Drs. Steven Vernino and David Gerber continue their conversation on their preferred treatment approaches and monitoring strategies for Lambert-Eaton myasthenic syndrome and small cell lung cancer.
David Gerber, MD: It’s important to discuss that most cases that present symptomatically will require treatment. When I think about small cell lung cancer, they’re the paraneoplastic neurologic syndromes that are autoimmune. There are also paraneoplastic humeral syndromes. SIADH, the syndrome of inappropriate antidiuretic hormone [secretion], presents with low sodium or paraneoplastic cushions, and patients have high ACTH [adrenocorticotropic hormone] and cortisol. It’s important to remember with paraneoplastic humeral syndrome that when I treat the cancer, [the] paraneoplastic syndrome improves within days because when the cancer begins to shrink and die, the source of the syndrome goes away (the produced protein or chemical that was causing it).
The sodium can rise spontaneously on its own within days to normal levels, but with these paraneoplastic neurologic conditions, whether it’s LEMS [Lambert-Eaton myasthenic syndrome] or another one—maybe because there’s already damage to that component of the nervous system or maybe because the antibodies are preformed—we must go in hoping that there will be improvement and potentially resolution. We expect that we’re going to need to manage this besides just giving the cancer treatment.
Steven Vernino, MD, PhD:My approach has been, even after we get clinical oncologic remission, we anticipate we will need a few more years of immunotherapy before we’re satisfied that the autoimmune condition has settled down and abated. That leads us into monitoring, and I’ll start with the neurological aspect of that.
It’s important that we monitor patients symptomatically. There are people who monitor the antibody levels, but there’s evidence that the clinical symptoms severity of weakness don’t correlate with the levels of the voltage-gated calcium-channel antibodies. It’s a great diagnostic test but not one that is useful for monitoring.
The physical exam and discussion with patients about their physical capabilities are the best way to monitor LEMS neurologically. In some cases, we may take them back to the EMG [electromyographic] laboratory, but that’s usually if we are not sure if their persistent fatigue, for example, is residual Lambert-Eaton syndrome or and adverse effect of chemotherapy and other issues. We’re monitoring them neurologically based on their symptom approach. If we’re using an immunotherapy agent, we will monitor blood counts and alike to ensure that we’re doing that safely.
How about on the cancer aspect?
David Gerber, MD: In cases that we’ve shared where you’re giving long-term therapy, and I may give episodic treatments of my own, it seems relatively feasible. Sometimes we worry about overlapping nephrotoxicity, hepatotoxicity, or myelosuppression, but usually we’re able to do it effectively. After I finish my early treatment, I will follow them clinically and with scans every few months. I might get a scan earlier than every 3 to 6 months wherever I am in the monitoring period due to new symptoms or if you inform me that the neurological condition has worsened because we know that can be a harbinger of cancer recurrence or progression.
Transcript edited for clarity.