Why haven’t doctors found a cure for cancer? It’s complicated


Cancer affects almost everyone – one in two men and one in three women can expect to be diagnosed with cancer at some point in their lives.

This is why so many people are personally committed to fighting it, from the hospital to the lab, and through generous donations of time and philanthropic support. Since 1971, when President Nixon declared a “War on Cancer” and signed the National Cancer Act, the United States has spent billions of dollars on cancer research.

Then why is there no cure? Will there ever be a cure, and how much longer will it take us to find one? The answers are complex. But here’s what’s clear: Progress over the past decade has been exponential and patients are benefiting from it.

First, it is important to know that we are not seeking a cure. Cancer is not a single disease, but a collective group of more than 200 diseases that differ from each other and arise from different causes that respond differently to treatment. Ironically, the more we learn, the more cancers we find! It is unlikely that we will find a universal remedy that effectively treats all types of cancer. We also need to rethink the word “heal”. We may not be able to cure all cancers, but treat them as a chronic disease, such as diabetes.

Understanding the differences between tumor subtypes through cancer research has led to great advances and increased cancer survival rates. For example, there are two main types of lung cancer, non-small cell lung cancer and small cell lung cancer, as well as additional subtypes within these categories. The different tumor subtypes may not come from the same parts of the lungs, grow or spread at the same rate, or respond to the same treatments. Breast cancer is not a single disease, but at least five major cancer subgroups, all requiring different therapeutic interventions.

In addition, cancer is as unique as each individual as it is influenced by complex factors unique to each individual. Cells do not grow independently of their environment, but are strongly influenced by the biome or ecosystem in which they live. For example, cancers that have spread (metastasized) to the bone can act very differently from the same cancer that has spread to the liver. The biome includes the microenvironment that directly surrounds the tumor, the patient environment affected by factors such as genetics, and the physical community affected by the foods we eat, living conditions, stress, and socio-demographic factors.

Scientists are still making discoveries about the basis of cancer development and progression, which provide insights and breakthroughs that we can translate into new therapies for patients.

It can take decades for these breakthroughs to develop into safe, effective treatments for patients – and sometimes what works in the lab doesn’t translate to people. But we see these efforts paying off. Between August 1, 2018 and July 31, 2019, the U.S. Food and Drug Administration approved 17 new cancer drugs, according to the American Association for Cancer Research’s Cancer Progress Report 2019. The FDA also issued 10 new approvals to treat additional cancers for previously approved therapies in this short time frame.

We are taking major steps against cancer on several fronts. For years, surgery, radiation therapy, and chemotherapy were the only cancer treatment options. Now there are other options, such as immunotherapy or targeted therapies, many of which have only been approved by the FDA in the past decade.

While we often rely on the standard treatments as they are still the most effective therapies in many cases, we have improved them. For example, we have found that a shorter chemotherapy treatment works just as well as a longer one to treat certain cancers. Numerous clinical trials are underway to confirm that a combination of older and newer treatments, such as chemotherapy and immunotherapy, are more effective together than both on their own.

We are also getting much better at preventing cancer and screening for early detection.


Karen E. Knudsen, Ph.D.

The HPV vaccine is a remarkable step forward. HPV infection causes almost all cases of cervical cancer and many cases of other cancers, including head and neck, anal, vaginal, and penile cancers. The vaccine can prevent these cancers from ever developing.

While smoking is still the leading preventable cause of death in the United States, the smoking rate, which was 42.4% in 1965, is the lowest it’s ever been – and it continues to decline. In 2017, 14% of adults in the US were smokers, compared to 20.9% in 2005, according to the Centers for Disease Control and Prevention. The next best thing to prevent cancer completely is to detect it early, when it is more treatable. Breast, prostate, cervix, colorectal, lung, and skin cancers can all be screened and have a very good survival rate if caught early.

Finally, genetic testing to identify heritable gene mutations that increase cancer risk is an evolving field related to cancer prevention and early detection. Researchers are gaining a better understanding of hereditary cancers as they develop methods to better identify people who should undergo genetic testing. Philadelphia is proud to have opened the first gentlemen clinic for genetic testing for prostate cancer in the country, housed at the Sidney Kimmel Cancer Center in Jefferson.

Most importantly, these collective advancements have drastically improved cancer prevention and care. As recently as the mid-1970s, the relative five-year survival rate among adults for all cancers combined was only 50%. Breakthroughs in cancer research and cancer care have improved survival rates to an average of 68%, with some cancer diagnoses further exceeding that average. For example, some early stage Hodgkin lymphomas and cervical cancers have a relative survival rate of over 90% at five years. In some early stage melanomas, breast, prostate, testicular and thyroid cancers, the relative five-year survival rate is more than 95%.

We have the privilege of treating these patients every day and they are a wonderful reminder that the small, steady steps of the past 40 years have really made a difference. The National Cancer Institute’s outstanding cancer centers in Philadelphia have been at the forefront of cancer research and clinical trial discoveries that continue to improve lives and accelerate the path to cancer cure.

Karen E. Knudsen, Ph.D., corporate director at the Sidney Kimmel Cancer Center – Jefferson Health, oversees cancer care and research at all SKCC locations in the Greater Philadelphia area. She occasionally writes on topics related to cancer.

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