Methods
Patients and clinical data
The flow chart of the study population was shown in Figure 1.Patients
included in this study were diagnosed in Qilu Hospital of Shandong
University, Cancer Hospital of Beijing Academy of Medical Sciences,
Cancer Hospital affiliated to Sun Yat-sen University, Shanghai General
Hospital, Fudan University Shanghai Cancer Center, Shandong Cancer
Hospital, and the Fourth Hospital of Hebei Medical University from
2010/02/01 to 2018/09/24, and all carried the germline BRCA1/2
pathogenic mutation. The patient did not receive any maintenance
regimen, such as PARPi, bevacizumab, etc., after first- and second-line
platinum therapy. The secondary PFI was more than 6 months in all
patients. Patients enrolled in the study group were treated with PARPi
monotherapy after secondary platinum-sensitive relapse and continued
treatment until disease progression, demonstrating resistance to PARPi.
Patients in control group were treated with platinum-based chemotherapy
after secondary platinum-sensitive relapse, without restriction on the
specific type and dose of platinum. After progression of PARPi, patients
treated with subsequent platinum-based chemotherapy were enrolled in
study group 2; Among patients in control group, patients with PFI≥6
months after third-line chemotherapy, and receiving subsequent
platinum-based chemotherapy were enrolled in control group 2, and
patients with PFI<6 months were enrolled in control group 3.
The determination of response of PARPi and platinum-based chemotherapy
were in accordance with Response Evaluation Criteria in Solid Tumors
(RECIST) 1.1 criteria; If clinical data were insufficient for RECIST
criteria assessment, the GCIG’s CA125 criteria were used as an
alternative12.
PFS was defined as third-line therapy (including PARPi monotherapy and
platinum-based chemotherapy) to disease progression or death, TFST was
defined as the time from fourth-line chemotherapy to next subsequent
therapy or death. PRS refers to the survival time after secondary
platinum-sensitive relapse. Additional clinical data were collected
including age at diagnosis, primary tumor location, CA-125 level at
secondary relapse, neoadjuvant chemotherapy, pathological type, BRCA1/2
germline mutational status, platinum-based chemotherapy regimens, PARPi
duration, efficacy and toxicity, primary and secondary PFI, and
survival.
Germline BRCA1/2 detection
The protocol of germline BRCA1/2 detection based on NGS technology
included the following six steps, namely, sample acquisition and
processing, nucleic acid extraction, library construction, sequencing,
data analysis and mutation interpretation, and each step included
corresponding quality control steps. For amplicon based and
hybridization capture methods, the detection regions included the entire
exon coding region of BRCA1/2 gene and the exon-intron interface region
(±20 base pairs). The average depth of each run was over 200×. Sanger
DNA sequencing was performed for all reported variations using specific
gene primers. All point mutations and small indels were confirmed by
sanger DNA sequencing using specific gene primers, and the large
fragment rearrangements were detected by multiplex ligation-dependent
probe amplification (MLPA) methods. Variants were named according to
HGVS nomenclature, and guidelines for the interpretation of sequence
variants into 5-class system adapted from the International Agency for
Research on Cancer13, 14.
Statistical analyses
Student’s t-test was used to compare differences in continuous variables
with normal distribution. Differences in clinical characteristics and
survival between defined groups of patients were assessed using
chi-square test and Kaplan–Meier methods, where appropriate, and hazard
ratios (HR) with 95% confidence intervals (CI) were calculated. In
univariate analysis, p value 0.10 was defined as the upper limit for
inclusion in multivariate analysis, in the latter, p<0.05 was
considered significant. The SPSS program (version 16.0) was used for all
statistical analysis. The significance levels were * p < 0.05
and ** p < 0.01, respectively.