Keywords
COVID-19 - SARS-CoV-2 - anti-SARS-CoV-2-antibody - cancer - seroconversion - chemotherapy
- India
Introduction
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing coronavirus
disease 2019 (COVID-19), emerged in December 2019 and has spread around the world
causing several cases and deaths.[1] Patients suffering from cancer are thought to be at a higher risk of developing
a severe course of COVID-19 and have higher mortality risk as their immune system
is generally compromised.[2]
[3] Due to this reason, adjuvant chemotherapies, surgeries, and other therapies are
either postponed or altered during the current pandemic.
According to literature, seroconversion of most patients with COVID-19 occurs between
7 and 14 days after diagnosis.[4]
[5]
[6] Earlier studies suggested that 40 to 60% of those infected become antibody-negative
early in the convalescence period,[7]
[8]
[9]
[10] while later studies reported sustained levels for at least 4 months[7]
[9]
[11]
[12] ([
Supplementary Table S1
]).
There is a paucity of data regarding SAR-CoV-2 seroconversion in cancer patients.[13]
[14] ([
Supplementary Table S1
]) To the best of our knowledge, there is no data in literature that has studied longitudinal
seroconversion of SAR-CoV-2 antibodies in this subset of patients. It is also not
known if these antibodies have long-term persistence and whether they provide protective
immunity against reinfection in cancer patients.
Response to pneumococcal and influenza vaccination has shown good response in patients
on chemotherapy.[15]
[16] However, COVID-19 vaccine trials have excluded cancer/immunocompromised patients.[17]
[18]
[19] Hence, there is no data on the safety and efficacy of COVID-19 vaccine in cancer
patients.
The aim of this study was to assess SARS-CoV-2 seroconversion in the cancer patients
and longitudinal changes of antibody levels in first 6 months after SARS-CoV-2 infection.
We also assessed its correlation with sex, age, anticancer treatment, and severity
of SARS-CoV-2 infection. Comparison was done with seroconversion in normal population
comprising of 100 recovered frontline health-care workers (HCW) with confirmed COVID-19
infection.
Materials and Methods
Study Design
This study was a retrospective analysis evaluating serial estimation of anti-SARS-CoV2-antibody
in cancer patients who recovered from SARS-CoV2 infection.
Study Setting
Study was performed at a tertiary care hospital, The study period was from April 30
to December 25, 2020.
Data Collection
All the demographic data, clinical information, laboratory parameters, and complications
during the hospital stay were retrieved from hospital medical records. Cases of acute
leukemia were not included in the study. All the data was analyzed at the cutoff date
of December 25, 2020.
Inclusion Criteria
All cancer patients who tested positive for SARS-CoV-2 by reverse transcriptase–quantitative
polymerase chain reaction (RT-qPCR) on nasal/throat swab and were tested at least
once for SARS-CoV2-antibodies were enrolled in this retrospective analysis.
Exclusion Criteria
-
All leukemia patients.
-
All cancer patients below age 18 years.
Primary Outcome
Seroconversion rate in cancer patients recovered from SARS-CoV-2 infection at first,
third, and sixth month.
Secondary Outcome
Comparison of seroconversion rate among cancer patients and healthy HCWs (internal
control).
Diagnostic Criteria
SARS-CoV-2 infection: The severity of the disease was defined according to the World
Health Organization (WHO) definition.[20]
Detection of SARS-CoV-2 RNA by RT-PCR
Presence of SARS-CoV-2 on nasopharyngeal/throat swab specimens was determined by real-time
RT-PCR. Allplex 2019 n-CoV Assay (Seegene Inc., Seoul, South Korea) was used to detect
SARS-CoV-2 by amplification of RdRp gene, E gene, and N gene according to the Indian
Council of Medical Research (ICMR) recommendations.[21]
Detection of SARS-CoV-2 Antibodies
We tested our patient samples using Roche Elecsys anti-SARS-CoV-2 immunoassay (Roche
Diagnostics, Rotkreuz, Switzerland) on a Cobas e801 analyzer. Elecsys anti-SARS-CoV-2
electrochemiluminescence immunoassay detects antibodies (including immunoglobulin
M [IgM], immunoglobulin A [IgA], and immunoglobulin G [IgG]) to SARS-CoV-2 in human
serum. The immunoassay utilizes a double-antigen sandwich test principle and a recombinant
protein representing the nucleocapsid antigen for the determination of antibodies
to SARS-CoV-2. Tests were performed according to the manufacturer’s instructions,
and assay results were interpreted as follows: cutoff index ≥ 1.0 was considered as
positive/reactive.[22]
In a previous study done at our institute (COVID-19 recovered HCW cohort),[23] we compared the performance of four high-through put commercial chemiluminescence
immunoassays [Abbott Architect SARS-CoV-2 IgG assay which detects antinucleocapsid
IgG, Roche Elecsys anti-SARS-CoV-2 total assay antinucleocapsid (IgG, IgM & IgG),
Ortho-Clinical Diagnostics VITROS anti-SARS-CoV-2 IgG (S1) and Ortho-Clinical Diagnostics
VITROS anti-SARS-CoV-2 total antispike {including IgA, IgM & IgG (S1)} to SARS-CoV-2]
most frequently used for the detection of SARS-CoV-2 antibodies worldwide. Comparisons
were done in terms of various statistical parameters like sensitivity, specificity,
and Cohen’s kappa agreement ([Fig. 1]).
