Intensity modulated radiation therapy planning for patients with a metal hip prosthesis based on class solutions

Purpose: With the aging of the population, an increasing number of patients with metallic hip implants are referred for radiotherapy treatment. Class solutions for intensity modulated radiation therapy (IMRT) treatment planning are generally not applicable for these patients due to the required avoidance of dose delivery through prostheses. In this work a new approach for IMRT planning is presented, allowing the use of a default beam setup. Methods and Materials: For IMRT planning, Monaco (Elekta; CMS Software, Maryland Heights, MO) was used. In addition to the target and organs at risk, so-called prosthesis avoidance volumes (PAVs) were delineated in the beam's eye view projection for beams in which the prosthesis was partially in front of the target. By putting strict constraints on these virtual organs at risk, entrance dose delivery through a prosthesis is avoided while exit dose delivery is allowed. In this way, uncertainties in the dose delivery to the target and organs at risk, as derived by the treatment planning system, are largely minimized. To show the advantages of this IMRT-PAV technique, for 2 prostate cancer patients, 1 with bilateral and the other with unilateral metallic hip prostheses, obtained IMRT plans were compared with conventional IMRT plans using a prosthesis-avoiding beam setup. Results: For both IMRT techniques a similar planning target volume coverage was achieved, but with the IMRT-PAV technique the mean doses to the bladder and the rectum were reduced by up to 25%. While the IMRT-PAV technique required more time for delineation, the time for treatment planning reduced because the default beam setup could be applied. The number of segments needed for dose delivery was comparable for both techniques. Conclusions: With the new IMRT-PAV technique IMRT class solutions can safely be applied for cancer patients with metallic hip prostheses, generally yielding a reduced dose delivery to organs at risk or improved target coverage.</p

Intraoperative validation of CT-based lymph nodal levels, sublevels IIa and IIb: is it of clinical relevance in selective radiation therapy?

PURPOSE: The objectives of this study are to discuss the intraoperative validation of CT-based boundaries of lymph nodal levels in the neck, and in particular the clinical relevance of the delineation of sublevels IIa and IIb in case of selective radiation therapy (RT). METHODS AND MATERIALS: To validate the radiologically defined level contours, clips were positioned intraoperatively at the level boundaries defined by surgical anatomy. In 10 consecutive patients, clips were placed, at the time of a neck dissection being performed, at the most cranial border of the neck. Anterior-posterior and lateral X-ray films were obtained intraoperatively. Next, in 3 patients, neck levels were contoured on preoperative contrast-enhanced CT scans according to the international consensus guidelines. From each of these 3 patients, an intraoperative CT scan was also obtained, with clips placed at the surgical-anatomy-based level boundaries. The preoperative (CT-based) and intraoperative (surgery-defined) CT scans were matched. RESULTS: Clips placed at the most cranial part of the neck lined up at the caudal part of the transverse process of the cervical vertebra C-I. The posterior border of surgical level IIa (spinal accessory nerve [SAN]) did not match with the posterior border of CT-based level IIa (internal jugular vein [IJV]). Other surgical boundaries and CT-based contours were in good agreement. CONCLUSIONS: The cranial border of the neck, i.e., the cranial border of level IIa/IIb, corresponds to the caudal edge of the lateral process of C-I. Except for the posterior border between level IIa and level IIb, a perfect match was observed between the other surgical-clip-identified levels II-V boundaries (surgical-anatomy) and the CT-based delineation contours. It is argued that (1) because of the parotid gland overlapping part of level II, and (2) the frequent infestation of occult metastatic cells in the lymph channels around the IJV, the division of level II into radiologic sublevels IIa and IIb may not be relevant. Sparing of, for example, the ipsilateral parotid gland in selective RT can even be a treacherous undertaking with respect to regional tumor control. In contrast, the surgeon's reasoning for preserving the surgical sublevel IIb is that the morbidity associated with dissection of the supraspinal accessory nerve compartment of level II is reduced, whereas there is evidence from the surgical literature that no extra risk for regional tumor control is observed. Therefore, in selective neck dissections, the division into surgical sublevels IIa/IIb makes sense

