Multiple primary versions can arise by themselves, experts say. Researchers look into past treatments, environments and genetics as the culprits.
Noelle Johnson, 42, was diagnosed with her first cancer — a soft tissue sarcoma under her right arm — in 1999 when she was 21. In 2013, her physicians found six different cancers in her breasts. In the years that followed, surgeons discovered and removed numerous masses they deemed “premalignant” from her ovary, her uterus, her leg, arm and chest wall, aiming to get them out before they turned cancerous.
Each tumor was distinct, that is, none resulted from the spread of any of the others. For Johnson, having multiple primary tumors diagnosed at an unusually young age was both scary and baffling. “It was crazy,” recalls Johnson, who lives in Windsor, Col., where she operates a day-care center in her home. “My world started to spin. It was a huge red flag.”
Many people assume that when cancer shows up following an earlier tumor, it is a metastasis from the first. But this is not always the case. Multiple primary cancers can arise by themselves, and researchers in recent years have begun to unravel some of the reasons.
“Cancer therapies have improved dramatically in the modern era, resulting in a growing population of cancer survivors — over 15 million,” says Stephen J. Chanock, director of the division of cancer epidemiology and genetics at the National Cancer Institute (NCI). “As these individuals live longer lives, some of them go on to develop second cancers, tumors unrelated to their original cancer. There likely are multiple factors involved, and we are still learning about their causes.”
Experts believe that many of these additional primary tumors are the result of earlier treatments for initial cancers that often occur in childhood. Radiation and chemotherapy, while successful in knocking out the first disease, also cause DNA damage. This can prompt new cancers to develop later, among them lymphomas, leukemias, and those of the breast, thyroid or soft tissues.
Other factors that can encourage new tumors probably include environmental exposures, such as tobacco or alcohol use, hormonal influences, viral infections — especially HIV — and genetics, which appears to be a major player. Also, experts believe that a combination of these is involved. “There are emerging data that suggest common inherited factors together with treatment can influence the risk of developing a second cancer,” Chanock says.
|Read on: Multiple primary cancers can afflict one patient|