A phase II trial of palbociclib plus letrozole after progression on second-line chemotherapy for women with hormone receptor-positive high-grade serous or endometrioid ovarian, fallopian tube, or peritoneal cancer (LACOG 1018).

OBJECTIVE

Treatment options for patients with ovarian high-grade serous carcinoma (HGSC) and high-grade endometrioid carcinoma (HGEC) who progress after receiving chemotherapy are limited. Considering that over 80 % of those patients express ER and/or PR, we aimed to evaluate the effectiveness of endocrine therapy combined with CDK inhibitors in this population.

METHODS

LACOG 1018, a phase II, single-arm, multicenter trial assessed the efficacy of letrozole 2.5 mg/day continuously plus palbociclib 125 mg/day for 21 days in 28-day cycles in patients with histologically proven ovarian HGSC or HGEC, fallopian tube or peritoneal cancer who had received at least two lines of chemotherapy (including one platinum-based regimen) and progressed on prior chemotherapy. Patients had centrally confirmed hormone positivity - estrogen or progesterone (>10 % by immunohistochemistry). The primary endpoint was investigator-assessed progression-free survival rate at 12 weeks (PFS-week12) by RECIST 1.1.

RESULTS

41 eligible patients were included (February/2020 to January/2022). The median age was 61 years (range 43-83). The PFS-week12 rate was 63.4 % (95 % CI, 46.8 to 76.1), median PFS 4.2 months (95 % CI, 2.7 to 5.5), and median overall survival 13.4 months (95 % CI, 10.4 to 20.1). The objective response rate was 7.7 % (3 partial responses) and the disease control rate 71.8 %. Treatment-related adverse event rates of any grade and grade 3-4 were 95.1 % and 51.2 %, respectively. Grade 3-4 neutropenia was reported in 17 patients (41.5 %), and febrile neutropenia in 1 (2.4 %).

CONCLUSIONS

The combination of Palbociclib plus letrozole has a favorable toxicity profile and appears to have clinical activity in recurrent hormone receptor-positive high-grade ovarian cancer.