Free Breathing versus Breath-Hold Scanning Beam Proton Therapy and Cardiac Sparing in Breast Cancer

Abstract

Purpose: To assess dose errors caused by the interplay effects of free-breathing (FB) motion and to assess the value of breath-hold (BH) in terms of cardiac dose reduction for scanning beam proton therapy (SBPT). Materials and Methods: Three patients with left-sided breast cancer previously treated with photon therapy were included in this dosimetric study: 2 following breast-conserving surgery with 2 hypothetical target volumes (whole breast alone and whole breast plus regional nodes, including supraclavicular, axillary, and internal mammary lymph nodes); and 1 postmastectomy, with the target volume including the chest wall plus regional nodes. SBPT plans were generated with various beam angles that ranged between 2 tangential directions. For treatment with FB, nominal dose and dose with interplay effects considered were calculated based on FB 4-dimensional computed tomography scans. SBPT plans on the BH computed tomography were also calculated for one of the patients, who was selected to be treated with photon therapy with BH. Results: Dosimetric differences between nominal and interplay dose were small (average target mean dose, −0.06 Gy; range, −0.23 to 0.06 Gy; average heart mean dose, 0.001 Gy; range, −0.12 to 0.05 Gy). The largest dose deviations occurred in plans calculated with tangential beam arrangements; the smallest was noted with the en face beam. The average value of the mean heart dose with FB was <1 Gy. For the selected patient, the mean heart doses were 0.5 and 0.2 Gy for FB and BH, respectively. Conclusion: Dose deviations caused by the interplay effects of respiratory motion during FB do not have a significant impact in SBPT with en face beam arrangement. BH does not significantly reduce cardiac dose. SBPT delivery is feasible with FB and can provide optimal target coverage and maximal sparing of the cardiopulmonary system, which can translate into improved clinical outcomes and a decrease in treatment-related morbidity in left-sided breast cancer patients or those who require internal mammary node coverage.

A Dosimetric Comparison of Breast Radiotherapy Techniques to Treat Locoregional Lymph Nodes Including the Internal Mammary Chain

“…PBT is superior to photon therapies, both for target volume coverage and OAR dose, as previously shown [12,15,24]. There seems to be no significant benefit in attempting to treat patients with PBT in vDIBH, consistent with findings from recent studies investigating this combination [25,26]. PBT is the only therapy capable of delivering a mean contralateral breast dose <1 Gy.…”

Can internal mammary lymph nodes irradiation bring survival benefits for breast cancer patients? A systematic review and meta-analysis of 12,705 patients in 12 studies

“…For complicated plans or patients with poor chest wall anatomy, new technologies such as VMAT and TOMO can also significantly reduce the cardiopulmonary dose of patients [ 32 , 33 ]. In addition, proton radiotherapy has shown a good ability to reduce the cardiopulmonary dose [ 34 , 35 ], and conditional centers can carry out proton radiotherapy to enhance the protection of organs at risk. It can be seen that although IMNI increases the dose of heart, lung and other important organs, we can still control it at a low level by modern technical means.…”

Impact of physiological breathing motion for breast cancer radiotherapy with proton beam scanning – An in silico study

“…Thus, abdominal compression could reduce motion, but might increase interfractional variations and could also limit some beam directions [8]. Similarly, gating, either as enhanced inspiration gating (EIG) or as deep inspiration breath hold (DIBH), could help maintain a fixed geometry relative to the beam and could also reduce the doses to organsat-risk (OARs), but not all patients comply with or are suitable for the gating procedure [5,9,10]. An alternative to reducing motion amplitude is to investigate whether the changes in dose distributions caused by breathing are likely to have a clinical impact.…”