LBCL is a cancer of the lymphatic system where B-cells (a type of white blood cell) experience uncontrolled growth. The standard treatment for LBCL is a combination of chemotherapy and immunotherapy, referred to as chemo-immunotherapy. Currently, the best results in the treatment of LBCL is with a chemo-immunotherapy combination called R-CHOP or Pola-R-CHP. Full doses of treatment are not suitable for elderly or frail patients due to potential to cause side effects and heart problems. Such patients either receive a reduced dose called mini-R-CHOP or receive alternatives (e.g. R-GCVP or R-CEOP). Additionally, some patients treated with R-CHOP or Pola-R-CHP may not respond or may respond initially before relapsing. For these patients, treatment is not standardised, and practice varies between hospitals. ALMANAC aims to collect data about the management and outcomes of patients with LBCL who are unsuitable for standard treatments because they are not well enough to tolerate the side effects or because they have not responded or relapsed following initial treatment. In doing so, it will guide research into LBCL leading to a better understanding of this condition and better outcomes.