Spontaneous remission of cancer occurs when cancer shrinks or disappears without curative treatment. It does not include cancer regression after therapies like chemotherapy or surgery. Spontaneous cancer remission is also quite rare. Only 12–24 cases appear in medical literature each year.

Top Spontaneous Cancer Remission Statistics

  • Yearly spontaneous cancer remission cases: 12–24
  • Rate of spontaneous cancer remission: 1–10 out of every 1,000,000 cancer cases
  • Cancers most prone to spontaneous remission: Kidney cancer, leukemia, lymphoma, melanoma and neuroblastoma

Studying spontaneous cancer remission might help find new treatments. This kind of research is challenging because spontaneous remission is so infrequent. Past studies have not yet found a definite cause for this phenomenon. But some factors seem to occur commonly across cases of spontaneous remission.

Understanding the factors linked to spontaneous remission might help make it more common. Continued research could positively impact patients with various cancers. This includes asbestos-related cancers like lung cancer and mesothelioma.

What Causes Spontaneous Cancer Remission?

Researchers don’t know for sure what causes spontaneous cancer remission. Evidence suggests it may depend on the type of cancer and patient characteristics. Some factors linked to spontaneous remission include fevers, infections and hormonal changes.

Researchers have linked the following factors to spontaneous remission:

  • Fever with infection or sepsis: Infection and fever may be the most common factors tied to spontaneous cancer remission. Many case reports indicate patients experienced spontaneous remission after a serious infection. Those infections often caused high fevers.
  • Hormonal changes: Some breast cancer patients experienced spontaneous remission after the onset of menopause. This observation led to the development of hormonal therapy for breast cancer. It is now a standard treatment option.
  • Immune system activation: Research has linked weak immune systems to higher rates of certain cancers. But spontaneous remissions have occurred in patients whose immune systems regained normal function.
  • Invasive procedures: Some cases of spontaneous remission happened after an invasive biopsy procedure. Researchers have suggested the procedure may have triggered remission.

What Is the Most Common Factor in Cases of Spontaneous Cancer Remission?

Answer: Infection with a high fever

The most common factor in reported spontaneous cancer remission cases seems to be an infection that causes a high fever.

Some types of cancer tend to have a higher chance of spontaneous remission. Neuroblastoma has the highest reported rate. Other cancers with higher rates of spontaneous remission include leukemia and lymphoma. Melanoma and kidney cancer also have a higher number of spontaneous remissions.

Neuroblastoma is a childhood cancer. It develops in nerve tissue and usually affects children under the age of 5.

However, spontaneous remission is, by far, most prevalent in neuroblastoma. In one study, 75% of untreated Stage 4 neuroblastoma patients experienced spontaneous remission. In fact, experts say it may happen as often as confirmed diagnoses of neuroblastoma. This means many neuroblastoma tumors may disappear before they can be diagnosed.

Spontaneous remission has also been reported in many other types of cancer, including lung cancer, pancreatic cancer and breast cancer.

How Long Does Spontaneous Cancer Remission Last?

There is no definitive time frame for how long spontaneous cancer remission may last. Reported spontaneous remission times range from about 2 months to more than 5 years.

Spontaneous remission duration is unpredictable and likely depends on a variety of factors. Because of this, doctors recommend continued close monitoring even after remission. This monitoring can help them catch recurrence, or cancer coming back, as soon as possible.

As research continues, doctors may learn more about what causes remission to last. Research may also help doctors develop new ways to treat cancer.

Research Into Spontaneous Remission of Cancer

Spontaneous cancer remission remains rare, which means related research is limited. But some studies have already generated key insights into this phenomenon. One recent study linked spontaneous remissions to COVID-19 infection. Another study tried to trigger spontaneous remission in pleural mesothelioma patients.

Spontaneous Cancer Remissions and COVID-19

At least 16 reported cases of spontaneous cancer remissions have been linked to COVID-19 infection or vaccination. Some of these cases were limited to transient remission, meaning the cancer returned.

Researchers have not yet determined if COVID-19 caused these remission cases. The study authors suggested the following ways COVID-19 may have contributed to remission:

  • Oncolytic activity: The virus itself may have killed cancer cells, causing tumors to shrink or disappear.
  • Unexpected immune response: The infection or vaccine might have caused unusual immune behavior. If so, it may have allowed the immune system to fight cancer.

Research into this area is ongoing.

Spontaneous Cancer Remission and Pleural Mesothelioma

Researchers attempted to trigger spontaneous remission in pleural mesothelioma patients. Patients were treated with a non-standard combination of chemotherapy drugs. This means the combination itself may have been inferior to current chemo regimens. During chemo treatment, patients’ bodies were warmed to simulate a high fever.

Infection with a high fever is one of the most common factors linked to spontaneous remission. Researchers wanted to know if supplementing chemo treatment with a simulated fever would trigger remission.

Study patients did not experience spontaneous remission. But the simulated fever may have helped the chemo drugs fight tumors. The reported survival time was about 19 months. This is about 7 months better than reported survival time for standard chemotherapy treatment. It is also similar to reported survival with newer immune checkpoint inhibitor drugs.

It is unclear how much difference the simulated fever made, but research is ongoing. Additional studies may lead to new insights and treatments for mesothelioma and other cancers.