Swanton and his colleagues also analyzed tumor tissue samples from another three patients with kidney cancer. From a total of 30 biopsies from all four patients, 26 tissue samples had mutations that were highly heterogenous, or varied, from one another.
Some advances have been made using targeted treatments. Tarceva (erlotinib) treats non-small-cell lung cancer by inhibiting epidermal growth factor receptor (EGFR) gene, and Herceptin (trastuzumab) is used to target breast cancers that are human epidermal growth factor receptor 2 (HER-2)-positive.
But once cancer has metastasized, it remains notoriously difficult to treat, Swanton said. "We have not made huge progress in curing advanced metastatic solid tumors over the last decade, despite the new array of targeted therapies," he noted.
The heterogeneity of tumors is likely one reason why, he added.
The targeted drugs that work probably target some ubiquitous, or common, mutations, such as HER-2 or EGFR. "Different parts of the tumor can evolve independently," he said. "What we think is that the drugs that are working are hitting the mutations that are present at every site of the disease."
Moving forward, the key may be figuring out what those common mutations are and targeting drugs there, he added. But finding those targets will be challenging, he added. One patient, he said, had three mutations in the same gene occurring in three regions of the primary tumor. And tumor cells also develop resistance to medications.
"The level of complexity is sobering in the extreme," he said.
Dr. Len Lichtenfeld, deputy chief medical officer for the American Cancer Society, called the research "elegant, important work."
"Cancer is not just a single mass of tissue that has the same genetic signature throughout it. There are chang
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