At San-Diego Comic-Con last year, Marvel Studios showcased nearly their entire slate for Phase 4 with many left-field announcements like a Blade movie starring two-time Oscar winner Mahershala Ali and officially revealing the earlier rumored Hawkeye series for Disney's streaming service.
Possibly one of the biggest shocks at this event was Natalie Portman walking on stage and returning as Jane Foster in Thor: Love and Thunder. No one imagined that Portman would return to the role, especially after her non-ideal experience with Marvel Studios with Thor: The Dark World. But, an even bigger surprise than Jane Foster's return was that Natalie Portman would actually wield Mjolnir.
To non-comic book fans, this may seem like Marvel Studios jumping the preverbal space-shark, but this has actually happened twice in the comics, most prominently in Jason Aaron's comic run of Thor. While Aaron started his tenure as writer for the character in 2012 with the aptly titled, Thor: God of Thunder, he would not give Jane Foster the hammer until 2014, which was accompanied by a relaunch of the series, simply titled Thor and later The Mighty Thor.
The latter two runs are what Taika Waititi has openly stated as being inspiration for the story being told in Thor: Love and Thunder. The big twist during this run of the character was that Jane Foster actually had cancer at the time, which became worse the more she used Mjolnir and turned into Thor.
However, when asked in February about this plot point being used in Thor: Love and Thunder, Waititi was unsure it would be in the final draft. So, while the New Zealand director has almost finished a final draft for the movie, The Direct will still make the case for why and how Jane Foster having cancer would almost make too much sense in Thor: Love and Thunder.
To give more context to Jason Aaron's comic run, after having her own life separate from Thor, Jane Foster discovers she has breast cancer and begins to treat it. Shortly after beginning her treatment, Thor became unworthy of lifting Mjolnir, so Foster picked it up in his stead, becoming the new Thor - often dubbed as Lady Thor or The Mighty Thor.
When Foster wielded the hammer and gained all the powers of Thor, it expunged all toxins from her body, purifying her. Unfortunately, since chemotherapy is essentially a foreign poison to the body, it purged from her system as well. The reason that the hammer didn't rid Jane of the cancer in her was due to it naturally occurring and it not being an outside ailment afflicted upon her.
So, this meant that every time she used Mjolnir, her treatment of chemo would be removed, leaving the cancer to worsen. Additionally, if the hammer ever left her grasp for too long, Foster would revert back to being a feeble cancer patient that couldn't defend herself.
Giving Jane Foster cancer goes beyond it just being accurate to the source material - it would be a legitimately good hook to have for the movie and character. It would give actual stakes to the story and add tension to whether or not Jane Foster would succumb to her cancer by the end of the movie. Fans don't know if Natalie Portman will continue to appear in the MCU after Love and Thunder, so her potential death from cancer would raise the stakes of the entire movie.
THE AETHER BEING THE CAUSE
Jane Foster had breast cancer in the comics, which one would imagine easily being curable in a universe filled with geniuses such as Reed Richards or masters of the mystic arts like Doctor Strange. It's especially ridiculous that a cure for various forms of cancer aren't common, as Wakanda claimed to have a cure for it at one point.
The technology of the Marvel Cinematic Universe is not too far off from the comics, as T'Challa's home was shown to easily heal life threatening spinal injuries. So, for audiences to believe that Jane couldn't just be cured from the tecnhology that already exits on Earth, the cause of the cancer would have to be other-worldly.
Jane's illness can't be something that the MCU's science or magic can just hand-wave away. This is why having the cause of this cancer be The Aether (Reality Stone) makes complete sense. This substance was one of the most powerful objects in the universe and existed since the dawn of creation itself. Jane had been infected with it in Thor: The Dark World, which was stated to be slowly killing her the longer it was in her body. Not to mention that she was directly told that Asgardian technology and medicine could not remove it.
When Jane contracts the Aether in The Dark World, it's visually shown to be spreading its dark tendrils across the universe like a cancer, which would make for retroactive foreshadowing. So, what if after it was removed by Malekith, the Reality Stone did more long-lasting damage to Jane's body than anyone expected? Maybe at one point, shortly after Avengers: Age of Ultron, she found out what it had done, what it left behind, and that nothing could be done to cure it - only delay it.
UNEXPLAINED BREAK UP
Obviously, at the time that Thor: Ragnarok was written, it seemed very unlikely that Natalie Portman would ever return to the role again after her frustration from the production of The Dark World, which meant that Marvel Studios had to write her out of the MCU without her actually appearing in the movie. So, audiences were treated to a giddy fan of Thor giving him her sympathy after Jane Foster "dumped" him.
