Comparison of proportions and prognostic impact of pathological complete response between evaluations of representative specimen and total specimen in primary breast cancer after neoadjuvant chemoradiotherapy: an ancillary study of JCOG0306.

BACKGROUND: In JCOG0306 trial, a phase II study to examine the efficacy of neoadjuvant chemotherapy followed by radiation therapy (NAC-RT) to primary breast cancer, pathological complete response (pCR) was evaluated from specimens of the representative cross-section including the tumor center that had been accurately marked [representative specimen (RS) method]. In this ancillary study, we examined if the RS method was comparable to the conventional total specimen (TS) method, which is widely employed in Japan, to identify the pCR group showing excellent prognosis. METHODS: We obtained long-term follow-up data of 103 patients enrolled in JCOG0306 trial. As histological therapeutic effect, pCR (ypT0 and ypT0/is) and quasi-pCR [QpCR, ypT0/is plus Grade 2b (only a few remaining invasive cancer cells)] were evaluated with RS and TS methods. Concordance of pCR between these two methods and associations of the pCR with prognosis were examined. RESULTS: ypT0, ypT0/is, and QpCR were observed in 28 (27.2%), 39 (37.9%), and 45 (43.7%) patients with RS method, whereas these were 20 (19.4%), 25 (24.3%) and 40 (38.9%) with TS method, respectively. Between RS and TS methods, concordance proportions of ypT0 and ypTis were 92.2% and 86.4%, respectively. Risk of recurrence of ypT0/is group was lower than that of non-ypT0/is group (HR 0.408, 95% CI [0.175-0.946], P = 0.037) and risk of death of ypT0/is group was lower than that of non-ypT0/is group (HR 0.251, 95% CI [0.073-0.857], P = 0.027). The ypT0 and ypT0/is groups with RS method showed excellent prognosis similarly with those with TS method, and RS method was able to differentiate the OS and RFS between pCR and non-pCR than TS method significantly even if pCR was classified ypT0 or ypT0/is. With TS method, QpCR criteria stratified patients into the better and worse prognosis groupsmore clearly than pCR criteria of ypT0 or ypT0/is. CONCLUSIONS: RS method was comparable to TS method for the evaluation of pCR in the patients who received NAC-RT to primary breast cancer provided the tumor center was accurately marked. As pCR criteria with RS method, ypT0/is appeared more appropriate than ypT0.

Datopotamab Deruxtecan in Advanced or Metastatic HR+/HER2- and Triple-Negative Breast Cancer: Results From the Phase I TROPION-PanTumor01 Study.

PURPOSE: Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate consisting of a humanized antitrophoblast cell-surface antigen 2 (TROP2) monoclonal antibody linked to a potent, exatecan-derived topoisomerase I inhibitor payload via a plasma-stable, selectively cleavable linker. PATIENTS AND METHODS: TROPION-PanTumor01 (ClinicalTrials.gov identifier: NCT03401385) is a phase I, dose-escalation, and dose-expansion study evaluating Dato-DXd in patients with previously treated solid tumors. The primary study objective was to assess the safety and tolerability of Dato-DXd. Secondary objectives included evaluation of antitumor activity and pharmacokinetics. Results from patients with advanced/metastatic hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer (BC) or triple-negative BC (TNBC) are reported. RESULTS: At data cutoff (July 22, 2022), 85 patients (HR+/HER2- BC = 41, and TNBC = 44) had received Dato-DXd. The objective response rate by blinded independent central review was 26.8% (95% CI, 14.2 to 42.9) and 31.8% (95% CI, 18.6 to 47.6) for patients with HR+/HER2- BC and TNBC, respectively. The median duration of response was not evaluable in the HR+/HER2- BC cohort and 16.8 months in the TNBC cohort. The median progression-free survival in patients with HR+/HER2- BC and TNBC was 8.3 and 4.4 months, respectively. All-cause treatment-emergent adverse events (TEAEs; any grade, grade ≥3) were observed in 100% and 41.5% of patients with HR+/HER2- BC and 100% and 52.3% of patients with TNBC. Stomatitis was the most common TEAE (any grade, grade ≥3) in both HR+/HER2- BC (82.9%, 9.8%) and TNBC (72.7%, 11.4%) cohorts. CONCLUSION: In patients with heavily pretreated advanced HR+/HER2- BC and TNBC, Dato-DXd demonstrated promising clinical activity and a manageable safety profile. Dato-DXd is currently being evaluated in phase III studies.

Clinical management, monitoring, and prophylaxis of adverse events of special interest associated with datopotamab deruxtecan.

Antibody drug conjugates (ADCs) are an emerging class of treatments designed to improve efficacy and decrease toxicity compared with other systemic therapies through the selective delivery of cytotoxic agents to tumor cells. Datopotamab deruxtecan (Dato-DXd) is a novel ADC comprising a topoisomerase I inhibitor payload and a monoclonal antibody directed to trophoblast cell-surface antigen 2 (TROP2), a protein that is broadly expressed in several types of solid tumors. Dato-DXd is being investigated across multiple solid tumor indications. In the ongoing, first-in-human TROPION-PanTumor01 phase I study (ClinicalTrials.gov: NCT03401385), encouraging and durable antitumor activity and a manageable safety profile was demonstrated in patients with advanced/metastatic hormone receptor-positive/human epidermal growth factor receptor2-negative breast cancer (HR+/HER2- BC), triple-negative breast cancer (TNBC), and non-small cell lung cancer (NSCLC). Improved understanding of the adverse events (AEs) that are associated with Dato-DXd and their optimal management is essential to ensure safe and successful administration. Interstitial lung disease/pneumonitis, infusion-related reactions, oral mucositis/stomatitis, and ocular surface events have been identified as AEs of special interest (AESIs) for which appropriate prevention, monitoring, and management is essential. This article summarizes the incidence of AESIs among patients with HR+/HER2- BC, TNBC, and NSCLC reported in TROPION-PanTumor01. We report our recommendations for AESI prophylaxis, early detection, and management, using experience gained from treating AESIs that occur with Dato-DXd in clinical trials.