275P Serological response to COVID-19 vaccine in patients with advanced breast cancer

Abstract

Background Patients (p) with solid tumor have an increased risk of severe coronavirus disease 2019 (COVID-19) and associate higher mortality compared to general population. Cancer patients were not included in pivotal trials of COVID-19 vaccines. A high proportion of p with solid tumors develop immunological responses following vaccination, and subsequent doses can result in seroconversion in those who were previously seronegative after the two first doses. In Advanced Breast Cancer (ABC) p knowledge of vaccine effects is scarce. Methods Prospective observational study analysed the serological response to COVID-19 vaccine in a series of patients (p) with ABC treated in a single institution. Between 01/03/2021 and 19/05/2021 we analysed the serological response by serial determination of COVID-19 antibodies (Ab) 21 or 28 days after each dose and 3, 6, 9 and 12 months (m) after the second dose. We considered an antibody titration of 2500 total Ig/ml as a robust antibody response (RAR). Results N=43 p. with ABC, 100% female; median age: 69 years (y). Comorbidity: 29 p (67%) hypertension, 6 p (14%) active smoking. Histological subtype: 21 p (49%) luminal, 19 p (44%) Her2 + and 3 p (7%) triple negative (TN). Treatment: 2 p (5%) chemotherapy (CT), 3 p (7%) immunotherapy and 29 p (88%); First-line: 20 p (48%), 2ndline 8 p (19%), 3rdor successive line 14 p (33,4)[MMDP1]. A previous COVID-19 infection: 1 p (2,3%); In the period of study 8 p were tested positive for COVID-19. Type of vaccine: Pfizer/BioNTech (Comirnaty): 33 p (78%) and Moderna (Spikevax) 10 p (23%). Adverse effects: 2 p (4.7%) with one requiring hospitalization (2.3%). After the first vaccine, 2/32 p (6.3%) had RAR. Following a second dose, the RAR rose to 8/35 p (23%). At 3 and 6 m after the second dose a RAR was observed in 4/23 p (17.4 %) and 10/25 p (40%) respectively. A 3rddose increased the RAR robust to 13/16 p ( 81%), and in those receiving a 4thvaccine (9/43) 77.8% achieved a robust Ab response. At the end of the follow-up, 7 p (16%) (7/43) died of cancer. The efficacy of vaccines was similar to general population regardless of cancer diagnosis and treatments. Conclusions In our series of ABC patients tested for COVID-19 vaccine seroconversion, a robust serological response was shown especially after the 3rdand 4thdose (in up to 80% of patients). Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure E. Galve-Calvo: Financial Interests, Personal, Invited Speaker: AstraZeneca, Daiichi Sankyo, Gilead, Novartis, Pfizer. All other authors have declared no conflicts of interest.