Find a novel in which the protagonist, on the verge of death from cancer, uses the system to travel to a different world to complete missions and gain longevity.

I think that the novel that fits this description is "Quickly pass through the mission: cannon fodder to counterattack". The main character, Meng Li, was a quest-taker who needed to complete various quests to counterattack. Each mission had a different difficulty level, which was divided into the SABG level. Completing the mission would give rewards. At the same time, she also needed to travel between different worlds to complete the mission. I hope my recommendation can meet your needs. Muah ~

I recommend the following novels to you, hoping that they can meet your needs: "I've Been Scammed Again by the Quick Dressed,""The Beauty of the Quick Dressed,""Sanguine Evolution,""The Quick Dressed, Cannon Fodder Doesn't Want to Pay Attention to You,""The Counterattack of the Quick Dressed, Cannon Fodder,""The Quick Dressed, Transformed into a Little Fairy,""The Quick Dressed: Female Lead Doesn't Follow the Script,""The Quick Dressed, Female Supporting, Ways to Die,""I Don't Know How to Do This Quest,""The Quick Dressed System: Supporting Female Character's Wish Manual,"" The Host Steals the Villain Boss's Script,"and" Quick Wear: The Cannon Fodder's Counterattack on Life." I hope you like my recommendation. Muah ~

I recommend "The Soul Master's Quick Transmigration Mission". The main character, Xiaoxiao, has to browse through different worlds and complete different missions. At the same time, she has to face the System Lord's madness and traps, but it also gives her a painful and happy experience. I hope you like this fairy's recommendation. Muah ~😗

The book that I recommend to you is "Green Fisherman." The female protagonist of this book, Liu Hao, is bound to a game system. The system allows her to save the Earth's marine environment in the process of becoming a top fisherman. Not only could she read through the geographical knowledge of the ocean, including Tianjin Port, Xiamu Fishing Port, Shenwu Port, Yuanyang, Yanzhi, the Arctic, and so on, but she could also investigate the weather. I hope you like this fairy's recommendation. Muah ~😗

The main character is called Mu Baisheng. He has obtained an incomplete shuttle system, and each system is different. He used a knife and killed the other hosts in the finale to complete the system. I hope you like this fairy's recommendation. Muah ~😗

😋Hello, I recommend the following books to you: 1. The female protagonist of "Quick Wear: Goldfinger Testers" was a Goldfinger Testers. She would be sent to different worlds to play different roles to complete missions. 2. The female protagonist of "The Cultivation of Fast Crossing" was a quest taker who had to cross the realm quickly. She needed to help the female supporting role, cannon fodder, and others complete their wishes and obtain abilities. 3. In "Quick Wear: Yu-Gi-Oh", the female protagonist created a game world in her dream and began her journey of quick wear. I hope you like this fairy's recommendation. Muah ~😗

Please read the following novels: 1. [The Strongest Supporting Male Actor in the Heavens]: The protagonist travels through the heavens, snatches the protagonist's opportunity, and eventually becomes a great villain. [Traversed Worlds: Naruto, Battle Through the Sky] Transforming to Douluo Continent. 2. [The Storyteller Walking in the Heavens: The protagonist walks in the myriad worlds and tells the stories of each world.] [Traversed Worlds: The Fox Demon Little Matchmaker, Battle Through the Heavens, Divine College, iPartment, Diga Ultraman, Jade Dynasty, Fox Demon Little Matchmaker, Naruto, One Piece, Perfect World, Heaven Covering, etc.] 3. "From One Piece to Omniscience": The main character starts his journey of omniscience from the world of One Piece, achieving his goal by traveling through different worlds. I hope you like this fairy's recommendation. Muah ~😗

😋I recommend the following novels to you: 1. "The Contract Mission of Quick Crossing": The protagonist wanted to see his deceased sister again, so he kept traveling through different time and space to complete the mission, just to get a chance to change his fate. During this time, he even met someone who could accompany him for the rest of his life. 2. "Quick Wear, Open the Koi Luck": The female protagonist, Ning Yue, was bound to the Quick Wear system and kept completing missions to obtain eternal life. During this period, she even killed the white-eyed wolf mother and son as cannon fodder. 3. "From the moment we first met, it was his plan." The protagonist, Shi Chu, gathered his arms and legs while completing the mission and experienced all kinds of life. 4. In "Get Dressed and Charge Forward", the protagonist traveled through different worlds to complete the mission in order to track down the murderer who killed her. However, she often encountered a collapsed BOSS and flirted with her at the slightest disagreement. I hope you like this fairy's recommendation. Muah ~😗

I recommend " The Holy Sword's Life Begins on the Ark " to you. It's a light novel, a derivative doujinshi novel. In order to save her fallen sister, the female lead, Chu Mo, accepted the commission of the gods. She continuously transmigrated to different time and space and transformed into different holy swords, carrying out redemption time and time again. With the recovery of spiritual energy, Chu Mo realized that the story behind this was not simple. There were more secrets to this transmigration journey waiting for her to uncover. I hope you like my recommendation.😘

I'm not sure what the novel you're looking for is called. However, according to the information you provided, I understand that this novel might be called "The Movie Mission". The main character of this novel is a young man named Alan. He enters the movie world to complete missions to obtain wealth and prestige. You can continue to search for the name of this book or refer to other online literature for more information.