The first time Dave Fuehrer was diagnosed with testicular cancer, he was knocked back. The twenty-something competitive bodybuilder, a recent New York State champion, was unprepared for his journey from wellness to disease, and then through treatments and their sequelae.

However, it was the second diagnosis of primary testicular cancer that really got to him, he said. This time, he was a recently married young professional who was working on starting a family. The second round of cancer took parenthood away from him and left him “feeling even more lost and ashamed” than the first diagnosis, he said in an interview. He felt isolated, alone, and very different from most of the other cancer patients he saw.

Now, Mr. Fuehrer and partners, all of whom have been affected by cancer, have developed a web-based mobile application they call Stupid Cancer . The app is designed to connect adolescents and young adults who have cancer, or are cancer survivors, with each other and with resources and information.

When users set up their profiles on the app, they indicate their status as person with cancer or family member/supporter, as well as their geographic region, age, and type and stage of cancer. Then, users can connect with each other in private one-on-one chats or in chat rooms. Users are anonymous.

The Stupid Cancer app, said Mr. Fuehrer, was a natural extension of the nonprofit of the same name – an event-based organization designed to serve the needs for information and connection with others that are in many ways unique to adolescents and young adults.

Mr. Fuehrer, who has a professional background in the pharmaceutical industry, said that he sorely missed that connection during his cancer journeys and saw a big unmet need. “I was the only guy my age in a roomful of men in their 60s and 70s at my urologist’s office,” said Mr. Fuehrer. “Nobody looked like me.”

But even within the adolescent and young adult community, the lived experience of cancer can be much different for a younger patient. “I feel like I missed out on part of my childhood,” said Dane Koomen. When he was diagnosed with advanced Burkitt lymphoma nearly 10 years ago, “Myspace was the only social media out there, and as an 11 year old, I wasn’t exactly going to be hanging out there,” he said.

If Twitter, Snapchat, or Instagram had been available when he was going through cancer treatment, said Mr. Koomen, he could have stayed in better touch with his friends as they finished 6th grade and prepared for the transition to junior high school. “There are experiences I missed – field trips I didn’t go on, parties I missed,” and even vicarious involvement through social media would have been better than the isolation he felt, he said.

He thinks social media could also have helped his friends understand his experience: “If I’d had Snapchat, then they could see what I’m going through, and it would have been easier for people to understand what’s going on,” he said.

Through social media with broader reach, like Twitter or Instagram, he could have found encouragement and hope from inspiring stories of other cancer patients who were completing treatment and reaching the cancer-free status he was hoping for, he said. And he also would have enjoyed telling his story to a wider audience, and gaining strength from others’ well wishes, on Twitter.

Ilia Buhtoiarov, MD , a pediatric oncologist at Cleveland Clinic Children’s Hospital, Ohio, said that he sees different groups using social media platforms in a variety of ways for support and information sharing.

Parents, he said in an interview, are big Facebook users. Beginning with the early, uncertain days after a cancer diagnosis, parents can share a lot of information “in a structured fashion,” through one post. “They can target the post to a number of people – so everyone hears exactly what you want to say,” he said. For parents and other caregivers, this strategy is efficient when time and energy are limited.

Facebook is also useful, he said, for marshaling resources, such as finding help with rides or after-school care for other children and for such things as letting friends know when the patient is feeling well enough to see others.

For young cancer patients, Dr. Buhtoiarov said, a platform like Instagram or Snapchat affords “the opportunity to start a conversation” with peers. “The barriers are lifted quite naturally,” he said, and he sees how “the likes, smiles, and emojis provide support” for the person with cancer as peers follow along with the cancer journey.

Like an increasing number of pediatric oncology programs nationwide, Cleveland Clinic Children’s Hospital has services tailored for adolescents and young adults with cancer, who may “fall through the cracks” between pediatric and adult oncology services. Dr. Buhtoiarov said that among his peers, Twitter is used extensively to keep apprised of clinical trial opportunities and to link to new research in the field. This is especially important for those caring for an age group that’s been identified as significantly underrepresented in clinical trials and for whom cancer survival rates are persistently flat.

Oncologists also need to help patients and families navigate the reams of sometimes unreliable information they’ll find on the Internet, said Dr. Buhtoiarov. Though professionals can connect with each other to help patients find an expert close to home, or to consider enrollment in a clinical trial, patients need to know that “this information should always be discussed with experts,” he said.

The need for support and interaction continues into cancer survivorship. Both Mr. Fuehrer and Mr. Koomen said that it’s hard for those who haven’t lived through life-threatening diagnoses and traumatic, protracted treatments to understand how the experiences stay with you. Mr. Fuehrer has to gear himself up for a trip to the dentist, where the bright lights, reclining posture, and sights, sounds, and smells trigger unwelcome memories of old trauma.

And Mr. Koomen said that given the opportunity, he wouldn’t rewrite his history to have lived a cancer-free life because the experiences he went through shaped so much of who he is today. Still, he feels different from many of his young adult peers and has enjoyed connecting with fellow young survivors through the Stupid Cancer app.

Also, Mr. Koomen, now a college student in Rochester, N.Y., who’s contemplating writing a book about his experiences, said that a smartphone might have helped him keep a lost link to his past: He wishes he had more pictures of his time in the hospital. “I wish I could remember more about my favorite nurses. I have some great memories with them.”

The American Society of Clinical Oncology maintains a list of resources for teens with cancer and those supporting them, as well as a general information page for teens diagnosed with cancer.

Dr. Buhtoiarov reported no relevant conflicts of interests. Mr. Fuehrer is the chief executive officer of Gryt Health , the developer of the Stupid Cancer app. Mr. Koomen reported no relevant conflicts of interest.