How would you treat a patient with Hodgkin lymphoma who has an isolated relapse within the CNS?
It's challenging to offer specific advice in this situation without knowing a lot more. First, it's important to recognize that CNS involvement by classical Hodgkin lymphoma is extremely rare and strictly requires a brain biopsy to make a diagnosis (even in a patient with active systemic CHL, a secondary process would be likely). Biopsy-proven isolated CNS relapse was found in only 4 cases globally over 20 years by Chan Cheah and colleagues.
In such unusual circumstances, what do we do? It, of course, depends on patient characteristics, disease characteristics, prior therapies, and goals of care. HL is, of course, a radiosensitive disease, so radiotherapy is a relevant consideration. A number of cytotoxic agents active in HL have CNS penetrance, and depending on the age and fitness of the patient, ICE or augmented ICE would be expected to have activity. Under appropriate circumstances, the response could be considered for consolidation with CNS-penetrant regimens such as thiotepa/busulfan/cytoxan.
Checkpoint inhibitors (pembro/nivo) have demonstrated activity in CNS malignancy, both in NHL and solid tumor contexts, and would certainly be a relevant therapeutic consideration.
I agree that a CNS biopsy would be essential. If relapse is truly restricted to CNS then ICE would be an option as might stereotactic radiation therapy.