Impact of four-dimensional cone-beam computed tomography on target localization for gastric mucosa-associated lymphoid tissue lymphoma radiotherapy: reducing planning target volume

Definitive Radiotherapy for Stage I Gastric Mucosa-Associated Lymphoid Tissue Lymphoma: A Retrospective Cohort of Unique-Dose Administration of 30 Gy in 15 Fractions and Analysis of Remission Duration

Background

Gastric mucosa-associated lymphoid tissue (MALT) lymphoma constitutes a significant proportion of primary stomach lymphomas. The optimal dosage for radiotherapy and standardized follow-up protocols are yet to be universally established. This study focuses on stage I gastric MALT lymphoma patients, presenting clinical outcomes of radiotherapy with a unique dose of 30 Gy in 15 fractions and analyzing remission time.

Methods

A retrospective cohort study, approved by the institutional review board, included consecutive stage I gastric MALT lymphoma patients undergoing curative radiotherapy between 2008 and 2022. Staging followed the Lugano Modification of the Ann Arbor Staging System. The prescribed dose was uniform dose of 30 Gy in 15 fractions.

Results

Fifty-three patients were eligible, with a median age of 63 years. All achieved complete remission (CR), with a median CR time of 3.9 months. At a median follow-up of 56.8 months, no deaths occurred, and three recurrences were noted. The 5-year overall survival, local control survival, and disease-free survival rates were 100%, 100%, and 97.7%, respectively. No severe acute adverse events were observed.

Conclusion

The study demonstrates sustained and favorable long-term disease control with a 30 Gy dose in 15 fractions for stage I gastric MALT lymphoma. Comparisons with existing literature highlight the efficacy and safety of radiotherapy in achieving durable remission. Ongoing efforts explore dose reduction and technological advancements to minimize toxicity. This study emphasizes the importance of awaiting clinical response confirmation to validate these outcomes in patients with gastric MALT lymphoma.

A markerless beam's eye view tumor tracking algorithm based on unsupervised deformable registration learning framework of VoxelMorph in medical image with partial data

PURPOSE

To propose an unsupervised deformable registration learning framework-based markerless beam's eye view (BEV) tumor tracking algorithm for the inferior quality megavolt (MV) images with occlusion and deformation.

METHODS

Quality assurance (QA) plans for thorax phantom were delivered to the linear accelerator with artificially treatment offsets. Electronic portal imaging device (EPID) images (682 in total) and corresponding digitally reconstructed radiograph (DRR) were gathered as the moving and fixed image pairs, which were randomly divided into training and testing set in a ratio of 0.7:0.3 to train a non-rigid registration model with Voxelmorph. Simultaneously, 533 pairs of patient images from 21 lung tumor plans were acquired for tumor tracking investigation to offer quantifiable tumor motion data. Tracking error and image similarity measures were employed to evaluate the algorithm's accuracy.

RESULTS

The tracking algorithm can handle image registration with non-rigid deformation and losses ranging from 10 % to 80 %. The tracking errors in the phantom study were below 3 mm in about 86.8 % of cases, and below 2 mm in about 80 % of cases. The normalized mutual information (NMI) changes from 1.182 ± 0.024 to 1.198 ± 0.024 (p < 0.005). The patient target had an average translation of 3.784 mm and a maximum comprehensive displacement value of 7.455 mm. NMI of patient images changes from 1.209 ± 0.027 to 1.217 ± 0.026 (p < 0.005), indicating the presence of non-negligible non-rigid deformation.

CONCLUSIONS

The study provides a robust markerless tumor tracking algorithm for multi-modal, partial data and inferior quality image processing.

The role of motion management and position verification in lymphoma radiotherapy

In the last decades, the substantial technical progress in radiation oncology offered the opportunity for more accurate planning and delivery of treatment. At the same time, the evolution of systemic treatment and the advent of modern diagnostic tools allowed for more accurate staging and consequently a safe reduction of radiotherapy (RT) target volumes and RT doses in the treatment of lymphomas. As a result, incidental irradiation of organs at risk was reduced, with a consequent reduction of severe late toxicity in long-term lymphoma survivors. Nevertheless, these innovations warrant that professionals pay attention to concurrently ensure precise planning and dose delivery to the target volume and safe sparing of the organs at risk. In particular, target and organ motion should be carefully managed in order to prevent any compromise of treatment efficacy. Several aspects should be taken into account during the treatment pathway to minimise uncertainties and to apply a valuable motion management strategy, when needed. These include: reliable image registration between diagnostic and planning radiologic exams to facilitate the contouring process, image guidance to limit positioning uncertainties and to ensure the accuracy of dose delivery and management of lung motion through procedures of respiratory gating and breath control. In this review, we will cover the current clinical approaches to minimise these uncertainties in patients treated with modern RT techniques, with a particular focus on mediastinal lymphoma. In addition, since uncertainties have a different impact on the dose deposition of protons compared to conventional x-rays, the role of motion management and position verification in proton beam therapy (PBT) will be discussed in a separate section.

Radiotherapy for gastric mucosa-associated lymphoid tissue lymphoma

Gastric mucosa-associated lymphoid tissue (MALT) lymphoma is a rare disease which is often associated with Helicobacter pylori (H. pylori) infection. First-line treatment of stage IE and IIE localized gastric MALT lymphoma is based on the eradication of H. pylori. The presence of H. pylori resistance factors such as translocation t (11;18), peri-gastric lymph node involvement and the degree of tumor infiltration of the gastric wall; or lack of response to antibiotic therapy are two main indications to treat with definitive radiotherapy (RT). RT is an effective treatment in localized gastric MALT lymphoma. A moderate dose of 30 Gy allows a high cure rate while being well tolerated. After treatment, regular gastric endoscopic follow-up is necessary to detect a potential occurrence of gastric adenocarcinoma.