Similar to what PaulB mentioned, I was told it was very important not to miss planned treatment days during the first half or so of TX due to cancer re-population concerns.

As I understood it, later in TX, the likelihood of significant re-population decreases.

Also, in my case they delayed my start of TX due to equipment update issues followed by a weekend. They said they needed a minimum of four treatments in a row before a normal two day week-end break to assure these early-on treatments would be optimally effective.