Integral Dose and Radiation-Induced Secondary Malignancies: Comparison between Stereotactic Body Radiation Therapy and Three-Dimensional Conformal Radiotherapy

Abstract

The aim of the present paper is to compare the integral dose received by non-tumor tissue (NTID) in stereotactic body radiation therapy (SBRT) with modified LINAC with that received by three-dimensional conformal radiotherapy (3D-CRT), estimating possible correlations between NTID and radiation-induced secondary malignancy risk. Eight patients with intrathoracic lesions were treated with SBRT, 23 Gy × 1 fraction. All patients were then replanned for 3D-CRT, maintaining the same target coverage and applying a dose scheme of 2 Gy × 32 fractions. The dose equivalence between the different treatment modalities was achieved assuming α/β = 10Gy for tumor tissue and imposing the same biological effective dose (BED) on the target (BED = 76Gy10). Total NTIDs for both techniques was calculated considering α/β = 3Gy for healthy tissue. Excess absolute cancer risk (EAR) was calculated for various organs using a mechanistic model that includes fractionation effects. A paired two-tailed Student t-test was performed to determine statistically significant differences between the data (p ≤ 0.05). Our study indicates that despite the fact that for all patients integral dose is higher for SBRT treatments than 3D-CRT (p = 0.002), secondary cancer risk associated to SBRT patients is significantly smaller than that calculated for 3D-CRT (p = 0.001). This suggests that integral dose is not a good estimator for quantifying cancer induction. Indeed, for the model and parameters used, hypofractionated radiotherapy has the potential for secondary cancer reduction. The development of reliable secondary cancer risk models seems to be a key issue in fractionated radiotherapy. Further assessments of integral doses received with 3D-CRT and other special techniques are also strongly encouraged.

Involved Node, Site, Field and Residual Volume Radiotherapy for Lymphoma: A Comparison of Organ at Risk Dosimetry and Second Malignancy Risks

“…For the oesophagus, the mechanistic model was used for risk calculation, using the a value of the stomach ( a ¼ 0.46 Gy À1 ) was adopted [23] and R was given the intermediate value of 0.5, in keeping with the work by D'Arienzo et al [32].…”

“…Parameters for thyroid were therefore taken from Cella et al [20] and for the oesophagus the a value used is that for the stomach, with an R of 0.5, in keeping with the work by D'Arienzo et al [32]. All other parameters are from [23].…”

A QA Analysis of a Contrast Localized Linac-Based Technique for Hypo-Fractionated Partial Breast Radiotherapy

“…Past research comparison of the Mu ratio vs. the integral dose has indicated that Conformal RT had a lower ratio than IMRT and a significantly lower ratio than the ratio of cyberknife (radiosurgery) [14] . The Left and Right Breast Statistical Analysis highlighted the structures of the cavity, PTV, Heart, Breasts, Right Lung, Left Lung, and spinal cord met dose/isodose, dose volume histogram criteria, and protocol 5 point dose limitation constraint of the protocol in all ten cases.…”

The risk of secondary cancer in nasopharyngeal carcinoma paediatric patients due to intensity modulated radiotherapy and mega‐voltage cone beam computed tomography

“…Radiation‐induced secondary malignancy is an issue of growing interest and recent studies have shown that treatment using radiation is associated with increasing in the risk of secondary cancers . Intensity Modulated Radiation Therapy (IMRT) is one of the commonly used methods for treating patients with Nasopharyngeal Carcinoma (NPC) .…”

“…Radiation-induced secondary malignancy is an issue of growing interest and recent studies have shown that treatment using radiation is associated with increasing in the risk of secondary cancers. 1 Intensity Modulated Radiation Therapy (IMRT) is one of the commonly used methods for treating patients with Nasopharyngeal Carcinoma (NPC). 2 This is because it is difficult to deliver a satisfactory radiation dose distribution to the NPC target volume by conventional radiotherapy techniques without significantly irradiating the critical tissue structures.…”