Between 2001 and 2018, there was a greater than 200% difference in the incidence trend between men and women for ages 15-34, wrote Yazan Abboud, MD, a postdoctoral research fellow in the pancreaticobiliary department of the Karsh Division of Gastroenterology and Hepatology at Cedars-Sinai Medical Center, Los Angeles, and colleagues.
“The exact cause of the trend among younger women is unclear and may be driven by sex-based disproportional exposure or response to known or yet-to-be-explored risk factors,” they wrote. “Future efforts should aim to elucidate the causes of such a trend with the goal to formulate possible preventive measures.”
Although previous studies have found increasing pancreatic cancer incidence rates, especially in younger women, the data haven’t been externally validated outside of the National Cancer Institute’s Surveillance Epidemiology and End Results (SEER) data, they wrote. In addition, there are limited data about the contributing factors, such as race, histopathological subtype, tumor location, and stage at diagnosis.
Using SEER-excluded data from the Centers for Disease Control and Prevention’s National Program of Cancer Registries (NPCR), Dr. Abboud and colleagues conducted a population-based time-trend analysis of pancreatic cancer incidence rates from 2001 to 2018 in younger adults under age 55, including the role of demographics and tumor characteristics. They analyzed age-adjusted incidence rates (aIR), mortality rates, annual percentage change (APC), and average annual percentage change (AAPC) for ages 55 and older and ages 55 and younger. In addition, the research team evaluated the impact of incidence trends on sex-specific mortality trends in younger adults using the CDC’s National Center of Health Statistics database.
Between 2001 and 2018, 748,132 patients were diagnosed with pancreatic cancer. After excluding SEER data, 454,611 patients met the inclusion criteria. About 48.9% were women.
The overall aIR of pancreatic cancer during that time was 12.18 per 100,000 people. Women had a significantly lower aIR, at 10.69 per 100,000, compared with men at 13.95 per 100,000.
In general, pancreatic cancer aIR significantly increased during that time (AAPC = 1.17%). Sex-specific trends increased among both women (AAPC = 1.27%) and men (AAPC = 1.14%), though they showed no significant difference and were parallel.
In ages 55 and older, 401,419 patients (49.7% women) were diagnosed with pancreatic cancer. The aIR significantly increased during the study period (AAPC = 1.11%), with sex-specific aIR increasing in both women (AAPC = 1.11%) and men (AAPC = 1.17%), without a significant difference.
However, a difference appeared in the 53,051 patients (42.9% women) who were ages 55 and younger. The aIR relatively increased (AAPC = 1.29%), with faster jumps in women (AAPC = 2.36%), compared with men (AAPC = .62%). There was an absolute significant difference of 1.74%.
The trends continued in breakdowns by age. For 50,599 patients (42.2% women) between ages 35 and 54, the aIR relatively increased (AAPC = 1.10%). Sex-specific aIR increased among women (AAPC = 2.09%) but remained stable among men (AAPC = 0.54%), with an absolute significant difference of 1.55%.
In the youngest cohort of 2,452 patients (57.3% women) between ages 15 and 34, aIR relatively increased (AAPC = 4.93). Sex-specific aIR also increased in both women (AAPC = 6.45%) and men (AAPC = 2.97%), with an absolute significant difference of 3.48%.
By race, although White women under age 55 experienced increasing aIR at a greater rate than men (AAPC difference = 1.59%), an even more dramatic increase was seen in Black women, as compared to counterpart men (AAPC difference = 2.23%). Sex-specific trends in people of other races were parallel.
Based on tumor characteristics in ages 55 and younger, the pancreatic ductal adenocarcinoma histopathological subtype had an AAPC difference of 0.89%, and a tumor location in the head-of-pancreas had an AAPC difference of 1.64%.
When evaluating tumors based on stage-at-diagnosis, the AAPC difference was nonsignificant in all subgroups. However, sex-specific trends differed in tumors diagnosed at localized stages, suggesting that aIR in women may be increasing at a greater rate than in men (AAPC difference = 1.64%).
Among 64,239 patients (39.3% women) who died from pancreatic cancer under age 55, the mortality rates were unchanged in women (AAPC = –0.09%) but declined in men (AAPC = –0.64%), with an absolute significant AAPC difference of 0.54%.
“Pancreatic cancer has a very poor overall survival, accounting for 7% of cancer-related deaths. The incidence of cancers, in general, is expected to rise as life expectancy increases in the United States,” said Danny Issa, MD, a gastroenterologist at the University of California, Los Angeles, who wasn’t involved with this study.
“Recently, noncomparative studies showed a possible increase in the incidence of pancreatic cancer in younger White women and in older White men and women. These reports had limitations,” he said. “The findings of this study are monumental as they confirmed that age-adjusted incidence rates have been increasing at a higher rate in younger women compared to younger men.”
In addition, Dr. Issa said, the significant increases among Black women for adenocarcinoma and for cancers located in the head of the pancreas are notable and should be studied further.
“Over the past few decades, research studies have helped improve cancer treatment by uncovering risk factors and identifying the most affected (or protected) population,” he said. “Therefore, epidemiologic studies are crucial, especially for hard-to-treat cancers such as pancreatic cancer.”
The study was supported in part by a philanthropic grant from The Widjaja Family Fund for Pancreatic Cancer Research. The authors disclosed no conflicts of interest. Dr. Issa reported no relevant disclosures.