Impact of cancer diagnosis, stage, and systemic therapies on immunogenicity after COVID-19 vaccination in patients with cancer: A systematic review and meta-analysis.

1537 Background: Patients (pts) with cancer are at increased risk of severe COVID-19. Both underlying malignancy and anti-cancer treatments influence the immune system, potentially impacting the level of vaccine protection achieved. Methods: A systematic literature search of PubMed, Embase, CENTRAL and conference proceedings (ASCO annual meetings and ESMO congress) up to 28/09/21, was conducted to identify studies reporting anti-SARS-CoV-2 spike protein immunoglobulin G seroconversion rates (SR) at any time point after complete COVID-19 immunization (mRNA- or adenoviral-based vaccines) in cancer pts. Complete immunization was defined as 1 dose of JNJ-78436735 vaccine or 2 doses of BNT162b2, mRNA-1273 or ChAdOx1 nCoV-19 vaccines. Subgroup analyses were performed to examine the impact of cancer diagnosis, disease stage, and anticancer therapies on the SR. Overall effects were pooled using random-effects models and reported as pooled SR with 95% confidence intervals (CI). Results: Of 1,548 identified records, 64 studies were included in this analysis reporting data from 10,511 subjects. The Table shows the SR in the overall population and specific subgroups. In pts with solid malignancies (SM), disease stage and primary site did not significantly impact the SR. In pts with hematologic malignancies (HM), SR were significantly lower in pts with chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL) compared to acute lymphoblastic leukemia (ALL), Hodgkin lymphoma (HL), and multiple myeloma (MM). Concerning the impact of cancer therapies on SR, pts with SM undergoing chemotherapy had numerically lower SR (N = 1,234, SR 87%, CI 81-92) compared to those treated with immune checkpoint inhibitors (N = 574, SR 94%, CI 88-97) or endocrine therapy (N = 326, SR 94%, CI 86-97) with or without another targeted therapy. Pts with HM treated with anti-CD20 therapy (within the last 12 months: N = 360, SR 7%, CI 2-20; or more than 12m: N = 175, SR 59%, CI 35-80), immune-modulating agents (BTK or BCL2 inhibitors) (N = 462, SR 47%, CI 32-64%) or other immunotherapies (anti-CD19/CART or anti-CD38) (N = 293, SR 37%, CI 23-53) had lower SR compared to pts treated with autologous (N = 353, SR 77%, CI 67-85) or allogenic stem cell transplantation (N = 509, SR 77%, CI 68-84). Conclusions: SR varies between cancer types and anticancer therapies with some cancer pts having low protection against COVID-19 even after complete vaccination. [Table: see text]