Editor's Note: Forty years ago this month, humans landed on the moon for the first time. We asked Christopher Wanjek why, four decades later, we can't cure cancer.
Will we ever win the war on cancer?
Richard Nixon had every reason to be optimistic when, during his 1971 State of the Union address, he called for a concerted effort to find a cure for cancer. After all, it took only three years for the Manhattan Project to produce the world's first atomic bomb. Nixon's own presidency witnessed the 1969 moon landing, a goal set forth by John F. Kennedy in 1961.
It seemed that given enough resources there was no job that Americans couldn't tackle quickly.
But with $200 billion spent and tens of millions of cancer deaths accumulated since 1971, most would say we are losing the war on cancer. Cancer is the top killer worldwide, responsible for 7.4 million or 13 percent of all deaths annually. In America cancer will soon overtake heart disease as the top killer, claiming more than half million lives annually.
The situation isn't entirely grim. We've made some strides, and new research on stem cells, immunotherapy and genomic medicine offers much hope.
But don't except the war to end anytime soon. We're only really very good at curing mice of cancer. The stumbling block has been translating basic science into human therapies.
Success is in the wording
Part of the reason for having no cancer "cure" is semantics. There will never be a single cancer cure because cancer refers to a family of more than 100 different diseases characterized by abnormal cell growth. These diseases arise from numerous causes, such as ionizing radiation, chemicals or even viruses. Different cancers call for different treatments.
Indeed, there are successful treatments. The greatest advancements have been in the area of childhood cancers. Childhood leukemia used to kill about 80 percent of kids with the disease. Today more than 80 percent survive. Similarly, testicular cancer once claimed 95 percent of its victims; today upwards of 95 percent survive.
Overall, during the mid-1970s, the five-year survival rate among adults for all cancers combined was 50 percent; today it is about 65 percent.
Admittedly this isn't that impressive given the amount of resources spent. Most of the success, actually, is not from miracle cures but rather simple screening procedures such as pap smears and colonoscopies, which detect cancer early when it is easier to treat.
Elusive foe
Cures for the major killers, such as cancers of the lung, breast and liver, remain elusive primarily because of the unpredictable nature of cancer cells.
When a normal cell divides, the cell's DNA is copied more or less perfectly. But each division of a cancer cell brings about new changes in the DNA. So a drug might be able to kill some but not all of the cancer because each cell is a little different.
More disconcerting is the ability of a cancer stem cell to hide. Chemotherapy might effectively kill an entire tumor, but cancer stem cells might evade the drugs and cause a relapse of the cancer years later.
Another problem is the lack of good animal models. Treatments rarely work well in humans because, among many issues, it is difficult to gauge the possibility of relapse years later when a mouse only lives two years.
Victory within reach?
Despite nearly unanimous acknowledgment among scientists that cancer is winning the war, optimism abounds. One powerful new tool is genomic medicine, which targets faulty genes or their pathways responsible for various kinds of cancers. Herceptin is one such miracle drug that blocks a faulty gene pathway found in 30 percent of breast cancers.
Immunotherapy is another new approach that stimulates immune cells to enhance their anticancer activity. Researchers use stem-like immune cells to kill large tumors, but so far only researchers and mice are benefiting from this.
The emerging field of cancer stem cells might lead to big advances, too. These are the cells thought to give rise to tumors. They often have unique markers on their surface, so drugs could be designed to target and destroy them. Also, biomarkers, such as PSA, a predictor of prostate cancer, can be used to detect cancers at their earliest stages. Much research is focused on identifying more biomarkers.
Many "cures" are at hand. Eliminating smoking would essentially end lung cancer, responsible for 30 percent of all cancer deaths. A diet rich in vegetables and whole grains reduces your cancer risk significantly.
Nevertheless, I write these words as two family members are dying from cancer.
No comments:
Post a Comment