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Background and purpose: A comprehensive individual toxicity risk profile is needed to improve radiation treatment optimisation, minimising toxicity burden, in head and neck cancer (HNC) patients. We aimed to develop and externally validate NTCP models for various toxicities at multiple time points.Materials and methods: Using logistic regression, we determined the relationship between normal tissue irradiation and the risk of 22 toxicities at ten time points during and after treatment in 750 HNC patients. The toxicities involved swallowing, salivary, mucosal, speech, pain and general complaints. Studied pre-dictors included patient, tumour and treatment characteristics and dose parameters of 28 organs. The resulting NTCP models were externally validated in 395 HNC patients.Results: The NTCP models involved 14 organs that were associated with at least one toxicity. The oral cavity was the predominant organ, associated with 12 toxicities. Other important organs included the parotid and submandibular glands, buccal mucosa and swallowing muscles. In addition, baseline toxicity, treatment modality, and tumour site were common predictors of toxicity. The median discrimination performance (AUC) of the models was 0.71 (interquartile range: 0.68-0.75) at internal validation and 0.67 (interquartile range: 0.62-0.71) at external validation.Conclusion: We established a comprehensive individual toxicity risk profile that provides essential insight into how radiation exposure of various organs translates into multiple acute and late toxicities. This comprehensive understanding of radiation-induced toxicities enables a new radiation treatment optimisation concept that balances multiple toxicity risks simultaneously and minimises the overall tox-icity burden for an individual HNC patient who needs to undergo radiation treatment. (C) 2021 The Author(s). Published by Elsevier B.V.

Purpose : Prevention of damage to critical normal tissues is of paramount importance for the quality of life of patients irradiated for cancers in the head and neck. The purpose of this paper was to evaluate the parotid gland sparing 3D conformal radiation therapy technique (3DCRT) in a prospective study in node negative cancer of the larynx. Materials and methods : Twenty-six patients with node negative squamous cell cancer of the larynx were irradiated by a 3DCRT technique (class solution) to both sides of the neck (elective dose 46 Gy to levels II, III and IV) and primary tumour (70 Gy). Dose distributions of the major salivary glands were correlated with objective (stimulated whole saliva flow, WS) and subjective (questionnaire; visual analogue scale, VAS) salivary gland function. Apart from the clinically used 3DCRT technique, in order to optimise 3DCRT dose distributions, intensity modulated (IMRT) treatment plans were generated for the same patient population. Dose–volume histograms of 3DCRT and IMRT treatment plans were analysed and compared. Results : For the 26 patients irradiated with the 3DCRT class solution technique: VAS scores and questionnaires reached their nadir 3 months post-radiotherapy; WS reached its nadir 6 months post-radiotherapy. WS flow rates improved significantly, but never normalised; 2 years post-treatment WS measurements were 48% of the pre-treatment values. VAS scores deteriorated during ERT from 0 pre-treatment to 6.1 immediately post-treatment. Compared to pre-treatment, questionnaires were answered affirmative by increasing numbers of patients. For all patients, IMRT treatment plans resulted in a significant reduction of the dose delivered to the parotid glands compared to the 3DCRT-treatment technique. Conclusions : The class solution for the 3DCRT salivary gland sparing technique is inadequate for fully preserving salivary gland function, given the dose distributions (DVHs) as well as the subjective- and objective salivary gland function assessments. The results can be optimised in the future, that is a further reduction of xerostomia can be achieved, by using IMRT techniques focused at sparing major and minor salivary glands.

Purpose : The aim of the study is to define the role and type of high-dose, high-precision radiation therapy for boosting early staged T1,2a, but in particular locally advanced, T2b-4, nasopharyngeal cancer (NPC). Materials and methods : Ninety-one patients with primary stage I–IVB NPC, were treated between 1991 and 2000 with 60–70Gy external beam radiation therapy (ERT) followed by 11–18Gy endocavitary brachytherapy (ECBT) boost. In 1996, for stage III–IVB disease, cisplatinum (CDDP)-based neoadjuvant chemotherapy (CHT) was introduced per protocol. Patients were analyzed for local control and overall survival. For a subset of 18 patients, a magnetic resonance imaging (MRI) scan at 46Gy was obtained. After matching with pre-treatment computed tomogram, patients (response) were graded into four categories; i.e. LD (T1,2a, with limited disease, i.e. disease confined to nasopharynx), LRD (T2b, with limited residual disease), ERD (T2b, with extensive residual disease), or patients initially diagnosed with T3,4 tumors. Dose distributions for ECBT (Plato-BPS v. 13.3, Nucletron) were compared to parallel-opposed three-dimensional conformal radiation therapy (Cadplan, Varian Dosetek v. 3.1), intensity modulated radiation therapy (IMRT) (Helios, Varian) and stereotactic radiotherapy (SRT) (X-plan, Radionics v. 2.02). Results : For stage T1,2N0,1 tumors, at 2 years local control of 96% and overall survival of 80% were observed. For the poorest subset of patients, well/moderate/poorly differentiated T3,4 tumors, local control and overall survival at 2 years with CHT were 67 and 67%, respectively, vs. local control of 20% and overall survival of 12% without CHT. For LD and LRD, conformal target coverage and optimal sparing can be obtained with brachytherapy. For T2b-ERD and T3,4 tumors, these planning goals are better achieved with SRT and/or IMRT. Conclusions : The dosimetric findings, ease of application of the brachytherapy procedure, and the clinical results in early staged NPC, necessitates ERT combined with brachytherapy boost to be the therapy of preference for LD and LRD. For locally advanced T3,4 tumors, our current protocol indicates neoadjuvant chemotherapy in conjunction with high cumulative doses of radiotherapy (81Gy); IMRT and/or SRT to be the preferred technique for boosting the primary tumor.

