Medical advances continue to help in cancer fight
As oncologists, we are often asked if we are really curing cancer. People normally ask for one of three reasons: 1) They think of cancer as one disease that can be cured with a few specific therapies. In reality cancer encompasses hundreds of diseases with overlapping molecular abnormalities. 2) They are frustrated with the often-touted “cancer breakthroughs” that are perceived as panacea cures. 3) Death rates from cancer are not changing rapidly. So what is the real story? Since President Richard Nixon declared the war on cancer in 1971, our successes have clustered in particular decades.
In the 1970s and 1980s, progress came from innovations in surgery, radiation therapy, chemotherapy and bone marrow transplantation. These advances increased cures in childhood cancers, leukemias, lymphomas and several types of solid cancers.
The 1990s were an era of major progress with the development of targeted therapies that focused on particular molecules on the surface of cancer cells. Discoveries in this area include the antibody rituximab, which targets certain forms of lymphoma and leukemia. Other related therapies target solid tumors. The antibody trastuzumab targets the product of a gene in breast cancers, and cetuximab (discovered by John Mendelsohn with Gordon Sato) disrupts a signaling system which stimulates cancer cells to grow and proliferate. These deliveries gave a boost to the concept of “targeted” drugs and “individualized therapies” for individual cancers.
The past three decades witnessed a quantum leap in understanding the molecular causes of cancer. Since 2000, targeted drugs, beginning with “tyrosine kinase inhibitors,” were developed to disrupt cancer cell signaling pathways. The most successful drug was imatinib (Gleevec), which revolutionized the treatment of chronic myeloid leukemia. Today, there are more than two dozen approved antibodies and drugs for cancer treatment, based on these approaches.
Thankfully, the current decade appears to hold more promise than any in the past. The pace of drug discoveries is increasing as more abnormal molecular signals and pathways are discovered.
In 2013, the journal Science designated cancer immunotherapy as its breakthrough of the year. This is an area where M.D. Anderson is considered a research leader.
Simply stated, this research aims to re-energize the body’s immune cells (T-lymphocytes) so they can more effectively recognize and kill cancer cells, much like soldiers who seek out and kill foreign enemies. One such new drug is ipilimumab, which produces lasting remissions in 20 percent of patients with metastatic melanoma, a previously deadly skin cancer.
These incremental advancements over the decades have improved cancer survival. Patients with acute leukemia, previously a fatal disease, now have cure rates of 40 percent to 90 percent; those with some types of aggressive lymphoma have cure rates of 60 percent to 80 percent. The drug imatinib improved 10-year survival in chronic myeloid leukemia from 20 percent to 90 percent. Survival rates for five years or longer have increased in many types of cancer and have doubled in our lifetimes. Tumors previously resistant are now responding to new treatments.
If we are serious about reducing cancer rates and deaths, we also need to get serious when it comes to prevention.
For example, smoking causes nearly one in three cancer deaths in the United States, and one in five deaths. The good news is that Americans have reduced smoking by 50 percent over the past four decades, and deaths from lung cancer are falling. However, we should remain vigilant: The tobacco industry continues to develop new filters and cigarette papers to enhance the delivery of nicotine to the lungs, leading to more addiction.
Obesity, on the increase, contributes to the risk of 20 percent of cancers. This could be reduced with education and application of information about healthier diets and exercise.
The human papilloma virus (HPV) causes 5 percent of cancers (cervix, oropharynx, others), and liver cancer in China is due primarily to hepatitis B virus. New vaccines can prevent most of these cancers.
Two-thirds of stomach cancers, the second-most common cancer worldwide, are caused by a bacterium, Helicobacter pylori. Treating this bacterial infection early with antibiotics has reduced the occurrence of both stomach ulcers and cancers.
While there is no doubt that the war on cancer is challenging, the answer to the question “are we winning the war on cancer?” is a definite “yes.”