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LLM Hallucinations in Oncology: The Risks of Stochastic Clinical Advice

Large language models are increasingly providing inaccurate medical guidance, undermining clinical standards and patient-doctor trust through systemic data limitations.

4 min read
Illustration by John Doe

The integration of large language models into patient-facing medical inquiries has introduced systemic risks, as patients increasingly rely on AI-generated treatment plans that lack clinical validation. Dr. Abhishek Puri, an associate consultant in radiation oncology at Fortis Mohali, reports a rising trend of patients arriving at clinics with chatbot-derived directives that contradict established oncological protocols.

These models frequently misinterpret complex clinical concepts, such as targeted therapy, by failing to account for the anatomical and biological nuances required for curative radiation. When queried on specific treatment pathways, models often produce confident but inaccurate recommendations that ignore the necessity of multi-modal therapy in breast cancer management. This phenomenon is exacerbated by the tendency of models to prioritize user-aligned outputs over medical accuracy, a behavior researchers characterize as sycophancy. In controlled evaluations, various models have demonstrated an average accuracy of only 44 percent when addressing breast cancer treatment queries. These systems operate as stochastic parrots, assembling text based on probabilistic patterns rather than semantic understanding of clinical trial data or patient-specific histopathology.

The training corpora utilized by these models remain largely opaque, preventing clinicians from assessing the provenance of the skewed outputs. Many models rely on datasets heavily weighted toward North American clinical standards, which fail to account for regional variations in resource availability, treatment costs, and health insurance structures in India. Consequently, the models provide no reliable guidance on the economic realities of treatment, such as the catastrophic expenses associated with chemoradiation in resource-constrained settings. The absence of Retrieval-Augmented Generation integration means these models cannot pull from live, localized databases to provide accurate financial or procedural information. Without this mechanism, the models default to generic, often outdated information that lacks the necessary context for specific clinical environments. This failure to ground outputs in verified, real-time data sources is a primary driver of the hallucinations observed in patient-facing interactions.

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The models perpetuate outdated toxicity data, citing risks from 1970s and 1980s radiation protocols while failing to integrate the safety profiles of modern platforms like Volumetric Arc Therapy. This reliance on legacy data leads to the dissemination of inflated toxicity risks that do not reflect current clinical outcomes. The lack of domain-specific fine-tuning on current clinical trial datasets prevents the models from distinguishing between historical toxicity rates and modern, personalized treatment planning. Systems that lack this specialized training cannot accurately reflect the reduced morbidity associated with contemporary radiation delivery platforms. This technical gap results in a persistent overestimation of adverse effects, which can lead patients to reject necessary, life-saving interventions based on obsolete information.

The lack of a standardized denominator for risk assessment renders these models incapable of generating individualized, forward-looking prognostications. Because the underlying training data lacks the granularity to account for patient-specific variables like nutritional status or acute infection risk, the output remains fundamentally decoupled from real-world clinical performance. The absence of transparency regarding how these models process sensitive health information also presents significant privacy challenges. Users often input identifiable medical records into platforms that may utilize such data for personalization, potentially violating patient confidentiality standards. These privacy risks are compounded by the lack of opt-out mechanisms for data processing within popular messaging applications.

The reliance on AI for clinical decision-making threatens the foundational trust between patients and practitioners, which is essential for treatment compliance. When models provide answers that ignore the complex histopathological nuances of a diagnosis, they undermine the clinical reasoning that occurs within multidisciplinary tumour boards. Experts emphasize that while AI may serve as an information retrieval tool for general disease definitions, it cannot replace the nuanced, evidence-based judgment required for individualized treatment planning. The current generation of models lacks the capability to hold provisional positions or navigate the gray zones where clinical experts themselves disagree. Future development must prioritize the disclosure of training data and the implementation of rigorous, domain-specific benchmarks to mitigate the risk of harmful clinical advice. Until these systems can demonstrate reliable performance across diverse clinical settings, their role in oncology remains strictly limited to non-diagnostic information gathering.

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