Partial breast radiotherapy with simple teletherapy techniques

Abstract

A prospective pilot study of partial breast irradiation (PBI) with conventional vs hypofractionated schedules was set out. The study aimed to determine efficacy, acute and late side effects, and the preference of photon vs electron irradiation based on individual features. Patients were enrolled according to internationally accepted guidelines on PBI. Conformal radiotherapy plans were generated with both photon and electron beams, and the preferred technique based on dose homogeneity and the radiation exposure of healthy tissues was applied. For electron dose verification, a special phantom was constructed. Patients were randomized for fractionation schedules of 25 × 2 vs 13 × 3Gy. Skin and breast changes were registered at the time of and ≥1 year after the completion of radiotherapy. Dose homogeneity was better with photons. If the tumor bed was located in the inner quadrants, electron beam gave superior results regarding conformity and sparing of organ at risk (OAR). If the tumor was situated in the lateral quadrants, conformity was better with photons. A depth of the tumor bed ≥3.0cm predicted the superiority of photon irradiation (odds ratio [OR] = 23.6, 95% CI: 5.2 to 107.5, p < 0.001) with >90% sensitivity and specificity. After a median follow-up of 39 months, among 72 irradiated cases, 1 local relapse out of the tumor bed was detected. Acute radiodermatitis of grade I to II, hyperpigmentation, and telangiectasia developed ≥1 year after radiotherapy, exclusively after electron beam radiotherapy. The choice of electrons or photons for PBI should be based on tumor bed location; the used methods are efficient and feasible.

Individually selected teletherapy technique for accelerated partial breast irradiation

“…138 patients were enrolled into the study in 2 cohorts (n = 72, November 2009 - December 2012 and n = 66, September 2015 – July 2018). The first cohort received 3D-CRT (photon or electron) [ 10 ], the other cohort VMAT (n = 58), IMRT (n = 2), 3D-CRT (n = 2) or photon-electron mixed technique (n = 4). The actual radiotherapy technique was selected according to availability.…”

“…According to five reports [ 11 – 14 , 33 ] about the application of the mixed beam technique, the addition of electrons to photon fields decreased the ipsilateral breast dose while the heart and lung doses were different according to the study and obviously the PTV location [ 14 ]. Evidently, the use of an additional electron beam is feasible only in the case of superficial tumour beds [ 10 ]. According to our results, the use of 3D-CRT and a supplementary electron field was beneficial in patients with a tumour bed situated < 25 mm from the body surface.…”

“…Due to the rising number of patients needing APBI, and to eliminate the special infrastructural and expertise needs of brachytherapy, the implementation of conformal teletherapy methods, such as 3D-conformal radiation therapy (3D-CRT) with multiple static photon and/or electron fields, intensity-modulated RT (IMRT), volumetric-modulated arc therapy (VMAT), tomotherapy, robotic radiosurgery systems and proton beam therapy has begun emerging [ 8 – 11 ]. The utilization of a mixed technique combining photon with an ‘en face’ electron field may result in improved planning target volume (PTV) coverage and organ at risk (OAR) exposure [ 10 – 14 ]. IMRT optimizes dose distribution using structure-based planning and alterable intensity beam fluencies, providing improved dose homogeneity within the PTV, and reduced high dose exposure of normal tissues.…”

Individualised radiotherapy serving reduced toxicity in breast and prostate cancer

“…All agreed that this approach may lower the ipsilateral breast dose; lung and heart doses varied according to study, and obviously the situation of the tumour bed [92]. Clearly, the use of electrons should be reserved for tumours non-deeply located [94]. In the present study, the addition of a shaped electron field to 3D-CRT provided benefit in cases with d<25 mm.…”