First case of spontaneous lung cancer regression reported in LEMS

Immune attack may have contributed to regression in man in Japan: Report

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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An illustration shows a close-up view of damaged lungs.

In the first documented case of its kind, spontaneous cancer regression was seen in a man in Japan with Lambert-Eaton myasthenic syndrome (LEMS) associated with lung cancer.

Given that cancer-associated LEMS is thought to be triggered by the immune system attacking cancer cells, scientists believe such a LEMS-driving immune attack might have contributed to cancer regression in this patient.

“Our findings suggest that autoimmune mechanisms associated with LEMS may be related to the [spontaneous regression] of the tumor,” the researchers wrote.

The study, “Spontaneous regression of small cell lung cancer associated with Lambert-Eaton Myasthenic Syndrome: Case report,” was published in the journal Radiology Case Reports.

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An illustration shows a close-up view of damaged lungs.

Man in Japan Develops LEMS While on Small Cell Lung Cancer Treatment

Cancer regression occurred despite man receiving no treatment

LEMS is caused by the immune system making antibodies that target voltage-gated calcium channels, known as VGCCs, which are proteins that help nerve cells communicate with muscle cells. This autoimmune attack causes problems with nerve-muscle communication, ultimately leading to symptoms like muscle weakness and fatigue.

While LEMS can occur in the absence of other diseases, it often arises in people who have cancer — particularly small-cell lung cancer, an aggressive form of lung cancer.

In these cases, it’s thought that the immune system produces antibodies targeting VGCCs as part of its response to fight off cancer. However, these antibodies also end up attacking VGCCs in nerve cells, leading to the onset of LEMS.

In this report, researchers in Japan described the case of a 56-year-old man who was referred to their center after imaging tests revealed the presence of a tumor in his lung.

The man also reported a wide range of symptoms that suggested LEMS, including muscle weakness, double vision, and difficulty swallowing. Lab tests came back positive for antibodies against VGCCs, confirming the diagnosis of the rare autoimmune disorder.

Cancers are characterized by abnormal cell growth, and without treatment, cancerous tumors will nearly always enlarge and expand over time. Spontaneous regression happens when a tumor gets smaller or even disappears without treatment. But this is an extremely rare phenomenon, especially in small-cell lung cancers that usually grow quite aggressively.

In this patient, imaging tests showed that spontaneous regression had occurred. Initial CT scans of the man’s chest indicated the tumor measured about 45 mm in diameter. A month later, however, it had shrunk to 31 mm, and a month after that, it was down to 27 mm.

Over the course of this period of time, the patient had not been given any cancer treatment.

The man then underwent surgery to remove the tumor. The results of a biopsy were consistent with the diagnosis of small-cell lung cancer. After surgery, the man was also given a course of chemotherapy to kill any residual cancer cells.

All LEMS symptoms the man experienced eased immediately after he underwent tumor removal surgery. In the two years since, there have been no signs of the cancer or LEMS returning.

This case report suggests that [small-cell lung cancer] may be spontaneously reduced by an autoimmune response induced by … antibodies associated with LEMS.

While it’s impossible to definitively say why this man experienced spontaneous cancer regression, researchers said the regression of his cancer might be linked to LEMS. The team speculated that the immune system’s attack on the cancer may have effectively destroyed the tumor, though it also ended up triggering the onset of LEMS in the process.

“This case report suggests that [small-cell lung cancer] may be spontaneously reduced by an autoimmune response induced by VGCC antibodies associated with LEMS. This finding may help elucidate the mechanisms of tumor immunity and mechanisms that inhibit tumor growth and regress tumors,” the researchers wrote.

Better understanding these mechanisms may aid in the development of new cancer therapies that work by leveraging the power of the immune system to fight off cancer, the team noted.