Spontaneous Remission of Cancer Incidence and Causes

Spontaneous remission of cancer is defined as the remission of cancer without any treatment, or with treatment that would not be expected to cause a tumor to decrease as much as it does. Spontaneous remission may be partial or complete and may be temporary or permanent.

It's unclear what triggers this phenomena. However, many reports have linked spontaneous remission to certain types of infection or hormonal changes.

This article discusses the potential causes of spontaneous remission, as well as how often it occurs.

How Often Spontaneous Remission Happens

Though we have clearly documented cases of spontaneous regression, it's hard to know how common this phenomenon actually is. There are over a thousand case studies in the literature.

In addition to those studies, which document a cancer that goes away without any treatment, it's not clear how often a cancer may go away despite treatment or at least decrease in size despite treatment. Some have estimated the incidence to be roughly one out of 100,000 people. However, it's difficult to know if that number is even in the ballpark.

Some types of tumors have a higher rate of spontaneous remission, such as neuroblastomas, testicular cancers, renal cell carcinomas, melanomas, and lymphomas. Spontaneous remission has also been reported in breast cancer and lung cancer.

While most studies of spontaneous remission look back in time trying to determine why a cancer simply went away, a 2008 prospective study suggested that spontaneous remission is much more common than we think.

A study published in the Archives of Internal Medicine looking at screening mammography raised the hypothesis that some breast cancers detected by mammograms may spontaneously regress. Further research is needed in order to clarify this hypothesis.

Since these tumors did not present with any symptoms (such as feeling a lump), it would have been difficult to detect invasive cancer without screening. Because there aren't screening methods for many types of cancers, it's possible for early invasive cancers to occur and go away before a diagnosis can even be made. That said, spontaneous remission may be more common than we think.

What Causes Spontaneous Remission of Cancer?

Researchers are not entirely sure of the molecular basis behind spontaneous regression of cancer. Theories range from spiritual reasons to immune causes. That said, an immunologic basis could certainly make sense.

Infection and the Immune System

Looking at people who have had a spontaneous remission of their cancers, it's quickly noted that most of these regressions are associated with an acute infection. Infections often result in a fever and stimulation of the immune system.

We know that our immune systems have the ability to fight off cancer. That is, in fact, the logic behind immunotherapy. 

Immunotherapy medications, while still in their infancy, have resulted in dramatic remissions of cancer for some people, even in the advanced stages of cancer. These drugs work in different ways, but a common theme is that they essentially enhance the ability of our own immune systems to fight cancer.

Infections that have been associated with spontaneous remission include diphtheria, measles, hepatitis, gonorrhea, malaria, smallpox, syphilis, and tuberculosis.

Hormonal Changes

Some cases of spontaneous remission may be triggered by hormonal changes. This type of remission has been linked to certain types of cancer, including breast and prostate cancers.

There has also been a report about a person who experienced complete natural remission of her endometrial and ovarian cancers following pregnancy and childbirth. Researchers think this may have been related to the high levels of progesterone occurring during pregnancy.

Case Reports of Spontaneous Remission

Lung Cancer

A 2010 report in Surgery Today brought up what others have found in the past, and what is well documented as a spontaneous remission from lung cancer.

A 69-year-old woman was found to have lung adenocarcinoma, a form of non-small cell lung cancer. Her cancer had spread to her adrenal glands—adrenal metastases—and therefore, was labeled as stage IV non-small cell lung cancer. Stage IV lung cancer is the most severe stage of the disease with the poorest survival rate.

One month following her diagnosis, and before she had any treatment, both the tumor in her lung and the metastasis to her adrenal gland had shrunk considerably on both a CT scan and a PET scan. She then underwent surgery for lung cancer and was doing well 14 months later.

Neuroblastoma

A 2023 report published in the International Journal of Clinical and Experimental Medicine describes the case of a 2-month-old female who was found to have two large adrenal masses (and liver metastases) on CT.

A biopsy of the liver tissue confirmed a diagnosis of neuroblastoma. She was determined to have stage 4 disease based on the International Neuroblastoma Staging System (INSS).

The patient received a trial dose of chemotherapy, which was discontinued when a follow-up ultrasound revealed the masses had increased in size. She was issued a do-not-resuscitate (DNR) order and received no further treatment.

After being discharged from the hospital, the patient had regular follow-up visits. Approximately 18 months later, a follow-up ultrasound showed the cancer had disappeared spontaneously.

Lessons to Learn From Spontaneous Remission

Spontaneous remission is uncommon, and it would be casting false hope to spend too much time considering this possibility. Yet talking about the rare occurrence of spontaneous remission emphasizes something important for everyone living with cancer.

People Are Not Statistics

Statistics are numbers. They tell us how the "average" person did in the past during treatment. They are less reliable at predicting how any one single person will do, or how anyone will respond now that newer and better treatments are available.

As our understanding of cancer increases, we also now recognize that no two cancers are alike. Even though two cancers may be of the same cell type and same stage, and even look identical under the microscope, they may be very different on a molecular level.

It is at the molecular level, however, that the behavior of a tumor originates, and will dictate the response to treatment and ultimately prognosis.

The Study of Exceptional Patients or "Outliers" is Important

In the past, people who survived cancer despite the odds being against them were often dismissed as being an anomaly or an exception. Medicine has now acknowledged that these outliers should be closely examined rather than dismissed.

This approach has been confirmed as we better understand how cancer develops. An example is the use of EGFR inhibitors in lung cancer. When these drugs were first available, it wasn't clear how they worked. However, they were considered fair to poor drugs as they only worked on around 15% of people with the disease.

We now know that they work on people who have EGFR mutations in their tumor. When the drugs are given only to people who test positive for the mutation, the majority of people respond. Further, those who don't have the mutation aren't subjected to a treatment that will be ineffective.

Taking a look at some of the characteristics of "exceptional patients" with cancer may give us some clues about how to raise our odds as well.

Summary

Spontaneous remission refers to a partial or full recovery from cancer without treatment or in the presence of inadequate treatment. The cause of this rare phenomena is not entirely understood, though it has been linked to an immune response to infection, as well as hormonal changes.