Clinical characteristics of the study population

Clinical characteristics of the study population

Among the 1,496 patients screened, 13 were found to be positive for the SARS-CoV-2 infection. All these patients were asymptomatic at the time of testing, giving an asymptomatic infection prevalence of 0.86% (95%-confidence interval 0.3–1.2). The clinical and laboratory characteristics for the 13 patients are given in [Table 2].

Patient characteristics of asymptomatic SARS-CoV-2 positive patients

The SARS-CoV-2 infection was detected using RT-PCR in 10 cases and rapid antigen testing in three other cases. The median age of the SARS-CoV-2 infection positive patients was 53 years (range: 17–64 years), out of which six were male, and seven were female. The most common malignancies among the SARS-CoV-2 infection positive patients were breast cancer (n = 5, 38%) followed by gastrointestinal (n = 2, 15%) and lung (n = 2, 15%) cancers. The abnormalities in complete blood counts observed among the patients were as follows: neutropenia (n = 2; one grade 1 and one grade 2), neutrophilia (n = 1, 10%), anemia (n = 1, grade 1), and thrombocytopenia (n = 1, grade 1). The hematological changes were all grade 1 or 2 and not clinically significant.

Number of times tests repeated

Discussion

People with active cancer and cancer survivors are at an increased risk of COVID-19 and its complications, including hospitalization and 30-day mortality than the general population, due to factors like old age, smoking, comorbidities (diabetes, asthma, other respiratory, cardiac, neurological, renal, and liver diseases) and the effects of cancer treatment. Patients with cancer who are hospitalized are at a higher risk of severe COVID-19 infection compared to non-cancer controls.[20] [21] About 30% of the people with COVID-19 are asymptomatic, and at least 50% of the transmission is estimated to happen from persons without symptoms.[22] These findings suggest that protective measures and strategic testing of asymptomatic patients will be necessary for slowing the spread of COVID-19 until a majority of the people are vaccinated.

Before getting admitted into a ward or a closed enclosure such as the daycare chemotherapy unit, screening all asymptomatic patients would be the best way to prevent the inter-patient spread of the SARS-CoV-2 infection and maintain confidence among health care workers. In previously reported studies, screening was conducted by three methods—RT-PCR, antibody testing, or antigen testing. We screened our daycare chemotherapy patients with the SARS-CoV-2 antigen testing. Although RT-PCR would have been ideal because of its higher sensitivity, this was not viable in our setting because of the two reasons—the cost of the test and the time taken for the RT-PCR report (more than 6 hours). This would necessitate patients staying back 1 day whereas, with rapid antigen testing, the results would be available within 1 hour, reducing delays in inpatient care.

In resource-poor settings, molecular testing results may take a few days or are altogether unavailable.[23] A recent study revealed comparable sensitivity (98.33%) and specificity (98.73%) for rapid SARS-CoV-2 antigen test with the real-time RT-PCR assay.[24] This was the same kit that we also used. Therefore, this rapid SARS-CoV-2 antigen detection test has enormous potential in resource-poor settings. In three previous studies, a serologic test was used.[25] In one, the rapid serological testing was not useful—it failed to detect the active asymptomatic COVID-19 infection and increased the cost of care and delayed therapy administration.[26] However, a similar study found it helpful in identifying the silent carriers and triaging patients for safe continuation of anticancer therapies.[27]

The prevalence of asymptomatic infections in our study was low (0.86%). The test positivity rate in the state of Kerala at the time of this study was 10 to 11%. In a similar study from Chennai, India, the testing of 761 patients was planned for chemotherapy using RT-PCR, out of which 11 (1.45%) patients were positive for COVID-19.[28] Our data was comparable to the low prevalence reported from developed nations like the United States of America (New York: 0.64%),[29] United Kingdom (Birmingham: 0.6%),[17] and Austria (Vienna: 0.4%).[30] The low prevalence of asymptomatic infections in our patients with cancer could be because they were more cautious and followed social distancing, hygiene, and masking rigorously. Additionally, Kerala's higher literacy rate of 96.2%-probably helped, as educating our patients was easier.

In comparison, data from Germany reported an asymptomatic infection rate of 6.1%-in their cancer patient population.[31] Similarly, in the study by Al-Shamsi et al from the United Arab Emirates (UAE), the RT-PCR positivity was 8.24%- (7/85 patients).[32] All the RT-PCR positive cases later developed the symptomatic disease, two with severe illness, requiring admission in the intensive care unit. In our cohort, only one patient developed the symptomatic disease.

