Tom Parker performs in 2013.
CNN  — 

British singer Tom Parker, best known for being part of popular boy band The Wanted, has told fans there has been a “significant reduction” in the size of his inoperable brain tumor.

The 32-year-old said in October that he was undergoing treatment after being diagnosed with a grade four glioblastoma tumor.

In an update posted on Instagram on Thursday, he said he had been responding well to treatment.

“Significant reduction. These are the words I received today and I can’t stop saying them over and over again,” he wrote.

Parker went on to thank the UK’s National Health Service, which he called “wonderful,” his wife Kelsey Hardwick and their two children, as well as his fans.

“To everyone on here – your love, light and positivity have inspired me. Every message has not been unnoticed they have given me so much strength,” wrote Parker. “This journey is a rollercoaster that’s for sure.”

In October Parker told Britain’s OK! Magazine that doctors described the tumor as a “worst-case scenario” and had informed the couple that it was terminal.

The singer said he went to hospital after suffering two seizures over the summer. Parker told OK!: “They pulled the curtain around my bed and said, ‘It’s a brain tumour.’ All I could think was, ‘F*****g hell!’ I was in shock. It’s stage four glioblastoma and they’ve said it’s terminal. It was a lot to deal with by myself. I still haven’t processed it.”

The average survival time for patients with a grade four glioblastoma, one of the most serious kinds of tumors, is between a year and 18 months, according to UK nonprofit The Brain Tumour Charity.

Parker rose to fame as part of The Wanted, a five-piece boy band whose hits included “All Time Low” and “Heart Vacancy.”

The group enjoyed a string of top five singles in the UK, including two number ones, while their 2011 track “Glad You Came” made it to number 3 in the US Billboard charts. They split up in 2014 to pursue solo projects.

CNN’s Rob Picheta contributed to this report.