Intestinal mucositis, systemic inflammation and bloodstream infections following high‐dose methotrexate treatment in childhood acute lymphoblastic leukaemia: Comparison between the <scp>NOPHO ALL</scp> 2008 protocol and the <scp>ALLTogether1</scp> pr

Severe intestinal mucositis (IM) increases the risk of bloodstream infections (BSI) and inflammatory toxicity during acute lymphoblastic leukaemia (ALL) induction treatment. However, the implications of IM in subsequent ALL therapy phases after achieving remission remain unknown. This study investigated the relationship between IM (measured by plasma citrulline and the chemokine CCL20) and the development of BSI and systemic inflammation (reflected by C-reactive protein, CRP) in children with ALL during high-dose methotrexate (HDMTX) treatment, an important part of ALL consolidation therapy. The study compared patients treated according to the NOPHO ALL 2008 protocol (n = 52) and the ALLTogether1 protocol (n = 42), both with identical HDMTX procedures but different scheduling. One week post-HDMTX, citrulline dropped to median levels of 14.5 and 16.9 μM for patients treated according to the NOPHO ALL 2008 and ALLTogether1 protocols, respectively (p = 0.11). In a protocol and neutrophil count-adjusted analysis, hypocitrullinaemia (<10 μmol/L) was associated with increased odds of BSI within 3 weeks from HDMTX (OR = 26.2, p = 0.0074). Patients treated according to the NOPHO ALL 2008 protocol exhibited increased mucosal- and systemic inflammation post-HDMTX compared to patients treated according to ALLTogether1, with increased CCL20 (14.6 vs. 3.7 pg/mL, p < 0.0001) and CRP levels (10.0 vs. 1.0 mg/L, p < 0.0001). Both citrulline and CCL20 correlated with CRP for these patients (r_s = -0.44, p = 0.0016 and r_s = 0.35, p = 0.016, respectively). These results suggest that hypocitrullinaemia following HDMTX increases the risk of BSI, confirming previous observations from more intensive treatments. Moreover, these data indicate that the patients' vulnerability to mucositis and inflammatory toxicity after chemotherapy varies with treatment protocol.