Apparently you saw information which originated in an article/newsletter by Naturopathic oncologist Jacob Schor, who maintains that N-Acetyl Cysteine blocks the oxidative reaction in cancer cells which lead to their death. Such information runs counter to indications that NAC actually inhibits cancer growth by blocking mitochondrial oxidative stress which drives tumor growth. See for example:
If you do a search for "N-Acetyl cysteine for cancer treatment", other than the Schor article you will pretty much find positive information about using NAC for cancer. N-Acetyl Cysteine is considered an essential by both myself and Naturopathic PhD Marc Swanepoel (who devised the SutherlandiaOPC line of oleander-based supplements) and what we have recommended has been extremely successful.