Substantial Proportion of Patients Diagnosed With Incident Cancer Have Survived a Prior Cancer

A significant number of patients diagnosed with incident cancer in the US are survivors of prior cancers, according a study published in JAMA Oncology.

As the US cancer survivor population continues to grow, cancer survivors are frequently excluded from cancer clinical trials and observational research, noted the authors of the study.

“Although considerable scientific progress has been made understanding risk of developing a future primary cancer among specific groups of cancer survivors, this earlier work does not address how many patients diagnosed with incident cancer have survived a prior cancer,” wrote the authors. “Understanding prevalence of prior cancer among patients with different types of incident cancer has important implications for both treatment and research.”

The authors analyzed 740,990 individuals from the Surveillance, Epidemiology, and End Results (SEER) program that were recently diagnosed with cancer from January 2009 to December 2013. The authors linked observations across 9 SEER registries to estimate the prevalence of prior cancer by incident type and age (under age 65 versus over age 65).

The authors characterized incident cancers as:

• First or only primary
• Second order or higher primary in the same cancer site
• Second order or higher primary in a different cancer site

For patients with more than 1 cancer diagnosed within the same year (n = 23,150), the authors were unable to determine the order of diagnoses, and thus randomly selected 1 cancer for analysis.

From the study participants, there were 765,843 incident cancers diagnosed, of which 141,021 were characterized as a second order or higher primary cancer. Results showed that 25.2% of older adults (65 years or older) and 11% of young adults (aged 20 to 64) had a history of prior cancer.

Prevalence also differered by incident cancer type, ranging from 3.5% to 36.9%. For young adults, prior cancer was most prevalent among myeloid and monocytic leukemia (24.8%); cancer of the anus, anal canal, and rectum (18.2%); cancers of the cervix and other female genital organs (15%); and lung and other respiratory cancers (14.6%). Prior cancers for this age group often occurred in a different cancer site; however, second order breast, cervical, and other female genital, male genital, and testicular cancers were more often in the same site.

For older adults, incident cancers with highest prevalence of prior cancer were melanoma (36.9%); myeloid and monocytic leukemia (36.9%); cancer of the bone and joints (34%); and cancers of the urinary bladder and other organs (32.5%). Aside from breast cancer melanoma, most prior cancers among the group occurred in a different site.

“As the cancer survivor population continues to grow, understanding the nature and impact or a prior cancer is critical to improving trial accrual, generalizability of results from trials and observational studies, disease outcomes, and patient experience,” concluded the authors.