Why Have Cancers Not Yet Been Completely Cured?

Today, more than 50% of all cancers are preventable and 2 out of 3 can be treated . Given this, successes rather than failures are now being discussed—and should be discussed—when it comes to cancer. Scientists around the world take important steps every day to improve cancer outcomes further. Nevertheless, cancer remains the most complex group of diseases we face.

"Ignorance is the greatest enemy to be defeated..." M. K. Atatürk

Despite major advances in many areas of medicine, there are many claims that progress against cancer has been slow. Although extraordinary efforts and hundreds of billions of dollars have been devoted to treating and understanding cancers, especially over the last 40 years, more than 10 million people die from cancer annually. Why, then, can cancers still not be completely cured?

There Are 3 Main Reasons Cancers Have Not Yet Been Completely Cured:

1. This group of diseases involves thousands of molecular and genetic mechanisms of many types, some still not clearly understood;
2. Cancers organize themselves within a complex tumor microenvironment in the human body; and
3. Cancer cells behave almost like intelligent organisms, adapting rapidly to environmental conditions and consequently developing resistance to drugs.

The discovery of chemotherapies , the first drugs used to treat cancer, dates to World War 2. The marked fall in white blood cell counts in people exposed to mustard gas suggested that these chemicals might be used against rapidly proliferating cells such as cancer cells. Different chemicals were therefore tested on tumors, and newly discovered drugs (chemotherapy) partially eliminated them. Yet chemotherapy’s tumor-shrinking or tumor-destroying effects were limited, and cancers frequently recurred. This also created an interesting situation: efforts were being made to develop treatments before cancer’s causes and mechanisms of development were understood.

According to World Health Organization statistics:

• 8,2 million people die from cancer each year (13% of all deaths)
• Newly diagnosed cancer cases are expected to rise by 70% in 20 years
• Cancer is not a single disease: there are more than 100 main cancer types, exceeding 1000 when subtypes are included, and each has its own diagnosis and treatment

With the great acceleration of science from the 1970s onward, serious efforts began to investigate and understand cancer’s causes. We owe great thanks to those who advanced our knowledge of cell biology and genetics. This has enabled the development of targeted smart drugs that recognize particular features of cancer cells at the molecular level.

A cancer diagnosis does not mean a person will soon die; first, we must overcome this fear with its thousands of years of history. We certainly do not claim all cancers can be treated, but advances in treatment cannot be ignored. As recently as the 1970s, only 1 in every 3 cancer patients survived at least 5 years; today, 2 in every 3 live at least 5 years.

The graph above summarizes progress in cancer medicine. As shown, averaged across all cancer types, 5-year survival rates, which express complete recovery from the disease, approach 70%. Although progress has been slower for cancers such as lung, liver, and pancreatic cancer, after 2013 cancer immunotherapies entered clinical practice, lung cancer survival rates also began showing rapid improvement.

Childhood cancers and breast cancers are now treated successfully much more often than before, many even completely cured. Yet much work and many important steps remain—for example, discovering what other routes cancer cells use to evade the immune system beyond those already known.

Another important development in recent years is the growing understanding of cancer as a group of diseases triggered by molecular mechanisms caused by specific gene mutations , rather than a disease specific to individual organs.

An example will make this clearer:

Cells have a protein called EGFR on their surface. This receptor normally helps cells grow and multiply. Due to a genetic mutation, some lung cancer cells carry excessive EGFR on their membranes, causing them to proliferate faster. EGFR inhibitors are new-generation targeted smart drugs (such as erlotinib = Tarceva) that can interrupt EGFR protein signals driving continual cell division. This can prevent cancer growth and spread. Studies have found EGFR mutations not only in some lung cancers but also in cancers of other organs, such as the pancreas, colon, and brain. In this situation, the disease can be called “EGFR-positive cancer” rather than “cancer of the ... organ.” Similar examples exist for Her2 mutations (such as using a medicine developed for breast cancer in stomach cancer).

However, mutations can also occur in different regions of the same EGFR protein. As we know, proteins consist of amino acids . Changing a single amino acid causes a protein to lose its function. Consequently, even EGFR-positive cancers have subgroups, reducing the effectiveness of targeted treatments. In other words, drugs targeting a mutation in a single region of the EGFR protein do not target other mutations.

In summary, our point is that cancers are a highly complex group of diseases involving numerous molecular mechanisms, organized within a microenvironment, and capable of developing resistance to treatment. It therefore stretches the imagination to think that a single drug, a single approach, or particularly the alternative products much debated recently (such as herbal extracts) could completely cure especially advanced cancers.

A promising new form of cancer treatment effectively reprograms the body’s immune system to fight cancer: immunotherapy. In fact, activating the immune system to treat cancer is a very old idea (for example, Coley’s toxins). However, interactions between cancer and immune cells have only recently been understood at the molecular level, and medicines capable of intervening in this relationship have only recently been developed.

Immunotherapies have shown effectiveness in many advanced cancers, particularly melanoma, lymphoma, kidney, lung, bladder, and head and neck cancers, achieving especially long-lasting disease control in some patients. Nearly half of patients using immunotherapy medicines are currently participating in clinical trials. Developing tests to predict who will benefit from immunotherapies and new-generation targeted drugs is another focus of cancer research.

It is indisputable that cancer drugs developed so far (chemotherapies, hormonal therapies, targeted drugs, and immunotherapies), alongside surgery and radiotherapy, are slowly but steadily extending our patients’ lives! Although the world cannot yet completely cure many types of cancer, in the coming decades, especially as personalized medicine and one example of it, precision oncology mature, our hope that cancer can become a survivable disease is stronger than at any other time in history.

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