Adaptive replanning intensity-modulated radiotherapy for choroidal metastasis of breast cancer using optical coherence tomography

Swept source optical coherence tomography (SS-OCT) is a convenient method for precise, early-stage detection of choroidal metastatic lesions, involving assessment of tumor response, and for regular follow-up studies. Using information obtained with SS-OCT, we performed intensity-modulated radiotherapy (IMRT) for a patient with choroidal metastasis from breast cancer with more accuracy than had been previously possible. We made replanning adaptive radiotherapy (ART) three times based on the rapid tumor shrinkage detected by weekly assessments with SS-OCT. Accordingly, the planning target volume (PTV) decreased from 1.6 cm3 to 0.61 cm3 (38%), with 0.95 cm3 (59%) and 0.75 cm3 (46%) as intermediate values during the treatment course. The D0.1cm3 of the right optic nerve was also reduced from 1.70 Gy/fraction to 0.69 Gy/faction, with 1.41 Gy/fraction and 1.29 Gy/fraction as intermediate values. Adaptive replanning IMRT made it possible to perform locally curative treatment of the metastatic choroidal lesion with a higher dose for the PTV, and a lower dose for organs at risk (OARs). (author)