RapidArc, SmartArc and TomoHD compared with classical step and shoot and sliding window intensity modulated radiotherapy in an oropharyngeal cancer treatment plan comparison

Abstract

BackroundRadiotherapy techniques have evolved rapidly over the last decade with the introduction of Intensity Modulated RadioTherapy (IMRT) in different forms. It is not clear which of the IMRT techniques is superior in the treatment of head and neck cancer patients in terms of coverage of the planning target volumes (PTVs), sparing the organs at risk (OARs), dose to the normal tissue, number of monitor units needed and delivery time.The present paper aims to compare Step and Shoot (SS) IMRT, Sliding Window (SW) IMRT, RapidArc (RA) planned with Eclipse, Elekta VMAT planned with SmartArc (SA) and helical TomoHDTM (HT).MethodsTarget volumes and organs at risk (OARs) of five patients with oropharyngeal cancer were delineated on contrast enhanced CT-scans, then treatment plans were generated on five different IMRT systems. In 32 fractions, 69.12 Gy and 56 Gy were planned to the therapeutic and prophylactic PTVs, respectively. For the PTVs and 26 OARs ICRU 83 reporting guidelines were followed. Differences in the studied parameters between treatment planning systems were analysed using repeated measures ANOVA.ResultsMean Homogeneity Index of PTVtherapeutic is better with HT(.06) followed by SA(.08), RA(.10), SW(.10) and SS(.11). PTVprophylactic is most homogeneous with RA. Parotid glands prescribed mean doses are only obtained by SA and HT, 20.6 Gy and 21.7 Gy for the contralateral and 25.6 Gy and 24.1 Gy for the ipsilateral, against 25.6 Gy and 32.0 Gy for RA, 26.4 Gy and 34.6 Gy for SW, and 28.2 Gy and 34.0 Gy for SS. RA uses the least monitor units, HT the most. Treatment times are 3.05 min for RA, and 5.9 min for SA and HT.ConclusionsIn the treatment of oropharyngeal cancer, we consider rotational IMRT techniques preferable to fixed gantry techniques due to faster fraction delivery and better sparing of OARs without a higher integral dose. TomoHD gives most homogeneous target coverage with more sparing of spinal cord, brainstem, parotids and the lower swallowing apparatus than most of the other systems. Between RA and SA, SA gives a more homogeneous PTVtherapeutic while sparing the parotids more, but the delivery of RA is twice as fast with less overdose to the PTVelective.

Helical Tomotherapy in Head and Neck Cancer: A European Single-Center Experience

“…The dose to the OARs, including the spinal cord and the brainstem, was kept as low as possible respecting the prescription to the PTV. The reference dose constraints have been reported in a preliminary planning study [30].…”

Intensity Modulated Arc Therapy in Bilaterally Irradiated Head and Neck Cancer: A Comparative and Prospective Multicenter Planning Study

“…Despite the number of dosimetric studies, these results should be interpreted carefully because the calculation algorithm and resolution of the planning systems are different (16,17). The algorithm used for each technique has some specificity due to delivery techniques.…”

Volumetric modulated arc therapy (VMAT) and simultaneous integrated boost in head-and-neck cancer: is there a place for critical swallowing structures dose sparing?

“…In addition, it is also expected that the relation of PTVs to swallowing critical organs can differ considerably among various studies. In the van Gestel study, 35 the authors explicitly excluded from the analysis some OARs as upper pharyngeal constrictor owing to a major overlap with the PTV, suggesting that the other swallowing OARs (as medium and lower pharyngeal constrictor and glottic and SGL) do not present major overlaps with PTVs. In our study, we have shown that the PCM and SGL present a median overlap of 96% and 56% with the low-risk nodal area, a situation that actually prevents a dose reduction in the low-intermediate range without compromising PTV coverage for most of the patients.…”

“…[33][34][35] This, despite the worldwide implementation of this technique, is gradually replacing fixed-field IMRT, thanks to its advantages in terms of treatment efficiency. VMAT planning optimization process is much more complex than fixed-field IMRT.…”

“…A few planning studies, [33][34][35] aiming to compare fixed-field IMRT with rotational IMRT and/or tomotherapy, also considered critical swallowing structures in the evaluation of the various techniques' efficacy. Most of the results in these studies are not in agreement with our data as we do find higher average doses to swallowing-related structures.…”