Early-stage breast cancer survivors treated with whole breast irradiation (WBI) are at a greater risk of developing a secondary cancer than patients treated with accelerated partial breast irradiation (APBI), according to a new study published in Radiotherapy and Oncology.
The authors calculated Lifetime Attributable Risks (LAR) to investigate the survival of breast cancer patients. Overall, WBI has the highest total LAR, equaling a “4.3 percent excess risk of secondary cancer for a patient treated at age 50 years.”
“Our study shows that all APBI techniques produce less scatter dose compared to whole breast radiotherapy, which translates into a lower secondary cancer risk.” wrote Nienke Hoekstra of Erasmus MC Cancer Centre in Rotterdam, Netherlands, and colleagues. “The use of APBI could eventually halve the lifetime secondary cancer risk.”
The authors also noted that lung cancers make up most secondary cancers, calculating that the absolute lifetime excess risk of lung cancer is 3.7 percent for patients treated with WBI at the age of 60.
In addition, a high percentage of secondary lung cancers occur 10 years after the patient was treated for breast cancer. This may explain, the authors wrote, why previous studies “did not fully capture the risk of lung cancer mortality.”
Hoekstra and colleagues concluded that, whenever possible, care providers should choose treatment techniques that limit scatter dose as much as possible. When the disease is more aggressive, of course, selecting such techniques may not be feasible.
“The present study finds an excess of lung cancer mortality due to irradiation that appears larger than the excess of cardiac mortality for early stage breast cancer patients having a very long survival,” the authors wrote. “This risk can be greatly reduced using partial breast irradiation techniques minimizing the mean dose to the lung in addition to smoking prevention.”