Cranial radiation for pediatric T-lineage acute lymphoblastic leukemia: a systematic review and meta-analysis

There are heterogeneous approaches to cranial radiation therapy (CRT) for T-lineage acute lymphoblastic leukemia (T-ALL). We performed a systematic review of studies that specified a radiation strategy and reported survival for pediatric T-ALL. Our analysis included 62 publications reporting 78 treatment groups (patient n = 5844). The average event-free survival (EFS) was higher by 6% per 5 years (P < 0.001). Adjusting for year, EFS differed by radiation strategy. Compared to the reference group (CRT for all) which had a year-adjusted EFS of 65% (95% confidence interval, CI: 61-69%) the adjusted EFS was significantly worse (rate difference (RD) = -9%, 95% CI: -15 to -2%) among studies that used a risk-directed approach to CRT (P = 0.004). The adjusted EFS for the other strategies were not significantly different compared to the reference group: CRT for central nervous system positive patients only (RD = -3%, 95% CI: -14 to 7%, P = 0.49); CRT omitted for all patients (RD = 5%, 95% CI: -4 to 15%, P = 0.33). CRT may not be necessary with current chemotherapy for T-ALL. These findings, however, are susceptible to bias and caution should be applied in drawing conclusions on the comparative effectiveness of alternative CRT strategies.