The GOG-B21 trial found that while adding pembrolizumab to chemotherapy benefits the dMMR subgroup, it paradoxically leads to worse outcomes in the pMMR subgroup. This highlights the critical need for molecular testing to avoid potential harm.

The four TCGA molecular profiles (e.g., POLE-mutated, p53-abnormal) have evolved beyond predicting outcomes to actively guiding treatment, such as de-escalating therapy for low-risk groups and escalating for high-risk ones.

Based on translational data from the RUBY trial, experts are most cautious about recommending frontline checkpoint inhibitors for patients in the "No Specific Molecular Profile" (NSMP) subgroup of pMMR endometrial cancer, suggesting this group may not benefit.

The PORTEC3 study revealed that the benefit of adding chemotherapy to pelvic radiation was concentrated in patients with p53-abnormal tumors. In contrast, those with POLE-mutated or mismatch repair deficient (dMMR) cancers saw little to no benefit, suggesting molecular subtypes should guide adjuvant therapy decisions.

When considering escalating therapy for a patient with a high-risk p53 mutation, clinicians are adopting a key checkpoint: confirming the absence of a concurrent POLE mutation. The presence of a POLE mutation is thought to mitigate the aggressiveness of p53-mutated tumors, potentially making treatment escalation unnecessary.

The failure of the PERSEVERA trial, which tested a similar drug in an unselected patient population, highlights the critical importance of SERENA-6's biomarker-driven approach. It proves that targeting only patients with the ESR1 mutation is necessary for efficacy, reinforcing the core value of precision oncology.

The initial broad enthusiasm for PARP inhibitors in ovarian cancer has been refined. New data confirms a lack of overall survival improvement for patients with HRD-negative (or HR proficient) tumors, pushing clinicians toward a precision medicine approach where these drugs are reserved for patients with BRCA mutations or HRD-positive disease who are most likely to benefit.

While circulating tumor DNA (ctDNA) is currently hard to act on for escalating treatment, its most promising near-term application may be in identifying patients who can safely stop or reduce therapy, rather than determining when to start it.

The Avera trial's strong results for jiridestrant were overwhelmingly driven by patients with ESR1 mutations. Analysis revealed minimal benefit for patients without the mutation (wild-type), suggesting the mutation is a key predictive biomarker and the drug may not be for "all comers."