R. Nishikawa

Comparison of dosimetric parameters in the treatment planning of magnetic resonance imaging–based intracavitary image-guided adaptive brachytherapy with and without optimization using the central shielding technique

Abstract This study aimed to compare dosimetric parameters between non-optimized and optimized treatment planning (NOP and OP, respectively) of magnetic resonance imaging (MRI) –based intracavitary (IC) image-guided adaptive brachytherapy (IGABT) using the central shielding (CS) technique for cervical cancer. Fifty-three patients treated with external beam radiotherapy using CS and MRI-based IGABT with the IC approach alone were evaluated. The total high-risk clinical target volume (HR-CTV) D90 was aimed at >70 Gy equivalent dose in 2 Gy fractions (EQD2). In the small HR-CTV group (≤30 cm3), the mean D90s for NOP/OP were 98.6/80.7 Gy. In the large (30.1–40 cm3) and extensive (>40 cm3) HR-CTV groups, the mean D90s were 81.9/77.5 and 71.1/73.6 Gy, respectively. The mean D2cc values for organs at risks (OARs) in OP were acceptable in all groups, despite the high bladder D2cc in the NOP. The correlation between HR-CTV at first brachytherapy (BT) and NOP D90 was stronger than that between HR-CTV at first BT and OP D90. The targeted HR-CTV D90 and dose constraints of D2cc for OARs were both achieved in 16 NOP/47 OP patients for the bladder, 39/50 for the rectum, and 47/50 for the sigmoid colon (P < 0.001, P = 0.007, and P = 0.34, respectively). For small tumors, the role of optimization was to reduce the D2cc for OARs while maintaining the targeted D90. However, optimization was of limited value for extensive tumors. Methods of optimization in IGABT with CS for cervical cancer should be standardized while considering its effectiveness and limitations.

Image‐Guided Adaptive Brachytherapy for Cervical Cancer Using Magnetic Resonance Imaging: Overview and Experience

Image-guided adaptive brachytherapy (IGABT) using magnetic resonance imaging (MRI) has been accepted as a novel treatment technique for cervical cancer. During the development of MRI-based IGABT, a very important concept called “High-risk clinical target volume (HR-CTV)” was introduced. However, computed tomography (CT)-based IGABT is the most common modality in Japan. MRI-based IGABT was initiated in September 2014 at Kobe University Hospital and 50 patients were treated through March 2016. Although a total HR-CTV D90 ranging from 80 to 85 Gy equivalent dose in 2 Gy fractions in combination with 45 Gy of external beam radiotherapy (EBRT) and 7 Gy×4 fractions of IGABT is the most standard treatment aim in European institutions, our aim for a total HR-CTV D90 was a 70–80 Gy because of the use of the central shielding technique for the protection of organs at risk in the late phase of EBRT. The mean total HR-CTV D90 for our 50 patients was 77 Gy. Although our aim was achieved, it was relatively low because Japanese radiotherapy protocols for cervical cancer still differ from those in European institutions. Therefore, a new treatment protocol, which is closer to the global standard, should be established.

Investigation of the efficacy and safety of CyberKnife hypofractionated stereotactic radiotherapy for brainstem metastases using a new evaluation criterion: ‘symptomatic control’

Abstract The treatment of brainstem metastases remains a challenge as the brainstem itself is considered a neurological organ at risk. We aimed to investigate the efficacy and safety of CyberKnife hypofractionated stereotactic radiotherapy (HFSRT) for brainstem metastases, and to examine the balance between efficacy and safety for the management of neurological symptoms. A total of 26 lesions [pons (n = 18), medulla (n = 4) and midbrain (n = 4)] in 20 patients treated with CyberKnife hypofractionated stereotactic radiotherapy were retrospectively analyzed. The total radiation doses (18–30 Gy) were delivered in 3 or 5 equal fractions. The median follow-up was 6.5 (range, 0.5–38.0) months. The 6- and 12-month local control rates were 100% and 90%, respectively. Symptomatic failures, defined as the worsening and appearance of neurological symptoms due to the brainstem lesion after CyberKnife HFSRT, were observed in 6 patients [local failure (n = 1) and adverse events (n = 5). The symptomatic control and overall survival rates were 90% and 72% (after 6 months), respectively, and 76% and 53% (after 12 months), respectively. Longer symptomatic control was associated with site of lesion origin, and longer overall survival was associated with a graded prognostic assessment score of >2. To our knowledge, this is the second study to investigate the efficacy and safety of CyberKnife HFSRT for brainstem metastases. The local control rate was comparable with that of prior stereotactic radiosurgery studies. We propose a new evaluation criterion—‘symptomatic control’—to evaluate the efficacy and safety of brainstem radiotherapy.

Radiotherapy for brainstem gliomas in children and adults: A single‐institution experience and literature review

To evaluate the treatment results of radiotherapy (RT) in children and adults with brainstem gliomas (BSGs) and review the previous literature.