To study the effect of deep inspiration breath hold (DIBH) on Fast-Forward trial for left-sided breast radiotherapy dosimetrically using tangential field-in-field (FiF), flattening filtered volumetric-modulated arc therapy (FF-VMAT) and flattening filter free volumetric-modulated arc therapy (FFF-VMAT) in comparison with free breathing (FB).

Computed tomography images were acquired on 15 patients with carcinoma of left breast in FB and DIBH. Planning target volume (PTV) and organs at risk were contoured on both image sets. Dose of 26 Gy in five daily fractions was prescribed to PTV. FiF, FF-VMAT and FFF-VMAT plans were created in treatment planning system on both FB and DIBH. PTV V95%, V107%, D0·1 cc, CI and HI, heart V1·5 Gy, V7 Gy, lung left V8 Gy, monitor units (MU) and beam ON time were used for evaluation. Different technique analysis in same breathing condition and FB versus DIBH for same planning technique were performed.

Mean of all 15 patients was reported as mean ± 1 standard deviation. PTV V95% was 97·55 ± 0·10 (FiF), 95·75 ± 0·66 (FF-VMAT) and 96·15 ± 0·46 (FFF-VMAT) in FB while 97·34 ± 0·50 (FiF), 96·03 ± 0·71 (FF-VMAT) and 95·86 ± 0·63 (FFF-VMAT) in DIBH. Heart V7 Gy was 8·53 ± 4·26 (FiF), 8·86 ± 2·20 (FF-VMAT) and 9·27 ± 2·46 (FFF-VMAT) in FB while 6·30 ± 2·98 (FiF), 5·23 ± 2·20 (FF-VMAT) and 4·68 ± 2·01 (FFF-VMAT) in DIBH. p-value of heart V7 Gy between FB and DIBH was 0·278 (FiF), 0·009 (FF-VMAT) and 0·003 (FFF-VMAT). Beam ON time for FFF-VMAT was reduced by 65% (FF-VMAT) and 11% (FiF).

Conformal dose to PTV was achieved better with VMAT plans. FFF-VMAT was delivered in less time compared to FF-VMAT and FiF for 26 Gy in five fractions. Heart dose can be significantly minimised with DIBH for VMAT plans.

Breast cancer is the most commonly diagnosed cancer among women and the second leading cause of cancer-related death in Canadian women. Surgery is often the first line of treatment for low-risk early stage patients, followed by adjuvant radiation therapy to reduce the risk of local recurrence and prevent metastasis after lumpectomy or mastectomy. For high-risk patients with node positive disease or are at greater risk of nodal metastasis, radiation therapy will involve treatment of the intact breast or chest-wall as well as the regional lymph nodes.

We retrospectively evaluated the treatment plans of 354 patients with breast cancer with nodes positive or were at high risk of nodal involvement treated at our cancer centre. All patients were treated with a prescription dose of 50 Gy in 25 fractions to the intact breast or chest-wall and 50 Gy in 25 fractions to the supraclavicular region and, based on patient suitability and tolerance, were treated either using the deep inspiration breath hold (DIBH) or free-breathing (FB) techniques.

Based on patient suitability and tolerance, 130 (36·7%) patients were treated with DIBH and 224 (63·3%) with FB techniques. There were 169 (47·7%) patients treated with intact breast, whereas 185 (52·3%) were treated for post-mastectomy chest-wall. The mean PTV_eval V92%, V95%, V100% and V105% for all patients are 99·4 ± 0·7, 97·6 ± 1·6, 74·8 ± 7·9 and 1·5 ± 3·2%, respectively. The mean ipsilateral lung V10Gy, V20Gy and V30Gy are 30·0 ± 5·3, 22·4 ± 4·7 and 18·4 ± 4·3% for intact breast and 30·9 ± 5·8, 23·5 ± 5·4 and 19·4 ± 5·0% for post-mastectomy patients with FB, respectively. The corresponding values for patients treated using DIBH are 26·3 ± 5·9, 18·9 ± 5·0 and 15·6 ± 4·7% for intact breast and 27·5 ± 6·5, 20·6 ± 5·7 and 17·1 ± 5·2% for post-mastectomy patients, respectively. The mean heart V10Gy, V20Gy, is 1·8 ± 1·7, 0·9 ± 1·0 for intact breast and 3·1 ± 2·2, 1·7 ± 1·6 for post-mastectomy patients with FB, respectively. The corresponding values with the DIBH are 0·5 ± 0·7, 0·1 ± 0·4 for intact breast and 1·1 ± 1·4, 0·4 ± 0·7 for post-mastectomy patients, respectively.

The use of 3 and/or 4 field hybrid intensity-modulated radiation therapy technique for radiation therapy of high-risk node positive breast cancer patients provides an efficient and reliable method for achieving superior dose uniformity, conformity and homogeneity in the breast or post-mastectomy chest-wall volume with minimal doses to the organs at risk. The development and implementation of a consistent treatment plan acceptability criteria in radiotherapy programmes would establish an evaluation process to define a consistent, standardised and transparent treatment path for all patients that would reduce significant variations in the acceptability of treatment plans.

Evaluating the improvements of placing the treatment isocentre at the boost centre of mass (CoM) in a hybrid treatment for breast cancer radiotherapy.

