NEWS | August 13, 2018

Study of cancer survival over 20-year period in California finds improvements for some, but not all


Over the past 20 years, survival for individuals with cancer in California has significantly improved for most types of cancer, but significant disparities in survival exist by race/ethnicity and socioeconomic status, according to a report posted online today by the UC Davis Institute for Population Health Improvement.

Cancer Survival in California report coverThe report, “Cancer Survival in California,” is the first of its kind comprehensive, population-based assessment of cancer survival in California over the past two decades. Using data from the California Cancer Registry (CCR), which has collected information on all cancers diagnosed among California residents since 1988, the report evaluates cancer survival  among 1.4 million Californians aged 20 years and older diagnosed with one of the 27 most commonly occurring types of cancer. These 27 types of cancer account for more than 90 percent of all cancers diagnosed in the state. 

The report found that there was an overall relative 12 percent gain in cancer survival improvement (i.e., survival for all types of cancer combined) in California over the past two decades, rising from a five-year survival rate of 58 percent for cancers diagnosed from 1990-1994, to 65 percent for cancers diagnosed between 2006 and 2010. (The absolute survival gain of seven percent represents a relative gain of 12 percent.) This improvement was due largely to better treatments and improved screening programs that detect cancer at earlier stages when treatment of the disease is more likely to be effective.

The biggest relative improvements in cancer survival over the past 20 years were seen in cancers of the liver  (183  percent), stomach (53 percent), esophagus (42 percent) and several hematopoetic (blood-related) cancers, including multiple myeloma (64 percent), acute myeloid leukemia (69 percent), chronic myeloid leukemia (88percent), acute lymphocytic leukemia (55 percent), and non-Hodgkin’s lymphoma (42 percent). Survival for the most common cancers - breast, prostate, colon and lung - improved 4percent to-7percent. However, survival did not improve during the study period for cervical, laryngeal, testicular, bladder and uterine cancers. 

Although survival improved for 22 of the 27 most common cancers, significant race/ethnic disparities in survival gains were observed for 23 cancer types. Compared to all other race/ethnic groups, African Americans had the poorest five-year survival for 15 cancer types, while Asian/Pacific Islanders had the highest five-year survival for 13 of the cancer types examined. 

“While the absolute improvements in survival for most types of cancer over time are encouraging, the slower rate of improvement for African-Americans and persons of low socioeconomic status compared to other groups are significant population health problems that need to be addressed,” said senior author of the report and IPHI Director Kenneth W. Kizer. “These results underscore the need to better understand and address previously documented treatment disparities in these population subgroups. The quality of care and chance of surviving from cancer should not be dependent on one’s skin color or bank account.” 

Stage of disease at the time of diagnosis is the single strongest prognostic factor for cancer survival, underscoring the importance of timely screening and detection; 86 percent of patients diagnosed with early, localized stage 1 disease were alive 10 years after diagnosis, compared to 14 percent of patients diagnosed with stage 4 or advanced, metastatic cancer.

“These results underscore the importance of early detection for cancers which have reliable screening tests and improving access to and utilization of care, particularly in vulnerable populations. Many deaths from cancer could be prevented by screening and better access to care,” Kizer said.

Of note, in 2016, IPHI provided detailed information on the outcomes of cancer screening in each county in California, showing where there are significant opportunities for improvement for screenable cancers (Heat Maps: Trends in Late Stage Diagnoses of Screenable Cancers in California Counties, 1988-2013. See also, Cancer Stage at Diagnosis in California, 2009-2013.)

In recent years, cancer has been the first or second leading cause of death in California, depending on the year, and is the second leading cause of death nationwide. 

IPHI’s California Cancer Reporting and Epidemiologic Surveillance (CalCARES) Program works in partnership with the California Department of Public Health to manage the day-to-day operations of the California Cancer Registry (CCR), the state mandated population-based cancer surveillance system. CalCARES researchers routinely review cancer registry data to monitor cancer incidence and mortality trends and identify opportunities to improve cancer control efforts and reduce the occurrence of cancer. Other authors of the report include Cyllene R. Morris, Brenda Giddings, Fran Maguire, Yi Chen, Jordan Killion, and Arti Parikh-Patel 

Download executive summary from the Cancer Survival in California report (PDF)