1049 Background: This is a single center phase 1b study of a regimen of pembrolizumab (PBZ) and pegylated liposomal doxorubicin (PLD) in endocrine-resistant breast cancer. PLD was chosen as chemotherapy component because it is mildly myelosuppressive and non-immunosuppressive and contains doxorubicin, a strong immunogenic cell death inducer. Methods: Patients with estrogen receptor positive, HER2 negative, metastatic breast cancer, whose disease progressed on hormonal and biological therapy and up to 2 chemotherapy lines were eligible for enrollment. PLD, 30 mg/m2, and PBZ, 200 mg flat dose, were infused on day 1 of every 3-week cycles. The main study objectives were safe dose clearance, characterization of dose-limiting toxicities (DLT), tumor response, and pharmacokinetic analysis of PLD and PBZ during the first 3 cycles of treatment in a 1st cohort of 6 patients and a 2nd confirmatory cohort of 6-9 patients. Patients with partial response (PR) or stable disease (SD) continued on the extended phase of the study consisting of 9 additional cycles during which further safety information was collected. All patients were followed-up for survival. Results: 12 patients were recruited (median age 61 y, range 45-91). 9 patients had received prior doxorubicin treatment. 82 treatments have been administered (median: 7, range 2-13). Overall, treatment was well tolerated. DLT including infusion reactions, grade ≥2 myelosuppression, hair loss and mucocutaneous toxicity were not observed in the first 3 cycles. Subsequently, skin toxicity (grade 2-3 palmar-plantar erythema) was observed forcing treatment delays of 1-2 weeks. Except for 2 cases of subclinical hypothyroidism, there were no other apparent PBZ-related side-effects. There was no evidence of cardiac toxicity. There were 2 early deaths (days 25 and 45) probably related to disease progression. Upon reevaluation on week 9, we observed: 2 patients with PD, 4 with SD, 2 with PR (15+ and 5+ mth), 1 with no measurable disease, and 1 early to evaluate. Three out of 5 patients responded well to post-study chemotherapy with durable improvement or stabilization (range, 5 to 11+ mth). Median follow-up is 14 mth. Median survival has not been reached with 4 deaths and a longest survivor of 19+ mth. Median progression-free survival is 6.0 mth. The clearance of PLD was slow with high Cmax, long T½ and small Vd. There was a significant increase in the AUC of PLD between the 1st and 3rd cycle (median: 2,649 vs 3,422 mg*h/l, p = 0.039). Analysis of PBZ plasma levels is ongoing. Conclusions: The combination of PLD and PBZ is well tolerated and feasible for extended treatment. Dose interval of PLD should be lengthened to 4 weeks after 2-3 cycles to prevent skin toxicity. The late appearance of skin toxicity is probably related to a delay in PLD clearance after 2 treatment cycles with PLD and PBZ. Clinical trial information: NCT03591276 .
Long-Term Cardiac Safety and Survival Outcomes of Neoadjuvant Pegylated Liposomal Doxorubicin in Elderly Patients or Prone to Cardiotoxicity and Triple Negative Breast Cancer. Final Results of the Multicentre Phase II CAPRICE Study