Comparing Ribociclib versus Palbociclib as a Second Line Treatment in Combination with Fulvestrant in Metastatic Breast Cancer: A Randomized Clinical Trial.

aimAssessment of CBR, PFS, QOL and toxicity profile of palbociclib and ribociclib.

methodsThis is an interventional concurrent randomised phase III open label clinical trial. It took place at the Oncology Centre Mansoura University, Egypt from July 2022 till December 2023. Patients with pathologically proved ER+ HER2- metastatic breast cancer who either progressed on adjuvant hormonal or progressed on 1st line hormonal for metastatic disease. Patients in arm A received palbociclib 125 mg/day orally for 3 weeks and 1 week rest, plus fulvestrant. Patients in Arm B received ribociclib at a dose of 600 mg, administered orally once daily for 3 weeks and 1 week rest, plus fulvestrant. Pre- and peri-menopausal women received the LHRH agonist goserelin. Patients who lost their endorsement and were considered to be lost to follow up. Quality of life was analysed using the (EORTC) quality-of-life questionnaire (QLQ)-C30 V3.0. Patients were asked to complete the questionnaires at screening; at the 2nd and 6th month. Toxicity was assessed and graded using (CTCAE) v5.0. Patients were evaluated clinically for response and toxicity monthly and radiologically by CT and tumor markers/ 3 months. Treatment continued until objective Progressive Disease (PD), symptomatic deterioration, unacceptable toxicity or death.

resultsBoth arms had similar baseline characteristics. There was no statistically significant difference regarding the CBR (58.6% for both arms at 6 months and 13.8% in the palbociclib VS 17.2% in the ribociclib arm at 12 months). The median PFS to the whole population was 13 months. COX multivariate analysis revealed that postmenopausal had 2.85 more likely to survive than premenopausal patients. Patients with ECOG performance status 2 and 3 are 0.13 and 0.39 less likely to survive compared to patients with PS 1. Dose reduction increased the likelihood of survival 3.36 compared with no dose reduction. The median PFS was 13.67 months in the palbociclib arm and 12.69 months in the ribociclib arm with no statistically significant difference. During follow up, there was statistically significant improvement in insomnia in both arms and constipation in the palbociclib arm alone. Comparing the two arms, no statistically significant deterioration in the QOL domains except in fatigue and financial difficulties, with more deterioration in the palbociclib arm. Regarding common toxicities there was no statistically significant difference between the 2 arms.

conclusionsBoth Ribociclib and palbociclib have similar CBR, PFS and toxicity profile.