Lower detection rates of SARS-COV2 antibodies in cancer patients versus health care workers after symptomatic COVID-19.

The diagnosis of coronavirus disease 2019 (COVID-19) is based on the detection of the severe acute respiratory syndrome coronavirus 2 (SARS-COV2) virus using RT-PCR from nasopharyngeal samples at the time of active infection.1, 2, 3 Most patients infected with SARS-COV2 develop antibodies (Ab) against SARS-COV2 proteins.1, 2, 3 The survival of cancer patients presenting with RT-PCR+ COVID-19 has been reported to be very poor, with up to 30% mortality at 30 days. ,

In this work, we retrospectively analyzed cancer patients presenting with a suspicion of COVID-19 from 1 March 2020 to 16 April 2020 as part of an Institutional Review Board approved clinical trial (Oncovid-19, approved 12 March 2020) and a series of health care workers (HCWs, nurses and doctors) as part of a voluntary testing procedure in the Centre Leon Berard.

All 85 cancer patients were tested both with SARS-nCoV2 RT-PCR on nasopharyngeal samples and a point-of-care Ab diagnostic test, Toda Coronadiag® (TODA Pharma, Strasbourg France). Coronadiag is a rapid lateral flow immunoassay (LFIA) providing results in 10 min using a finger-pricked blood sample. This test was carried out 15 days or more after a positive RT-PCR or COVID-19 symptoms.

The LFIA test was carried out in all 244 HCWs. In addition, SARS-CoV2 RT-PCR was found positive previously (>15 days) in 14 HCWs presenting with clinical symptoms, and was carried out in the three HCWs testing positive for SARS-COV2 Ab.

Ten of 85 (12%) cancer patients had documented SARS-CoV2 on RT-PCR, and five (6%) had a positive Ab detection test. Three of the 10 (30%) RT-PCR-confirmed infected patients had detectable Ab anti-SARS-COV2 15 days after the clinical start of the infection. Two of the 75 (2.3%) remaining cancer patients screening negative for RT-PCR had detectable SARS-COV2 immunoglobulin G.

In parallel, all 244 HCWs were tested with the LFIA test, including 14 with a RT-PCR-documented SARS-COV2 infection: 10 of these 14 (71%) RT-PCR-confirmed infections had detectable Abs 15 days or later after clinical symptoms. Three of the remaining 230 (1.3%) HCWs had detectable Ab but a negative test for RT-PCR carried out at the same time. Two of these reported possible COVID-19 symptoms in the previous weeks.

The rate of seroconversion 15 days after documented SARS-COV2 on RT-PCR was therefore significantly lower in cancer patients versus HCWs (30% versus 71%, P = 0.04). Importantly, six of the seven serodiagnostic-negative cancer patients had received cytotoxic therapy or major surgical intervention in the previous 4 weeks, compared with none of the five remaining patients (P = 0.003). None of these patients died.

In this series, 5 of 85 (5.9%) and 13 of 244 (5.4%) cancer patients and HCWs, respectively, had detectable Ab against COVID-19. However, cancer patients had a significantly lower detection rate of SARS-COV2 Ab 15 days or later after symptoms and RT-PCR+ testing. Anti-SARS-COV2 Ab were more often undetectable in patients receiving cancer treatments in the month before testing. Additional studies will be needed to confirm whether immune response to the virus is influenced by recent cancer treatments.