<p>Comparison of Radiation-Induced Secondary Malignancy Risk Between Sequential and Simultaneous Integrated Boost for the Treatment of Nasopharyngeal Carcinoma: Intensity-Modulated Radiotherapy versus Volumetric-Modulated Arc Therapy</p>

Abstract

This study aimed to compare the secondary cancer risk (SCR) between the sequential boost (SEQ) technique and simultaneous integrated boost (SIB) technique in intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) in patients with nasopharyngeal carcinoma (NPC) using the concepts of organ equivalent dose (OED) and excess absolute risk (EAR). Patients and Methods: IMRT-SEQ, VMAT-SEQ, IMRT-SIB, and VMAT-SIB plans were created with identical objective functions for five patients with early-stage NPC. Three different planning tumor volumes (PTVs; PTV 1 , PTV 2 , and PTV 3) were delineated for each patient, and the prescribed doses were 50 Gy, 60 Gy, and 70 Gy (2 Gy/fraction), respectively, for the SEQ technique and 52.8 Gy, 59.4 Gy, and 69.3 Gy (33 fractions), respectively, for the SIB technique. Results: All plans were clinically acceptable. There was no difference in most OED-based SCRs between IMRT and VMAT when the same fractionation scheme was used. Compared with the SEQ technique, the SIB technique in IMRT and VMAT was associated with the lowest OEDs for the oral cavity, pharynx, parotids, and submandibular glands, resulting in SCR reduction. SCR for the parotids was much lower than that for the other assessed organs when the SIB technique was used. Conclusion: Our findings suggest that OED-based SCRs are lower with the SIB technique than with the SEQ technique in IMRT and VMAT in most organs for which SCR was calculated; furthermore, SCR for the parotids is much lower than that for other organs when the SIB technique is used in patients with NPC.

Risk factors of secondary cancer in nasopharyngeal carcinoma patients after radiotherapy

“…The nomogram was established based on the risk factors of age, race, AJCC, and chemotherapy. Important factors of radiation therapy technique, radiation dose and its distribution were not included due to the limitation of SEER database [19][20][21]. Thus, the nomogram could not provide well-discriminating ability.…”

Recommendations for reducing exposure to medical X‑ray irradiation (Review)

“…Following the discovery of X-rays, it was found that frequent exposure experienced by physicians increased their risk of developing cancer (13)(14)(15)(16)(17)(18). Studies on atomic bomb survivors (19)(20)(21)(22)(23)(24) and patients with cancer receiving radiation therapy (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) have found that the risk of tumorigenesis is associated with acute or fractionated high-dose radiation exposure. although opinions differ as regards the harm of low-dose radiation to the human body, the impact of low-dose radiation on cancer risk has gained scientific attention.…”

Development of clinical application program for radiotherapy induced cancer risk calculation using Monte Carlo engine in volumetric-modulated arc therapy

“…Researches regarding SCR have been reported that SCR increases as the volume of organs receiving radiation increases and as the distance from the source reduces [ 11 , 15 ]. In Hall et al’s studies, it was reported that SCR is approximately 1.0–1.8% higher (10 years survival rate) in IMRT than CRT [ 13 , 16 ]. It is also reported that secondary scattered doses at locations approximately at 20–50 cm from the iso-center were approximately 1.0–5.0 mGy per 1 Gy for planning target volume (PTV) in IMRT [ 17 ].…”