Researchers at the University of California, Davis, analyzed data from 48,400 patients aged 15 to 39 who had initially been diagnosed with non-metastatic cancer. Over a follow-up period of approximately seven years, 9.5% of these patients experienced metastasis (the spread of cancer to other parts of the body).
The results showed that sarcoma—a rare cancer affecting connective tissue—and colon cancer were the most likely to recur and spread among the seven cancers included in the study. Researchers believe that the difficulty in treating these types of cancer contributes to their high recurrence rate, even after patients have achieved stable treatment.
Dr. Anne Bronson, lead author of the study and an analyst at the University of California, said that improved survival rates among younger patients present new challenges, stressing that analyzing large-scale, statewide data helps in understanding disease recurrence trends and guiding future research.This study is the first of its kind to track cancer recurrence among young adults on this scale. Researchers relied on data from the California Cancer Registry, including cases diagnosed between 2006 and 2018 of melanoma, sarcoma, breast, cervical, colon, testicular, and thyroid cancers.
The average age of the patients was 33 years, and women comprised 67% of them. Those aged 30-39 made up approximately 60% of the participants, compared to 28% in the 20-29 age group and 4% in the 15-19 age group.
Thyroid cancer was the most common at 28.5%, followed by breast cancer (25%), testicular cancer (14.5%), and skin cancer (13%). Sarcoma was the least common (4.5%).
In contrast, sarcomas accounted for 24.5% of cases of recurrence and metastasis, followed by colon (22%), cervical (16%), and breast (15%) cancers. Patients diagnosed at an advanced stage—particularly stage III—were also found to be more likely to experience cancer recurrence, with a rate exceeding 30% across different types.
The study revealed that patients whose cancer recurred and spread were three times more likely to die. The risk of death increased between 1.5 and 2 times among patients with cervical, skin, sarcoma, and colon cancers, while no increased risk of death was observed in patients with testicular or thyroid cancer upon recurrence.
Although cancer is rare among young people—about 80,000 Americans between the ages of 20 and 39 are diagnosed each year, representing only 4% of all cases—incidence rates have risen in recent years. A study published in May revealed an increase in 14 types of cancer among those under 50, most notably colon and breast cancer.
The reasons for this increase are still unclear, and doctors attribute it to a combination of factors including obesity, lack of exercise, microbiome disorders, and environmental toxins, without providing a full explanation for the emergence of the disease in people who are otherwise fit and healthy.
The study was published in the journal JAMA Oncology.
