At the time of this writing, it’s been over a year since SARS-CoV-2, the virus that causes COVID-19, was confirmed in the U.S. Scientists around the world scrambled to unravel the mysteries of this coronavirus while millions of people around the globe have died. At this time, there are a reported 114 million active cases of COVID worldwide, with 28.5 million of them in the U.S.

And yet, within these 12 months, pharmaceutical companies have created, tested, and are now producing effective vaccines. This is an enormous step toward weakening the virus and eventually restoring life after COVID.

Side effect of the vaccine mimics cancer metastasis

Again, as of this writing, there are two different 2-part vaccines being distributed: one from Pfizer and the other from Moderna. Both are injected into the arm just below the shoulder, and the CDC allows up to 42 days (6 weeks) between doses. Either manufacturer’s product can cause side effects, most notably after the 2nd dose—a sign that the immune system has been activated. Side effects can include pain/swelling at the injection site, and systemic symptoms such as fever, chills, fatigue and headache.

Recently, the journal Radiology published a paper by Özütemiz, et al. (2021) on a COVID-19 vaccine side effect that may unduly alarm cancer patients because it’s similar to a sign that their cancer has spread.^[i] The sign is swollen lymph nodes in the armpit on the side where the injection was given.

Lymph nodes exist throughout the body, and they are an important part of the immune system. According to one health information site, “They filter harmful substances like bacteria and cancer cells from your body, and help fight infections.” In addition, for patients dealing with cancer, enlarged lymph nodes play an important part in detecting, diagnosing, and predicting the course of cancer in a person’s body. The presence of cancer cells in the lymph node system can be a sign of metastasis, since the system has its own circulation that can be a source of cancer cell transport even while the immune system is trying to deal with the cancer cells.

According to the Özütemiz paper, clinical trials of the Moderna vaccine reported swollen or tender lymph nodes in the same-side armpit in 11.6% of 1st dose recipients and 16% of 2nd dose recipients. Percentages were much lower with the Pfizer vaccine. Thus, lymph node enlargement was noted as a vaccine side effect.

However, when cancer patients undergo imaging (PET/CT, MRI and ultrasonography) as part of monitoring their disease, it is concerning for their imaging radiologists/oncologists to detect swollen armpit lymph nodes—and, in turn, it can be alarming for the patients.

The Özütemiz team report the cases of five cancer patients who were found on imaging to have enlarged lymph nodes. This was “… concerning for metastasis; however, further investigation revealed that these patients had received COVID-19 vaccinations prior to imaging.” In three of the patients, pathology examination (removal of lymph nodes for analysis) revealed no cancer, and it was assumed based on radiological and clinical information that the COVID vaccine had triggered this response in all five individuals. Of note, all patients had received the Pfizer vaccine.

No doubt the five patients experienced one of those “Whew, that was close!” moments when informed of the test results. The publication of this paper does both patients and clinicians a great favor. As the authors write, “Radiologists, oncologists, and internists should be aware of this secondary effect of vaccination to obviate unnecessary changes in management, unnecessary patient emotional stress or biopsy.”

The coronavirus pandemic has brought enough havoc and confusion to our world in general. In this paper, we see how the noble effort to protect us all from the virus can lead to an unintended false alarm for cancer patients. We are all well advised to learn about the vaccine side effects in order to remain calm and avoid jumping to scary conclusions.

NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.

[i] Özütemiz C, Krystosek LA, Church AL, Chauhan A et al. Lymphadenopathy in COVID-19 Vaccine Recipients: Diagnostic Dilemma in Oncology Patients. Radiology. 2021 Feb 24;210275.