Systematic review for deep inspiration breath hold in proton therapy for mediastinal lymphoma: A PTCOG Lymphoma Subcommittee report and recommendations

Proton Pencil Beam Scanning Facilitates the Safe Treatment of Extended Radiation Targets for Hodgkin Lymphoma: A Report from the Proton Collaborative Group Registry

Because proton beam therapy (PBT) can lower the dose of radiation to the heart, lungs, and breast, it is an established radiation modality for patients with Hodgkin lymphoma (HL). Pencil beam scanning (PBS) PBT facilitates the treatment of more extensive targets. This may be especially of value for lymphoma patients who require RT to both mediastinal and axillary targets, defined here as extended target RT (ETRT), given the target distribution and need to minimize the lung, heart, and breast dose. Using the Proton Collaborative Group registry, we identified patients with HL treated with PBT to both their mediastinum and axilla, for which DICOM-RT was available. All patients were treated with PBS. To evaluate the dosimetric impact of PBS, we compared delivered PBS plans with VMAT butterfly photon plans optimized to have the same target volume coverage, when feasible. Between 2016 and 2021, twelve patients (median 26 years) received PBS ETRT (median 30.6 Gy (RBE)). Despite the large superior/inferior (SI, median 22.2 cm) and left/right (LR, median 22.8 cm) extent of the ETRT targets, all patients were treated with one isocenter except for two patients (both with SI and LR > 30 cm). Most commonly, anterior beams, with or without posterior beams, were used. Compared to photons, PBS had greater target coverage, better conformity, and lower dose heterogeneity while achieving lower doses to the lungs and heart, but not to the breast. No acute grade 3+ toxicities were reported, including pneumonitis. Proton ETRT in this small cohort was safely delivered with PBS and was associated with an improved sparing of the heart and lungs compared to VMAT.

Contemporary radiation therapy use in Hodgkin lymphoma

Radiation therapy assumes a pivotal role in Hodgkin lymphoma management, especially within combined modality therapy. It serves as a cornerstone in early-stage disease and in mitigating high-risk instances of local relapse in advanced stages. Over recent decades, radiation therapy has undergone significant advancements, notably alongside diagnostic imaging improvements, facilitating the reduction of radiation field size and dosage. This progress has notably led to minimized toxicity while upholding treatment efficacy. This comprehensive review extensively evaluates the indications and advancements in radiation therapy for Hodgkin lymphoma, with a primary focus on enhancing treatment efficacy while minimizing radiation-related toxicities. The exploration encompasses a detailed examination of various radiation fields, techniques and delivery modalities employed in Hodgkin lymphoma treatment, including intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), and proton therapy. It delves into the intricacies of optimal dose selection and treatment planning strategies aimed at achieving maximal disease control while concurrently minimizing the risk of long-term side effects.

Ischaemic heart disease in patients with cancer

Cardiologists are encountering a growing number of cancer patients with ischaemic heart disease (IHD). Several factors account for the interrelationship between these two conditions, in addition to improving survival rates in the cancer population. Established cardiovascular (CV) risk factors, such as hypercholesterolaemia and obesity, predispose to both IHD and cancer, through specific mechanisms and via low-grade, systemic inflammation. This latter is also fuelled by clonal haematopoiesis of indeterminate potential. Furthermore, experimental work indicates that IHD and cancer can promote one another, and the CV or metabolic toxicity of anticancer therapies can lead to IHD. The connections between IHD and cancer are reinforced by social determinants of health, non-medical factors that modify health outcomes and comprise individual and societal domains, including economic stability, educational and healthcare access and quality, neighbourhood and built environment, and social and community context. Management of IHD in cancer patients is often challenging, due to atypical presentation, increased bleeding and ischaemic risk, and worse outcomes as compared to patients without cancer. The decision to proceed with coronary revascularization and the choice of antithrombotic therapy can be difficult, particularly in patients with chronic coronary syndromes, necessitating multidisciplinary discussion that considers both general guidelines and specific features on a case by case basis. Randomized controlled trial evidence in cancer patients is very limited and there is urgent need for more data to inform clinical practice. Therefore, coexistence of IHD and cancer raises important scientific and practical questions that call for collaborative efforts from the cardio-oncology, cardiology, and oncology communities.

Pencil beam scanning proton therapy for mediastinal lymphomas in deep inspiration breath-hold: a retrospective assessment of plan robustness

PURPOSE/BACKGROUND

The aim of this study was to evaluate pencil beam scanning (PBS) proton therapy (PT) in deep inspiration breath-hold (DIBH) for mediastinal lymphoma patients, by retrospectively evaluating plan robustness to the clinical target volume (CTV) and organs at risk (OARs) on repeated CT images acquired throughout treatment.  Methods: Sixteen mediastinal lymphoma patients treated with PBS-PT in DIBH were included. Treatment plans (TPs) were robustly optimized on the CTV (7 mm/4.5%). Repeated verification CTs (vCT) were acquired during the treatment course, resulting in 52 images for the entire patient cohort. The CTV and OARs were transferred from the planning CT to the vCTs with deformable image registration and the TPs were recalculated on the vCTs. Target coverage and OAR doses at the vCTs were compared to the nominal plan. Deviation in lung volume was also calculated.

RESULTS

The TPs demonstrated high robust target coverage throughout treatment with D98%,CTV deviations within 2% for 14 patients and above the desired requirement of 95% for 49/52 vCTs. However, two patients did not achieve a robust dose to CTV due to poor DIBH reproducibility, with D98%,CTV at 78 and 93% respectively, and replanning was performed for one patient. Adequate OAR sparing was achieved for all patients. Total lung volume variation was below 10% for 39/52 vCTs.

CONCLUSION

PBS PT in DIBH is generally a robust technique for treatment of mediastinal lymphomas. However, closely monitoring the DIBH-reproducibility during treatment is important to avoid underdosing CTV and achieve sufficient dose-sparing of the OARs.

Interplay Effect of Splenic Motion for Total Lymphoid Irradiation in Pediatric Proton Therapy

(1) Background: The most significant cause of an unacceptable deviation from the planned dose during respiratory motion is the interplay effect. We examined the correlation between the magnitude of splenic motion and its impact on plan quality for total lymphoid irradiation (TLI); (2) Methods: Static and 4D CT images from ten patients were used for interplay effect simulations. Patients' original plans were optimized based on the average CT extracted from the 4D CT and planned with two posterior beams using scenario-based optimization (±3 mm of setup and ±3% of range uncertainty) and gradient matching at the level of mid-spleen. Dynamically accumulated 4D doses (interplay effect dose) were calculated based on the time-dependent delivery sequence of radiation fluence across all phases of the 4D CT. Dose volume parameters for each simulated treatment delivery were evaluated for plan quality; (3) Results: Peak-to-peak splenic motion (≤12 mm) was measured from the 4D CT of ten patients. Interplay effect simulations revealed that the ITV coverage of the spleen remained within the protocol tolerance for splenic motion, ≤8 mm. The D100% coverage for ITV spleen decreased from 95.0% (nominal plan) to 89.3% with 10 mm and 87.2% with 12 mm of splenic motion; (4) Conclusions: 4D plan evaluation and robust optimization may overcome problems associated with respiratory motion in proton TLI treatments. Patient-specific respiratory motion evaluations are essential to confirming adequate dosimetric coverage when proton therapy is utilized.