Treatment planning and evaluation of gated radiotherapy in left-sided breast cancer patients using the CatalystTM/SentinelTM system for deep inspiration breath-hold (DIBH)

BACKGROUND

There is a potential for adverse cardiovascular effects in long-term breast cancer survivors following adjuvant radiotherapy (RT). For this purpose, the deep inspiration breath-hold technique (DIBH) has been introduced into clinical practice, to maximally reduce the radiation dose to the heart. However, there are a variety of DIBH delivery techniques, patient positioning and visual patient feedback mechanisms. The aim of the present study was to evaluate the application of radiotherapy in DIBH using the Catalyst^TM/Sentinel^TM system, with a special emphasis on treatment planning and dosimetric plan comparison in free breathing (FB) and DIBH.

PATIENTS AND METHODS

A total of 13 patients with left-sided breast cancer following breast conserving surgery were included in this prospective clinical trial. For treatment application the Catalyst^TM/Sentinel^TM system (C-RAD AB, Uppsala, Sweden) was used and gating control was performed by an audio-visual patient feedback system. CT and surface data were acquired in FB and DIBH and dual treatment plans were created using Pencil Beam and Collapsed Cone Convolution. Dosimetric output parameters of organs at risk were compared using Wilcoxon signed-rank test. Central lung distance (CLD) was retrieved from iView^TM portal images during treatment delivery.

RESULTS

The system contains a laser surface scanner (Sentinel^TM) and an optical surface scanner (Catalyst^TM) interconnected to the LINAC systems via a gating interface and allows for a continuous and touchless surface scanning. Overall, 225 treatment fractions with audio-visual guidance were completed without any substantial difficulties. Following initial patient training and treatment setup, radiotherapy in DIBH with the Catalyst^TM/Sentinel^TM system was time-efficient and reliable. Following dual treatment planning for all patients, nine of 13 patients were treated in DIBH. In these patients, the reduction of the mean heart dose for DIBH compared to FB was 52 % (2.73 to 1.31 Gy; p = 0.011). The maximum doses to the heart and LAD were reduced by 59 % (47.90 to 19.74 Gy; p = 0.008) and 75 % (38.55 to 9.66 Gy; p = 0.008), respectively. In six of the nine patients the heart completely moved out of the treatment field by DIBH. The standard deviation of the CLD varied between 0.12 and 0.29 cm (mean: 0.16 cm).

CONCLUSION

The Catalyst^TM/Sentinel^TM system enabled a fast and reliable application and surveillance of DIBH in daily clinical routine. Furthermore, the present data show that using the DIBH technique during RT could significantly reduce high dose areas and mean doses to the heart.

TRIAL REGISTRATION

DRKS: DRKS00010929 registered on 5. August 2016.

Reduction of cardiac and coronary artery doses in irradiation of left-sided breast cancer during inspiration breath hold : A planning study

BACKGROUND AND PURPOSE

The radiation dose received by the heart during adjuvant left-sided breast irradiation plays a crucial role in development of late toxicity. Although the absolute risk of cardiotoxicity can be reduced with modern irradiation techniques, cardiotoxic chemotherapy increases the risk of late damage. Thus, the radiation dose to the heart should be minimized. This study evaluated the influence of different amplitudes of inspiration breath hold (IBH) during simulated left-sided breast irradiation on cardiac doses compared to free breathing (FB).

PATIENTS AND METHODS

CT data of 11 lung cancer patients were retrospectively used as left-sided pseudo-breast cancer cases. Two CT scans were used, one during IBH and one during FB, and two treatment plans were generated. Relevant heart, lung, and left anterior descending artery (LAD) parameters were derived from dose-volume histograms. The normal tissue complication probabilities (NTCPs) for the heart were calculated based on the relative seriality model. Inspiration depth was quantified using chest volume and diameter, and correlated thereafter to a possible sparing of heart tissue.

RESULTS

Mean reduction of heart dose for IBH compared to FB was 40 % (1.65 vs. 0.99 Gy; p = 0.007). Maximum dose to the heart and LAD could be decreased by 33 % (p = 0.011) and 43 % (p = 0.024), respectively. The mean anteroposterior shift was 5 mm (range 0.9-9.5 mm). Significant negative correlations between the relative change in LAD mean dose and the mean thoracic diameter and volume change, as well as with the absolute change in thoracic diameter were seen. The NTCP for cardiac mortality could be decreased by about 78 % (p = 0.017).

