Trial of Therapies With IT cDC1s Combined w/ IT Trastuzamab for Her+ or IT Nivolumab for Her- BC LMD

Inclusion Criteria: * Histologically or cytologically confirmed diagnosis of BC by ASCO/CAP guidelines (Wolff et al, 2018), or radiographically definite LMD from BC. * Trial participants must have a diagnosis of LMD. They must have the presence of malignant cells in the CSF (CSF+; note now cytology is considered diagnostic of LMD if the cytology is read as positive or suspicious; \[Chamberlain et al., 2017\] OR characteristic radiographic abnormalities of LMD). Signs and symptoms of LMD in and of themselves are not sufficient for inclusion. * Patients must have an ECOG performance scale of ≤2. * Proton cranial spinal RT OR cranial spinal RT using IMRT are the preferred modalities of RT to treat LMD if possible, before study. At least WBRT is required for participation. * Coincident brain or spinal cord metastases are allowed if these are stable and do not require local therapy at the time of enrollment. Individuals with previously treated stable brain metastases are eligible to participate. * Stereotactic radiosurgery (SRS) and/or prior radiotherapy is permitted ≥2 weeks before the initial dendritic cell (DC) vaccine dose. A follow-up brain MRI should be obtained before the DC vaccine to determine the stability of the lesions. An interval of at least 2 weeks after the end of brain radiation or surgical resection of brain lesions or cytotoxic, targeted, immune, or investigational agent is required. * Must be ≥18 years of age on the day of signing the consent. * Life expectanc…