What is the risk of bone marrow cancer after breast cancer treatment?

This paper studied the occurrence of bone marrow neoplasms after adjuvant breast cancer therapy. 

Adjuvant therapy (treatment given after initial cancer therapy) has helped to improve survival of patients with early stage breast cancer. However, there are still some short and long term complications that can negatively impact individual patients. It is important to study treatment-related complications so that patients can be better informed of their options. For instance, myeloid neoplasms refers to cancer in the bone marrow; this occurs when there are too many white blood cells produced. 

20,063 patients with stage I,II, or III breast cancer were studied and followed-up for an average 5.1 years. At 10 years, 78% of patients had survived without any symptoms of cancer while 80% had survived overall.

0.25% of patients were diagnosed with myeloid neoplasms after adjuvant therapy. The average time from breast cancer to myeloid neoplasm was 4.9 years. For patients who were diagnosed with myeloid neoplasms, the overall survival was 62% after 5 years and 9% after 10 years.  Patients who developed myeloid neoplasms were older compared to patients who did not develop myeloid neoplasms.

The authors compared the occurrence of myeloid neoplasms according to treatments patients received. There was a 6.8 times increased risk of myeloid neoplasms among patients treated with both surgery and chemotherapy compared with surgery alone. There was a 7.6 times increased risk of myeloid neoplasms among patients treated with surgery plus radiation plus chemotherapy compared with surgery alone.

The authors studied the incidences of myeloid neoplasms according to genetics. Two thirds of patients had abnormal myeloid neoplasm-associated genes.  

The authors concluded that the risk of myeloid neoplasm after adjuvant treatment was low but varied according to treatment received. 

The authors did not study in detail the exact amount of treatment each patient received.