Length of hospital stay and outcome in primary central nervous system lymphoma: a French retrospective multicentric study.

Primary central nervous system lymphoma (PCNSL) is a rare form of lymphoma with a poor prognosis. We used the LOC network database, including 365 patients from 14 voluntary centers. Inclusion criteria were age ≥ 60 years, immunocompetence, confirmed PCNSL diagnosis and treatment with curative intent with MPV-based regimen (Methotrexate, Procarbazine, Vincristine) between 2011 and 2021. We analyzed LOS from first day of chemotherapy to dismissal from hospital. Using the MAXStat method we found the LOS threshold of 15 days, to be one of most statistically significant and most convenient to separate two groups with different OS. The median age of the whole population was 71 years, median Karnofsky performance score (KPS) was 70%. The main differences between short and long LOS groups were median KPS at diagnosis (70% vs 50%) and deep structure involvement status (51% vs 67%). With a median follow up of 22.8 months, the median OS was respectively 62.2 and 20 months for short and long LOS. Median PFS was respectively 18 and 9.3 months. Multivariate analysis found in our cohort that age was associated with OS (P = 0.01) and LOS with OS (P = 0.005) and PFS (P = 0.014). KPS at diagnosis is a cofounder to LOS in the analysis. LOS remains associated with OS (P = 0.016) in a subgroup analysis of patients with baseline KPS < 70%. Altogether, the LOS > 15 days identifies a population of patients with poorer outcome in elderly PCNSL patients. Its underlying drivers require further investigation in larger and prospective cohorts.