title: Involved field radiation for Hodgkin's lymphoma: the actual dose to breasts in close proximity.
abstract: To decrease the risk of late toxicities in Hodgkin's lymphoma (HL) patients treated with radiation therapy (RT) (HL), involved field radiation therapy (IFRT) has largely replaced the extended fields. To determine the out-of-field dose delivered from a typical IFRT to surrounding critical structures, we measured the dose at various points in an anthropomorphic phantom. The phantom is divided into 1-inch-thick slices with the ability to insert TLDs at 3-cm intervals grid spacing. Two treatment fields were designed, and a total of 45 TLDs were placed (equally spaced) at the margin of the each of the 2 radiation fields. After performing a computed tomography simulation, 2 treatment plans targeting the mediastinum, a typical treatment field in patients with early stage HL, were generated. A total dose of 3060 cGy was delivered to the gross tumor volume for each field consecutively. The highest measured dose detected at 1 cm from the field edge in the planning target volume was 496 cGy, equivalent to 16% of the isocentric dose. The dose dropped significantly with increasing distance from the field edge. It ranged from 1.1-3.9% of the isocentric dose at a distance of 3.2-4 cm to <1.6% at a distance of >6 cm. Although the computer treatment planning system (CTPS) frequently underestimated the dose delivered, the difference in dose between measured and generated by CTPS was <2.5% in 90 positions measured. The collateral dose of radiation to breasts from IFRT is minimal. The out-of-field dose, although mildly underestimated by CTPS, becomes insignificant at >3 cm from the field edge of the radiation field.
authors.affiliation: Departments of Radiation Oncology, Radiation Physics at the University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA. bdabaja@mdanderson.org
authors.forename: Bouthaina
authors.initials: B
authors.lastname: Dabaja
authors.forename: Zhonglo
authors.initials: Z
authors.lastname: Wang
authors.forename: Marilyn
authors.initials: M
authors.lastname: Stovall
authors.forename: Jamie S
authors.initials: JS
authors.lastname: Baker
authors.forename: Susan A
authors.initials: SA
authors.lastname: Smith
authors.forename: Meena
authors.initials: M
authors.lastname: Khan
authors.forename: Leslie
authors.initials: L
authors.lastname: Ballas
authors.forename: Mohammad R
authors.initials: MR
authors.lastname: Salehpour
mesh_terms: D001940:Breast / Q000528:radiation effects*; D001943:Breast Neoplasms; D005260:Female; D006689:Hodgkin Disease / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D006801:Humans; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects*; D019047:Phantoms, Imaging; D011859:Radiography; D011874:Radiometry / Q000295:instrumentation*; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000379:methods