Toxicity Reduction after Craniospinal Irradiation via Helical Tomotherapy in Patients with Medulloblastoma: A Unicentric Retrospective Analysis

Inter-Fraction Motion and Dosimetric Analysis of Volumetric Modulated Arc Therapy for Craniospinal Irradiation in Adult Medulloblastoma Patients

Background/Objectives. Adult medulloblastoma (AMB) patients should receive postoperative craniospinal irradiation (CSI) as a standard treatment. Volumetric intensity-modulated arc therapy (VMAT) is a promising method for CSI. This report summarizes the repositioning and dosimetric data outcomes for six AMB patients. Methods. Complete CSI and posterior cranial fossa irradiation, or tumor bed boost irradiation with Linac-based VMAT, was performed and evaluated. Patients were immobilized in the supine position with two thermoplastic masks (head-neck and abdomen). To ensure inter-fraction reproducibility during radiotherapy (RT), a single cone-beam CT (CBCT) scan for each isocenter and real-time surface-guided RT using AlignRT® were performed daily before and during the RT session. Match values of all three translational axes (x = lateral, y = longitudinal, z = vertical) were recorded. Results. From August 2022 to September 2023, six AMB patients were treated with CSI: three women and three men with a median age of 32 (22-42). All cases were classical MB, four were low risk, and two were defined as high risk due to the metastatic disease. All patients underwent surgery; two received a gross total resection. Low-risk patients received 36 Gy for CSI and a 54 Gy boost, while high-risk patients received 39 Gy for CSI. No significant toxicities greater than G2 were observed during RT, and only two cases reported decreased platelet counts. The dose to the organs at risk was low and acceptable. The mean dose to the heart, lungs, eyes, stomach, and thyroid were 4.4 Gy, 8.5 Gy, 12 Gy, 8.7 Gy, and 11 Gy, respectively. In terms of repositioning data, 124 CBCT scans were analyzed. Inter-fraction CBCT mean values for the study population in all translational directions were inferior to 2 mm in more than 90% of cases. Conclusions. VMAT is a convenient and effective treatment for AMB. Positioning and immobilization with masks (head and neck plus abdomen) reduce inter-fraction motion.

The top 100 most cited articles in helical tomotherapy: a scoping review

Objective

The purpose of this scoping review was to explore the top 100 most cited articles in helical tomotherapy (HT) through bibliometric analysis and visualization tools, help researchers comprehensively understand the research hotspots of HT, and provide clear and intuitive network visualization.

Methods

The Web of Science Core Collection and the search strategy of "Title (TI)=(tomotherapy)" were used to search for articles related to HT as of 27 May 2023. The top 100 most cited articles were obtained by sorting "citations: highest first". From these top 100 most cited articles, the following information was extracted: journals, years and months, countries, authors, types of tumor treated, and topics. The VOSviewer software was introduced for visualizing all the articles related to HT.

Results

The top 100 most cited articles in HT were published between 1999 and 2019. The citation counts of these articles ranges from 326 to 45, with a total of 8,422 citations at the time of searching. The index of citations per year (CPY) ranges from 22.32 to 2.45. These articles originated from 17 countries, with most publications from the United States (n=50), followed by Canada (n=12), Italy (n=10), Germany (n=7) and Belgium (n=5). The International Journal of Radiation Oncology, Biology, Physics published the highest number of articles (n=31), followed by Radiotherapy and Oncology (n=20), Medical Physics (n=13) and Strahlentherapie und Onkologie (n=12). In terms of specific tumor types, head and neck cancer (n=15) is the most common disease, followed by cancers with complex target structures (n=14), breast cancer (n=12), prostate cancer (n=10) and lung cancer (n=8). The most common research topics also include dosimetric comparison (n = 44), quality assurance (n = 12) and Megavoltage CT (n = 8).

Conclusion

This scoping review provides a comprehensive list of the 100 most cited articles in HT. This analysis offers valuable insights into the current research directions of HT that can be utilized by researchers, clinicians, and policy-makers.

Tomotherapy for Cranio-Spinal Irradiation

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Tomotherapy is safe and effective for cranio-spinal irradiation, both in paediatric patients and in adults, with similar disease-specific outcomes and toxicities as other techniques such as 3DCRT or IMRT/VMAT.

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Tomotherapy offers several technical advantages when compared to other radiotherapy techniques such as higher target conformity and better dose homogeneity.

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Helical Tomotherapy provides good organ-at-risk sparing for several structures, especially the vertebrae, parotids, and optic system.

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Reported treatment time/ beam-on-time is longer with helical Tomotherapy compared to other techniques.

Tomotherapy is a method of delivering rotational IMRT offering various advantages, notably for complex and large targets such as the cranio-spinal axis. This systematic literature review reports on main clinical outcomes and toxicities in patients with various cancer types that received whole craniospinal axis irradiation (CSI) using Tomotherapy and offers a comprehensive comparison between Tomotherapy and other radiotherapy delivery techniques. Databases including PubMed, PubMed Central, Embase, and Cochrane were searched using the keywords “tomotherapy” AND “craniospinal”. Fifty-six papers were included in the review. Patient population was adult in 9 papers, paediatric in 26 papers and mixed in 14 papers. Patients treated with helical Tomotherapy had similar disease-specific clinical outcomes and toxicities as patients treated using other techniques. Compared to any other technique, Tomotherapy provides better target coverage, homogeneity, and conformity in 23, 34 and 22 reports. Tomotherapy showed better organ-at-risk sparing for the thyroid, parotids, cochlea, eyes, heart and esophagus. Beam-On-Time (BOT) was reported to be longer for Tomotherapy in most studies (Median BOT: HT = 11 min, VMAT = 5.49 min, 3DCRT = 1.46 min). In conclusion, Tomotherapy offers good cranio-spinal axis coverage with improved homogeneity and conformity compared to other techniques, but with a considerably longer treatment time. Clinical outcome and toxicities suggest using Tomotherapy for CSI is efficient and safe.

Pulmonary toxicity of craniospinal irradiation using helical tomotherapy

Craniospinal irradiation using helical tomotherapy (HT-CSI) has advantages in aspects of homogeneous dose distribution. Physicians, however, still have concerns of pulmonary toxicity due to HT-CSI’s relatively large, low-dose irradiated volume from continuous and 360° rotation delivery. In this study, we investigated the pulmonary toxicity of HT-CSI. We retrospectively reviewed 105 patients who received HT-CSI between January 2014 and December 2019. Grade 2 + pulmonary toxicities were evaluated. Intensive systemic treatment was defined as systemic treatment administration before, during, and after HT-CSI. V_{X Gy} was defined as % volume receiving ≥ X Gy. Thirteen patients (12.4%) presented with grade 2 + pulmonary toxicities after HT-CSI. Of these patients, only one experienced grade 2 radiation pneumonitis combined with pembrolizumab-induced pneumonitis. Conversely, pneumonia was observed in 12 patients. Intensive systemic treatment (p = 0.004), immunosuppressive drugs (p = 0.031), and bilateral lung V_{5 Gy} ≥ 65% (p = 0.031) were identified as independent risk factors for pneumonia. The risk factor for pneumonia in pediatric patients were immunosuppressive drugs (p = 0.035) and bilateral lung V_{5 Gy} ≥ 65% (p = 0.047). HT-CSI can be a safe treatment modality with tolerable pulmonary toxicities. Intensive systemic treatment, immunosuppressive drugs, and bilateral lung V_{5 Gy} ≥ 65% were significantly associated with pneumonia. In these patients, close follow-up should be considered for proper management of pneumonia.