Hello all:
Yes, Mepitel Film (not plain Mepitel or Mepitel One--these are different products) is great! Used it for 33 sessions of breast radiation including underarm, collarbone lymph nodes and neck. There are many medical journal articles highlighting Mepitel film's usefulness. There is an excellent article in the Journal of Clinical Oncology, Dec. 2022, "Mepitel Film for the prevention of acute radiation dermatitis in breast radiation".
There are other medical journal articles--use search terms: Mepitel breast radiation.
The Mepitel Film helped me a lot!
There are some in-service YouTube videos produced by the manufacturer (a Swedish company called Molnlycke) of Mepitel on how to apply it. One tip is to use one sheet on the underarm. That's not a place to patchwork it.
When showering, place a small towel over your shoulder so rhat the water does not directly hit the top of the Mepitel on your shoulder or chest.
Good luck everyone!