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Background: The PRIMA/ENGOT‐OV26/GOG‐3012 (NCT02655016) trial was amended to prospectively evaluate the safety and efficacy of an individualized starting dose (ISD) regimen of niraparib for first‐line maintenance therapy in patients with newly diagnosed advanced ovarian cancer. Methods: In the phase 3 PRIMA trial, patients with newly diagnosed advanced ovarian cancer with a complete/partial response to first‐line platinum‐based chemotherapy (N = 733) were initially treated with a fixed starting dose (FSD) regimen of 300 mg once daily. Subsequently, the protocol was amended so newly enrolled patients received an ISD: 200 mg once daily in patients with baseline body weight < 77 kg or baseline platelet count < 150,000/µL, and 300 mg once daily in all other patients. Efficacy and safety outcomes were assessed by starting dose. Results: Overall, 475 (64.8%) patients were assigned to an FSD (niraparib, n = 317; placebo, n = 158) and 258 (35.2%) were assigned to an ISD (niraparib, n = 170; placebo, n = 88). Efficacy in patients who received FSD or ISD was similar for the overall (FSD hazard ratio [HR], 0.59 [95% CI, 0.46–0.76] vs. ISD HR, 0.69 [95% CI, 0.48–0.98]) and the homologous recombination–deficient (FSD HR, 0.44 [95% CI, 0.30–0.64] vs. ISD HR, 0.39 [95% CI, 0.22–0.72]) populations. In patients with low body weight/platelet count, rates of grades ≥3 and 4 hematologic treatment‐emergent adverse events, dose interruptions, and dose reductions were lower for those who received ISD than for those who received FSD. Conclusions: In PRIMA, similar dose intensity, similar efficacy, and improved safety were observed with the ISD compared with the FSD regimen. Results from the phase 3 PRIMA trial of niraparib first‐line maintenance therapy that prospectively evaluated fixed versus individualized dosing support the selection of a niraparib starting dose based on an individual's body weight and platelet count. In prespecified analyses, patients who received the individualized starting dose of niraparib experienced similar progression‐free survival and improved safety outcomes compared with patients who received the fixed starting dose of niraparib. [ABSTRACT FROM AUTHOR]

This document provides a summary of results from the article that evaluated the safety and efficacy of the fixed and individualized starting doses of niraparib in the PRIMA study. The original article was published in the journal Cancer in March 2023. The PRIMA study included adult patients with newly diagnosed advanced ovarian cancer who had finished treatment with chemotherapy and surgery. Once patients entered the study, they were treated with an oral (by mouth) medication called niraparib or placebo (substance with no effects that a doctor gives to a patient instead of a drug). The amount of drug (dose) prescribed for patients to take at the start of treatment was determined by the study plan (a document that describes in detail how the study will be performed). Some patients were treated with a fixed starting dose (300 milligrams [mg] once daily), while others were treated with an individualized dose (200 or 300 mg once daily) based on how much they weighed and the results of their blood test. The individualized dose was tested to see if it improved patient safety without changing its efficacy (how well the drug worked). The individualized starting dose of niraparib improved patient safety, with a lower proportion of patients experiencing side effects than the fixed starting dose. The individualized starting dose of niraparib also delayed the cancer from coming back (recurring) or getting worse (progressing) compared with placebo. The delay in the cancer coming back or getting worse with niraparib treatment was generally similar in patients who received the individualized starting dose and those who received the fixed starting dose of niraparib. The results support the use of the individualized starting dose of niraparib, which uses a patient's body weight and blood test results to determine how much drug they should receive at the start of treatment. The study found that the individualized starting dose improved safety compared with the fixed starting dose while still delaying the cancer from coming back or getting worse. Clinical Trial Registration: NCT02655016 (PRIMA study) (ClinicalTrials.gov) [ABSTRACT FROM AUTHOR]