Journal Article Sequential histological findings and clinical response after carbon ion radiotherapy for unresectable sarcoma

Hayashi, Katsuhiro  ,  Yamamoto, Norio  ,  Shirai , Toshiharu  ,  Akihiko Takeuchi  ,  Kimura , Hiroaki  ,  Miwa , Shinji  ,  Higuchi , Takashi  ,  Abe , Kensaku  ,  Yuta Taniguchi  ,  Aiba , Hisaki  ,  Kiyohara , Hiroki  ,  Imai , Reiko  ,  Ikeda , Hiroko  ,  Hiroyuki Tsuchiya

Background and purpose: The efficacy of carbon ion radiotherapy (CIRT) for bone and soft tissue sarcomahas been reported recently. Although histological assessment after CIRT requires skilled interpretation,little information is presently available. In this study, we report sequential histological findings aftertreatment with CIRT, and evaluate the association between these findings and clinical response.Material and methods: Seven patients with unresectable sarcoma underwent needle biopsy 12 times at anaverage of 14.3 months after CIRT and were included in this study.Results: One patient underwent two biopsies after CIRT for chordoma. Although a few suspected residualchordoma cells were observed at 19 and 30 months after CIRT, the tumor continued to shrink at 75 months.Immunohistochemical analysis of post-CIRT specimens revealed CK AE1/3, EMA, and S100 expression, as inthe pre-CIRT specimen. In total, viable tumor cells were found in 9 of 12 specimens; however, only 2patients showed recurrent masses on radiological examination. The other 5 patients had stable disease.Conclusions: Viable tumor cells after CIRT did not always cause recurrence. This may be due to observationof dying cells or radiation-induced deformed cells. Histological evaluation after CIRT should be donecarefully.

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