Twenty-two patients were planned in two isocentre locations with two forward intensity-modulated radiation therapy (fIMRT) tangentials to the breast and a volumetric-modulated arc therapy (VMAT) to the boost. A simultaneous integrated boost technique was used. Breast Boost (BB) Vector was investigated as a criterion for selecting an appropriate isocentre placement. Various metrics for boost, breast and hybrid plans were analysed using analysis of variance statistics.

Comparing hybrid plans at the boost CoM vs. hybrid plans at the breast CoM, no significant differences were found. Analysis of relative variations of planning target volume (PTV) boost coverage vs. BB Vector indicated an upgrade in boost CoM isocentre strategy. Dose to organs at risk was comparable: V5Gy (26·24 vs. 25·69%, p = 0·8), V20Gy (14·66 vs. 14·58%, p = 0·959) and the mean dose (7·37 Gy vs. 7·26 Gy, p = 0·879) to ipsilateral lung; V5Gy (15·60 vs. 15·22%, p = 0·903), and the mean dose (4·91 Gy vs. 4·86 Gy, p = 0·950) to heart and dose to free breast of boost (46·71 Gy vs. 46·62 Gy, p = 0·408).

The hybrid fIMRT–VMAT technique centred at the boost CoM resulted equivalent to plans centred at the breast CoM, while benefiting from an enhancement in PTV boost coverage for patients with BB Vector superior to 5.

During left-sided breast radiotherapy, the heart is often exposed to radiation dose. Shielding can be utilised to reduce heart exposure, but compromises the dose delivered to the breast tissue and, in a proportion of patients, to the tumour bed. Deep inspiration breath hold (DIBH) can be used as a technique to move the heart away from the treatment area and thus reduce heart dose. This study examines the efficacy of the Elekta Active Breathing Coordinator (ABC), a DIBH method, in reducing heart dose.

In total, 12 patients receiving radiotherapy to the left breast were planned for treatment with both a free-breathing (FB) and an ABC scan. The dose volume histogram data for the plans was analysed with respect to heart V13, V5 Gy, mean heart dose and ipsilateral lung V18 Gy. Tumour bed D98%, threshold lung volume in breath hold (BH) and the maximum BH time for each patient was also measured. Patients then received their radiotherapy treatment using the ABC plan and the systematic error in the craniocaudal, lateral and vertical axes was assessed using orthogonal imaging.

The median heart V13 Gy for FB and DIBH patients was 3% (range, 0·85–11·28) and 0% (range, 0–1·56), respectively, with a mean heart dose of 2·62 Gy (range, 1·21–4·93) in FB and 1·51 Gy (range, 1·17–2·22) in ABC. The median lung V18 Gy was 8·7% (3·08–14·87) in FB plans and 9% (4·88–12·82) in ABC plans. The mean systematic set-up errors in all three planes were within the departmental set-up tolerance of 5 mm for both techniques. Median FB tumour bed D98% was 97·4% (92·8–99·5) and 97·5% (97·3–98·5) for ABC.

ABC represents a good method of reducing radiation dose to the heart while not compromising on dose to the tumour bed, and it has a clear advantage over FB radiotherapy in reducing the risk of cardiac toxicity. It is tolerated well by patients and does not produce any difficulties in patient positioning.

To investigate the dosimetric advantage of quasi-continuous couch motion-enabled trajectory modulated arc radiotherapy therapy (TMAT) over the coplanar tangential partial arcs volumetric modulated arc radiotherapy (VMAT) for treating left breast and chest wall patients.

Treatment plans of 43 patients who received radiotherapy for left breast (17) or for left chest wall (26) using coplanar partial tangential arcs VMAT (reference plan) were considered for this study. For each patient, in addition to the treatment plan, a TMAT plan was also generated using quasi-continuous couch rotation. The TMAT plan consisted of original two 30° tangential arc beams and two supplementary beams having a couch rotation of ±10°, ±20° and ±30°, respectively. The difference in PTV volume coverage (PTV V95%) between TMAT plan and VMAT plan was calculated for all the cases and normalised to the plan’s prescription dose. Similarly, differences in PTV_V105% and several dose-volume parameters related to organs at risk (OAR) were also computed and tabulated.

TMAT shows an increment in the PTV dose coverage V95% with respect to reference plan by 4·7±2·5% when averaged overall prescription dose levels. Mean PTV dose (averaged overall prescription levels) for reference and TMAT plan was 4638·6±423·8 and 4793·5±447·2 cGy, respectively, and statistically insignificant (p=0·06). However mean PTV_V105% values for TMAT and for reference plans were 6·7±4·8 and 7·2±5·2%, respectively, and were not statistically different (p=0·85). Mean heart dose in TMAT was less than in VMAT plans, but not significantly. As regarding D1% to heart, TMAT plan was again found to be better with a mean difference of 137·1 cGy over VMAT plan. Other parameters evaluated were: mean dose and D1% to contralateral breast, and V20 Gy and V5 Gy for lung.

TMAT plans were found to be better than VMAT plans in terms of PTV coverage and D1% for heart. For evaluated dose parameters apart from PTV coverage and D1% to the heart, no significant differences were observed. Thus, TMAT plans yielded better dose distribution in terms of PTV dose coverage, hot spots and OAR doses.