Outcomes of SARS-Cov-2 infection in patients undergoing active anti-cancer treatment

In a recent study posted to the medRxiv* preprint server, researchers demonstrated that irrespective of the type of anti-cancer treatment (ACT), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection rates in patients receiving ACT remained comparable to the general population.     

Background

Globally, cancer patients under systemic ACT (SACT), due to their already suppressed immunity, remain vulnerable to SARS-CoV-2 infection and related severe illness. Studies have reported that patients with hematological cancers and solid organ cancers are at a higher risk of severe SARS-CoV-2 illness.

Moreover, studies examining cases of solid organ cancers have shown that male gender, increasing age, comorbidities, etc., are linked with higher coronavirus disease 2019 (COVID-19) mortality risk. However, previous studies could not establish a relationship between mortality and SACT.

Real-world, longitudinal data via studies with long follow-up periods are needed to examine lower or delayed immune responses in these patients to maintain anti-cancer care during the ongoing COVID-19 pandemic.

About the study

In the present longitudinal study, termed the Scottish COVID CAncer iMmunity Prevalence (SCCAMP), researchers evaluated the response to SARS-CoV-2 infection and vaccination in 766 patients undergoing ACT during May 2020-October, 2021.

They sourced control data from Public Health Scotland (PHS) data sources; likewise, PHS provided information related to COVID-19 vaccination for the cancer cohort. More patient-related information, including cancer type, treatment, and clinical outcome, was accessed electronically from the National Records of Scotland (NRS).

The average age of the eligible study participants receiving ACT for a solid tumor was 62.7 years, and 66.5% were female. Of these, 79% were on cytotoxic chemotherapy, 14% were receiving immunotherapy, and the remaining 7% participants were receiving some other form of anti-cancer therapy, such as radiotherapy.

The researchers collected blood samples for standard-care reverse transcriptase-polymerase chain reaction (RT-PCR) screening and a total SARS-CoV-2 antibody (immunoglobulin G (IgG), IgM, and IgA) assay to comprehensively assess COVID-19 infections and antibody response to infection and vaccination. The blood samples were collected every time patients attended ACT starting at baseline date (date of first sample collection) and serially after 1.5, three, six, and 12 months for follow-up studies.

During the study period, they detected 48 (6.3%) SARS-CoV-2-positives by RT-PCR; however, the antibody assay results raised this figure to 58 (7.6%) by diagnosing infection that occurred in some of the participants before vaccination.

Study findings

Until May 2021, the overall SARS-CoV-2 infection rate was similar in patients undergoing ACT and the age-matched general population. Notably, SARS-CoV-2 infection rates did not significantly change with the type of ACT. After May 2021, the observed SARS-CoV-2 infection rates in the general population were higher than in the SCCAMP cohort, suggesting a protective effect from vaccination.

The authors also noted a significant reduction in the number of SARS-CoV-2-positives among patients who had received two or more doses of any COVID-19 vaccination. Further, the authors noted that the observed COVID-19 mortality rates between those who died within 90 days of a positive SARS-CoV-2 RT-PCR test and those who never contracted the infection were 10.4% and 10.6%, respectively.

Intriguingly, irrespective of the cause, the death rate was lowest among vaccinated patients of the cancer cohort. Moreover, all the patients who died after testing SARS-CoV-2-positive at any time during the study were unvaccinated.

After correcting for gender, age, comorbidities, socioeconomic status, and the number of previous medications, multivariate analysis showed that vaccination was associated with a significantly reduced SARS-CoV-2 infection rate regardless of ACT. They observed hazard ratios (HRs) of 0.307 and 0.314 in vaccinated patients receiving chemotherapy and immunotherapy, respectively.

Furthermore, regardless of the type of cancer treatment, 96.3% of patients successfully generated anti-SARS-CoV-2 antibodies at some point after vaccination, as measured via total SARS-CoV-2 antibody assay.

Conclusions

To summarize, the study demonstrated that cancer patients undergoing ACT, specifically SACT, mounted a robust antibody response against SARS-CoV-2 infection after the COVID-19 vaccination.

According to the authors, the small number of cases in the study cohort, with relatively few lung cancer patients (a group considered at higher risk of SARS-CoV-2 infection), restricted them from making inferences about the overall risk. Nevertheless, they did not observe a higher SARS-CoV-2 risk in cancer patients on ACT compared to the regional population.

In addition, the observed rate of vaccination in the cancer cohort was quite high. Nearly 50% of patients had received a booster COVID-19 vaccination at the time of data censoring on October 31, 2021, compared to the general vaccination rate of 13.2% in Scotland at the time of the study. This further rationalizes why cancer patients on the ACT were not at high SARS-CoV-2 risk.

Future studies should evaluate immunological profiles of specific subgroups of this vulnerable population in greater detail, encompassing the trend of COVID-19 antibodies over time and the effect of ACT.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Neha Mathur

Neha is a digital marketing professional based in Gurugram, India. She has a Master’s degree from the University of Rajasthan with a specialization in Biotechnology in 2008. She has experience in pre-clinical research as part of her research project in The Department of Toxicology at the prestigious Central Drug Research Institute (CDRI), Lucknow, India. She also holds a certification in C++ programming.