Weessies Menke, Bellezzo Murillo, Hupkens Britt J P, Verhaegen Frank, Vilches-Freixas Gloria
Department of Radiation Oncology (Maastro) GROW School for Oncology and Reproduction Maastricht University Medical Centre Maastricht The Netherlands.
Phys Imaging Radiat Oncol. 2025 Feb 4;33:100721. doi: 10.1016/j.phro.2025.100721. eCollection 2025 Jan.
Cancer affects 1 in 1000-2000 pregnancies annually worldwide, creating challenges in balancing cancer treatment and fetal safety. This study compares out-of-field radiation doses between two treatment modalities: 6MV external photon radiotherapy (XRT) and pencil beam scanning proton-therapy (PBS-PRT) for breast cancer, including imaging, to evaluate PBS-PRT as a potential new treatment option.
For breast cancer involving lymph node levels 1-4 and the intramammary lymph nodes, treatment plans were created for XRT (with Flattening Filter (FF) and FF-Free (FFF)) and PBS-PRT, prescribing 15 × 2.67 Gy(RBE). Measurements were conducted using an adapted anthropomorphic phantom representing 20- and 30-week pregnancy. Bubble detectors placed in the phantom's abdomen assessed neutron dose from PBS-PRT, while a Farmer ion chamber was used for imaging and XRT dose.
At 20 weeks, PBS-PRT including imaging delivered 22.4 mSv, reducing dose 3.4-fold versus 6FF XRT and 2.5-fold versus 6FFF XRT. At 30 weeks, the PBS-PRT dose was 25.4 mSv, resulting in 7.6-fold and 6.3-fold reductions compared to 6FF and 6FFF XRT, respectively.
This study presents the first one-by-one comparison between PBS-PRT and different XRT modalities for pregnant breast cancer patients with an adapted anthropomorphic phantom. PBS-PRT measurements showed that the total equivalent dose was below the 100 mSv threshold outlined in AAPM Task Group Report No. 36 for a 30-week pregnancy, even under a worst-case scenario, maintaining treatment goals. These findings support the adoption of PBS-PRT as the preferred approach for treating pregnant breast cancer patients, should radiotherapy be required.
全球每年每1000 - 2000例妊娠中就有1例受癌症影响，这给平衡癌症治疗与胎儿安全带来了挑战。本研究比较了两种治疗方式（6兆伏外照射光子放疗（XRT）和笔形束扫描质子治疗（PBS - PRT））用于乳腺癌（包括成像）时的体外辐射剂量，以评估PBS - PRT作为一种潜在的新治疗选择。
对于累及1 - 4级淋巴结及乳腺内淋巴结的乳腺癌，制定了XRT（有均整器（FF）和无均整器（FFF））和PBS - PRT的治疗计划，处方剂量为15×2.67 Gy（相对生物效应）。使用一个模拟20周和30周妊娠的改良人体模型进行测量。置于模型腹部的气泡探测器评估PBS - PRT产生的中子剂量，而一个 Farmer电离室用于成像和XRT剂量测量。
在20周时，包括成像在内的PBS - PRT剂量为22.4毫希沃特，与6FF XRT相比剂量降低了3.4倍，与6FFF XRT相比降低了2.5倍。在30周时，PBS - PRT剂量为25.4毫希沃特，与6FF和6FFF XRT相比分别降低了7.6倍和6.3倍。
本研究首次使用改良人体模型对妊娠乳腺癌患者的PBS - PRT和不同XRT方式进行了逐一比较。PBS - PRT测量结果表明，即使在最坏情况下，总等效剂量仍低于美国医学物理师协会任务组报告第36号中规定的30周妊娠100毫希沃特的阈值，维持了治疗目标。这些发现支持在需要放疗时采用PBS - PRT作为治疗妊娠乳腺癌患者的首选方法。
