In an interview with Variety, writer-director Jennifer Kaytin Robinson talked about the process of helping map Jane’s arc with Waititi, revealing that her introductory scene was initially supposed to appear even before the Marvel logo appeared:

“In the original draft, it was actually before the Marvel [Studios logo]. It was even earlier in Taika’s original draft. That always was a moving piece — ultimately, it did become [the origins for] Gorr and I think it’s awesome. But [Jane’s cancer] was never going to be a gotcha moment. It was always, like, this is the story of this woman. This is her arc. And this is where it starts.”

Jane’s cancer is also an integral part of her arc in the comics, and it is during this moment of her life that she is drawn to the power of the Mjolnir, which grants her enough strength to temporarily stave off her condition and assume the powers of The Mighty Thor. This meant that Waititi and Robinson had to take a responsible, humane approach to her story, without resorting to the overtly fantastical aspects of a superhero setting. 

This is reflected in the reveal that while the Mjolnir did give her the strength to empower her during short spells of time, it was not enough to cure her cancer — instead, it only slowed down her body’s ability to heal naturally, which eventually worsened her condition in the process. Despite knowing this, Jane chooses to fight the good fight and even helps guide back Gorr to reason, which is a testimony to the kind of person she is and the legacy she leaves behind.