161 Background: Patients and caregivers seek information about cancer from a variety of sources in addition to their medical team. In recent years, patients with specific lung cancer subtypes have created advocacy groups with active online forums for networking, support, and information exchange. We sought to describe the types of information that patients and caregivers learned from their peers online about lung cancer with targetable driver mutations. Methods: In this qualitative study, we enrolled patients with lung cancer with targetable driver alterations in EGFR, ALK, or ROS1 genes and their caregivers. We conducted individual, semi-structured interviews with participants from a single academic center, asking about their experiences learning about and living with lung cancer. Three reviewers used a framework analysis to code transcripts, and we synthesized the codes into themes. In this analysis, we focused on one theme that emerged from the data related to the information that participants learned from online forums. Results: Of 59 patients approached, 39 patients (mean age = 59, 56% female, median time from diagnosis 16 months) and 16 caregivers (69% male, all spouses or long-term partners) agreed to participate and completed interviews. Participants used online forums to compare their experiences with others to gain a preview of what might lie ahead. Specifically, they read about patients with long survival that were a source of hope, as well as patients’ experiences of progression and dying from cancer that made clinical estimates of prognosis more personal and vivid. Online forums provided a venue to learn about the latest research, available clinical trials, how to manage side effects, and where to find expert clinicians. Participants learned about the treatments received by patients at other centers. They were also exposed to emotionally intense stories of patients from around the world who lacked access to targeted therapy and sought advice from other forum members about how to find specialized care. Caregivers pointed out the distressing effect on patients of learning bad news about online peers as a downside of online forums, but overall found them beneficial and supported patients’ engagement with them. Conclusions: Online forums, particularly those that narrowly focus on specific diseases or treatments, provide patients and caregivers with anecdotal evidence that helps them with practical matters, such as how to manage side effects, as well as more existential issues, such as how long they can expect to live. These results suggest that clinicians should be open to and curious about the information that patients and caregivers learn from online forums in order to better understand the perspectives that patients and caregivers bring to discussions and decisions about their cancer.