ESTRO38 Congress Report

1. DONALD HOLLYWOOD AWARD LECTURE

Stem cell sparing IMRT for head and neck cancer patients: a double-blind randomized controlled trial (E38-2054) R.J.H.M. Steenbakkers, M.A. Stokman, R.G.J. Kierkels, M.S.S. Schuurman, J.G.M. van den Hoek, H.P. Bijl, M. Dieters, R.P. Coppes, J.A. Langendijk, P. van Luijk

University Medical Centre Groningen, The Netherlands

Context of the study This study looks at new approach to spare organs at risk to limit the side effects of radiotherapy in patients with head and neck cancer. This new approach is to avoid stem cells in human parotid glands which are normally unintentionally irradiated during treatment of patients with head and neck cancer. In this way the function of the parotid glands might be preserved and the presence of dry mouth syndrome (xerostomia) might be minimized, which has a large impact on quality of life. Overview of abstract Head and neck cancer patients treated with radiotherapy often suffer from dry mouth syndrome (xerostomia). The main cause of xerostomia is the loss of function of the main salivary (parotid) glands, because they are often unintentionally irradiated. Critical for this radiation response are the parotid gland stem cells, which are mainly located in the main ducts. Reducing dose to these High Stem Cell Density (HSCD) regions may prevent xerostomia. This double-blind randomized controlled trial (RCT) aimed to determine the impact of dose reduction to the HSCD regions on parotid gland stimulated salivary flow and patient-rated xerostomia 12 months after treatment. What were the three main findings of your research? The study population was composed of 102 patients and were double-blind randomized in two arms. 54 were assigned to receive standard radiotherapy (arm 1) and 48 HSCD-sparing radiotherapy (arm 2), figure 1. HSCD region sparing significantly reduced the dose to the HSCD region (contralateral: 16.4 to 12.6 Gy (p = 0.007) for arm 1 and arm 2, respectively, and ipsilateral: 25.0 to 17.4 Gy (p = 0.005), respectively). Compared to baseline, salivary flowwas reduced with 16.8% and 8.5% (p = 0.621) for arm 1 and arm 2, respectively and patient-rated xerostomia was 50.0% and 45.9% (p = 0.720), respectively. Multivariate analysis showed that the mean (ipsilateral) HSCD region dose and baseline xerostomia (none vs. any) were the most important predictors for patient-rated xerostomia. Subset analysis on patients without baseline xerostomia (n = 57) showed that the rate of patient-rated xerostomia was markedly lower, i.e. 40.0% v. 23.8% (p = 0.253) in arm 1 and arm 2, respectively.

What impact could your research have? In this double-blind randomized controlled trial, stem cell sparing radiotherapy (IMRT) did not significantly improve salivary flow or reduce xerostomia 12 months after radiotherapy. However, the radiotherapy dose delivered to the parotid High Stem Cell Density (HSCD) region was the most important dosimetric predictor for xerostomia, suggesting that dose to the HSCD region is more important for the development of xerostomia than dose to the entire parotid gland. For this reason, this study suggests that sparing stem cells in organs at risk might be more beneficial than sparing whole organs at risk, which is the current practice in radiation oncology. Is this research indicative of a bigger trend in oncology? A general concept in radiation oncology is to radiate the tumour as much as possible, while avoiding organs at risk. Avoiding organs at risk is in practise difficult and still many patients suffer from (permanent) radiation induced side effects which have large impact on quality of life. This study suggests that sparing stem cells in organs at risk might reduce these side effects and gives opportunities for a new approaches for organ sparing radiotherapy techniques.

Congress report | AWARDS

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