In neoadjuvant therapy, a patient's long-term outcome is better predicted by stopping tumor DNA shedding (ctDNA clearance) than by achieving pathologic complete response (pCR), the traditional gold standard. This redefines what constitutes a successful treatment response before surgery.

In adjuvant bladder cancer trials, ctDNA status is both prognostic and predictive. Patients with positive ctDNA after surgery are at high risk of relapse but benefit from immune checkpoint inhibitors. Conversely, ctDNA-negative patients have a lower risk and derive no benefit, making ctDNA a critical tool to avoid unnecessary, toxic therapy.

AI identified circulating tumor DNA (ctDNA) testing as a highly sensitive method for detecting cancer recurrence earlier than scans or symptoms. Despite skepticism from oncologists who deemed it unproven, the speaker plans to use it for proactive monitoring—a strategy he would not have known about otherwise.

The InVigor11 study was the first to show that detecting recurrence via a ctDNA test before it's visible on scans is not just a prognostic sign, but an actionable clinical state. Intervening with therapy at this early stage was proven to improve patient outcomes, establishing a new paradigm for cancer surveillance.

While doctors focused on the immediate, successful treatment, the speaker used AI to research and plan for the low-probability but high-impact event of a cancer relapse. This involved proactively identifying advanced diagnostics (ctDNA) and compiling a list of relevant clinical trials to act on immediately if needed.

Experts warn against over-interpreting a single negative ctDNA test after surgery, clarifying that these patients still face a significant 25-30% risk of recurrence. The biomarker's true prognostic power comes from serial testing that shows a patient remains persistently negative over time.

The main barrier to widespread ctDNA use is not its proven ability to predict who will recur (prognostic value). The challenge is the emerging, but not yet definitive, data on its ability to predict a patient's response to a specific therapy (predictive value).

The interpretation of ctDNA is context-dependent. Unlike in the adjuvant setting, in the neoadjuvant setting, remaining ctDNA positive post-treatment signifies that the current therapy has failed. These high-risk patients need a different therapeutic approach, not an extension of the ineffective one.

While a positive ctDNA test clearly signals the need for adjuvant therapy, a negative result is less actionable for deciding initial treatment. The key prognostic value comes from being *serially* undetectable over time, information that is not available when the immediate post-surgery treatment decision must be made.