ESTRO 2024 - Abstract Book

S138 ESTRO 2024 to eradicate microscopic disease around the GTV, and reducing the GTV to CTV margin should be explored in both HPV-positive and HPV-negative patients. However, validation in clinical trials addressing morbidity and quality of life outcomes is necessary. Nasopharyngeal cancer. A recent phase III trial examined reducing elective nodal coverage in nasopharyngeal carcinoma. Patients were randomized to receive either standard bilateral whole neck irradiation or selective upper neck irradiation. Both groups showed similar 3-year regional relapse-free survival rates. However, selective neck irradiation remains investigational, and further trials are required for confirmation before clinical application. Primary unknown. As biological knowledge and recurrence patterns have advanced, radiotherapy treatment for unknown primary of the head and neck (HNCUP) has increasingly adopted the philosophy of following a risk-adaptive radiation volume de-escalation approach in volume delineation. In a recent paper by Hamza Ghatasheh et al.( 2022), the CTV was defined according to pre-treatment clinical, radiological, pathological, and molecular risk features, with patients classified into 8 main categories. Testing this approach on 203 patients, the authors reported a high probability of tumor control with an acceptable rate of late toxicity in all subgroups ((Huang et al., 2017, Al-Mamgani et al., 2017) Invited Speaker

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Targeting the microbiota in cancer

Anne E Kiltie

University of Aberdeen, Rowett Institute/Aberdeen Cancer Centre, Aberdeen, United Kingdom

Abstract:

The most widely researched microbiota in the human body is the colonic microbiota (normal commensal microorganisms in the large intestine). This can be rapidly altered by changes to the diet. Dietary fibre is fermented by the bacteria in the colon to produce beneficial metabolites, including short chain fatty acids, including acetate, propionate and butyrate. These promote growth of other bacteria by ‘cross-feeding’ to produce more metabolites, and butyrate stimulates growth of normal colonic epithelial cells. Furthermore, the gut microbiota can influence anti tumour immunity, e.g. with immunotherapy. We have demonstrated in mice that various dietary fibres can slow tumour growth and increase tumour growth delay after ionising radiation.They can also reduce the damage to the small intestine from radiation in terms of increased regenerating crypts compared to a low fibre control in an intestinal crypt assay. Effects may result from their influence on the microbiota and/or be independent of the microbiota, and be immunologically- or non-immunologically mediated.

This means that dietary fibres can increase the radiotherapy therapeutic ratio 'in both directions’.

Placebo-controlled double-blind randomised clinical trials are needed to test the value of targeting the microbiota in cancer with specific dietary fibres. Attempts have been made in cancer patients to increase fibre intake from foods by altering the diet, but patients are reluctant to change to a high fibre diet at the time of being treated for a cancer. Therefore, taking fibre as a supplement is a more viable alternative, as this is more like taking a medicine.