Considerations for study design in the DAHANCA 35 trial of protons versus photons for head and neck cancer

Proton radiotherapy offers a dosimetric advantage compared to photon therapy in sparing normal tissue, but the clinical evidence for toxicity reductions in the treatment of head and neck cancer is limited. The Danish Head and Neck Cancer Group (DAHANCA) has initiated the DAHANCA 35 randomised trial to clarify the value of proton therapy (NCT04607694). The DAHANCA 35 trial is performed in an enriched population of patients selected by an anticipated benefit of proton therapy to reduce the risk of late dysphagia or xerostomia based on normal tissue complication probability (NTCP) modelling. We present our considerations on the trial design and a test of the selection procedure conducted before initiating the randomised study.

Late toxicity in the brain after radiotherapy for sinonasal cancer: Neurocognitive functioning, MRI of the brain and quality of life

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Compared with matched normative data, impaired cognitive function was substantial.

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Several correlations between radiation dose and cognitive impairment were present.

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Radiation-induced white matter hyperintensities were present in 2/27 participants.

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One participant displayed radiation-induced necrosis in the temporal lobe.

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The domains affecting quality of life the most were fatigue and quality of sleep.

Purpose

The aim of the study was to evaluate neurocognitive late effects, structural alterations and associations between cognitive impairment and radiation doses as well as cerebral tissue damage after radiotherapy for sinonasal cancer. Furthermore, the aim was to report quality of life (QoL) and self-reported cognitive capacity.

Materials and methods

Recurrence-free patients previously treated with intensity-modulated radiotherapy with a curative intent were eligible for the study. Study examinations comprised comprehensive neurocognitive testing, MRI of the brain, and self-reported outcomes.

Results

A total of 27 patients were included. Median age was 67 years (range 47–83). The majority of test outcomes were below normative values in any degree, and 37% of the participants had clinically significant neurocognitive impairment when compared with normative data. Correlations between absorbed doses to specific substructures of the brain and neurocognitive outcomes were present for Wechsler’s Adult Intelligence Scale-digit span and Controlled Oral Word Association Test-S. Structural MRI revealed macroscopic abnormalities in three patients; infarction (n = 1), diffuse white matter intensities (n = 2) and necrosis (n = 1). In the analysis of atrophy of cerebral tissue, no correlations were present with neither radiation dose to cerebral substructures nor neurocognitive impairment. The global QoL of the cohort was 75. The most affected outcomes were ‘fatigue’, ‘insomnia’, and ‘drowsiness’. A total of 59% of participants reported significantly impaired quality of sleep. Self-reported cognitive function revealed that ‘memory’ was the most affected cognitive domain. For the domains of ‘memory’ and ‘language’, self-reported functioning was associated with objectively measured neurocognitive outcomes.

Conclusion

Cerebral toxicity after radiotherapy for sinonasal cancer was substantial. Clinically significant cognitive impairment was present in more than one third of the participants, and several dose–response associations were present. Furthermore, the presence of macroscopic radiation sequelae indicated considerable impact of radiotherapy on brain tissue.

Early Mortality after Radical Radiotherapy in Head and Neck Cancer - A Nationwide Analysis from the Danish Head and Neck Cancer Group (DAHANCA) Database

AIMS

Curative-intent radiotherapy (RT) or chemoradiation (CRT) of squamous cell carcinoma of the head and neck (HNSCC) produces high survival rates, but is associated with substantial toxicity. However, there are no commonly accepted quality metrics for early mortality in radiation oncology. To assess the applicability of early mortality as a clinical quality indicator, this study investigated the temporal distribution, risk factors and trends of 90- and 180-day overall and non-cancer mortality in a nationwide cohort of HNSCC patients treated with RT/CRT.

MATERIALS AND METHODS

Information on all HNSCC patients treated with curative-intent RT/CRT in Denmark between 2000 and 2017 was obtained from the national Danish Head and Neck Cancer Group clinical database. Deaths in patients with residual or recurrent disease after RT/CRT were classified as cancer-related. Possible risk factors were investigated using logistic regression analysis.

RESULTS

Data from 11 419 patients were extracted. In total, 90- and 180-day mortality risks were 3.1% and 7.1%, respectively. There was a uniform temporal distribution of 180-day mortality. In multivariable analysis, increasing age, stage, performance status, earlier treatment year and hypopharyngeal cancer were significantly associated with an increased risk (P < 0.05). Risk factor estimates were comparable for 90- versus 180-day mortality as well as for overall versus non-cancer mortality. Between 2000 and 2017 there was a significant decrease in 180-day mortality, which was driven by a reduction in cancer-related events.

CONCLUSION

The distribution of 180-day overall and non-cancer mortality did not indicate a well-defined early high-risk period. Moreover, risk factor estimates were highly similar across risk periods and groups. Taken together, our findings question the applicability of early mortality as a standard metric for treatment-associated toxicity.

