Treatment decisions by CTC count may be suitable in metastatic breast cancer
medwireNews: Using circulating tumor cell (CTC) count to guide first-line treatment decisions in hormone receptor-positive, HER2-negative metastatic breast cancer could be a reliable alternative to a choice based on clinical features, research shows.
The phase 3 STIC CTC trial included 755 women who were randomly assigned to receive chemotherapy or endocrine therapy either based on CTC count (n=377) or physician’s choice (n=378).
In the CTC arm, patients with a count of 5 CTCs or more per 7.5 mL received chemotherapy (36.6%), while those with a lower CTC count received endocrine therapy (63.4%). In the control arm, 27.2% of patients were considered clinically high-risk by physicians and received chemotherapy and 72.8% were assessed as low-risk and received endocrine therapy.
As reported in JAMA Oncology, median progression-free survival was 15.5 months in the CTC arm and 13.9 months in the control arm, with a nonsignificant hazard ratio for progression of 0.94.
François-Clément Bidard (Institut Curie, Saint-Cloud, France) and co-authors note that, at 1.09, the upper limit of the 90% confidence interval did not exceed the prespecified noninferiority margin of 1.25, and therefore “the noninferiority of the CTC arm compared with the standard arm was concluded.”
A preplanned test for PFS superiority was also nonsignificant and there was no difference between the two groups in overall survival, at 47.3 months in the CTC arm and 42.8 months in the control arm.
Bidard et al say that their results “demonstrate the reliability and clinical utility of CTC count to guide the choice between single-agent endocrine therapy and chemotherapy as first-line treatment of hormone receptor–positive, [HER2-negative metastatic breast cancer], at the cost of a higher proportion of patients treated with chemotherapy.”
In an accompanying editorial, Tarah Ballinger, from the Indiana Cancer Pavilion in Indianapolis, USA, and co-authors stress that the “question of clinical utility is critical.”
They say: “The STIC CTC investigators chose a noninferiority design, reasoning that therapy would be deescalated from chemotherapy to hormone therapy in the subgroup of patients with high clinical risk and low CTCs.”
But “[i]n fact, patients were 10% more likely to receive chemotherapy when CTCs directed treatment,” highlight the commentators.
Ballinger et al believe that “[w]e should demand an improvement in outcomes before accepting a strategy that exposes more patients to more toxic therapy. Not worse simply is not good enough.”
They conclude: “The STIC CTC investigators argue for standardization of what is a multifaceted, complicated decision, but CTC count is not a replacement for shared clinical decision-making.”
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