Fig. 1 Comparison of chemiluminescent immunoassay platforms.
Results from antinucleocapsid antibody (IgG, IgM, and IgA) on Roche platform (used
subsequently for our study) were in complete agreement with IgG (S1) and total antispike
done on Ortho-Clinical Diagnostics platform (Supplementary Tables S2 and S3).
For the purpose of analysis, we divided first month data in three subsets from the
day of COVID-19 RT-PCR positivity, that is, less than 15 days, 15 to 22 days, 23 to
30 days, then at 3 and 6 months.
Sample Size
All consecutive cancer patients fulfilling the inclusion criteria during the study
period were included. A total of 135 patients were included in the study.
Statistical Analysis
To describe patient’s characteristic’s, demographic, clinical, laboratory investigations,
the data were summarized and analyzed using STATA (version 14, StataCorp., College
Station, Texas, United States) software. Quantitative data was expressed as median
(min, max). Qualitative data was reported as in numbers and percentages. Data was
tested for normality using the Kolmogorov–Smirnov test. Student’s t-test was used to observe the differences between demographic factors, cancer history,
clinical findings, laboratory parameters and disease outcome, between patients who
developed anti-SARS-CoV2-antibodies after COVID-19 infections versus those who did
not. Comparison of baseline and treatment characteristics was performed using Student’s
t-test. To establish the association between patients who developed antibodies versus
those who did not, with other qualitative characteristics, chi-squared test/Fisher’s
exact test was used. A value of p less than 0.05 was considered to represent statistical significance of the study.
Ethics
The study protocol was reviewed and approved by institute ethics committee (Dr. BL
Kapur Memorial Hospital Ethics Committee) on January 7, 2021. The approval letter
number is ETHICS COMMITTEE/AARCE/LETTER/JAN/2021/12.
Consent waiver was granted given retrospective nature of analysis confidentiality
was maintained by the deidentification of data. The procedures followed were in accordance
with the ethical standards of the responsible committee on human experimentation (institutional
or regional) and with the Helsinki Declaration of 1964, as revised in 2013.
Results
Patient Characteristics and Disease Status
A total of 135 patients were enrolled in the study. Their median age was 56 years
(range: 24–80 years) and median follow-up was 92 days (range: 12–239).
Details of site of tumor, stage, disease status, and preceding cancer treatment before
COVID-19 infection are shown in [Table 1]. Overall, 26 (19%) patients were classified with moderate or severe symptoms, and
41 (30%) patients were asymptomatic. Median duration of symptoms was 2 days (range:
0–10).
Table 1
Baseline demographics and cancer therapy details
|
Variable
|
n (%)
|
COVID-19 antibody positive patients
|
COVID-19 antibody negative patients
|
p-Value
|
|
Abbreviation: COVID-19, coronavirus disease 2019.
