GCT-28. THE IMPACT OF RESIDUAL TUMOR ON THE OUTCOMES OF CENTRAL NERVOUS SYSTEM GERMINOMA

Abstract

Abstract BACKGROUND The inclusion of chemotherapy in the treatment backbone of central nervous system germinoma has helped reduce the field and dose of radiotherapy. Typically, patients wirh residual disease after chemotherapy are treated with higher doses of radiotherapy, which may not be necessary. Hence, we aimed to assess the impact of residual disease at different points during therapy on the outcomes of germinoma patients. METHODS We performed an extensive review of all germinoma patients diagnosed at Hospital Garrahan in Argentina over the last 20 years. We evaluated the chemotherapy response after 2 cycles and 4 cycles of chemotherapy and after radiotherapy. RESULTS Thirty nine germinoma were included (localized 34; disseminated 5). All patients were treated as per the SIOP-CNS-GCT-96 strategy. At the end of 2 cycles of chemotherapy, 21 patients achieved a complete response (CR), 10 had a partial response (PR), and 8 patients didn’t have MRI evaluation. At the end of 4 chemotherapy cycles, 10 additional patients achieved a CR, 7 still had a PR, while one patient didn’t have MRI evaluation. Only 3 patients had residual tumour after radiotherapy; one had a second-look surgery that didn’t show any evidence of viable tumour. None of the patients with residual tumour at the end of chemotherapy or radiotherapy relapsed with a median follow up of 6.3 years. CONCLUSION Residual tumor at the end of both chemotherapy and radiotherapy does not have an impact on the outcomes. Clinical trials in germinomas may need to investigate administering the same dose of radiotherapy for patients regardless of the presence of residual disease at the end of chemotherapy. Furthermore, patients with no residual disease at the end of two cycles of chemotherapy may benefit from moving directly to radiotherapy without the need to receive two additional cycles of chemotherapy.