Abstract PD2-01: Local and lymphoid immune surveillance mechanisms in “exceptional survivors” of stage 4 cancers following standard of care chemo- and targeted therapies

Breast cancer patients with advanced metastatic disease can exhibit rapid disease progression, disease stabilisation or partial responses of varying duration. However, for reasons that are not fully elucidated, a small fraction of patients will elicit an exceptional durable response to standard anticancer treatments or survive significantly longer than patients with clinically comparable tumours. Here, we investigate the drivers of immune surveillance mechanisms across breast cancer subtypes in stage IV exceptional survivors (n=13) with matched control cohorts of stage IV typical responders (n=6), early breast cancer patients (n=5) and healthy volunteers (n=17). Peripheral blood mononuclear cells (PBMCs) from patients were stained with 8 panels providing 241 non-redundant immune parameters for flow cytometry analysis. Principle Component Analysis (PCA) showed distinct segregation of the exceptional survivors from the other control groups with an immune signature in exceptional survivors constituting of activated NK, CD8 T cells and gamma delta (gd) T cells pointing towards higher innate immunogenicity in these individuals. Specifically, although these metastatic exceptional responder patients possessed comparable NK cell frequencies, the proportion of NKG2D+CD56dimCD16+ NK cells were significantly enriched compared to the typical responders. Additionally, proportions of CD8+ central memory (CD45RA- CD27+) and effector memory (CD45RA- CD27-) gd T cells, were also seen to be significantly increased. Functional in vitro validation of these findings along with scRNA sequencing of lymph node and tumour tissue is currently underway. To our knowledge, this work is the first to explore in depth the immune signatures in the peripheral blood of exceptional survivors with metastatic breast cancer. Elucidating the immunological reasons for favourable atypical responses alongside functional tumour microenvironment analysis offers unique insights for predictive biomarker identification and discovery of axes that could be exploited therapeutically to benefit those with less favourable responses. Written informed consent was obtained from all individuals in accordance with the Declaration of Helsinki under the following research ethics committee; London-Chelsea approved study (REC ID 13/LO/1248).

Citation Format: Helen Kakkassery, Thanussuyah Alaguthurai, Rosalind Graham, Esme Carpenter, Farhana Hossain, Sean Keane, Sheeba Irshad. Local and lymphoid immune surveillance mechanisms in “exceptional survivors” of stage 4 cancers following standard of care chemo- and targeted therapies [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD2-01.

Abstract P2-20-02: Enrichment of atypical memory double negative (CD27— IgD—) tumour infiltrating B cells following neoadjuvant chemotherapy for early-stage breast cancer

Background: Humoral immune responses have previously been associated with improved outcomes, with B cell infiltrates able to independently predict pathologic complete response to neoadjuvant chemotherapy (NACT). B cells represent a diverse population of cells and the complex interplay between specific B cell subsets in the context of chemotherapy treated breast cancers remains unclear. Here, we investigate the dynamic changes in the B cell immune landscape before and after NACT treatment across different breast cancer subtypes. Methods: Treatment naïve, mid-treatment and post-NACT breast tumour tissue samples were dissociated into single cells, stained with two panels of B cell-specific antibodies recognising a total of 24 target proteins, and analysed by flow cytometry. In addition, PMBC before and after NACT were also profiled. B cell subsets were classified as either naïve (CD27—IgD+), class-switched memory (CD27+IgD—), unswitched memory (CD27+IgD+) or double negative (DN)(CD27—IgD—). DN B cells were further characterised into DN1 (CXCR5+CD21+) and DN2 (CXCR5—CD21—) subsets. In vitro co-cultures of breast cancer cell line spheroid and PBMC were carried out. Results: In both treatment naïve and chemotherapy treated samples, we observed a significant expansion in the DN B cell population within the TME compared to the periphery. DN B cells represented on average 40.96% of B cells in treatment naïve tumours vs 9.48% in PBMCs (p< 0.0001), and 71.80% vs 6.34% of B cells in post-NACT tumour vs PBMC samples respectively (p< 0.05). Interestingly, in treatment naïve PBMC and tumour tissue samples, the largest proportion of the DN subset consisted of DN1 cells, 69.35% and 64.11% respectively. In contrast, following NACT, DN2 cells constituted the majority of the DN population both within the TME (86.30%) and in the periphery (50.44%). Although the specific functions of these B cell subsets remain unclassified, deeper phenotyping suggests DN1 cells more closely resemble the phenotype of class-switched memory cells, whilst DN2 cells are thought to have antibody-secreting properties and more closely resemble the plasmablast phenotype. scRNA sequencing of B cells pre- and post NACT is currently underway. Conclusion: To our knowledge, this work is the first to identify an expanded population of DN B cells in breast tumour tissue and highlights the requirement for further investigation into these cells to decipher their role in the context of chemotherapy treatment and resistance in breast cancer.

