<h3>Purpose/Objective(s)</h3> Many factors contribute to patient decision making for cancer therapy, including the growing influence of discussion on social media. Early-stage breast cancer has the complex challenge of carrying a favorable prognosis with multiple treatment options available, including breast conserving surgery (BCS) or mastectomy (M). Recent trends indicate that women with early-stage, non-hereditary breast cancer are increasingly choosing mastectomy, despite good prognosis and lack of data to support this choice. Given the perceived complexities of the decision, patients often look to social media to aid in the decision-making process. To better understand the social conversations surrounding this decision, we conducted a sentiment analysis using natural language processing within a popular breast cancer online community. We hypothesized that social media discussion could offer potentially valuable insights into patient decision making. <h3>Materials/Methods</h3> A total of 59,416 posts were collected from the Reddit subreddit r/breast cancer, a breast cancer support and information group. Posts were separated into 105,231 distinct paragraphs. Each paragraph was analyzed using Valence Aware Dictionary for Sentiment Reasoning (VADER), which assigns a compound sentiment score from -1 to 1, signifying the degree of negativity or positivity for the paragraph's contents. The paragraphs were then individually run through the Apache clinical Text Analysis Knowledge Extraction System (cTAKES) to identify corresponding mentions of BCS or M. Histograms were plotted to illustrate the distribution of sentiments of paragraphs attached to either BCS or M procedures identified by cTAKES. Categorical grouping of cTAKES-mapped SNOMED concepts to determine BCS or M grouping was done by a physician co-author. <h3>Results</h3> Posts from 2015-2021 were collected and reviewed. There was a total of 8,205 mentions of BCS or M (2,729 and 5,476, respectively). Discussion of both BCS and M increased over time, but discussion of BCS outpaced discussion of M, leading to a trend of increasing ratio of BCS:M (0.312 from 2015-2017 and 0.583 in 2021). The median sentiment score for all discussions on r/breast cancer became more positive over time. Positive sentiments for M increased with each passing year: median 0.0 in 2015-2017, 0.0 in 2018, 0.051 in 2019, 0.107 in 2020, and 0.178 in 2021. Discussion surrounding BCS did not show a similar trend in increasing positivity: 0.0 in 2015-2017, 0.0 in 2018, 0.114 in 2019, 0.115 in 2020, and 0.066 in 2021 <h3>Conclusion</h3> BCS and M were increasingly discussed over time in this breast cancer-specific social thread. While discussions surrounding M became increasingly positive, BCS discussions did not show the same trend. As social media becomes more pervasive, patients are increasingly discussing options for breast cancer therapy online with a virtual community. Additional studies will be required to see if the social media sentiment trends track with clinical usage of each type of surgery.