Marrow-ablative consolidation chemotherapy (HDCT) to decrease the development of choroid plexus carcinoma (CPC) specific relapse in high-risk TP53-mutated (germline or somatic) young children with newly diagnosed CPC.

Abstract

2088 Background: Choroid plexus carcinomas (CPC) are highly malignant, early childhood cancers in which the loss of TP53 function is a central element of their development and defines unfavorable disease. To date, CPC-free survival rates have remained poor; recent data from St. Jude including complete TP53 mutation status, yielded CPC-free survival of only 29% with a non-marrow-ablative chemotherapy strategy. The rarity of CPC has constrained the ability to explore the role of HDCT with autologous hematopoietic progenitor cell rescue (AuHPCR). Previously reported results of the "Head Start" (HS) HDCT approach showed some promise of cure, but were limited by small patient numbers, short follow-up and incomplete TP53 mutation data. Consequently, the role of HDCT and AuHPCR in TP53-mutated CPC remains unclear. Methods: We have analyzed data on TP53 status, therapy, treatment responses, CPC-free and overall survivals (OS) and second cancers from the largest cohort of such patients, all who received initial therapy with the intent/consideration of undergoing consolidative HDCT. Results: Twenty-seven children with CPC (median age, 16 months) received HS-like induction chemotherapy regimens or ICE with the intent of utilizing consolidative HDCT. Twenty-three of 27 completed HDCT consolidation; the remaining 4 patients did not proceed with HDCT due to parental choice. Somatic or germline TP53 mutations were identified in 17 patients, while 4 patients exhibited TP53 wild type (TP53wt); TP53 status remains untested or unavailable in 6 patients. Five-year CPC-free survival and OS for the entire cohort were 47.8% and 44.4%. CPC-free survival for those with TP53 germline mutations (n=12) was 66%, for those with somatic tumor TP53 mutations (n=5) was 40% and for those with confirmed TP53wt (n=4) was 50%. The 5-year CPC-free survival for all 23 patients who underwent HDCT and AuHPCR was 52%, comprising 3/4 TP53wt patients, 10/12 TP53 germline mutated patients and all 5 TP53 somatic tumor mutated patients. Notably, all six survivors with TP53 mutations had undergone HDCT with AuHPCR, and all but one avoided irradiation. Eight out of 12 patients with documented genotypic (TP53 germline mutated) Li-Fraumeni Cancer Predisposition Syndrome (LFS) developed second malignancies. Conclusions: Our data indicate that HDCT with AuHPCR consolidation is associated with improved CPC-free survival compared with historical reports in young children with high-risk TP53 mutated CPC. However, the ultimate development of second cancers substantially affects outcomes for those with LFS, irrespective of HDCT treatment. These data justify the inclusion of HDCT and AuHPCR in the prospective international trial under development for young children with newly diagnosed TP53 mutated CPC.