TP53 Clonal Variants in Papanicolaou Test Samples May Aid in Diagnosing HGS-EOC

A study published in JAMA Network Open suggested that noninvasive early molecular diagnosis of high-grade serous epithelial ovarian cancer (HGS-EOC) is potentially attainable through detection of TP53 clonal variants in the DNA purified from Papanicolaou tests performed during cervical cancer screening.

However, the researchers suggested that the development of a clinically and analytically accurate diagnostic test in this setting would require a large, longitudinal prospective study to be conducted with appropriate numbers of patients and healthy controls using standardized sampling procedures and highly sensitive NGS-based approaches to monitor the entire TP53 gene.

“Women harboring BRCA1 or BRCA2 germinal variants could be suitable candidates to be recruited into such a study, given their high risk of HGS-EOC and their intensive monitoring,” the authors wrote. “Furthermore, only such ad hoc studies will ultimately allow a robust evaluation as to whether this early diagnostic approach might translate into survival benefits.”

In this cohort study, researcher analyzed women with histologically confirmed diagnosis of HGS-EOC recruited at San Gerardo Hospital in Monza, Italy, from October 15, 2015, to January 4, 2019. Specifically, serial dilutions of DNA extracted from tumor samples and DNA obtained from the Papanicolaou test samples of healthy women were analyzed to define the sensitivity and specificity of droplet digital polymerase chain reaction assays designed to detect the TP53 variants identified in tumors.

Notably, all available brush-based Papanicolaou test slides performed up to 6 years before diagnosis were assessed at the Mario Negri Institute in Milano, Italy and the data was analyzed from October 2018 to December 2019.

Of 17 patients included in the study, Papanicolaou tests withdrawn prior to diagnosis presented tumor-matched TP53 variants in 11 patients (64%). Even further, in 2 patients for whom longitudinal Papanicolaou tests were available, including 1 patient with Papanicolaou tests from 25 and 49 months before diagnosis and 1 patient with Papanicolaou tests from 27 and 68 months before diagnosis, the TP53 clonal variant was detected at all time points.

“Moreover, although most of the TP53 variants were located in variant hot spots, they were not found in healthy women’s samples, corroborating the etiopathogenetic role of selected TP53 variants in patients with HGS-EOC,” the authors wrote. “Considering the anatomical continuity between tubal lumen and cervical canal, it is plausible that cytological material could be a useful biological material to detect biomarkers associated with HGS-EOC many years before diagnosis, although a study focused on HGS-EOC etiopathogenesis is necessary to assess the viability of this model.”

Importantly, since the archival Papanicolaou test material was not originally intended to be used for DNA analysis, sampling procedures and storage conditions could have interfered with DNA quality. Therefore, it is reasonable to believe that the negative findings for TP53 variants observed in this study are, at least in part, due to deficient sample collection and storage.

In addition, only tumor-matched TP53 clonal variants were evaluated in this study. Somatic evolution in nonneoplastic tissues implies that, owing to aging or other physiological processes, multiple somatic variants are normally present ubiquitously at the mosaic level. Given this, the researchers suggested that prospective clinical studies conceived and designed on large populations of women are necessary to verify these study findings.

“Our results hint at a promising prospect to significantly improve the future diagnosis of HGS-EOC, thus increasing its potential curability,” the authors concluded.

Reference:

Paracchini L, Pesenti C, Marchette MD, et al. Detection of TP53 Clonal Variants in Papanicolaou Test Samples Collected up to 6 Years Prior to High-Grade Serous Epithelial Ovarian Cancer Diagnosis. JAMA Network Open. doi: 10.1001/jamanetworkopen.2020.7566.