Prediction of radiation-induced mucositis of H&N cancer patients based on a large patient cohort

PURPOSE/OBJECTIVE

Radiation-induced mucositis is a severe acute side effect, which can jeopardize treatment compliance and cause weight loss during treatment. The study aimed to develop robust models to predict the risk of severe mucositis.

MATERIALS/METHODS

Mucosal toxicity scores were prospectively recorded for 802 consecutive Head and Neck (H&N) cancer patients and dichotomised into non-severe event (grade 0-2) and severe event (grade 3+) groups. Two different model approaches were utilised to evaluate the robustness of the models. These used LASSO and Best Subset selection combined with 10-fold cross-validation performed on two-thirds of the patient cohort using principal component analysis of DVHs. The remaining one-third of the patients were used for validation. Model performance was tested through calibration plot and model performance metrics.

RESULTS

The main predicted risk factors were treatment acceleration and the first two principal dose components, which reflect the mean dose and the balance between high and low doses to the oral cavity. For the LASSO model, gender and current smoker status were also included in the model. The AUC values of the two models on the validation cohort were 0.797 (95%CI: 0.741-0.857) and 0.808 (95%CI: 0.749-0.859), respectively. The two models predicted very similar risk values with an internal Pearson coefficient of 0.954, indicating their robustness.

CONCLUSIONS

Robust prediction models of the risk of severe mucositis have been developed based on information from the entire dose distribution for a large cohort of patients consisting of all patients treated H&N for within our institution over a five year period.

NTCP model validation method for DAHANCA patient selection of protons versus photons in head and neck cancer radiotherapy

Introduction: Prediction models using logistic regression may perform poorly in external patient cohorts. However, there is a need to standardize and validate models for clinical use. The purpose of this project was to describe a method for validation of external NTCP models used for patient selection in the randomized trial of protons versus photons in head and neck cancer radiotherapy, DAHANCA 35. Material and methods: Organs at risk of 588 patients treated primarily with IMRT in the randomized controlled DAHANCA19 trial were retrospectively contoured according to recent international recommendations. Dose metrics were extracted using MatLab and all clinical parameters were retrieved from the DAHANCA database. The model proposed by Christianen et al. to predict physician-rated dysphagia was validated through the closed testing, where change of the model intercept, slope and individual beta's were tested for significant prediction improvements. Results: Six months prevalence of dysphagia in the validation cohort was 33%. The closed testing procedure for physician-rated dysphagia showed that the Christianen et al. model needed an intercept refitting for the best match for the Danish patients. The intercept update increased the risk of dysphagia for the validation cohort by 7.9 ± 2.5% point. For the raw model performance, the Brier score (mean squared residual) was 0.467, which improved significantly with a new intercept to 0.415. Conclusions: The previously published Dutch dysphagia model needed an intercept update to match the Danish patient cohort. The implementation of a closed testing procedure on the current validation cohort allows quick and efficient validation of external NTCP models for patient selection in the future.

Osteoradionecrosis of the mandible after radiotherapy for head and neck cancer: risk factors and dose-volume correlations

Background: The project aimed at determining the incidence of mandibular osteoradionecrosis (ORN) after radiotherapy, possible risk factors, and mandibular dose-volume effects in a large cohort of head and neck cancer patients (HNC). Methods: The cohort consisted of 1224 HNC patients treated with 66-68 Gy in 2007-2015 predominantly with IMRT. ORN cases were defined from clinical observations at follow-up and through hospital code diagnostics after oral-maxillofacial surgery and cross-checked with the national Danish Head and Neck Cancer database. In a nested case-control study, patients with ORN cases were matched with two controls (1:2) and pre-RT dental procedures including surgery to the mandible were documented. Multivariable Cox regression analysis was applied using demographic and treatment variables including dental procedures, smoking and tumor characteristics, and combined with dosimetric data. Mean mandibular dose (D_mean) was pre-selected for the multivariable model. Results: ORN was recorded in 56 cases (4.6%) with a median time to event of 10.9 months (range 1.8-89.7) after RT, 90% occurred within 37.4 months. Median follow-up time was 22 months (0.3-95). Average D_mean was significantly higher in the ORN event cohort and significant dose-volume differences were observed for population mean DVH doses between 30 Gy and 60 Gy. In univariable analysis, smoking (HR = 1.69; CI 1.14-2.5), pre-RT surgery/tooth extraction (HR = 2.76; 1.48-5.14), and several dosimetric parameters including D_mean (HR = 1.05, 1.02-1.08) were all significantly associated with ORN. D_mean and surgery/tooth extraction remained significant predictors of ORN in multivariable analysis, HR = 1.04 (CI 1.01-1.07) and HR = 2.09 (CI 1.1-3.98), respectively, while smoking only retained its significance in an interaction analysis with pre-RT dental procedures. Conclusion: The onset of ORN of the mandible was early (median 10.8 months) and the incidence low (4.6%) after IMRT in HNC cancer patients. Surgery to the mandible and pre-RT tooth extraction, tobacco smoking, and treatment dose were associated with the development of ORN.