Immunization before radiation to avoid complication

Radiation oncologists offer curative cancer treatment to many.  Despite irradiating the spleen for over 50 years, why don’t we routinely offer pneumococcal vaccination to avoid complications after treatment?  Since we just had World Pneumonia Day to raise awareness for children, I want to do the same for cancer patients.

A healthy spleen helps fight off pneumonia, sepsis and meningitis. Publications on infection from spleen radiation date back at least thirty years, but were limited to lymphoma and postsplenectomy patients.  Vaccination rates have improved when the spleen is surgically removed, but for cancer patients receiving radiation over half may not receive pneumococcal vaccination.

Radiation is often a key part of cancer treatment for cancers of the esophagus, stomach or pancreas – all near the spleen.  In the U.S., thousands of abdominal cancer patients may receive incidental spleen radiation each year.  But we don’t even know what dose the spleen receives in abdominal cancers, because it hasn’t been published.

I tried publishing a small IRB-exempt study measuring spleen dose for abdominal cancers, but peer reviewers at two journals didn’t see the relevance.  But the dose may matter.  With Hodgkin’s lymphoma, high doses to the spleen can cause atrophy.  But in a small study in children with a rare kidney tumor, lower doses may have no effect.

According to the latest update of a key cancer textbook, all patients receiving spleen radiation should receive pneumococcal vaccination.   But no information about whether the radiation dose matters … because there really aren’t any data to back it up.  And the textbook broadly applies the recommendation to all cancer patients, many of whom may qualify based on age or receiving chemotherapy.

Should we have to wait for the academic journals to publish a definitive study if there are broad recommendations and vaccination appears safe with more upside than down?  I still think it should be studied further, but if the journals won’t publish on it I’ll have to make do by synthesizing the data we have now.

I think it’s worthwhile for patients and doctors to discuss the risks and benefits, even when we don’t know the answer.  For that reason, you can be my peer review – here is our research.  Let me know what you think.

Matthew Katz is a radiation oncologist. 

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