Introduction: The treatment of midline tumors in the head and neck by conventional radiotherapy almost invariably results in xerostomia. This study analyzes whether a simple three-dimensional conformal radiotherapy (3D-CRT) technique with beam intensity modulation (BIM) (using a 10-MV beam of the MM50 Racetrack Microtron) can spare parotid and submandibular glands without compromising the dose distribution in the planning target volume (PTV). Methods: For 15 T2 tumors of the tonsillar fossa with extension into the soft palate (To) and 15 T3 tumors of the supraglottic larynx (SgL), conventional treatment plans, consisting of lateral parallel opposed beams, were used for irradiation of both the primary tumor (70 Gy) and the elective neck regions (46 Gy). Separately, for each tumor a 3-D conformal treatment plan was developed using the 3-D computer planning system, CadPlan, and Optimize, a noncommercial program to compute optimal beam profiles. Beam angles were selected with the intention of optimal sparing of the salivary glands. The intensity of the beams was then modulated to achieve a homogeneous dose distribution in the target for the given 3D-CRT techniques. The dose distributions, dose–volume histograms (DVHs) of target and salivary glands, tumor control probabilities (TCPs), salivary gland volumes absorbing a biologically equivalent dose of greater than 40 or 50 Gy, and normal tissue complication probabilities (NTCPs) of each treatment plan were computed. The parameters of the 3D-CRT plans were compared with those of the conventional plans. Results: In comparison with the conventional technique, the dose homogeneity in the target volume was improved by the conformal technique for both tumor sites. In addition, for the SgL conformal technique, the average volumes of the parotid glands absorbing a BED of greater than 40 Gy (V40) decreased by 23%, and of the submandibular glands by 7% (V40) and 6% (V50). Consequently, the average NTCPs for the parotid and submandibular glands were reduced by 7% and 6%, respectively. For the To conformal techniques, the V40 of the parotid glands was decreased on average by 31%, resulting in an average reduction of the NTCP by 49%. Both the average V50 and the NTCP of the submandibular glands were decreased by 7%. Conclusion: For primary tumors of the oropharynx, the parotid glands could be spared to a considerable degree with the 3D-CRT technique. However, particularly the ipsilateral submandibular gland could not be spared. For primary tumors of the larynx, the 3D-CRT technique allows sparing of all salivary glands to a considerable and probably clinically relevant degree. Moreover, the conformal techniques resulted in an increased dose homogeneity in the PTV of both tumor sites.

Introduction: Elective treatment of the clinically node-negative neck by radiation results in excellent control rates. However, radiation therapy with its organ-preserving properties is not without morbidity. Side effects of elective neck irradiation are mainly due to damage of the major and minor salivary glands, resulting in the dry mouth syndrome. Given that RT is the preferred treatment modality in case of elective treatment of the neck in many institutions, it is of utmost importance to try and reduce the associated sequelae of RT. Material and Methods: With the introduction of CT-planning systems and the development of 3D conformal radiation therapy (3D CRT) techniques, it has become feasible to deliver adequate doses of radiation to the target (neck) and at the same time saving (parts of) the salivary glands from doses beyond tolerance. A prerequisite for these techniques is that they require a precise knowledge of the target (i.e., of the elective neck) on CT. To be able to correlate borders of the surgical levels in the neck (I–VI) with structures seen on CT, an anatomical study, using two fixed (phenol, formaldehyde) human cadavers, was performed. Subsequently, the 6 potential lymph node regions in the neck on CT were defined. Results and Discussion: The reference for the current 3D CT-based definition of the lymph node regions in the neck is the official report of the American Academy of Otolaryngology, describing, based on surgical anatomy, the lymph node groups in the neck by Levels I–VI. The present investigation depicts reproducible landmarks on transversal CT images, corresponding to anatomical reference structures known from surgical levels (I–VI) and, this way, CT-based lymph node regions (1–6) were constructed.