title: Exploratory Analysis of TP53 Mutations in Circulating Tumour DNA as Biomarkers of Treatment Response for Patients with Relapsed High-Grade Serous Ovarian Carcinoma: A Retrospective Study.
abstract: BACKGROUND
  Circulating tumour DNA (ctDNA) carrying tumour-specific sequence alterations may provide a minimally invasive means to dynamically assess tumour burden and response to treatment in cancer patients. Somatic TP53 mutations are a defining feature of high-grade serous ovarian carcinoma (HGSOC). We tested whether these mutations could be used as personalised markers to monitor tumour burden and early changes as a predictor of response and time to progression (TTP).
  
  
  RESULTS
  We performed a retrospective analysis of serial plasma samples collected during routine clinical visits from 40 patients with HGSOC undergoing heterogeneous standard of care treatment. Patient-specific TP53 assays were developed for 31 unique mutations identified in formalin-fixed paraffin-embedded tumour DNA from these patients. These assays were used to quantify ctDNA in 318 plasma samples using microfluidic digital PCR. The TP53 mutant allele fraction (TP53MAF) was compared to serum CA-125, the current gold-standard response marker for HGSOC in blood, as well as to disease volume on computed tomography scans by volumetric analysis. Changes after one cycle of treatment were compared with TTP. The median TP53MAF prior to treatment in 51 relapsed treatment courses was 8% (interquartile range [IQR] 1.2%-22%) compared to 0.7% (IQR 0.3%-2.0%) for seven untreated newly diagnosed stage IIIC/IV patients. TP53MAF correlated with volumetric measurements (Pearson r = 0.59, p < 0.001), and this correlation improved when patients with ascites were excluded (r = 0.82). The ratio of TP53MAF to volume of disease was higher in relapsed patients (0.04% per cm3) than in untreated patients (0.0008% per cm3, p = 0.004). In nearly all relapsed patients with disease volume > 32 cm3, ctDNA was detected at ≥20 amplifiable copies per millilitre of plasma. In 49 treatment courses for relapsed disease, pre-treatment TP53MAF concentration, but not CA-125, was associated with TTP. Response to chemotherapy was seen earlier with ctDNA, with a median time to nadir of 37 d (IQR 28-54) compared with a median time to nadir of 84 d (IQR 42-116) for CA-125. In 32 relapsed treatment courses evaluable for response after one cycle of chemotherapy, a decrease in TP53MAF of >60% was an independent predictor of TTP in multivariable analysis (hazard ratio 0.22, 95% CI 0.07-0.67, p = 0.008). Conversely, a decrease in TP53MAF of ≤60% was associated with poor response and identified cases with TTP < 6 mo with 71% sensitivity (95% CI 42%-92%) and 88% specificity (95% CI 64%-99%). Specificity was improved when patients with recent drainage of ascites were excluded. Ascites drainage led to a reduction of TP53MAF concentration. The limitations of this study include retrospective design, small sample size, and heterogeneity of treatment within the cohort.
  
  
  CONCLUSIONS
  In this retrospective study, we demonstrated that ctDNA is correlated with volume of disease at the start of treatment in women with HGSOC and that a decrease of ≤60% in TP53MAF after one cycle of chemotherapy was associated with shorter TTP. These results provide evidence that ctDNA has the potential to be a highly specific early molecular response marker in HGSOC and warrants further investigation in larger cohorts receiving uniform treatment.
authors.affiliation: Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, United Kingdom.|Department of Oncology, Hutchison/MRC Research Centre, University of Cambridge, Cambridge, United Kingdom.|NIHR Cambridge Biomedical Research Centre, Cambridge, United Kingdom.|Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: Christine A
authors.initials: CA
authors.lastname: Parkinson
authors.affiliation: Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: Davina
authors.initials: D
authors.lastname: Gale
authors.affiliation: Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Piskorz
authors.affiliation: Department of Oncology, Hutchison/MRC Research Centre, University of Cambridge, Cambridge, United Kingdom.|NIHR Cambridge Biomedical Research Centre, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: Heather
authors.initials: H
authors.lastname: Biggs
authors.affiliation: Department of Oncology, Hutchison/MRC Research Centre, University of Cambridge, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: Charlotte
authors.identifier: http://orcid.org/0000-0002-2240-1740
authors.initials: C
authors.lastname: Hodgkin
authors.affiliation: Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: Helen
authors.initials: H
authors.lastname: Addley
authors.affiliation: Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: Sue
authors.initials: S
authors.lastname: Freeman
authors.affiliation: Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: Penelope
authors.initials: P
authors.lastname: Moyle
authors.affiliation: Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom.
authors.forename: Evis
authors.initials: E
authors.lastname: Sala
authors.affiliation: Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Karen
authors.initials: K
authors.lastname: Sayal
authors.affiliation: Department of Oncology, Hutchison/MRC Research Centre, University of Cambridge, Cambridge, United Kingdom.|NIHR Cambridge Biomedical Research Centre, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: Karen
authors.initials: K
authors.lastname: Hosking
authors.affiliation: Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Gounaris
authors.affiliation: Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: Mercedes
authors.identifier: http://orcid.org/0000-0002-8164-5462
authors.initials: M
authors.lastname: Jimenez-Linan
authors.affiliation: Department of Oncology, Hutchison/MRC Research Centre, University of Cambridge, Cambridge, United Kingdom.|NIHR Cambridge Biomedical Research Centre, Cambridge, United Kingdom.|Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: Helena M
authors.initials: HM
authors.lastname: Earl
authors.affiliation: Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: Wendi
authors.identifier: http://orcid.org/0000-0002-4238-3471
authors.initials: W
authors.lastname: Qian
authors.affiliation: Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: Nitzan
authors.initials: N
authors.lastname: Rosenfeld
authors.affiliation: Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, United Kingdom.|Department of Oncology, Hutchison/MRC Research Centre, University of Cambridge, Cambridge, United Kingdom.|NIHR Cambridge Biomedical Research Centre, Cambridge, United Kingdom.|Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom.|Cancer Research UK Major Centre-Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom.
authors.forename: James D
authors.initials: JD
authors.lastname: Brenton
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000097:blood; D002277:Carcinoma / Q000097:blood* / Q000235:genetics* / Q000378:metabolism; D004273:DNA, Neoplasm / Q000097:blood* / Q000235:genetics*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009154:Mutation; D009360:Neoplastic Cells, Circulating / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000097:blood* / Q000235:genetics* / Q000378:metabolism; D012189:Retrospective Studies; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D004273:DNA, Neoplasm; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53