Involved node radiation therapy in the combined modality treatment for early-stage Hodgkin lymphoma: Analysis of relapse location and long-term outcome

Limited, But Not Eliminated, Excess Long-Term Morbidity in Stage I-IIA Hodgkin Lymphoma Treated With Doxorubicin, Bleomycin, Vinblastine, and Dacarbazine and Limited-Field Radiotherapy

PURPOSE

Balancing disease control and toxicity from chemotherapy and radiotherapy (RT) when treating early-stage classical Hodgkin lymphoma (cHL) is important. Available data on long-term toxicity after RT for cHL mostly refer to RT techniques no longer in use. We aimed to describe long-term toxicity from modern limited-field (LF)-RT after two or four cycles of doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD).

PATIENTS AND METHODS

This study included all patients with cHL treated with two or four cycles of ABVD and 30 Gy LF-RT during 1999-2005 in Sweden. Patients (n = 215) and comparators (n = 860), matched for age, gender, and region of residence, were cross-checked against national health registries for malignancies, diseases of the circulatory system (DCS), and diseases of the respiratory system (DRS) from the day of diagnosis of cHL.

RESULTS

The risk of a malignancy was higher for patients than comparators, hazard ratio (HR) 1.5 (95% CI, 1.0 to 2.4), as was the risk for DCS 1.5 (95% CI, 1.1 to 2.0) and for DRS 2.6 (95% CI, 1.6 to 4.3). The median follow-up was 16 years (range, 12-19 years). Of individual diagnoses in DCS, only venous thromboembolism was statistically significantly elevated. If the first 6 months (ie, time of active treatment for cHL) were excluded and censoring at relapse of cHL or diagnosis of any malignancy, the increased HR for venous thromboembolism diminished. Most of the excess risk for DRS consisted of asthma, HR 3.5 (95% CI, 1.8 to 6.8). Patients diagnosed with DRS were significantly younger than comparators.

CONCLUSION

Compared with toxicity from earlier RT techniques, excess morbidity was not eliminated, but lower than previously reported. The elevated risk of DRS was driven by diagnosis of asthma, which could in part be explained by misdiagnosis of persisting pulmonary toxicity.

Less morbidity in Hodgkin lymphoma treated with chemotherapy and radiotherapy fields smaller than involved field

Radiotherapy of lymphomas

Radiotherapy for Hodgkin lymphomas has evolved a lot over time, but still plays an important role, almost always in addition to chemotherapy, for the management of the early stages. The major objective is to preserve the quality of life of patients who will be cured from this disease in the vast majority of cases. Also, the personalization of the indications for the purpose of de-escalating toxicity is very refined and is essentially based on the pre- and pertherapeutic assessment by FDG-PET. The indications for radiotherapy are more limited for non-Hodgkin lymphomas, but the same principles are found, regardless of the histological type. We present the update of the recommendations of the French society of oncological radiotherapy for radiotherapy of lymphomas, which remains a very evolving field in terms of therapeutic strategy and evaluation.

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.

Total tumor burden in lymphoma - an evolving strong prognostic parameter

Total metabolic tumor volume (TMTV), a new parameter extracted from baseline FDG-PET/CT, has been recently proposed by several groups as a prognosticator in lymphomas before first-line treatment. TMTV, the sum of the metabolic volume of each lesion, is an index of the metabolically most active part of the tumor and highly correlates with the total tumor burden. TMTV measurement is obtained from PET images processed with different software and techniques, many being now freely available. In the various lymphoma subtypes where it has been measured, such as diffuse large B-cell lymphoma, Hodgkin lymphoma, Follicular Lymphoma, and Peripheral T-cell lymphoma, TMTV has been reported as a strong predictor of outcome (progression-free survival and overall survival) often outperforming the clinical scores, molecular predictors, and results of interim PET. Combined with these scores, TMTV improves the stratification of the populations into risk groups with different outcomes. TMTV cut-off separating the high-risk from the low-risk population impacts the outcome whatever the technique used for its measurement and an international harmonization is ongoing. TMTV is a unique and easy tool that could replace the surrogate of tumor burden included in the prognostic indexes used in lymphoma and help tailor therapy. Other parameters extracted from the baseline PET may give an information on the dissemination of this total tumor volume such as the maximum distance between the lesions. Trials based on TMTV would probably demonstrate its predictive value.

Relapse localization in Danish pediatric patients with Hodgkin lymphoma

BACKGROUND

Pediatric Hodgkin lymphoma (pHL) is highly curable. However, a minority experience relapse and are subjected to toxic salvage regimens. Investigating the patterns of relapse could help to select the patients and/or the involved sites that would benefit from consolidating radiotherapy.

MATERIAL AND METHODS

The Danish Childhood Cancer Registry was used to identify children <18 years with relapsed pHL from 1990-2018. The lymphoma volumes involved at diagnosis and at relapse were contoured on the patients' original scans. Rigid image co-registration was used to merge the scans enabling a visual assessment of the anatomical relapse localization relative to the initially involved lymph nodes, and if irradiated, to the radiotherapy field.

RESULTS

From 185 patients with pHL, 24 patients with relapse were available for analysis. All patients received combination chemotherapy and seven had consolidating radiotherapy. Relapses exclusively in initially involved sites occurred in 14 patients. Relapses exclusively in new sites were rare and only observed in three irradiated patients. Seven patients relapsed in both initially involved and new sites. The median time to relapse was 6 months (range 2-59 months), however, in-field relapses in irradiated patients occurred later (54 months, range 10-59 months). Neither risk group, initial bulky disease, early response, or metabolic activity seemed to be associated with the site of a later relapse.

CONCLUSION

The number of relapses were small, and conclusions regarding the selection of patients for radiotherapy could not be drawn. Relapse exclusively in initially involved sites were the most common, most often in the exact same initially involved lymph nodes. Hence, modern involved site radiotherapy, focusing on the initially involved lymphoma volume and minimizing the radiation doses to normal tissues, should be applied when consolidating radiotherapy is used in patients with pHL.