Relative to serous borderline ovarian tumors, the proportion of low-grade serous ovarian cancers has decreased in recent years, paralleled by a trend toward decreased survival, results of a large, population-based study suggest.
The number of low-grade serous ovarian cancer (LGSOC) cases declined by almost 26% in the retrospective analysis of registry data from 1998 to 2000, with a relative decrease of survival by nearly 29% over that time period.
Those decreases in LGSOC incidence and survival may be explained by a “diagnosis shift” toward versus serous borderline ovarian tumors (SBOTs) over time, though it could also be due to earlier detection of SBOT, which may be a precursor lesion of LGSOC, said authors of the study, led by oncology researcher Koji Matsuo, MD, PhD, of the University of Southern California, Los Angeles.
Taken together, the findings support the need to distinguish between LGSOC and SBOT, given their “distinctly different” oncologic outcomes and treatment approaches, according to Dr. Matsuo and colleagues.
“Making a proper diagnosis for LGSOC versus SBOT is paramount, as it impacts surgical and postoperative management,” the authors wrote in their report on the study, which appears in Gynecologic Oncology.
The retrospective, population-based, observational study, based on data from the Surveillance, Epidemiology, and End Results program of the National Cancer Institute, included women with LGSOC or SBOT diagnosed between 1988 and 2000 in the United States. A total of 4,712 cases were analyzed.
The number of LGSOC from 23.2% in 1988 down to 17.2% by 2000, or a relative decrease of 25.9%, Dr. Matsuo and coauthors reported. The decrease was even more pronounced in stage I disease, with a relative decrease of 37.6% versus 21.1% for stage II-IV.
As compared with women with SBOT, women with LGSOC were more likely to be older, more likely to have stage II-IV disease at diagnosis, more likely to have undergone hysterectomy, and less likely to be residents of the western United States, results of a multivariable analysis showed.
There was a downward trend in 15-year overall survival among women with LGSOC, from 53.3% to 38.0% by 2000, representing a relative decrease of 28.7%, according to the investigators. By contrast, overall survival was unchanged in the SBOT cohort, at 76.7% in 1988 and 78.7% by 2000, for a relative increase of about 2.5%.
Gradual changes in diagnostic classification over time may explain these trends, according to the investigators.
That shift would have started with the recognition of borderline ovarian tumors as a separate entity by the World Health Organization until 1971, leading to an increasing number of SBOTs over time as diagnostic practice patterns gradually changed. Later, it would have been fueled by the recognition of LGSOC as a new classification in the mid-1980s, which may have accelerated the shift by enhanced discrimination of SBOT from other serous tumors, the investigators wrote.
On the other hand, since SBOT may be a precursor lesion to LGSOC, the shift in diagnosis over time could be caused at least in part by increasing use of transvaginal ultrasonography, leading to more early detection of SBOT before they could progress to LGGOC. “More study is necessary to identify if SBOT can progress to LGSOC,” Dr. Matsuo and coauthors wrote.
The study was funded by the Ensign Endowment for Gynecologic Cancer Research. Dr. Matsuo reported disclosures related to Chugai, Springer, and VBL Therapeutics. His coauthors provided additional disclosures related to Kiyatec, Merck, Biopath, M-Trap, Quantgene, Tesaro, GlaxoSmithKline, Celgene, Johnson & Johnson, Biogin, Clovis Oncology, Novartis, Elsevier, and UpToDate.
SOURCE: Matsuo K et al. Gynecol Oncol. 2020 Jan 15. doi: 10.1016/j.ygyno.2019.08.030.