A recent study from a team of researchers at the Johns Hopkins Kimmel Cancer Center indicates that the risk of leukemia following radiotherapy or chemotherapy in early stage breast cancer is approximately two times higher than suggested by previous studies.
The study entitled “Risk of Marrow Neoplasms After Adjuvant Breast Cancer Therapy: The National Comprehensive Cancer Network Experience” was recently published in the Journal of Clinical Oncology.
Adjuvant therapy improves survival outcomes in patients with breast cancer. Although any negative impact on survival from therapy-related complications is already accounted for in the observed average improvements in disease-free survival (DFS) and overall survival (OS) after adjuvant therapy, some long-term complications such as leukemia can still occur.
The research team analyzed data from the National Comprehensive Cancer Network (NCCN) Breast Cancer Outcomes and registered the frequency of marrow neoplasms (MNs) after a diagnosis of early-stage breast cancer in a cohort of 20,063 patients after a median follow-up of 5.1 years. Of these patients, 50 developed leukemia within 10 years after adjuvant therapy in the form of radiation therapy, chemotherapy, or both, showing an increased risk of 0.5%. This result was twice the one found in a previous randomized controlled trial, that reported an increased risk of leukaemia of 0.25 in patients with early breast cancer treated with adjuvant therapies.
In a recent press release, Judith Karp, senior author of the study said “The frequency of bone marrow cancers such as leukemia is small, there’s no question about it,” “However, the cumulative risk over a decade is now shown to be twice as high as we thought it was, and that risk doesn’t seem to slow down five years after treatment.”
“Most medical oncologists have come to think that the risk is early and short-lived. So this was a little bit of a wake-up call that we are not seeing any plateau of that risk, and it is higher,” Dr. Karp added.
Study author Dr. Antonio Wolff further explained, “Our study provides useful information for physicians and patients to consider a potential downside of preventive or adjuvant chemotherapy in patients with very low risk of breast cancer recurrence. It could be a false and dangerous security blanket to some patients by exposing them to a small risk of serious late effects with little or no real benefit from the treatment. The good news is that the majority of patients with stage 1 breast cancer will survive their breast cancer diagnosis, and of all the solid tumors, breast cancer is among the most curable of them.”
The researchers concluded that in this large early-stage breast cancer cohort, MN risk after radiation and/or adjuvant chemotherapy was low but higher than previously described. This risk continued to increase beyond 5 years. According to the authors, individual risk of MN should be balanced against the absolute survival benefit of adjuvant chemotherapy.