My periods were crazy all over the place all my life so most of my life I was on contraceptive pill which regulated it wonderfully. When diagnosed with bc my doctor said get off them immediately, the estrogen in the pill is feeding the cancer. So I went from wonderfully regular to off the pill and nothing, nada, zip.
Several weeks after surgeries and into my second dose of chemo i got the muther of all periods and had to be very careful to keep up my iron levels. My oncologist said this is normal as chemo also does wierd things to periods. I am happy to say over a year since chemo and surgery I don't have periods at all any more, not even spotting. Saving me a fortune in pads and tampons I tell you lol. I will be 55 next month.