Expert consensus recommendations on the daily clinical use of pembrolizumab for early triple-negative breast cancer.
Authors: Yeo Winnie , Chan Yolanda HY , Leung Roland Ching-Yu , Chan Sharon Wing Wai , Chow Lorraine Chi Yan , Foo William , Fung Sara , Kwok Carol , Lau Stephanie Hiu Yan , Leung Alex , Ng Ting Ying , Tsang Janice , Wong Iris , Yau Chun Chung , Yuen Ho Yan , Cheung Polly Suk Yee 
Published: July 2024

e12521 Background: Triple-negative breast cancer (TNBC) accounts for 10–15% of all breast cancer cases and is associated with poor outcomes. Neoadjuvant chemotherapy is the standard treatment for early TNBC (eTNBC) to achieve a pathologic complete response which is associated with long-term clinical outcomes and to guide adjuvant treatment for residual disease after definitive surgery. Pembrolizumab, a programmed death 1 (PD-1) inhibitor, is approved for the peri-operative treatment of stage II and III TNBC. The Hong Kong Breast Cancer Foundation (HKBCF) convened a multi-disciplinary consensus consisting of surgeons, and clinical and medical oncologists to discuss the implementation of immunotherapy in the peri-operative setting and provide expert guidance on topics lacking definitive evidence from the KEYNOTE-522 study in daily clinical routine. Methods: The panel included 7 breast surgeons, 6 clinical oncologists, and 3 medical oncologists representing the academic, public, and private settings in Hong Kong. A modified Delphi panel was conducted, testing the panel on 7 different topics and 45 statements relating to the peri-operative treatment of eTNBC. Evidence was graded according to GRADE. Statements were initially voted by online form on a 6-point Likert scale, and the results were discussed during a consensus meeting. Consensus to accept was considered at a median ≥5 and an IQR ≤1.75 and consensus to reject at median ≤2 and an IQR ≤1.75. Results: Key findings are that the panel considered 1) the uncommon subtype “oestrogen receptor (ER)-low” does not formally meet the definition of TNBC but should be treated as TNBC; 2) pembrolizumab as a viable addition in the peri-operative setting; 3) guideline-recommended NAC for cT1c disease may be considered; but 4) this does not necessarily mean immunotherapy should be added, though it may be considered case-by-case. Furthermore, the panel 5) agreed that pembrolizumab prescription does not need to be guided by PD-L1 expression, and 6) that for patients with residual disease after NAC plus pembrolizumab, the addition of capecitabine to pembrolizumab is acceptable, however, 7) was divided about the addition of a PARPi to pembrolizumab for patients with a germline BRCA1/2 mutation (g BRCA1/2m) and residual disease — guided by the lack of routine g BRCA1/2m testing in Hong Kong. Finally, the panel 8) proposed to recommend adhering to the KEYNOTE-522 weekly paclitaxel regimen with a subclause to consider 3-weekly regimen as an alternative for specific technical or logistical challenges. Conclusions: The KEYNOTE-522 study has provided robust evidence on the efficacy and safety of peri-operative pembrolizumab in eTNBC patients. However, several clinical questions remain unanswered, and until further evidence is available, the HKBCF recommendations provide expert guidance on the use of pembrolizumab for eTNBC patients in daily clinical practice.