Could a fraction of the standard pembrolizumab dose still boost outcomes in triple-negative breast cancer (TNBC)? At the European Society for Medical Oncology (ESMO) 2025 congress, Dr Atul Batra (Additional Professor, Department of Medical Oncology, All India Institute of Medical Sciences (AIIMS), New Delhi, India) presented a late-breaking study exploring just that. In a randomized trial of 160 patients, adding only 50mg of pembrolizumab – about one-tenth the standard dose – to standard anthracycline and taxane chemotherapy increased pathological complete response rates by 13.3%. The data challenges current dosing and could potentially expand critical access to immunotherapy in low- and middle-income countries.
The late-breaking abstract, ‘Low Dose Pembrolizumab in Addition to Neoadjuvant Anthracycline and Taxane in Triple Negative Breast Cancer: A Randomized Controlled Trial’ (LBA15) was presented at the European Society for Medical Oncology (ESMO) congress on 17th-21st October 2025 in Berlin, Germany.
Q1. What was the rationale behind investigating low-dose pembrolizumab with neoadjuvant chemotherapy in triple-negative breast cancer (TNBC)?
The standard pembrolizumab dose is 200mg every three weeks, but early pharmacologic studies showed that PD-1 receptor saturation occurs at much lower doses. Even doses as low as 0.1mg/kg can fully engage the immune system and stimulate T cell responses. Based on this, we chose a 50mg dose – approximately 1mg/kg for an average 50-kg Indian patient – which is sufficient to activate the immune system without unnecessary drug exposure.
Q2. What was the design and eligibility criteria of your study?
This was a randomized, two-arm trial with open-label treatment, though pathology assessments were blinded. The control arm received standard neoadjuvant chemotherapy – four cycles of doxorubicin and cyclophosphamide followed by four cycles of a taxane. The experimental arm received the same chemotherapy with the addition of 50mg of pembrolizumab every six weeks for three doses. Surgery followed, and the primary endpoint was pathological complete response (pCR).
Q3. What were the key findings?
We enrolled 160 patients, with three excluded from analysis. The pCR rate was 40.5% in the control arm versus 53.8% in the experimental arm, a 13.3% absolute increase. This improvement is both statistically significant and clinically meaningful. In cross-trial comparisons with the KEYNOTE-522 trial, the benefit is similar to what was achieved with nearly ten times the dose of pembrolizumab.
Q4. How do these findings challenge current pembrolizumab dosing standards?
While we are not advocating an immediate change to clinical practice, the data suggest that lower doses deserve further exploration. Importantly, in low- and middle-income countries where access to full-dose pembrolizumab is limited – affecting up to 70% of patients – this approach could expand treatment options. Long-term data on disease-free and overall survival are still required before any changes to standard dosing can be recommended. Larger comparative studies are needed to confirm the impact on survival outcomes.
Disclosure: Atul Batra has no financial or non-financial conflicts of interest to declare in relation to this interview.
This content has been developed independently by Touch Medical Media for touchONCOLOGY. It is not affiliated with the European Society for Medical Oncology (ESMO). Views expressed are the speaker’s own and do not necessarily reflect the views of Touch Medical Media.
Cite: ESMO25: Pembrolizumab at low dose: could Less be more in triple-negative breast cancer? touchONCOLOGY. November 6th, 2025
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