As a lesion located in the uterus cavity, endometrial cancer usually causes abnormal bleeding, which is much more prevalent in women elder than 45 or postmenopausal phase[3]. During last decades, the mortality and morbidity of EC keep rising, which even surpassed cervical cancer in certain areas and significantly threatened women’s health[2, 15]. Thus, an effective approach for the screening and early detection of EC is urgently needed.
According to previous studies, human cancers (including EC) are commonly characterized by a rapid growth and increased need of energy and material supplies. Due to the lack of energy and oxygen, necrosis was quite common in tumor mass and caused the fell off of cancer cells into nearby cavities like oesophagus, stomach, urinary and uterine/vaginal tracts[16–19]. This proposed an opportunity to collect the exfoliated cells from EC tumor using a vaginal tampon, which is much less invasive than the previously reported uterine cavity brush or D&C[20, 21]. In this research, we proposed a non-invasive method, UterCAD, which relies on tampon-based whole genome DNA sequencing technology.
In this study, we used a tampon to collect the exfoliated cells from upper genital tract and investigated its CNVs for the early diagnosis of EC. As data shown, the UterCAD technology achieved a sensitivity of 83.3% and a high specificity of 96.2%, proposing it may be a powerful non-invasive method for the early detection of EC. Interestingly, 5 EEC patients (diagnosed in other hospitals via D&C) presented no cancer cells after hysterectomy in our hospital, indicating these small lesions might be only localized in endometrium. Consistently, UterCAD analysis detected no CNVs in all these 5 cases, implying the superior specificity of this technology.
Similarly, several previous studies have reported the Pap test could collect samples from vagina, cervix surface, cervical canal, uterine cavity, and even fallopian tubes, which might be an attractive approach for the non-invasive diagnosis of EC. As previously reported, Kinde et al. and Wang et al. detected EC-derived DNA in 41% and 29% of associated Pap samples in two independent patients groups, the low detection rate might be caused by the short period (just a few seconds) for sample-collecting using Pap-smear, which significantly limited the quantity of tumor cells[17, 18]. In the current study, we improved the cells-collection using a vagina tampon (6-hour protocol) and demonstrated it could harvest many more cells for UterCAD test.
In fact, the presence of chromosomal CNV may have a stronger indication for an underlying carcinogenic event, since not all mutations lead to gene dysfunction and cancer events. According with TCGA data, the application of UterCAD for EC early diagnosis is endorsed by the fact that this malignancy is particularly rich in CNVs, especially in these high grade tumors like USC and clear cell carcinoma[22]. With regards to our cohort, UterCAD detected significant CNVs in all these 4 USCs, which was in consistent with previous researches[23]. In addition, women with positive findings indicated by UterCAD might be in risk for the more aggressive USC and warrants immediate actions.
While this study was a pilot study to test DNA copy numbers, further large-sample-size validations should be performed in our future work. Some previous studies also showed a small proportion of endometrial tumors are characterized with immense gene single nucleotide mutations but negligible copy number variations[24]. The Cancer Genome Atlas provided us an overview of endometrial cancer and the over-represented point mutations. A panel of high frequent mutations may be further necessary in improving the overall diagnosis sensitivity, especially with regards to certain subtypes of EC[14].
Collectively, we firstly investigated the efficiency of UterCAD, a genome sequencing method based on tampon-collected DNA, in a group of suspicious EC. Our results proposed a special effect of UterCAD for the early detection of ECs (especially type II tumors with more frequent CNVs). The high sensitivity and specificity warrant UterCAD as a non-invasive procedure before endometrium biopsy.