Breast cancer screening for childhood cancer survivors after craniospinal irradiation with protons versus x-rays: a dosimetric analysis and review of the literature.

INTRODUCTION: Screening for secondary malignancies is paramount in the pediatric cancer survivorship population, but the risk of secondary breast cancer after craniospinal radiation has not been well characterized previously. The aim of this study was to examine the dose to the breast from craniospinal irradiation (CSI) delivered with x-ray therapy versus proton beam therapy to contribute to understanding the specific screening needs of this population.
METHODS: Six female patients who received CSI with double-scattered proton therapy at the Children's Hospital of Philadelphia were identified. For each patient, photon and proton beam plans were designed in order to compare the radiation dose to the breast. A comprehensive literature review was also performed.
RESULTS: The dose to the breast tissues was near zero after proton therapy to the spine [average maximum and mean proton doses were 0.22 and 0.05 Gy(RBE), respectively]. In contrast, after photon treatment to the spine, average maximum and mean photon doses were 23 and 4 Gy, respectively (P<0.0001).
CONCLUSIONS: These data suggest that early screening for breast cancer may be unnecessary after CSI with proton beam therapy; however, after x-ray therapy, early breast cancer screening should be considered given doses to the breast that approach the Children's Oncology Group-recommended threshold.