Anyone have PCI for Limited stage SCLC neuroendocrine

I have cancer f unknown primary. Tumour in neck lymph node with histology type Neuroendocrine with suspected primary SCLC based on pathology of neck tumour.
Had radiation on neck along with neck dissection, plus chemotherapy (cisplatin & etoposide).
Medical oncologist suggests PCI for prevention of brain Mets as a recommendation for limited (suspected) small cell lung cancer.
Radiation oncologist suggests 3 month brain mri scans in lieu of pci / whole brain radiation.
Anyone have this treatment of pci? Hard to sign up for it when it's still unknown primary but suspected sclc