Citation Format: Esme Carpenter, Thanussuyah Alaguthurai, Farhana Hossain, Rosalind Graham, Helen Kakkassery, Sean Keane, Sheeba Irshad. Enrichment of atypical memory double negative (CD27— IgD—) tumour infiltrating B cells following neoadjuvant chemotherapy for early-stage breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-20-02.

Immunogenicity of SARS-CoV-2 vaccines in patients with cancer

Transmission of the SARS-CoV-2 virus and its corresponding disease (COVID-19) has been shown to impose a higher burden on cancer patients than on the general population. Approved vaccines for use include new technology mRNA vaccines such as BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna), and nonreplicating viral vector vaccines such as Ad26.COV2.S (Johnson & Johnson) and AZD1222 (AstraZeneca). Impaired or delayed humoral and diminished T-cell responses are evident in patients with cancer, especially in patients with haematological cancers or those under active chemotherapy. Herein we review the current data on vaccine immunogenicity in cancer patients, including recommendations for current practice and future research.

Boosting of Waned Humoral and Cellular Responses to SARS-CoV-2 Variants of Concern Among Patients with Cancer

This study offers longitudinal insight into the impact of three SARS-CoV-2 vaccinations on humoral and cellular immunity in patients with solid cancers, patients with hematologic malignancies, and persons without cancer. For all cohorts, virus-neutralizing immunity was significantly depleted over a period of up to 9 months following the second vaccine dose, the one striking exception being IL2 production by SARS-CoV-2 antigen-specific T cells. Immunity was restored by the third vaccine dose, except in a substantial number of patients with hematologic malignancy, for whom both cancer type and treatment schedule were associated with nonresponse. Thus, whereas most patients with myelodysplastic syndrome were conspicuously good responders, some patients with other hematologic malignancies receiving cancer therapies within 2 weeks of vaccination showed no seroconversion despite three vaccine doses. Moreover, SARS-CoV-2 exposure during the course of the study neither prevented immunity waning, even in healthy controls, nor guaranteed vaccine responsiveness. These data offer real-world human immunologic insights that can inform health policy for patients with cancer.

Safety and immunogenicity of one versus two doses of the COVID-19 vaccine BNT162b2 for patients with cancer: interim analysis of a prospective observational study

BACKGROUND

The efficacy and safety profiles of vaccines against SARS-CoV-2 in patients with cancer is unknown. We aimed to assess the safety and immunogenicity of the BNT162b2 (Pfizer-BioNTech) vaccine in patients with cancer.

METHODS

For this prospective observational study, we recruited patients with cancer and healthy controls (mostly health-care workers) from three London hospitals between Dec 8, 2020, and Feb 18, 2021. Participants who were vaccinated between Dec 8 and Dec 29, 2020, received two 30 μg doses of BNT162b2 administered intramuscularly 21 days apart; patients vaccinated after this date received only one 30 μg dose with a planned follow-up boost at 12 weeks. Blood samples were taken before vaccination and at 3 weeks and 5 weeks after the first vaccination. Where possible, serial nasopharyngeal real-time RT-PCR (rRT-PCR) swab tests were done every 10 days or in cases of symptomatic COVID-19. The coprimary endpoints were seroconversion to SARS-CoV-2 spike (S) protein in patients with cancer following the first vaccination with the BNT162b2 vaccine and the effect of vaccine boosting after 21 days on seroconversion. All participants with available data were included in the safety and immunogenicity analyses. Ongoing follow-up is underway for further blood sampling after the delayed (12-week) vaccine boost. This study is registered with the NHS Health Research Authority and Health and Care Research Wales (REC ID 20/HRA/2031).

