Irradiating Residual Disease to 30 Gy with Proton Therapy in Pediatric Mediastinal Hodgkin Lymphoma

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.

Targeted radiotherapy for early-stage, low-risk pediatric Hodgkin lymphoma slow early responders: a COG AHOD0431 analysis

Children's Oncology Group (COG) trial AHOD0431 reduced systemic therapy and used response-adapted involved-field radiotherapy (IFRT) in early-stage pediatric classic Hodgkin lymphoma. We investigated the impact of positron emission tomographic response after 1 cycle (PET1) and on IFRT outcomes and pattern of relapse. Patients in AHOD0431 underwent PET1 response assessment after AVPC (doxorubicin, vincristine, prednisone, and cyclophosphamide). "Rapid early responders" (RERs) had a negative PET1 (PET1-); "slow early responders" (SERs) had a positive PET1 (PET1+). Patients with a partial response by computed tomographic and functional imaging after 3 chemotherapy cycles received 21-Gy IFRT, whereas complete responders had no IFRT. Progression-free survival (PFS) was evaluated for RERs and SERs treated with or without IFRT. Recurrence sites were initial, new, or both. Relapses involving initial sites were characterized as "within the PET1+ site" or "initially involved but outside the PET1+ site." Median follow-up was 118 months. The 10-year PFS rate among RERs was 96.6% with IFRT and 84.1% without IFRT (P = .10), whereas SERs were 80.9% with IFRT and 64.0% without IFRT (P = .03). Among 90 RERs who did not receive IFRT, all 14 relapses included an initial site. Among 45 SERs receiving no IFRT, 14 of 16 relapses were in the initial site (9 PET1+ site only). Among 58 patients receiving IFRT, 5 of 10 relapses were in the PET1+ site. After 3 cycles of AVPC alone, RERs showed favorable results. Conversely, SERs had unfavorable outcomes with AVPC alone, although they improved with 21-Gy IFRT. RT remains an important component of treatment for SERs. This trial was registered at www.clinicaltrials.gov as #NCT00302003.

Radiation therapy related cardiac disease risk in childhood cancer survivors: Updated dosimetry analysis from the Childhood Cancer Survivor Study

BACKGROUND AND PURPOSE

We previously evaluated late cardiac disease in long-term survivors in the Childhood Cancer Survivor Study (CCSS) based on heart radiation therapy (RT) doses estimated from an age-scaled phantom with a simple atlas-based heart model (H_Atlas). We enhanced our phantom with a high-resolution CT-based anatomically realistic and validated age-scalable cardiac model (H_Hybrid). We aimed to evaluate how this update would impact our prior estimates of RT-related late cardiac disease risk in the CCSS cohort.

METHODS

We evaluated 24,214 survivors from the CCSS diagnosed from 1970 to 1999. RT fields were reconstructed on an age-scaled phantom with H_Hybrid and mean heart dose (D_m), percent volume receiving ≥ 20 Gy (V₂₀) and ≥ 5 Gy with V₂₀ = 0 ( [Formula: see text] ) were calculated. We reevaluated cumulative incidences and adjusted relative rates of grade 3-5 Common Terminology Criteria for Adverse Events outcomes for any cardiac disease, coronary artery disease (CAD), and heart failure (HF) in association with D_m, V₂₀, and [Formula: see text] (as categorical variables). Dose-response relationships were evaluated using piecewise-exponential models, adjusting for attained age, sex, cancer diagnosis age, race/ethnicity, time-dependent smoking history, diagnosis year, and chemotherapy exposure and doses. For relative rates, D_m was also considered as a continuous variable.

RESULTS

Consistent with previous findings with H_Atlas, reevaluation using H_Hybrid dosimetry found that, D_m ≥ 10 Gy, V₂₀ ≥ 0.1%, and [Formula: see text]  ≥ 50% were all associated with increased cumulative incidences and relative rates for any cardiac disease, CAD, and HF. While updated risk estimates were consistent with previous estimates overall without statistically significant changes, there were some important and significant (P < 0.05) increases in risk with updated dosimetry for D_m in the category of 20 to 29.9 Gy and V₂₀ in the category of 30% to 79.9%. When changes in the linear dose-response relationship for D_m were assessed, the slopes of the dose response were steeper (P < 0.001) with updated dosimetry. Changes were primarily observed among individuals with chest-directed RT with prescribed doses ≥ 20 Gy.

CONCLUSION

These findings present a methodological advancement in heart RT dosimetry with improved estimates of RT-related late cardiac disease risk. While results are broadly consistent with our prior study, we report that, with updated cardiac dosimetry, risks of cardiac disease are significantly higher in two dose and volume categories and slopes of the Dm-specific RT-response relationships are steeper. These data support the use of contemporary RT to achieve lower heart doses for pediatric patients, particularly those requiring chest-directed RT.