When it comes to diagnosing gynecologic cancers, next-generation DNA sequencing technologies may dramatically change how early we can detect signs of cancer and what information we can gather from cancer cells. These advances are leading to promising discoveries, including techniques for early detection of gynecologic cancers for which there are no available screening tests.
Early Detection Challenges
Early detection of ovarian cancer is a significant challenge for clinicians, and early and accurate detection of endometrial cancer remains problematic.
In particular, the symptoms associated with ovarian cancer are non-specific, may come and go, and are frequently mistaken for other health conditions, prolonging the time it takes for a woman and her physician to correctly recognize the cause of the symptoms. The overwhelming majority (80%) of ovarian cancers are thus only detected once they have spread. Later detection has significant consequences for the patients' treatment and overall survival.
Endometrial cancer, the most common gynecologic malignancy in the U.S., is often detected following the onset of postmenopausal bleeding. However, postmenopausal bleeding also results from non-cancer/benign causes. Indeed, 90 percent of women with postmenopausal bleeding do not have cancer, so distinguishing between malignant and non-malignant etiologies presents a clinically relevant opportunity.
Since there are no screening tools available for endometrial and ovarian cancer, clinicians must rely on the results of clinical exams, blood tests, ultrasonography, and radiologic scans performed after the patient presents with symptoms. If these imaging and clinical exams remain consistent with a likelihood of cancer, patients will require additional invasive tests. In the case of endometrial cancer, hysteroscopy is a gold standard for diagnosing and distinguishing between malignant and nonmalignant processes. Hysteroscopy is a procedure that involves looking at the inside of the uterus using a special scope, taking scrapings of suspicious tissue, and sending these samples to the pathology lab for cytologic analysis.
At Western Connecticut Health Network and with our colleagues in the Department of Obstetrics/Gynecology & Reproductive Sciences at the Icahn School of Medicine at Mount Sinai, our research team is developing innovative technology such as liquid biopsy to advance gynecologic cancer care. A liquid biopsy identifies cancer cells or pieces of tumor-derived DNA that can be circulating in blood or other fluids and which arose from cancer somewhere else in the body.
The holy grail of liquid biopsies is to detect cancer in its earliest stages when it is most treatable—in some cases, these cancers are still undetectable using traditional imaging tests or other diagnostic exams. Liquid biopsy has the potential to be used as an alternative to a traditional tissue biopsy procedure to diagnose cancer, as the removal of abnormal cells can be technically difficult and assumes the surgeon already has a suspicion where to sample from.
Overwhelmingly, however, the promise of liquid biopsies has been focused on issues related to advanced disease in already diagnosed patients under active treatment. Advances in early detection remain limited in degrees of success. Constraints cited include the rarity of finding circulating tumor DNA molecules and circulating tumor cells when a tumor is still small and in an early stage; detection of a signal does not, yet, provide information on tumor type or origin; analytic techniques will need to improve to overcome issues related to signal-to-noise ratio; and the realization that age-associated mutations are prevalent in individuals without obvious disease.
Promising Cancer Screening
According to the NCI, the incidence of endometrial cancer is rising in the U.S. and around the world. These higher endometrial cancer incidence rates are likely linked to the rise in obesity. Ovarian cancer, which affects more than 22,000 women in the U.S. each year according to the CDC, is notoriously difficult to detect in its early stages. Late detection is directly linked to the high mortality rate; nearly 14,000 women with ovarian cancer will die in the U.S. each year.
A novel liquid biopsy technique—uterine lavage—could theoretically be used to identify precancerous DNA mutations before they turn into cancer. A uterine lavage involves rinsing the inside of the uterus with a small amount of fluid to collect cells and free DNA from within the uterus, since this fluid would come into contact with both endometrial and ovarian tumors arising from or in contact with, respectively, this space. It's been demonstrated that mutations present in these cancers can be detected in uterine lavage fluid; this opens the door for development of a cancer screening test. What we have most recently demonstrated is that analysis of uterine lavage fluid detected mutations in an asymptomatic woman, without histologic evidence of cancer, who 1 year later was diagnosed with endometrial cancer (Cold Spring Harb Mol Case Stud 2018; doi:10.1101/mcs.a003269).
Ten months after her negative histology diagnosis, the patient returned reporting postmenopausal bleeding. An in-office biopsy identified the presence of endometrial cancer and she was brought to the operating room for surgical debulking and staging. Remarkably, the tumor that was removed was stage IA and microscopic in size. The limitation on the amount of tissue meant that we could only obtain DNA for research purposes using laser capture microdissection. When the mutation profiles of the microscopic tumor and the cell pellet DNA obtained from the lavage nearly 1 year before were compared, the two PTEN mutations matched exactly. The likelihood of this occurring by chance alone was p< 3x10-7. Using this liquid biopsy technique, the PTEN precancerous mutations were detected even before a microscopic-sized tumor was detected by histopathologic examination.
Just as a Pap test can detect precancerous changes in the cells of the cervix, this liquid biopsy technique could enable clinicians to detect precancerous changes in the uterine lining and provide treatment before tumors develop. This discovery could also have a marked impact on incidence and mortality rates and revolutionize the treatments for difficult-to-diagnose gynecologic cancers and the precancerous conditions that cause them.
While these findings might herald a potential paradigm shift for early cancer detection, the clinical dilemma remains that next-generation sequencing studies are revealing a highly prevalent landscape of cancer driver mutations in endometrial cells from women even in the absence of endometrial cancer or morphologically recognized premalignant lesions. We next need to define the roadmap that distinguishes between those cells driving down an inevitable cancer pathway, or those veering away from that destination.
Convenient, Cost-Effective Screening
In addition to the scientific and medical advances this discovery represents, this screening test could be easily and conveniently performed in a physician's office and save time and costs associated with imaging tests and invasive hysteroscopy procedures that require a patient to be under anesthesia in an operating room.
Because our liquid biopsy screening technique identifies actual DNA from cancer cells, there is too high a risk of false-positive results. This will need to be addressed before the research-based test can be translated and made clinically relevant.
JOHN MARTIGNETTI, MD, PHD, is Network Director of the Laboratory for Translational Research at the Western Connecticut Health Network Rudy L. Ruggles Biomedical Research Institute and the Icahn School of Medicine at Mount Sinai.