Assessment of photodynamic therapy as a salvage treatment for local failure after chemoradiotherapy or radiotherapy for esophageal cancer in patients aged 80 years or older oleh Michiko Nishikawa, Yoshinobu Yamamoto, Saeko Kushida, Taku Hirabayashi, Syunta Tanaka, Naoki Takegawa, Takuya Mimura, Hidetaka Tsumura, Ikuya Miki, Masahiro Tsuda