FINDINGS

151 patients with cancer (95 patients with solid cancer and 56 patients with haematological cancer) and 54 healthy controls were enrolled. For this interim data analysis of the safety and immunogenicity of vaccinated patients with cancer, samples and data obtained up to March 19, 2021, were analysed. After exclusion of 17 patients who had been exposed to SARS-CoV-2 (detected by either antibody seroconversion or a positive rRT-PCR COVID-19 swab test) from the immunogenicity analysis, the proportion of positive anti-S IgG titres at approximately 21 days following a single vaccine inoculum across the three cohorts were 32 (94%; 95% CI 81-98) of 34 healthy controls; 21 (38%; 26-51) of 56 patients with solid cancer, and eight (18%; 10-32) of 44 patients with haematological cancer. 16 healthy controls, 25 patients with solid cancer, and six patients with haematological cancer received a second dose on day 21. Of the patients with available blood samples 2 weeks following a 21-day vaccine boost, and excluding 17 participants with evidence of previous natural SARS-CoV-2 exposure, 18 (95%; 95% CI 75-99) of 19 patients with solid cancer, 12 (100%; 76-100) of 12 healthy controls, and three (60%; 23-88) of five patients with haematological cancers were seropositive, compared with ten (30%; 17-47) of 33, 18 (86%; 65-95) of 21, and four (11%; 4-25) of 36, respectively, who did not receive a boost. The vaccine was well tolerated; no toxicities were reported in 75 (54%) of 140 patients with cancer following the first dose of BNT162b2, and in 22 (71%) of 31 patients with cancer following the second dose. Similarly, no toxicities were reported in 15 (38%) of 40 healthy controls after the first dose and in five (31%) of 16 after the second dose. Injection-site pain within 7 days following the first dose was the most commonly reported local reaction (23 [35%] of 65 patients with cancer; 12 [48%] of 25 healthy controls). No vaccine-related deaths were reported.

INTERPRETATION

In patients with cancer, one dose of the BNT162b2 vaccine yields poor efficacy. Immunogenicity increased significantly in patients with solid cancer within 2 weeks of a vaccine boost at day 21 after the first dose. These data support prioritisation of patients with cancer for an early (day 21) second dose of the BNT162b2 vaccine.

FUNDING

King's College London, Cancer Research UK, Wellcome Trust, Rosetrees Trust, and Francis Crick Institute.

B Cells in Patients With Melanoma: Implications for Treatment With Checkpoint Inhibitor Antibodies

The contributions of the humoral immune response to melanoma are now widely recognized, with reports of positive prognostic value ascribed to tumor-infiltrating B cells (TIL-B) and increasing evidence of B cells as key predictors of patient response to treatment. There are disparate views as to the pro- and anti-tumor roles of B cells. B cells appear to play an integral role in forming tumor-associated tertiary lymphoid structures (TLSs) which can further modulate T cell activation. Expressed antibodies may distinctly influence tumor regulation in the tumor microenvironment, with some isotypes associated with strong anti-tumor immune response and others with progressive disease. Recently, B cells have been evaluated in the context of cancer immunotherapy. Checkpoint inhibitors (CPIs), targeting T cell effector functions, have revolutionized the management of melanoma for many patients; however, there remains a need to accurately predict treatment responders. Increasing evidence suggests that B cells may not be simple bystanders to CPI immunotherapy. Mature and differentiated B cell phenotypes are key positive correlates of CPI response. Recent evidence also points to an enrichment in activatory B cell phenotypes, and the contribution of B cells to TLS formation may facilitate induction of T cell phenotypes required for response to CPI. Contrastingly, specific B cell subsets often correlate with immune-related adverse events (irAEs) in CPI. With increased appreciation of the multifaceted role of B cell immunity, novel therapeutic strategies and biomarkers can be explored and translated into the clinic to optimize CPI immunotherapy in melanoma.