In a new study, researchers found that patients receiving chest radiation to treat Wilms tumor – a rare form of childhood kidney cancer – had an increased risk of future breast cancer.

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Breast cancer is the most common form of invasive cancer in females worldwide.

Most information regarding incidences of breast cancer in survivors from childhood cancer comes from patients with Hodgkin lymphoma – a fact that the study, published in CANCER, seeks to address.

Previous research had identified an association in Hodgkin lymphoma survivors with chest radiation therapy and breast cancer. Until now, though, information regarding breast cancer development in survivors of Wilms tumor was limited.

Wilms tumor, also known as nephroblastoma, is a form of kidney cancer that most commonly affects children ages 3-4. Treatment is regularly effective, with cure rates approaching 90%. The disease is normally treated with surgery and chemotherapy, although in certain cases the child may require radiation therapy.

As this form of cancer can spread to the lungs, patients can be given radiation therapy to the chest; this is normally 12-14 Gray, a relatively low dose. Possible side effects include diarrhea and nausea, but the new study suggests that these conditions may not be the full extent of the risk.

Dr. Norman Breslow, of the University of Washington and the Fred Hutchinson Cancer Research Center in Seattle, WA, led a team assessing 2,492 women who received treatment for Wilms tumor during childhood and had reached at least 15 years of age.

Participants had all enrolled on the National Wilms Tumor Study (NWTS) and were followed from either their 15th birthday or from 5 years after the onset of their Wilms tumor – whichever date occurred latest.

The researchers found that over 20% of the participants who received chest radiation therapy went on to develop breast cancer by the age of 40, compared with only 0.3% of survivors who did not receive chest radiation. Three quarters of the breast cancer cases were invasive.

A 4% risk of breast cancer was also observed among Wilms tumor survivors who received abdominal radiation but no chest radiation.

Unexpectedly, the rates for the female survivors developing breast cancer after receiving chest radiation, abdominal radiation and no radiation therapy were around 30 times, six times and two times higher than those usually found in women of comparable age who had not had Wilms tumor.

The authors note that their study is limited by the relatively small number of patients with breast cancer and the fact that screening for breast cancer was possibly more intense among the patients who had received chest radiation. Despite this, they still believe their findings are robust.

Dr. Breslow says their findings suggest that the seemingly high risk of early breast cancer among Wilms tumor survivors may warrant early screening and changes to current guidelines:

Current guidelines call for early screening for breast cancer among survivors of childhood cancer if they have received 20 or more Gray of radiation therapy to breast tissue. This would exclude a large majority of patients who had received whole chest radiation for Wilms tumor.”

Dr. Jennifer Dean and Dr. Jeffrey Dome, of the Children’s National Health System in Washington, DC, suggest in an accompanying editorial that high-risk Wilms tumor survivors should begin breast cancer surveillance from the age of 25.

Unfortunately, they note that less than half of childhood cancer survivors follow through with recommended surveillance guidelines for breast cancer if they are identified as high-risk. “Barriers such as education of both survivors and providers should be addressed and mitigated,” they advise.

Recently, Medical News Today reported on a study examining whether genomic sequencing could aid breast cancer prevention by identifying people who are most likely to benefit from screening.