|
|
Age
|
|
|
|
|
|
Median (range)
|
56 (24–80)
|
|
|
|
|
≤ 60 y
|
93 (61)
|
85
|
8
|
|
|
> 60 y
|
42 (39)
|
37
|
5
|
0.376
|
|
Sex
|
|
|
|
|
|
Male
|
39 (29)
|
35
|
4
|
|
|
Female
|
96 (71)
|
87
|
9
|
0.55
|
|
Type of tumor
|
|
|
|
|
|
Breast
|
50 (37)
|
46
|
4
|
|
|
Lung
|
8 (5.7)
|
5
|
3
|
|
|
Head and neck
|
5 (3.7)
|
4
|
1
|
|
|
Hepato-Pancreato-
|
11 (7.4)
|
11
|
0
|
|
|
Biliary
|
20 (15.5)
|
18
|
2
|
|
|
Gastrointestinal
|
8 (5.7)
|
8
|
0
|
|
|
Genitourinary
|
14 (10.3)
|
14
|
0
|
|
|
Gynecological
|
8 (5.7)
|
8
|
0
|
|
|
Others
|
|
|
|
|
|
Hematological tumors
|
|
|
|
|
|
Lymphoma
|
8 (5.7)
|
5
|
3
|
0.03
|
|
Multiple myeloma
|
3 (2.2)
|
3
|
0
|
|
|
Cancer status
|
|
|
|
|
|
Cured + remission
|
40 (29.6)
|
36
|
4
|
|
|
Response to active disease or treatment naïve or relapse/refractory disease
|
95 (70.4)
|
86
|
9
|
0.57
|
|
Comorbidity
|
|
|
|
|
|
None
|
81 (60)
|
74
|
7
|
|
|
One
|
29 (21.5)
|
25
|
4
|
|
|
≥ two
|
25 (18.5)
|
23
|
2
|
0.71
|
|
Cancer stage
|
|
|
|
|
|
I–III
|
55 (40.7)
|
49
|
6
|
|
|
IV
|
80 (59.3)
|
73
|
7
|
0.77
|
|
Chemotherapy (received) within last 4 weeks (
n
= 98)
|
|
|
|
|
|
Cytotoxic
|
67 (49.6)
|
60
|
7
|
|
|
Targeted
|
9 (6.7)
|
9
|
0
|
|
|
Hormonal
|
18 (13.3)
|
17
|
1
|
|
|
Immunotherapy
|
5 (3.7)
|
5
|
0
|
0.86
|
|
Symptoms
|
|
|
|
|
|
Fever
|
76 (56.3)
|
70
|
6
|
0.31
|
|
Cough
|
55 (40.7)
|
50
|
5
|
0.55
|
|
Sore throat
|
46 (34)
|
43
|
3
|
0.29
|
|
Myalgia
|
75 (55.6)
|
70
|
5
|
0.15
|
|
Anosmia
|
34 (25.2)
|
33
|
1
|
0.11
|
|
Dysguesia
|
36 (26.7)
|
35
|
1
|
0.09
|
|
Symptoms duration (d)
|
|
|
|
|
|
Median
|
2
|
71
|
7
|
|
|
≤ 2 d
|
78 (57.8)
|
51
|
6
|
0.59
|
|
> 2 d
|
57 (42.2)
|
|
|
|
|
Severity
|
|
|
|
|
|
Asymptomatic + mild
|
109 (80.7)
|
98
|
11
|
|
|
Moderate + severe
|
26 (19.3)
|
24
|
2
|
0.52
|
|
Survivors
|
123 (91)
|
113
|
10
|
|
|
Nonsurvivors
|
12 (9)
|
9
|
3
|
0.09
|
COVID-19 Antibody
Seroconversion rate of overall population was 90.4% (122 of 135). This was 75% at
15 days, 78% at 15 to 22 days, and 84% at 23 to 30 days. It increased to 95% at third
month and maintained at 94.6% at sixth month ([Table 2]).
Table 2
COVID-19 antibody positivity
|
COVID-19 antibody test time (d)
|
Positive test/test done (%)
|
|
Abbreviation: COVID-19, coronavirus disease 2019.
|
|
< 1– 30
|
65/80 (81.25)
|
|
<15 d
|
9/12 (75)
|
|
15–22
|
25/32 (78)
|
|
23–30
|
32/38 (84)
|
|
61–90
|
39/41 (95)
|
|
151–180
|
35/37 (94.6)
|
Multiple clinical and laboratory covariates were assessed for association with antibody
production (age, sex, stage, type of cancer, COVID-19 severity, etc.) and none were
found to be correlating with antibody presence. Notably, type, and treatment of cancer
and severity of COVID-19 symptoms did not affect production of antibody and its durability
([Table 1]).
Seroconversion in Cancer Patients as Compared with HCWs
A total of 96 of 100 HCWs had antinucleocapsid antibodies positivity. Overall seroconversion
rate in cancer patients was 90.4% that was comparable with HCW (96%; p = 0.82).
Loss of Seroconversion
Only three (2.4%) patients became seronegative in subsequent evaluation. All three
had borderline positivity for antibody (1.3–2.88 index value) and loss happened at
33, 112, and 127 days, respectively.
