Hispanic and non-Hispanic Black breast cancer survivors may experience higher rates of mortality after being diagnosed with a second primary cancer than breast cancer survivors of other ethnic and racial groups, according to a new study published by Deng et al in the Journal of the National Cancer Institute.

Background

About 50% of cancer survivors live for more than 10 years, and approximately 20% of patients diagnosed with cancer have a history of cancer, according to the National Cancer Institute (NCI). Therefore, it may be critical to determine the risk factors associated with second cancers so they can be prevented or diagnosed and managed as early as possible.

Many of these factors—including the diagnosis of aggressive tumors, cumulative treatment and type of treatment received, lifestyle factors, and social determinants of health—may contribute to the poor survival rates observed after a second cancer diagnosis.

A previous study—published by Deng et al in NPJ Breast Cancer—demonstrated that cancer survivors with a second primary cancer had a 27% increased risk of cancer mortality and 18% increased risk of all-cause mortality compared with survivors who had primary cancers.

“We believe this to be one of the first studies to comprehensively examine the racial and ethnic disparities in survival outcomes after a second cancer [diagnosis],” explained senior study author Kala Visvanathan, MD, MHS, Professor of Epidemiology in the Division of Cancer Epidemiology at the School of Medicine, Director of the Cancer Epidemiology Track in the Department of Epidemiology at the Bloomberg School of Public Health, and Director of the Clinical Cancer Genetics and Prevention Service at the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University. “The [new] findings are extremely concerning given the increasing prevalence of second cancers at a young age among [patients] diagnosed with breast cancer. A multipronged approach is needed to identify biological factors [as well as] patient-, provider-, and systems-level contributors to survival outcomes among breast cancer survivors,” she emphasized.

Study Methods and Results

In the new study, investigators used the NCI’s Surveillance, Epidemiology, and End Results 18 Program database to evaluate the outcomes of 39,209 breast cancer survivors who developed second primary tumors from 2000 to 2014. The patients were followed until December 31, 2016 or at least 2 years after their second cancer diagnosis.

The patients involved in the study were categorized by their ethnicities: Hispanic, non-Hispanic Asian, non-Hispanic Black, and non-Hispanic White. Patients who identified as non-Hispanic American Indian or Alaska Native as well as those of Pacific Islander descent were excluded from study because of the small number of records for these populations. The investigators then looked at several variables—including 5-year survival rate, age and year of diagnosis, marital and insurance status, initial treatments, median household income, education level, and cause of death.

Among the 39,029 patients who received second cancer diagnoses, 38.7% (n = 15,117) of them died. The strongest associations with cancer mortality were among non-Hispanic Black survivors with a second breast cancer or endometrial cancer diagnosis and among Hispanic survivors with a second breast cancer diagnosis.

The investigators also stressed that non-Hispanic Black survivors had the highest cumulative mortality rate during the follow-up period, followed by Hispanic survivors, non-Hispanic White survivors, and non-Hispanic Asian survivors. Later stage disease and more aggressive tumor characteristics also contributed to increased cancer mortality among Hispanic and non-Hispanic Black survivors after receiving their second cancer diagnoses.

The investigators discovered that the risk of mortality from a second primary cancer was 12% higher among non-Hispanic Black survivors and 8% higher among Hispanic survivors compared with non-Hispanic White survivors. Additionally, non-Hispanic Black survivors had a 44% higher risk of cardiovascular disease–related mortality after a second cancer diagnosis than non-Hispanic White survivors.

The investigators noted that cancer survivors in racial and ethnic minorities were diagnosed with second primary cancers up to 6 years younger than non-Hispanic White survivors, and within a shorter period of time following their first cancer diagnosis.

Second primary cancers occurred at an earlier median age in Hispanic survivors at 62.2 years, non-Hispanic Asian survivors at 63.4 years, and non-Hispanic Black survivors at 63.5 years compared with non-Hispanic White survivors, who developed second primary cancers at a median of 68.8 years.

The investigators revealed that breast cancer was the most common second cancer diagnosed across all racial and ethnic groups, followed by lung cancer, colorectal cancer, and endometrial cancer. They emphasized that second cancers in non-Hispanic Black survivors were less likely to be diagnosed at a local stage and that Hispanic and non-Hispanic Black survivors were more likely to undergo chemotherapy for their first and second cancers compared with other groups.

Conclusions

The investigators underscored that the higher cancer mortality rates observed among non-Hispanic Black and Hispanic survivors as well as the higher cardiovascular mortality rates seen among non-Hispanic Black survivors indicated a significant need for future studies focusing on factors contributing to these disparities in an effort to implement effective mitigation strategies.

Disclosure: The research in this study was supported by the Breast Cancer Research Foundation. Additional funding was provided in part by Cepheid. For full disclosures of the study authors, visit academic.oup.com.