Cycle of chemotherapy

 It's usually around 4 to 8 treatment for the patients. 

After each round of treatment you have a break, to allow your body to recover. So if your cycle lasts 4 weeks, you may have treatment on the 1st, 2nd and 3rd days and then nothing from the 4th to the 28th day. Then the cycle starts again.

Or, as another example, you may have a 3 week cycle where you have treatment on the 1st and 8th days, but nothing on days 2 to 7 and days 9 to 21.