CONCLUSION

For left-sided breast cancer patients, cardiac doses can be significantly decreased with tangential irradiation and IBH.

Dosimetric effect due to the motion during deep inspiration breath hold for left-sided breast cancer radiotherapy

Deep inspiration breath-hold (DIBH) radiotherapy for left-sided breast cancer can reduce cardiac exposure and internal motion. We modified our in-house treatment planning system (TPS) to retrospectively analyze breath-hold motion log files to calculate the dosimetric effect of the motion during breath hold. Thirty left-sided supine DIBH breast patients treated using AlignRT were studied. Breath-hold motion was recorded — three translational and three rotational displacements of the treatment surface — the Real Time Deltas (RTD). The corresponding delivered dose was estimated using the beam-on portions of the RTDs. Each motion was used to calculate dose, and the final estimated dose was the equally weighted average of the multiple resultant doses. Ten of thirty patients had internal mammary nodes (IMN) purposefully included in the tangential fields, and we evaluated the percentage of IMN covered by 40 Gy. The planned and delivered heart mean dose, lungs V20 (volume of the lungs receiving > 20 Gy), percentage of IMN covered by 40 Gy, and IMN mean dose were compared. The averaged mean and standard deviation of the beam-on portions of the absolute RTDs were 0.81 ± 1.29 mm, 0.68 ± 0.85mm, 0.76 ± 0.85 mm, 0.96° ± 0.49°, 0.93° ± 0.43°, and 1.03° ± 0.50°, for vertical, longitudinal, lateral, yaw, roll, and pitch, respectively. The averaged planned and delivered mean heart dose were 99 and 101 cGy. Lungs V20 were 6.59% and 6.74%. IMN 40 Gy coverage was 83% and 77%, and mean IMN dose was 4642 and 4518 cGy. The averaged mean motion during DIBH was smaller than 1 mm and 1°, which reflects the relative reproducibility of the patient breath hold. On average, the mean heart dose and lungs V20 were reasonably close to what have been planned. IMN 40 Gy coverage might be modestly reduced for certain cases.

Clinical experience with 3-dimensional surface matching-based deep inspiration breath hold for left-sided breast cancer radiation therapy

PURPOSE

Three-dimensional (3D) surface matching is a novel method to administer deep inspiration breath-hold (DIBH) radiation therapy for left-sided breast cancer to reduce cardiac exposure. We analyzed port (x-ray) films to assess patient setup accuracy and treatment times to assess the practical workflow of this system.

METHODS AND MATERIALS

The data from 50 left-sided breast cancer patients treated with DIBH were studied. AlignRT (London, UK) was used. The distance between the field edge and the anterior pericardial shadow as seen on the routine port films (dPORT), and the corresponding distance seen on the digitally reconstructed radiographs (DRR) from the planning (dDRR) were compared as a quantitative measure of setup accuracy. Variations of dPORT - dDRR over the treatment course were assessed. In a subset of 21 patients treated with tangential beams alone, the daily treatment durations were analyzed to assess the practical workflow of this system.

RESULTS

Considering all 50 patients, the mean absolute systematic uncertainty between dPORT and dDRR was 0.20 cm (range, 0 to 1.22 cm), the mean systematic uncertainty was -0.07 cm (range, -1.22 to 0.67 cm), and their mean random uncertainty was 0.19 cm (range, 0 to 0.84 cm). There was no significant change in dPORT - dDRR during the course of treatment. The mean patient treatment duration for the 21 patients studied was 11 minutes 48 seconds. On intrapatient assessments, 15/21 had nonsignificant trends toward reduced treatment durations during their course of therapy. On interpatient comparisons, the mean treatment times declined as we gained more experience with this technique.

CONCLUSIONS

The DIBH patient setup appears to provide a fairly reproducible degree of cardiac sparing with random uncertainties of ≈ 0.2 cm. The treatment durations are clinically acceptable and appear not to change significantly over time on an intrapatient basis, and to improve over time on an interpatient basis.