A simplified CT-based definition of the lymph node levels in the node negative neck

Introduction and purpose: Using three dimensional (3D) conformal radiotherapy (CRT) techniques for elective neck irradiation (ENI) may allow for local disease control to be maintained while diminishing xerostomia by eliminating major salivary glands (or parts thereof) from the treatment portals. The standardization of CT based target volumes for the clinically negative (elective) neck is a prerequisite for 3DCRT. The aim of the present study was to substantially modify an existing ('original') CT-based protocol for the delineation of the neck target volume, into a more practical ('simplified') protocol. This will allow for rapid contouring and the implementation of conformal ENI in routine clinical procedures. Material and Methods: An earlier ('original') version of the CT-based definition for elective neck node regions 2-5 was re-evaluated, using 15 planning CT scans of previously treated patients. The contouring guidelines were simplified by (1) using a smaller number of easily identifiable soft tissue- and bony anatomical landmarks, which in turn had to be identified in only a limited number of CT slices, and (2) by subsequently interpolating the contoured lymph node regions. The adequacy of target coverage and the sparing using both 'original' and 'simplified' delineation protocols was evaluated by DVH analysis after contouring the primary tumor, the neck and the major salivary glands in a patient with supraglottic laryngeal (SGL) carcinoma who was treated using a 3DCRT technique. Results: The BEV projections of the 'original' and the 'simplified' versions of the 3D elective neck target showed good agreement and were found to be reproducible. The DVH's of the target and parotid glands were not significantly different using both contouring protocols. Conclusions: The 'simplified' protocol for the delineation of the 3D elective neck target produced both comparable target coverage and sparing of the major salivary glands. When used together with an interpolation program, this 'simplified' protocol substantial reduced the contouring time and makes ENI with sparing of the major salivary glands a practical and achievable goal

Trismus in patients with oropharyngeal cancer: Relationship with dose in structures of mastication apparatus

Background. Our aim was to assess the correlation between the radiation therapy (RT) dose to the mastication apparatus and trismus of oropharyngeal cancer patients. Methods. Eighty-one patients treated with RT were analyzed. The masseter, pterygoid, and temporalis muscles and the coronoid and condyl were delineated on axial CT slices. The mean dose in these structures was correlated with outcome of quality of life questionnaires. Results. Fifty-six (88%) patients responded; 16% of the patients scored grade 3/4 on the Head & Neck 35 "opening mouth" question. A significant correlation was observed between dose in masseter and pterygoid muscles and trismus (p =.02). Conclusion. Patients treated with brachytherapy received a lower dose in masticatory muscles. A steep dose-effect relationship between mean dose in masseter muscle and pterygoid muscles and the probability of having trismus complaints was observed; with every additional 10 Gy to the pterygoid muscle, an increase of the probability of trismus of 24% was observed. (c) 2008 Wiley Periodicals, Inc

Results of fiberoptic endoscopic evaluation of swallowing vs. radiation dose in the swallowing muscles after radiotherapy of cancer in the oropharynx

Background and purpose: Dysphagia is a serious complaint but frequently underreported. This paper assesses for oropharyngeal cancer (OPC) the relationship between the dose received by the swallowing structures, and the findings of a fiberoptic endoscopic evaluation of the swallowing process (FEES). Materials and methods: Between 2000 and 2005, 60 of 67 OPC patients local-regionally NED for at least one year following treatment responded to three types of QoL questionnaires; i.e. Performance Status Scales, EORTC H&N35, and M.D. Anderson Dysphagia Inventory. Twenty-four patients agreed to the FEES procedure. The main swallowing muscles were delineated, with the mean dose per muscle calculated using the original 3D CT-based treatment plans. Regression analysis was performed between FEES variables and the doses in the different swallowing muscles and the dysphagia related questionnaires. Results: A significant relationship was found between the results of FEES and the mean dose in the superior constrictor muscle (SCM). Some of the subjective dysphagia complaints were significantly correlated with the FEES variables in this retrospectively study. Conclusion: A higher dose in the SCM generally results in worsening of the findings obtained by the FEES examination. (C) 2008 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 89 (2008) 57-63