Abstract
BackgroundHodgkin's lymphoma (HL) survivors who undergo radiotherapy experience increased risks of second cancers (SC) and cardiac sequelae. To reduce such risks, extended-field radiotherapy (RT) for HL has largely been replaced by involved field radiotherapy (IFRT). While it has generally been assumed that IFRT will reduce SC risks, there are few data that quantify the reduction in dose to normal tissues associated with modern RT practice for patients with mediastinal HL, and no estimates of the expected reduction in SC risk.MethodsOrgan-specific dose-volume histograms (DVH) were generated for 41 patients receiving 35 Gy mantle RT, 35 Gy IFRT, or 20 Gy IFRT, and integrated organ mean doses were compared for the three protocols. Organ-specific SC risk estimates were estimated using a dosimetric risk-modeling approach, analyzing DVH data with quantitative, mechanistic models of radiation-induced cancer.ResultsDose reductions resulted in corresponding reductions in predicted excess relative risks (ERR) for SC induction. Moving from 35 Gy mantle RT to 35 Gy IFRT reduces predicted ERR for female breast and lung cancer by approximately 65%, and for male lung cancer by approximately 35%; moving from 35 Gy IFRT to 20 Gy IFRT reduces predicted ERRs approximately 40% more. The median reduction in integral dose to the whole heart with the transition to 35 Gy IFRT was 35%, with a smaller (2%) reduction in dose to proximal coronary arteries. There was no significant reduction in thyroid dose.ConclusionThe significant decreases estimated for radiation-induced SC risks associated with modern IFRT provide strong support for the use of IFRT to reduce the late effects of treatment. The approach employed here can provide new insight into the risks associated with contemporary IFRT for HL, and may facilitate the counseling of patients regarding the risks associated with this treatment.
Highlights
Hodgkin's lymphoma (HL) survivors who undergo radiotherapy experience increased risks of second cancers (SC) and cardiac sequelae
In large part to reduce the risks of SC and cardiac toxicity, extended field radiotherapy for HL has generally been superceded by involved field radiation therapy (IFRT) delivered following chemotherapy [10]
Compared to 35 Gy mantle RT, 35 Gy involved field radiotherapy (IFRT) reduced the median value of the mean dose to the female breast by 64%, the lung by 24%, the whole heart by 29%, and the proximal coronary arteries by 2%
Summary
Hodgkin's lymphoma (HL) survivors who undergo radiotherapy experience increased risks of second cancers (SC) and cardiac sequelae. To reduce such risks, extended-field radiotherapy (RT) for HL has largely been replaced by involved field radiotherapy (IFRT). It has long been established that Hodgkin's lymphoma (HL) survivors experience increased risks of secondary cancer (SC), in particular breast and lung cancer, and cardiac disease attributable in part to radiotherapy (RT) [16]. In large part to reduce the risks of SC and cardiac toxicity, extended field radiotherapy for HL has generally been superceded by involved field radiation therapy (IFRT) delivered following chemotherapy [10]. No difference in SC rate was found among 603 patients treated in British National Lymphoma Investigation (BNLI) Study [14]
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