Systemic versus local therapy

Local treatments can cure a cancer that is truly confined but cannot reach cells that have already escaped, while systemic drugs reach everywhere but rarely eradicate a bulky tumour on their own; most curative treatment therefore combines them, with drugs before surgery (neoadjuvant) or after (adjuvant) to deal with microscopic spread. In metastatic disease systemic therapy is the mainstay, with local treatments added to relieve symptoms or, in oligometastatic disease, to remove every visible deposit. Intermediate approaches deliver drugs regionally (into the liver's artery, into the abdominal cavity as HIPEC, into the bladder), and radioligands blur the line by delivering radiation systemically.