Dr Mayer on PRO Data With Camizestrant Plus CDK4/6 Inhibition in ESR1+ Breast Cancer

“For many patient-reported symptoms and functioning [scales], there was a distinct difference and a distinct prolongation of QOL. That speaks to how the early switch to camizestrant is preventing subclinical progression ahead of clinical progression. Those data are extremely meaningful for patients.”

Erica L. Mayer, MD, MPH, the director of Breast Cancer Clinical Research at Dana-Farber Cancer Institute and an associate professor of medicine at Harvard Medical School, discussed patient-reported outcomes (PROs) from the phase 3 SERENA-6 trial (NCT04964934) investigating the switch to camizestrant plus a CDK4/6 inhibitor following the emergence of an ESR1 mutation during treatment with initial endocrine-based therapy in patients with estrogen receptor–positive, HER2-negative advanced breast cancer.

Previously reported findings from SERENA-6 showed that switching to camizestrant at the time of the emergence of an ESR1 mutation in advance of clinical progression significantly prolonged progression-free survival (PFS) vs an aromatase inhibitor plus a CDK4/6 inhibitor (adjusted HR, 0.44; 95% CI, 0.31-0.60; P < .0001). The median PFS was 16.0 months (95% CI, 12.7-18.2) in the camizestrant arm (n = 157) compared with 9.2 months (95% CI, 7.2-9.5) in the control arm (n = 158). Beyond survival metrics, the previous presentation established that the switch to camizestrant was associated with a substantial delay in the deterioration of global health status (GHS) quality of life (GHS/QOL). The median time to deterioration (TTD) in GHS/QOL was 21.0 months for the camizestrant arm compared with 6.4 months for the control arm (adjusted HR, 0.54; 95% CI, 0.34-0.84).

The subsequent deep dive into the PRO data, presented at the 2025 ESMO Congress, illustrated that this benefit extends across numerous specific patient-reported symptom and functioning domains. For pain, the median TTD was 16.6 months (95% CI, 8.3-not calculable [NC]) for the camizestrant arm vs 6.5 months (95% CI, 2.7-13.8) for the control arm (HR, 0.57; 95% CI, 0.37-0.86). For physical functioning, the median TTD was 23.0 months (95% CI, 17.4-NC) vs 15.7 months (95% CI, 8.3-NC), respectively (HR, 0.74; 95% CI, 0.44-1.24). Moreover, significant delays in deterioration were noted for exploratory end points, demonstrating reduced risk for issues such as emotional functioning (HR, 0.51; 95% CI, 0.29-0.87) and shortness of breath/dyspnea (HR, 0.52; 95% CI, 0.28-0.93).