Response to Initial Treatment of Multisystem Langerhans Cell Histiocytosis: an Important Prognostic Indicator

Background: Reliable prediction of prognosis allowing risk-adapted therapy remains a major issue in the management of multisystem Langerhans cell histiocytosis (LCH). In a recent publication of the International LCH Study Group, response to initial therapy appears to be a reliable outcome predictor. The aim of this study is to test this observation in a cohort of patients treated with more intensive initial therapy. Furthermore, we compare the predictive value of response to initial therapy to some other well-established stratification systems.

Procedure: Response to initial combination chemotherapy (prednisolone, vinblastine, and etoposide) at 6 weeks and its prognostic value was evaluated retrospectively in 63 patients with multisystem LCH from the DAL-HX 83 and 90 Studies, and correlated to some established scoring systems from the literature.

Results: After 6 weeks of therapy, 50/63 (79%) patients qualified as responders, 4/63 (7%) patients showed intermediate response, and 9/63 (14%) patients did not respond. Probability of survival at 5 years was 0.94 +/- 0.03 for responders, 0.75 +/- 0.22 for patients with intermediate response, and only 0.11 +/- 0.10 for non-responders.

Conclusions: Response to initial therapy appears to be a reliable prognostic predictor. Compared to the published international LCH-I Study, our results suggest that more intensive initial treatment allows a better discrimination between responders and non-responders. This allows to identify a subgroup of patients with extremely poor prognosis (mortality rate 90%) relatively early in the disease course.