From this weeks Mishpacha News page 12 (my translation).
Rav Sternbuch replied when asked by "Mishpacha Magazine, "When you are dealing with a case of pikuach nefesh - there is no basis to be lenient to refrain from giving treatments which are harsh such as radiation or chemotherapy. If two doctors say that there it is necessary to have these treatments there is no option of avoiding them because of concern for serious side effects. In addition it is impossible to replace the conventional treatments for non-conventional treatments in cases of malignant illnesses since these non-conventional treatments are not considered treatments at all. These alternative medical treatments can be supplements to regular treatment but under no circcumstances can they be used instead of chemotherapy and radiation treatment - even if a homopathetic or natural doctor asserts that they can be.