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Patients who undergo primary surgical resection for a Head and Neck Squamous Cell Carcinoma (HNSCC) are stratified post-operatively, based on the presence or absence of pathological risk factors for recurrence, to estimate their risk of treatment failure. Post-operative radiotherapy, with or without concurrent chemotherapy, is offered if there is a significant risk of recurrence, in order to eradicate potential microscopic residual cancer cells and ultimately improve loco-regional control and survival. This review will offer practical guidelines for delineation of the post-operative primary and nodal Clinical Target Volumes (CTVs) based on a geometric expansion of the pre-operative primary and nodal Gross Tumour Volumes (GTVs), as already implemented in the definitive radiotherapy setting. Nodal levels requiring elective treatment are defined for inclusion in the prophylactic CTV. Optimising patient selection for post-operative treatment is discussed as well as areas of controversy, relating to the dose prescription and extent of nodal volumes to be included in the CTV. Finally, clinical trials exploring the prospect of adjuvant treatment de-intensification after transoral surgery for HPV-positive oropharyngeal cancer are outlined. The aim is to improve consensus amongst clinicians and contribute towards improving outcomes for surgically treated patients with HNSCC.

Uranium in the deep sea The ratio of 234 U to 238 U in seawater underlies modern marine uranium-thorium geochronology, but it is difficult to establish the ratio precisely. Chen et al. report two 234 U/ 238 U records derived from deep-sea corals (see the Perspective by Yokoyama and Esat). The records reveal a number of important similarities to and differences from existing records of the past 30,000 years. Higher values during the most recent 10,000 years than during earlier glaciated conditions may reflect enhanced subglacial melting during deglaciation. Science , this issue p. 626 ; see also p. 550