# The Influence of Radioligand Therapy on Immunogenicity Against SARS-CoV-2—A Retrospective Single-Arm Cohort Study of Metastatic Prostate Cancer Patients Receiving PSMA Radioligand Therapy

## TL;DR

This study found that radioligand therapy for prostate cancer does not reduce the effectiveness of COVID-19 vaccines in patients.

## Contribution

The study is the first to show that PSMA radioligand therapy does not interfere with SARS-CoV-2 vaccine-induced immunity in cancer patients.

## Key findings

- 96.7% of patients developed a strong immune response after receiving the third SARS-CoV-2 vaccine dose.
- Immune titers in patients were comparable to those in the general population.
- Radioligand therapy did not negatively impact vaccine effectiveness or immune response maintenance.

## Abstract

Cancer patients with weakened immune systems may struggle to fight off infections, and some treatments can make vaccines less effective. Researchers investigated whether a specific cancer treatment, radioligand therapy, affects the body’s ability to respond to COVID-19 vaccines. They examined records of 30 patients with advanced prostate cancer who had undergone this therapy and received COVID-19 vaccinations. Nearly all patients successfully developed immunity after their vaccinations, despite receiving radioligand therapy. Their immune response was comparable to the general population, suggesting that this cancer treatment does not negatively affect COVID-19 vaccine effectiveness. This finding is significant because it means that patients undergoing radioligand therapy do not need to delay their vaccinations. Protecting cancer patients from COVID-19 is crucial, and ensuring they can safely receive both treatment and vaccines without interference supports their overall health. The study provides reassurance to doctors and patients, emphasizing that life-saving cancer treatment and vaccinations can work together without reducing protection against the virus.

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a rising threat for immunocompromised cancer patients. The reduced immune defense may be a result of the malignancy itself or a side effect of therapy. While many chemotherapies can severely diminish the effect of vaccines against SARS-CoV-2, the effect of radioligand therapy has not yet been studied so far. Methods: In our database, 64 patient records of patients with metastatic castration-resistant prostate cancer that were treated with PSMA-directed radioligand therapy (PRLT) were randomly selected and checked for specific information (vaccination status, past corona virus disease 2019 (COVID-19) infections, the period between PRLT and vaccination, and antibody titers). A total of 30 patient records had sufficient information to examine the interference between PRLT and the vaccination against SARS-CoV-2. Results: In the analyzed cohort, 96.7% of the patients achieved seroconversion after receiving—on average—the third (booster) vaccination against SARS-CoV-2 and two PRLT cycles with average administered activities of 16.1 ± 7.2 GBq (435.1 ± 194.6 mCi) of lutetium-177 and 13.7 ± 6.6 MBq (0.37 ± 0.18 mCi) of actinium-225 (as part of ‘TANDEM therapies’) per patient. Conclusions: In the reviewed population, neither the initial response nor the maintenance of a positive immune response against the SARS-CoV-2 virus was undesirably affected by PRLT. The seroconversion rate and the absolute immune titers (in many cases >25,000 BAU/mL) are comparable to the normal population. This result implies the clinically important conclusion that neither an initial nor a booster vaccination against COVID-19 must be postponed if a PRLT is planned (and vice versa).