Methods for the treatment of pulmonary cancers (primary, secondary, metastatic, etc.) using an electronic breath actuated droplet delivery device to deliver a cancer therapeutic directly to the pulmonary system of a subject in need thereof is disclosed. An in-line droplet delivery device and related methods for delivering precise and repeatable dosages to a subject for pulmonary use is disclosed. The in-line droplet delivery device includes a housing, an ejector mechanism, and at least one differential pressure sensor. The in-line droplet delivery device is automatically breath actuated by the user when the differential pressure sensor senses a predetermined pressure change within housing. The in-line droplet delivery device is then actuated to generate a plume of droplets having an average ejected particle diameter within the respirable size range, e.g, less than about 5-6 µm, so as to target the pulmonary system of the user.
