expect a 30 percent better outcome than men following an early stage melanoma diagnosis. That gap, researchers say, may be rooted in basic differences in gender biology.
"The 30 percent advantage applies to survival," said study author Dr. Arjen Joosse, from the department of public health at Erasmus University Medical Center in Rotterdam, the Netherlands. "It also applies to having a metastasis [spread]: women have a 30 percent lower chance to experience a metastasis to the lymph nodes and to other organs."
Joosse and colleagues from Belgium, Switzerland, Germany and France published their findings in the April 30 online edition of the Journal of Clinical Oncology.
In an editorial accompanying the study, Dr. Vernon Sondak, chair of the department of cutaneous oncology at the Moffitt Cancer Center in Tampa, Fla., noted that just over 70,000 Americans were diagnosed with invasive melanoma in 2011, and about 43 percent of those were women. But, among the roughly 8,800 melanoma-related deaths that year, only 35 percent were female patients.
Joosse noted that the fact that women tend to fare better than men following a melanoma diagnosis is a well-established observation based on prior research, some of which was conducted by the current study team. However, the reasons behind the prognosis gap have remained elusive.
And the new research found an association between gender and melanoma survival, not a cause-and-effect.
To explore the question, Joosse and his team analyzed data concerning nearly 2,700 melanoma patients that was gleaned from four different melanoma treatment trials conducted in Europe.
All of the male and female melanoma patients had been diagnosed with either stage 1 (early) or stage 2 (localized) cancer. During and following treatment, all the patients were tracked for disease remission, relapse, spread and death.
The result: male melanoma patients were found to have worse disease characteristics at diagnosis and worse disease progression.
On the latter measure, female patients were found to have a "highly consistent and independent advantage" over men in terms of overall survival, both before and after menopause.
The sole exception was seen in cases of head and neck melanomas, where the gender differences disappeared. But the team cautioned that even this exception could ultimately be dismissed as misleading, due to key study peculiarities.
In theory, estrogen level differences could play a role, although the team noted that the evidence so far suggests the hormone does not have much effect on melanoma.
Other possibilities include gender differences with respect to vitamin D metabolism, immune system function, male testosterone levels and what is known as "oxidative stress" in the body.
"However, our data could not support or disprove any of these hypotheses," Joosse acknowledged.
Sondak said that while the gender gap is probably real, it is likely a function of both biology and environment.
"I believe that the message here is that if you're a man, think like a woman," said Sondak. "And that's because most of us feel that a big part of this has to do with the fact that women are a little more likely to be paying attention to their skin and to notice something on their skin, and most importantly, to do something about it right away. And with melanoma, early detection is key," he stressed.
"So, I think in large part this is a behavioral issue, not a genetic issue," Sondak added. "However, that's not the whole issue. It is also the case that what we now call melanoma, one disease, may actually be many different diseases caused by many different things. And with that there may be genetic differences, all else being equal, in how men and women get these different diseases in the first place. This study didn't look at that. But that's another important aspect to consider."
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