herceptin weekly vs every 3 weeks

[suzan w]

I am going to be starting herceptin in 3 weeks...my onc. says every 3 weeks, then I hear of women getting it weekly. Until I have a chance to ask onc. about this..are there any differences in weekly/3 weeks? Also...I was planning on being gone for a month in Dec. (trip put off for way too long!) how might that impact things...skipping a dose...any insights greatly appreciated!!! Thanks!