The SONImage Study

SONImage Study: Can Molecular Imaging Predict Outcome to First-line Endocrine Treatment ± CDK 4/6 Inhibition in Advanced ER+ Breast Cancer

SONImage is a multicenter prospective imaging side study, in which a baseline FES-PET is added to conventional work up, in 100 patients with ER+ MBC who will receive endocrine treatment ± CDK 4/6 inhibition within the SONIA study (NCT03425838). SONImage will be executed in two Dutch centers: UMCG and Amsterdam UMC-location VUMC. The aim of the SONImage study is to (1) assess the relationship between FES/FDG-PET heterogeneity patterns at baseline and PFS for first-line endocrine treatment ± CDK 4/6 inhibition in ER+ MBC, and (2) to further improve that by developing a prediction model, within the SONIA study. This molecular imaging based multivariable prediction model may provide a unique measure of benefit of adding CDK 4/6 inhibition to first-line endocrine treatment, allowing patients and providers to weigh individual benefits and (long term) burden for optimized treatment decisions.

Estrogen receptor positive (ER+) breast cancer is the most common cancer and the most frequent cause of cancer-related death in women in the Western World. Cyclin-dependent kinase 4 and 6 (CDK 4/6) inhibitors improve outcome, when added to standard first- and second-line endocrine therapy. However, they also add patient- and financial burden due to (long term) increased toxicity and hospital visits. Therefore, benefits of additional CDK 4/6 inhibitors should be weighed against their burden. Tools to support such treatment decisions by patients and providers are currently lacking. Whole body heterogeneity of ER expression, measured by 16α-[18F]fluoro-17β-estradiol (FES)-PET scan and 18F-fluorodeoxyglucose (FDG)-PET scan was related to time to progression on combined treatment in previous work. Therefore in SONImage a baseline FES-PET is added to conventional work up, in 100 patients with ER+ MBC who will receive first line endocrine treatment ± CDK 4/6 inhibition within the SONIA study. The objectives are 1. to correlate PFS1 (according to SONIA criteria) to baseline FES/FDG-PET heterogeneity; 2. to assess interaction between baseline FES/FDG-PET heterogeneity, treatment allocation, and PFS1 (according to SONIA criteria); 3. to correlate response measurements of individual lesions to baseline FES/FDG heterogeneity and detailed FES/FDG imaging features; 4. to develop a multivariable model to predict individual PFS benefit to first-line AI ± CDK 4/6 inhibition, based on detailed FES/FDG image features and standard clinicopathological information, in n=100 SONIA patients; 5. to validate this prediction model in two independent patient cohorts with baseline FES/FDG-PET scans (Dutch IMPACT-MBC trial; international ET-TRANSCAN trial). This molecular imaging based multivariable prediction model may provide a unique measure of benefit of adding CDK 4/6 inhibition to first-line endocrine treatment, allowing patients and providers to weigh individual benefits and (long term) burden for optimized treatment decisions. Particularly for the approximately 25% of patients with ER+ MBC who have an excellent- or poor outcome despite CDK 4/6 inhibition in the first-line, this could have profound implications, as they may refrain from combined treatment. Ultimately, this could potentially contribute to FES/FDG-PET based treatment decisions in clinical practice, reduction of unnecessary toxicity and costs, while improving patient outcome and QoL.

One visit to either the UMCG or Amsterdam UMC-location VUMC is required for the FES-PET scan, and possibly one additional visit for an FDG-PET. A FES- or FDG-PET scan plus low dose CT will each induce an extra radiation burden of about 6.1 mSv (210 MBq injected for an average patient of 70 kilogram body weight).

One visit to either the UMCG or Amsterdam UMC-location VUMC is required for the FES-PET scan, and possibly one additional visit for an FDG-PET. A FES- or FDG-PET scan plus low dose CT will each induce an extra radiation burden of about 6.1 mSv (210 MBq injected for an average patient of 70 kilogram body weight).

Progression-free survival after first line treatment (PFS1) defined as time from randomization until objective disease progression, symptomatic deterioration, or initiation of a new therapeutic agent on first line treatment, death, or progression during a break in initial therapy and without further therapy within one month, whichever occurs first.

Change in size (=response measurement) per individual lesion at the largest measurable response measured on CT compared to baseline CT

- Per patient trajectory of change in size of target lesions according to RECIST 1.1, from baseline CT until CT at progression of disease.

Cox-regression to estimate HRs for PFS and corresponding 95% CIs between FES/FDG heterogeneity groups, while adjusting for treatment allocation.

Inclusion Criteria: Patient is eligible and participates in the SONIA trial for ER+ MBC. Able to give written informed consent and to comply with the SONImage protocol. Documentation of histologically confirmed diagnosis of estrogen receptor (ER) expression >10% breast cancer based on local results. The receptor status can be determined on the primary tumor or on a tumor biopsy of a metastatic lesion. Exclusion Criteria: A patient who meets the exclusion criteria of the SONIA trial (see SONIA protocol). Contra-indication for PET imaging. Use of estrogen receptor ligands (i.e. tamoxifen or fulvestrant) ≤ 5 weeks before FES-PET imaging.