With Cass beside him, Jason recovered from his battle with testicular cancer. But no sooner had they begun to celebrate, Cass’ cancer returned.

Sadly the Kanahooka teenager lost her battle with brain cancer in November 2013; but her love of life and selflessness will never be forgotten. 

Cass and Jason not only supported each other, they helped others as ambassadors for the Sony Foundation’s You Can campaign, which is establishing youth cancer centres in Australia. 

They’d also planned to write a book about their experiences to help others; a dream that Jason, now 23, has completed in her memory.

The book, By Your Side, is being released by Random House on Monday, before an official launch at Jason’s former high school Corpus Christi at Oak Flats on Thursday.

‘’I hope that people who read the book will be inspired by the way Cass lived – I hope that her zest for life will have an impact on them like it had on me,’’ Jason, of Shellharbour, said.

‘’Even though Cass was battling this devastating disease, she didn’t let it change the person she was. She remained the laughing, bubbly caring person we all knew, and she helped others going through similar journeys.’’

Jason – and Cass’ family – have never let her memory fade. They organised the You Can Walk for Cass in Wollongong on the first anniversary of her death, raising more than $80,000 for cancer research.

Cass’ mother, Gloria, was named the 2014 Barnardos Mother of the Year for her own support of young cancer patients while nursing her daughter. And in 2015 Jason was named Shellharbour’s Young Citizen of the Year.

‘’When I was diagnosed with cancer at 18 I was feeling lonely and confused – but Cass came to be by my side,’’ Jason said. ‘’She showed me I was not alone and helped me through my battle, and then I tried to do the same for her.’’

By Your Side: A  True Story of Courage, Love and Loss, RRP $34.99, is available from Monday.