In 2010, all young patients treated for intrathoracic Hodgkin lymphoma (HL) at one of 10 radiotherapy centers in the province of Quebec received 3D conformal photon therapy. These patients may now be at risk for late effects of their treatment, notably secondary malignancies and cardiac toxicity. We hypothesized that more complex radiotherapy, including intensity‐modulated proton therapy (IMPT) and possibly IMRT (in the form of helical tomotherapy (HT)), could benefit these patients. With institutional review board approval at 10 institutions, all treatment plans for patients under the age of 30 treated for HL during a six‐month consecutive period of 2010 were retrieved. Twenty‐six patients were identified, and after excluding patients with extrathoracic radiation or treatment of recurrence, 20 patients were replanned for HT and IMPT. Neutron dose for IMPT plans was estimated from published measurements. The relative seriality model was used to predict excess risk of cardiac mortality. A modified linear quadratic model was used to predict the excess absolute risk for induction of lung cancer and, in female patients, breast cancer. Model parameters were derived from published data. Predicted risk for cardiac mortality was similar among the three treatment techniques (absolute excess risk of cardiac mortality was not reduced for HT or IMPT (p>0.05,p>0.05) as compared to 3D CRT). Predicted risks were increased for HT and reduced for IMPT for secondary lung cancer (p<0.001,p<0.001) and breast cancers (p<0.001,p<0.001) as compared to 3D CRT.PACS numbers: 87.55.dh, 87.55.dk
IMPT may significantly reduce the risks of radiation-induced cardiac mortality and secondary cancer in the lungs and breasts of young patients receiving radiotherapy for HL, NHL, or breast cancer.
Purpose: Evaluate the risk of induction of secondary lung cancer and any solid cancer for patients receiving external beam radiotherapy in the abdomen using intensity modulated photon therapy (IMRT) or 3D conformal radiotherapy (3D' CRT) as compared to intensity modulated proton therapy (IMPT). Methods: Six patients (5 male, 1 female; ages 3–24; previously treated with IMRT or 3D‐CRT in the abdomen) were re‐planned for IMPT using commercially available treatment planning software. Plan dose volume histograms were used to assess the risk of induction of secondary cancer, specifically lung cancer and any solid tumor in the body. Excess Absolute Risk for lung cancer was predicted using the Schneider modified linear quadratic model. Risk for secondary solid cancer in the body was predicted using two Methods: Excess Relative Risk (ERR) based on a linear relationship between risk and integral dose, and Excess Absolute Risk (EAR) and lifetime cumulative risk implementing the Schneider Organ Equivalent Dose using linear, linear‐exponential, and plateau models. An estimate of risk due to neutron dose was calculated for each patient and included in IMPT risk calculations. Results: EAR for lung cancer was on average reduced for IMPT by 49% and 48% as compared to 3D‐CRT and IMRT respectively. ERR for secondary solid cancer was on average reduced for IMPT by 28% and 24% as compared to 3D‐CRT and IMRT respectively. EAR for secondary solid cancer was on average reduced for IMPT by 32% and 36% as compared to 3D‐CRT and IMRT respectively. Lifetime cumulative risk for secondary cancer induction was on average reduced for IMPT by 31% and 35% as compared to 3D‐CRT and IMRT respectively. Conclusions: Models predict the risk for induction of secondary lung cancer and any solid cancer is reduced for IMPT as compared to 3D‐CRT and IMRT for all patients in this study. This work is supported by a grant from the Fonds de recherche sante Quebec.
Purpose: To determine secondary cancer risk in paediatric patients treated with intensity modulated proton radiation therapy (IMPT) compared to IMRT. Methods: Proton therapy plans were created for fifteen patients previously treated with photon beam IMRT. IMPT plans were planned using the Eclipse treatment planning system (Varian Medical Systems, Palo Alto, CA) with a scanned proton beam model. The proton plans were planned to the same prescription dose as the photon plans. Each proton plan consisted of one to three fields, depending on tumour location, and photon plan constraints were used as a guide for IMPT constraints. Proton and photon plans were compared for dose conformity, homogeneity, volumes of tissue receiving low doses, integral dose, and second cancer induction risk. Second cancer risk was determined using two methods. The relative risk of secondary cancer was found by applying a linear relationship between integral dose and relative risk of secondary cancer. The second approach used the organ equivalent dose concept to describe the dose in the body and then calculate the excess absolute risk (EAR) for solid cancers. Results: IMPT and IMRT plans had similar target conformity, homogeneity, near minimum, near maximum and median doses however IMPT plans had reduced integral dose and volumes of the body receiving low dose. IMPT plans resulted in a 0.313±0.098 smaller relative risk of secondary cancer than IMRT plans. The EAR of secondary cancer in the body 30 years after treatment was reduced by 20.89±9.56, 24.30±8.46 and 22.91±7.91 patients per 10000 patients per year for the linear, linear exponential and plateau dose‐response models respectively in IMPT compared to IMRT plans. Conclusions: Two methods were used to determine the risk of secondary cancers following radiation therapy in paediatric patients. Both methods indicated that IMPT results in a lower risk of secondary cancer than photon beam IMRT.
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