What are the best radiation therapy options for a young adult with 3 brain metastases from myeloid sarcoma that hasn’t responded well to intrathecal therapy?

The prognosis for young adults with Acute Myeloid Leukemia (AML) experiencing a Central Nervous System (CNS) relapse is generally poor, with most studies reporting a 5-year overall survival rate of ~11%, indicating a very grim prognosis due to the aggressive nature of CNS involvement in AML.

The precise answer to this question depends on the goals of treatment (curative versus palliative). If the goal of treatment is curative, it is important to consider whether the patient will undergo Total Body Irradiation as conditioning for a Bone Marrow Transplant (coordination with the BMT team is paramount).

Assuming that the goal is curative, and that the patient has bone marrow reserves, this young adult could be treated with Craniospinal Irradiation (CSI), 24 Gy at 1.5 or 2 Gy/fraction, with a simultaneous integrated boost (SIB) to the 3 brain metastases to bring the dose to these lesions to 30 Gy.

If the SIB is difficult to integrate in the context of CSI, a sequential SRS boost to each of the 3 lesions could be added. A  follow-up brain MRI at the end of the CSI could inform about the need for a boost after 24 Gy. Most reports and my personal experience indicate that doses of 25-30 Gy are effective in achieving a CR for most cases, but the response is also a function of size of the lesion. Chen et al., PMID 24148102