Of 11,541 women in the study with ovarian cancer, 3,582 (31%) survived for more than 10 years following diagnosis.
What is more, the study - published in the Journal of Obstetrics and Gynecology - identified long-term survival in some women with ovarian cancer who had factors associated with poor survival - such as older age and later-stage diagnosis.
"The perception that almost all women will die of this disease is not correct," says lead study author Rosemary Cress, of the Department of Public Health Sciences at the University of California-Davis (UC Davis).
"This information will be helpful to physicians who first diagnose these patients and the obstetricians/gynecologists who take care of them after they receive treatment from specialists," she adds.
Around 21,290 women in the US will be diagnosed with ovarian cancer this year, and more than 14,000 are expected to die from the disease. The cancer is most common among older women, with more than half of cases diagnosed in women aged 63 or older.
According to the National Cancer Institutes's Surveillance, Epidemiology and End Results Program (SEER), the 5-year survival rate for women diagnosed with ovarian cancer is 45.6%. While few studies have investigated longer-term survival for patients with ovarian cancer, the rate of survival past 5 years after diagnosis is estimated to be poor.
Over 30% of women survived more than 10 years after ovarian cancer diagnosis
For their study, Cress and colleagues set out to estimate the 10-year survival rates for women diagnosed with ovarian cancer.
The team analyzed data from the California Cancer Registry, identifying 11,541 women who had been diagnosed with epithelial ovarian cancer - the most common form of the disease, accounting for 9 in 10 cases - between 1994 and 2001.
The researchers found that of these women, 3,582 (31%) survived for more than 10 years following diagnosis. Among these survivors were 954 women who had been considered high risk of dying from the cancer because they were an older age at time of diagnosis, had a higher tumor grade or were diagnosed with later-stage cancer.
"We were a little surprised at the large number of long-term survivors of this disease that is commonly perceived as highly fatal cancer," Cress told Medical News Today.
Though this research is unable to pinpoint exactly why so many women with ovarian cancer are surviving, study co-author Gary Leiserowitz, of the Department of Obstetrics and Gynecology at UC Davis, says it may be down to the BRCA1 and BRCA2 gene mutations present in some patients with the disease; women with these mutations often respond to chemotherapy better than those without.
In addition, Leiserowitz says that among patients with advanced ovarian cancer, biological differences may impact individual treatment outcomes, and some patients may receive more effective treatment than others, increasing their likelihood of survival.
"This information is important for patient counseling. Many patients and physicians know that ovarian cancer is a dangerous cancer, but they don't realize that there is significant biological variability among patients. It's not a uniformly fatal prognosis."
While further research is required to determine the exact reasons why some women with ovarian cancer experience long-term survival, these present findings offer hope to the thousands of women diagnosed with the disease each year.
Jacqueline Price - a 74-year-old ovarian cancer survivor and a patient of Leiserowitz - was diagnosed with stage 3 disease at the age of 60. She believes the findings of this latest research will help women diagnosed with ovarian cancer understand that it is not an "automatic death sentence" and boost optimism - an emotion that previous research has indicated can benefit cancer survival.
Cress told MNT that more research should be done to gain a better understanding of the long-term survival for patients with ovarian cancer, but she notes that researchers do not have the resources to follow patients for long periods of time.
"The strength of our study was the availability of population-based cancer registry data for patients diagnosed more than 10 years ago," she added. She points out, however, that future research should investigate the underlying mechanisms behind long-term ovarian cancer survival.
"Future studies could supplement cancer registry data with more detailed treatment information and with genomic data derived from analysis of ovarian tumors to determine the contribution of these factors to survival," she told us.
In June, MNT reported on a study published in JAMA Oncology, in which researchers identified a new class of gene mutations that may play a role in ovarian cancer treatment outcomes.