By Dr. Sanjay Gupta
It’s been more than four decades since the U.S. National Cancer Act was signed into law, marking the unofficial start of the “war on cancer.” Cancer death rates continue to decline, as a result of earlier diagnosis and improved treatment. Today, two out of three people with cancer are expected to survive. But the war is far from over. About 1.6 million new cancer cases are expected to be diagnosed and more than 580,000 Americans will die from the disease this year, according to the American Cancer Society.
Some of the most exciting breakthroughs in cancer research center around the genetic basis of the disease. In 2003, scientists completed the Human Genome Project, mapping nearly 25,000 human genes. Medical experts are exploring the complicated and infinite ways those genes mutate to cause cancer. The goal is to treat patients with personalized medicine, based on their individual genetics.
“The problem is that every cancer genome is different,” said Otis Brawley, MD, FACP, chief medical officer for the American Cancer Society. “The most important thing in this genomic revolution is that we’re no longer looking at genes — we’re looking at genomics.”
Genomics is the study of how genes interact. Healthy human cells divide and then die off, but cancer cells grow out of control. This cell proliferation is caused by a set of faulty genes or genetic mutations that’s unique to each cancer patient.
“The way to think of a genetic mutation is of a 400,000-letter word that is misspelled,” said Dr. Brawley. “There’s a host of ways I can misspell a 400,000-letter word.”
Thanks to cancer genomics research, women can take a simple blood test to detect the BRCA1 and BRCA2 gene mutations that raise breast cancer risk up to 80 percent and ovarian cancer risk up to 50 percent.
Patients who test positive have several preventive options. More intensive screening with mammography, ultrasound, and magnetic resonance imaging can spot early-stage cancers. Clinical studies have shown the drug tamoxifen may reduce the risk of developing breast cancer by as much as 50 percent. There are also prophylactic surgeries to remove at-risk tissue, such as the double mastectomy that actress Angelina Jolie had after discovering she carried the BRCA1 mutation, and oophorectomy or removal of the ovaries.
Cancer genomics is helping scientists develop treatments for certain types of cancer with rare gene expressions. The drug crizotinib, for instance, is effective in treating people with the anaplastic lymphoma kinase (ALK) gene mutation present in fewer than 7 percent of patients with non-small cell lung cancer.
Funded by the National Cancer Institute and the National Human Genome Research Institute, the Cancer Genome Atlas Program (CGAP) is a 3-year pilot program mapping the cancer genomes of 10,000 patients, and all their genetic “misspellings.”
“What the [program] is doing is trying to understand cancer,” said CGAP director Kenna Shaw, PhD. “We’re not just looking at the letters but also how the letters work. The reality is that CGAP is not a study that is meant to change clinical care today.” Shaw said researchers have completed 60 percent of the project, and she expects to have all 10,000 patients sequenced by the end of the year.
Cancer patients are becoming better educated, and they can access up-to-date information on gene mutations and related therapies. The website My Cancer Genome allows users to research their condition by its biomarkers and learn about experimental treatments or clinical trials.
Steven K. Libutti, MD, vice chair of surgery and director at Montefiore Einstein Center for Cancer Care, cautions that patients should not allow independent research to guide their treatment plan. “I don’t think patients should be going on their own to have their tumor sequenced,” said Dr. Libutti. “I think they’re going to wind up getting confused or frustrated.”
Harnessing the power of DNA has shed new light on cancer diagnosis and treatment, but some scientists like eminent biologist James Watson remain skeptical. Watson commented earlier this year that genetic research was “not likely to produce the truly breakthrough drugs that we now so desperately need.”
Libutti agrees current research has its limitations. Since there are multiple mutations in cancerous tissue, for example, it’s difficult to decipher which ones are driving the proliferation of cancer cells and which are just “passengers along for the ride.”
“It’s a little bit naive and over-simplified to think that by sequencing tumors you’re going to be able to determine which mutations are most important and therefore simply develop targeted therapies,” Libutti said. He points to other areas of cancer research that merit more exploration and funding, such as examining the microenvironment in which cancer cells grow.
As the American Cancer Society enters its second century, experts believe that even if personalized medicine doesn’t deliver a near-term cure, it can help change how we view the disease and patients’ prospects for survival. Cancer will no longer be a death sentence, according to Brawley. “What’s more likely in the next 50 to 100 years is that cancer will become a chronic condition like diabetes.”
Last Updated: 05/22/2013