It comes just days after the former Upper Hutt Posse member was awarded the Independent Spirit Award, recognising her longstanding contributions to music and advocacy for Pacific artists.
The 51-year-old made the revelation about her cancer diagnosis to Sunday Star Times reporter André Chumko, in her first interview in more than two years.
She said she had received her diagnosis in 2022 - the same year her debut album was meant to be released.
"I had to walk around my house going 'BRAIN TUMOUR' just randomly, just to shock my brain into thinking, I've actually got a brain tumour. Then it was two brain tumours and I was like, what? I had to shift my mindset. I had to get myself into a mindset of I have children, I have grandchildren. I might not be here in the next six months," she tells Sunday Star Times.
"My goal is to keep focusing on living, on focusing on a healing light within my body."
The cancer is sitting in her optic chiasm, which is at the bottom of the brain and extremely close to the bone. Chemotherapy is not an option.
During her previous interview, with RNZ's Kim Hill on Saturday Morning, she spoke about Daughter of a Housegirl, which was more than three decades in the making.
The album was never released - she now reveals to the Sunday Star Times that part of the reason was her shock diagnosis.
At the time of the Kim Hill interview, she also had been diagnosed with an autoimmune disorder but never opened up publicly about it until now.
Rapley started her music career as a teenager in the late '80s performing with politically conscious hip hop group Upper Hutt Posse.
In the years following, she has worked with countless musical acts including Moana and The Moahunters, Dam Native, Mark de Clive Lowe, Che Fu and King Kapisi - who is also Rapley's husband.
Upper Hutt Posse emerged at the forefront of the NZ's growing rap culture with their unique fusion of rap and reggae. Their songs which combine both Māori and English languages paved the way for future bi-lingual music in New zealand and were an inspirational injection into the local music scene and a powerful vehicle for their socio-political perspectives.
'Ragga Girl' peaked at number 48 on the NZ Singles chart.
In 2021, Rapley was made a Member of the NZ Order of Merit for services to music and television.
"I love music, music is me, there's no way to separate it from who I am and what I do," she told the crowd while accepting her Independent Spirit award at the Taite Music Awards on Tuesday.
"Thank you for all of you musicians and managers and mums and dads and everyone who makes up this ecosystem, mauri ora."