The most prevalent cancers in our study were breast cancer, followed by gastrointestinal and lung cancers. In comparison, the most common diagnoses were gastrointestinal cancers in the study from New York[26] and breast cancer in the series from the UAE and Vienna.[30] In a study using serial testing from UAE, 25 (78.1%) were diagnosed in the asymptomatic state, and seven (21.9%) developed symptoms after an initial negative RT-PCR test. Although initially asymptomatic, the majority (84.4%) of patients with COVID-19 subsequently developed the symptomatic disease.[33] This was in sharp contrast with our study, where only one patient was positive on subsequent testing.

Similar to the study by Berghoff et al, our study also provides information on the SARS-CoV-2 prevalence in patients undergoing active anticancer therapy.[33] The universal screening of all patients in our department for the SARS-CoV-2 infection allowed us to identify positive patients and their contacts quickly. This helped prevent the spread of COVID-19 to health care workers as well as other patients.

Another factor we sought to explore in our study was the delay in therapy due to the pandemic. The delay becomes significant in patients undergoing curative-intent therapy and probably might be less concerning in metastatic diseases. Prior studies have documented that more than 4 weeks of treatment delay may affect outcomes across all cancer treatment modalities.[34] In our cohort of 13 patients who tested positive, 10 were on adjuvant therapy and three had metastatic disease. The median delay in initiation or continuation of cancer treatment was 30 days. The delay of more than 4 weeks occurred in eight patients. The curative intent adjuvant cytotoxic therapy was delayed for more than 4 weeks for seven patients. This was similar to other studies. We conducted contact tracing among all our patients but could not identify the source of infection for any. The possible source of infection or contact tracing was not mentioned in any of the previous studies.

There are some limitations in our study. Ideally, screening with RT-PCR SARS-CoV-2 testing would be preferable as it has higher sensitivity for COVID-19 detection than the available serological tests and rapid antigen tests. We used rapid antigen testing in most patients because of the shorter turnaround time and cost. As the sensitivity of this test is low, it would have missed some patients. However, a recent study by Chaimayo et al showed that the sensitivity and specificity were comparable with the real-time RT-PCR assay.[25] Given the results, antigen testing may be used in resource-poor settings. To the best of our knowledge, ours is the first study that used antigen testing from an LMIC. Our study included only patients who presented to the hospital for systemic anticancer treatment. The prevalence may differ in the community and the public sector hospital as the population of patients seeking treatment is different. Prevalence can also vary during the different periods of the year. Another limitation of our study is the retrospective study design. However, our sample size was large. Based on these findings screening of high-risk patients (age ≥60 years, performance status ≥2, patient on prolonged immunosuppressive regimens and with comorbidities—cardiovascular, chronic obstructive pulmonary disease, diabetes, renal failure) and universal testing when the community prevalence is high may be a more cost-effective strategy.

Ongoing studies are needed to understand better the efficacy and safety of COVID-19 treatment approaches in cancer patients, comorbidities, and clinical outcomes. Patients with cancer and COVID-19 included in various studies were small in number and a heterogeneous group. Clinical outcomes and the biological basis for the comorbidity of cancer and COVID-19 remain to be resolved. Cancer treatment cannot be delayed, so we need to find ways to deliver cancer care on time by implementing screening strategies among the high-risk group and augmenting the vaccination drive.

Conclusion

Our study presents the findings of the universal screening strategy conducted for screening of COVID-19 among patients receiving anti-cancer treatment. The prevalence of asymptomatic COVID-19 infections in our study was low (0.86%). Our study results reflect that with proper health education, clinical triaging, and screening, it is possible to continue cancer treatment during the peak of the COVID-19 pandemic, even in LMICs.

Summary Points

We aimed to determine the prevalence of asymptomatic SARS-CoV-2 in patients with cancer planned for systemic anticancer treatment from an LMIC using rapid antigen tests and/or RT-PCR. In total, 1,722 asymptomatic SARS-CoV-2 tests were performed among 1,496 patients. The prevalence of asymptomatic COVID-19 infections in the study reported was low (0.86%). Clinical triaging with screening can detect asymptomatic cases and help continue planned anti-cancer treatment without any interruption.

Conflict of Interest

None declared.

Authors' Contributions

The authors were fully responsible for all content, and editorial decisions were involved at all stages of manuscript development and they approved the final version.

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Publication History

Article published online:
18 April 2022

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