Department of Radiation Oncology and Radiotherapy, University Hospital Heidelberg, Germany; Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany.
Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany.
Radiother Oncol. 2019 Apr;133:120-124. doi: 10.1016/j.radonc.2018.12.017. Epub 2019 Jan 24.
To quantify the impact of tumor-associated resistance factors on local tumor control after split doses of carbon (C-) ions or photons in an experimental prostate tumor model.
Three sublines (AT1, H, HI) of syngeneic rat prostate tumors (R3327) differing in growth rate, differentiation and hypoxic status were irradiated with split doses of either C-ions or 6MV photons. Dose-response curves were determined for the endpoint local tumor control within 300 days. The relative biological effectiveness (RBE) of C-ions was calculated from the TCD-values (dose at 50% control probability) of photons and C-ions.
Experimental findings demonstrated: (i) The RBE was highest for the least differentiated AT1-tumor (2.39 ± 0.16 (AT1) vs 2.06 ± 0.11 (H) and 2.03 ± 0.17 (HI)). (ii) TCD-values between the three tumor sublines differed much less for C-ions (26.0-37.9 Gy) than for photons (53.7-90.6 Gy). (iii) While the slope of the dose-response curves for photons and C-ions were very similar for the AT1- and H-tumors, the histologically heterogeneous HI-tumor showed a shallow dose-response curve for photons, which is transformed into a steep dose-response curve after C-ion irradiation.
The response to carbon ion irradiations is much less dependent on biological differences between and within the tumor-sublines. Tumors showing a high resistance against photon treatments, also exhibit the largest RBE for carbon ions. Carbon ions could therefore be of clinical advantage for the treatment of tumors with known resistance factors against photons.
在实验性前列腺肿瘤模型中，量化肿瘤相关耐药因素对碳（C-）离子或光子分割剂量后局部肿瘤控制的影响。
三种亚系（AT1、H、HI）的同源大鼠前列腺肿瘤（R3327）在生长速度、分化和缺氧状态方面存在差异，分别用 C-离子或 6MV 光子进行分割剂量照射。确定了终点局部肿瘤控制在 300 天内的剂量反应曲线。C-离子的相对生物学效应（RBE）是从光子和 C-离子的 TCD 值（控制概率为 50%的剂量）计算得出的。
实验结果表明：（i）最分化的 AT1 肿瘤的 RBE 最高（2.39±0.16（AT1）比 2.06±0.11（H）和 2.03±0.17（HI））。（ii）三种肿瘤亚系之间的 C-离子 TCD 值差异远小于光子（26.0-37.9Gy）。（iii）虽然光子和 C-离子的剂量反应曲线斜率对于 AT1-和 H-肿瘤非常相似，但组织学上异质的 HI-肿瘤的光子剂量反应曲线较浅，经 C-离子照射后转化为陡峭的剂量反应曲线。
对碳离子照射的反应受肿瘤亚系之间和内部生物学差异的影响较小。对光子治疗有高抵抗力的肿瘤，对碳离子的 RBE 也最大。因此，碳离子在治疗已知对光子有抵抗力的肿瘤方面可能具有临床优势。