A little frustratingly, if convenient for this idea, audiences are never actually told the reason as to why she suddenly dumped him. It could be inferred, from the last movie in this franchise, that she broke up with Thor due to him frequently being off world. Maybe instead, she ended their relationship to stop him from blaming himself for what happened to her, sparing him any further pain from her eventual death.
After all, there was extensive talk in Thor: The Dark World about the fleetness of human life compared to Asgardians and how Thor would only experience pain by staying with her. Loki even tells Thor that he'll never be ready the day she dies. When Loki says this, Thor doesn't actually object to this assertion. He really would never be ready.
Considering Thor's emotional journey through Infinity War and Endgame, with him losing practically everyone close to him and failing in stopping Thanos - he broke down for those five years between. If Jane were to be afflicted by a cosmic cancer slowly eating away at her until her death, it's easy to imagine Thor not taking that well and why Jane decided to not tell him and spare him from watching her slowly die.
FOSTER'S SUDDEN RETURN
After not appearing on screen since 2013 in Thor: The Dark World, it'd seem a bit odd for Jane Foster to return without any real explanation after unceremoniously dumping Thor off-screen. There is no definitive survival rate after being diagnosed with cancer, especially since there are so many different forms of it, but it's typically a five-year survival rate, but, again, many live pass this rate.
The point is that after being afflicted with this extreme form of cancer by The Aether and discovering it between 2013 and 2017, Jane was getting closer to Death's door and likely would not have survived to 2023. However, by the end of Avengers: Infinity War, Thanos succeeds in his plan of wiping out half of all life. Unknown to most, Jane Foster was actually a victim of Thanos' plan too, which was shown on page 8 of the Avengers: Endgame screenplay.
Her having been turned to dust would have essentially put a pause on her cancer for five years. Once Hulk successfully brought everyone back again, Foster could realize that she doesn't want to die without telling Thor the truth. So, she gets in contact with him in order for both of them to have some proper closure.
This could give an opportunity for Chris Hemsworth and Natalie Portman to have a different kind of dynamic, something that Waititi did when he and Marvel Studios changed Thor's personality in Ragnarok. He could do the same for Jane Foster by putting her in such a dramatically different position, which could perhaps give both actors a new kind of chemistry.
TAIKA WAITITI IS MORE THAN JOKES
If this storyline were to be adapted into the MCU, it's easy to imagine fans being concerned that Waititi would not give it the gravitas it deserves. This is understandable for those not familiar with his filmography outside Thor: Ragnarok, as the filmmaker included numerous jokes and zingers during some of the dramatic scenes in his Marvel movie.
But, if fans were to watch more of Waititi's movies, they would realize that he has handled drama and heavy subject matters before with the gravity they deserve. Just because this New Zealand director leans into comedy doesn't mean that he wouldn't be able to portray Jane Foster as a cancer patient seriously.
Many of Waititi's movies have sprinkles of darkness and sadness in them, even some his funniest films, like Nick's painfully slow transformation into a vampire in What We Do In The Shadows, the bitter loss of a loved one in Hunt for the Wilderpeople, and most recently and devastatingly, Jojo Rabbit.
Jojo Rabbit views the innocence of a young boy enticed by Nazi propaganda until his worldview is slowly chipped away and he frees himself from its clutches - but not without losing much of that childhood innocence. Waititi is clearly capable of tackling darker subjects like pain, betrayal, loss, and filling a void with hate. Taika Waititi could totally adapt Foster's cancer into the movie, while still giving it weight and of course adding his own brand of humor to it.
A lot of elements already introduced in the MCU thus far would fit perfectly with Foster having cancer and getting it this way. This would help make Thor: The Dark World a more meaningful movie on rewatches, allow an organic explanation for Jane breaking it off with Thor and coming back to the franchise, give some meaningful stakes to her return, and present Natalie Portman with an opportunity to flex her acting as both a cancer patient and a totally badass goddess of thunder.
Not to mention, this could change the dynamic with other characters like Peter Quill. If the Guardians of the Galaxy do have a limited role in Love and Thunder, it'd be compelling to watch Quill sympathize with Thor about Jane, since he lost his mother in similar circumstances to brain cancer.
Peter Quill could even encourage Thor to go be with Jane and not do what he did with his mother, making his last moments with the person he loves most count. It'd be a nice way of fleshing out both characters and concluding their one-sided rivalry seen in Infinity War and the conclusion of Endgame when Thor hitches a ride with them.