Her E J, Ebert M A, Kennedy A, Reynolds H M, Sun Y, Williams S, Haworth A
School of Physics, Mathematics and Computing, University of Western Australia, Perth, Australia.
Department of Radiation Oncology, Sir Charles Gairdner Hospital, Perth, Australia.
Phys Med Biol. 2021 Feb 5;66(4):045007. doi: 10.1088/1361-6560/ab9354.
Hypofractionation of prostate cancer radiotherapy achieves tumour control at lower total radiation doses, however, increased rectal and bladder toxicities have been observed. To realise the radiobiological advantage of hypofractionation whilst minimising harm, the potential reduction in dose to organs at risk was investigated for biofocused radiotherapy. Patient-specific tumour location and cell density information were derived from multiparametric imaging. Uniform-dose plans and biologically-optimised plans were generated for a standard schedule (78 Gy/39 fractions) and hypofractionated schedules (60 Gy/20 fractions and 36.25 Gy/5 fractions). Results showed that biologically-optimised plans yielded statistically lower doses to the rectum and bladder compared to isoeffective uniform-dose plans for all fractionation schedules. A reduction in the number of fractions increased the target dose modulation required to achieve equal tumour control. On average, biologically-optimised, moderately-hypofractionated plans demonstrated 15.3% (p-value: <0.01) and 23.8% (p-value: 0.02) reduction in rectal and bladder dose compared with standard fractionation. The tissue-sparing effect was more pronounced in extreme hypofractionation with mean reduction in rectal and bladder dose of 43.3% (p-value: < 0.01) and 41.8% (p-value: 0.02), respectively. This study suggests that the ability to utilise patient-specific tumour biology information will provide greater incentive to employ hypofractionation in the treatment of localised prostate cancer with radiotherapy. However, to exploit the radiobiological advantages given by hypofractionation, greater attention to geometric accuracy is required due to increased sensitivity to treatment uncertainties.
前列腺癌放疗的大分割照射可在较低的总辐射剂量下实现肿瘤控制，然而，已观察到直肠和膀胱毒性增加。为了在将危害降至最低的同时实现大分割照射的放射生物学优势，研究了生物聚焦放疗中危及器官剂量的潜在降低。通过多参数成像获取患者特异性肿瘤位置和细胞密度信息。针对标准放疗方案（78 Gy/39次分割）和大分割放疗方案（60 Gy/20次分割和36.25 Gy/5次分割）生成了均匀剂量计划和生物优化计划。结果表明，对于所有分割方案，与等效均匀剂量计划相比，生物优化计划对直肠和膀胱的剂量在统计学上更低。分割次数的减少增加了实现同等肿瘤控制所需的靶区剂量调制。平均而言，与标准分割相比，生物优化的中度大分割计划显示直肠和膀胱剂量分别降低了15.3%（p值：<0.01）和23.8%（p值：0.02）。在极高度大分割照射中，组织保护效应更为明显，直肠和膀胱剂量平均分别降低43.3%（p值：<0.01）和41.8%（p值：0.02）。这项研究表明，利用患者特异性肿瘤生物学信息的能力将为在局部前列腺癌放疗中采用大分割照射提供更大的动力。然而，由于对治疗不确定性的敏感性增加，为了利用大分割照射带来的放射生物学优势，需要更加关注几何精度。
