The Oncotype DX score effectively predicts the overall risk of recurrence for early-stage breast cancer, but it provides no information about the biological behavior of the tumor if it does recur. A tumor with a low-risk score can unfortunately return as a highly aggressive, dangerous disease, highlighting a critical limitation of the prognostic test.
Clinicians currently struggle to decide between an oral SERD or a PAM inhibitor when both ESR1 and PAM pathway mutations are present. Dr. Wander frames this as a temporary problem that will be solved within five years by the arrival of combination therapies featuring next-generation versions of both drug classes, making the choice unnecessary.
Dr. Wander favors liquid biopsies for tracking disease progression because they are safer and easier for patients. While acknowledging that tissue biopsies can sometimes detect mutations missed by liquid ones (10-30% discordance), he believes rapidly advancing technology will soon minimize these discrepancies, making them the standard for monitoring.
An AI algorithm, trained on thousands of samples, can analyze a simple photo of an unstained tumor slide and predict its ER-positive or ER-negative status with high confidence. This technology could revolutionize diagnostics and guide endocrine therapy in resource-limited settings where standard IHC testing is unavailable.
The Lidara study showed SERD benefit in patients without pre-existing ESR1 mutations. Success is likely multifactorial: SERDs are more effective and better tolerated than AIs. Critically, they also prevent the most common resistance mechanism—the acquisition of ESR1 mutations—from developing in the first place, altering the disease's future trajectory.
Up to a third of CDK inhibitor resistance cases show no known DNA mutations. Dr. Wander suggests epigenetic factors, like DNA methylation altering chromatin architecture, are responsible. These "dark matter" events turn genes on or off without changing the DNA code, requiring new blood-based profiling technologies to detect and understand resistance.
Dr. Wander notes a strong clinical correlation: a BRCA mutation found on a somatic NGS test with a ~30-60% allelic frequency is very likely germline. However, this cannot replace a dedicated, CLIA-approved germline test for formal diagnosis and family counseling. This distinction is crucial for patient management and has genetic implications for relatives.
New CDK inhibitors that also target CDK2 show great activity in models resistant to current CDK4/6 agents. Instead of being reserved for later use, they are already being tested in frontline trials. The strategy, similar to that of ALK inhibitors in lung cancer, is that using the best drug first may prevent or significantly delay the onset of resistance.
Before CDK inhibitors, second-line fulvestrant provided ~12 months of progression-free survival (PFS). Now, after progression on a CDK inhibitor, PFS on fulvestrant is merely 2-3 months. This demonstrates how a powerful frontline therapy can alter a tumor's genomic structure, making it more virulent and resistant to subsequent standard treatments.
The TK test measures tumor cell division via a simple blood draw, much like PSA in prostate cancer. For CDK inhibitors, a rapid drop in TK levels within the first cycle predicts a better patient outcome. A subsequent rise can signal subclinical progression months before scans would, offering a dynamic, universal biomarker that breast cancer has lacked.