Discussion
Studies evaluating seroconversion in COVID-19 infected individuals have shown results
approaching 90%[7]
[8]
[9]
[10]
[11]
[12] ([
Supplementary Table S1
]). There are studies showing its subsequent loss,[7]
[8]
[9]
[10] whereas a large study from Iceland showed persistence of antibodies for at least
4 months in ≥90% of recovered patients[11] ([
Supplementary Table S1
]). Persistence of antibodies has also been documented by other studies.[9]
[12]
Anti-COVID-19 Antibody in Cancer Patients
Seroconversion rate in our study population was 81.25% by first month, 95% at third
month, and 94% by six month.
There are two published studies addressing positivity of antibody in cancer patients
with COVID-19 infection. Solodky et al reported 30% antibody positivity rate (3 out
of 10 patients) in cancer patients at day 15 or later after clinical symptoms as compared
with 71% in noncancer patients (30 vs. 71%, p = 0.04).[13] However, this was a small study with only 10 cancer patients. A study from Wuhan
showed anti-COVID-19 antibody prevalence of 72.5% in 40 cancer patients ([Supplementary Table S1]).[14] In this study, the antibodies were tested at 21 days from symptom onset, whereas
our study calculated time from RT-PCR positivity (often performed after appearance
of symptoms). Our 15 days’ data of 75% seroconversion is comparable to this study.
Our larger study reinforces early appearance of antibodies in majority of cancer patients.
In our study cohort, overall, 90.4% seropositivity was seen at the median follow-up
of 92 days, which was similar to general population reported in previous studies.[10]
[11] We also compared overall seroconversion rate of cancer patients with HCW at our
institute and found it similar (90.4 vs. 96%). Patients suffering from cancer have
equivalent humoral responses compared with general population.
In our study, 35 out of 37 patients showed persistence of COVID-19 antibodies at sixth
month. No loss of antibodies was observed between third and sixth month. Persistence
of antibodies up to 6 months has been shown for the first time in cancer patients.
In the study, 67 patients received chemotherapy within 4 weeks prior to COVID-19 infection.
Seroconversion rate among these patients was 90% (at a median of 33 days) that is
similar to the overall cohort of cancer patients. We did not observe any poor antibody
responses in patients on chemotherapy.
Protective nature of these antibodies has been documented by studies on pseudoneutralization
assay[24]
[25]
[26] and clinical data on reinfection rates.[27]
[28] Though the titer of antibody that can be considered to be protective is not known,
maintained antibody levels are reassuring. Low incidence of reinfection worldwide
is another indirect evidence of its protective nature. Sustained responses can possibly
prevent reinfection in cancer patients thus avoiding treatment delays, morbidity,
and mortality. None of our patients had reinfection till the date of censoring. This
is the first such study to report this in patients suffering from cancer.
Low Levels May Become Negative
Of 135 patients, 10 patients had antibody levels between 1 and 3 index values at time
of first test. Of these 10, three patients (30%) lost their antibody levels in subsequent
testing. The patients with low index value need serial testing. Such cases may represent
false positive or lower immune responses. These are small numbers and more studies
are required to assess true incidence and implication of this subset.
Rituximab
In the cohort, eight patients were of non-Hodgkin lymphoma. Six out of these eight
patients had received rituximab in the past. Among these six patients, three patients
did not seroconvert and the other three patients had very low titer of antibodies.
Rituximab may thus be playing a role in blunted humoral responses.[29] Lower immune responses possibly can increase the risk of reinfection and also can
impact response to vaccination.
Vaccination in Cancer Patients
Pfizer and AstraZeneca trials have excluded patients of cancer/immunosuppressed states
from vaccine trial,[17]
[18] whereas Moderna[19] does not have clear information regarding the same. Hence, we do not know how the
cancer patients would develop immune response to the same. Our data so far supports
for the vaccination of cancer patients as there is no adverse impact on antibody production
in them even on chemotherapy. The same cannot be said regarding patients on rituximab.
Limitations of the study are its retrospective nature and unadjusted demographic data.
Reference date for calculation was taken as date of COVID-19 RT-PCR positivity but
patients had symptoms before that. So, the date of antibody positivity may not be
the actual date from COVID-19 infection. This data is most mature for 3 months as
the median follow-up is 92 days and inference on stability of antibody at 6 months
is based on a small number of patients (27.4%).
Future Research Directions
The study is ongoing and we would come up with 9 months follow-up. Longer follow-up
will provide the information regarding the durability of COVID-19 antibody response
in cancer patients.
Conclusion
To conclude, cancer patients even on chemotherapy produce sustained and equivalent
antibody response to COVID-19 as general population. Their reinfection rates are low.
Cancer patients are therefore likely to respond well to COVID-19 vaccine and should
be considered as priority group due to known high case fatality. However, antibody
response in rituximab treated patients may be suboptimal and needs further assessment.
