McCurdy, who was diagnosed back in 1995, had been in remission for 15 years when breast cancer returned in 2010. The disease had spread through her body and into her brain.
"Jennette has suffered an unimaginable loss," her rep said in a statement. "Please respect her and her family's privacy at this time of mourning. She appreciates the love and support of her fans."
Jennette McCurdy also thanked her fans personally, tweeting out message Saturday morning.
Overwhelmed by the love and support coming my way. Thank you tremendously.— Jennette McCurdy (@jennettemccurdy) September 21, 2013
Her boyfriend, Detroit Piston's forward Andrew Dummond, shared his sadness on his Twitter.
Damn— Andre Drummond (@DRE_DRUMMOND_) September 20, 2013
In a dark place right now....— Andre Drummond (@DRE_DRUMMOND_) September 20, 2013
First time in my life, I don't have all the answers for something.. ugh— Andre Drummond (@DRE_DRUMMOND_) September 21, 2013