Retrospective Analysis of Spectrum of Presentation and Treatment Outcome in Extremity Sarcomas: A Single-Centre Experience

Introduction. The most common site for soft tissue sarcoma is extremity. As complete surgical resection is possible in majority, outcome of this subset is relatively better. There is paucity of data regarding extremity soft tissue sarcoma (STS) from sub-Himalayan and hilly geographical regions. Materials and Methods. Retrospective analysis was done for extremity STS visiting the study center over a period of 5 years. Data were collected and analyzed for demography, disease characteristics, treatment modalities, and outcome. Result. Extremity STS constituted 32.8% of all STS enlisted. Most common subtype noted was pleomorphic STS. Metastatic disease at presentation was noted among 7/43 cases with lung being the most common metastasis site. Wide local excision was done in 37 cases while amputation was required in 5 cases. Adjuvant radiotherapy was given in 27 cases while 18 cases received adjuvant chemotherapy. At median follow-up of 47 months, the overall survival and event-free survival were noted as 47.64% and 41.49%, respectively. Conclusion. This study depicts single-center experience of extremity STS. The population analyzed was from sub-Himalayan region with significant lost to follow-up. Pooling of data from different centers has been advocated to derive conclusive results.

Exploration and recency as the main proximate causes of probability matching: a reinforcement learning analysis

ABSTRACTResearch has not yet reached a consensus on why humans match probabilities instead of maximise in a probability learning task. The most influential explanation is that they search for patterns in the random sequence of outcomes. Other explanations, such as expectation matching, are plausible, but do not consider how reinforcement learning shapes people’s choices.We aimed to quantify how human performance in a probability learning task is affected by pattern search and reinforcement learning. We collected behavioural data from 84 young adult participants who performed a probability learning task wherein the majority outcome was rewarded with 0.7 probability, and analysed the data using a reinforcement learning model that searches for patterns. Model simulations indicated that pattern search, exploration, recency (discounting early experiences), and forgetting may impair performance.Our analysis estimated that 85% (95% HDI [76, 94]) of participants searched for patterns and believed that each trial outcome depended on one or two previous ones. The estimated impact of pattern search on performance was, however, only 6%, while those of exploration and recency were 19% and 13% respectively. This suggests that probability matching is caused by uncertainty about how outcomes are generated, which leads to pattern search, exploration, and recency.