A Prospective Randomized Phase 2 Study of Dose and Volume De-escalation Radiotherapy With Sentinel Lymph Nodes Mapping for Contralateral Irradiation in Unilaterally Node Positive Head and Neck Squamous Cell Carcinomas (SEMIRAHN)

The risk of lymph drainage to the contralateral side of the neck is limited to maximum 50% of the patients. Moreover, the risk of occult metastases lies between 20 and 40%. As a consequence, the rule of irradiating the contralateral neck with a prophylactic intent ("elective nodal irradiation") in nearly all HNSCC patients roughly doubles the irradiated volume and, hence, increases the risk of developing more frequent and more severe acute and late side effects. The use of sentinel lymph node mapping to assess the contralateral side of the neck should help to determine the individual drainage to the contralateral side of the neck and, in case of drainage, determine which nodes need to be irradiated. The ultimate goal is to reduce the volume irradiated at prophylactic dose to decrease the risk of severe late side effects (volume de-escalation strategy). This strategy is proposed based on the recent completion of a similar study led by the coordinating investigator, together with the head and neck team of the CHU-UCL-Namur, in HNSCC patients without macroscopic nodes in the neck and treated with (chemo)radiotherapy. It was shown that sentinel lymph node mapping helped to safely individualize and de-escalate the elective nodal irradiation volume and significantly reduce the risk of severe late side effects. Anyway, it is unknown if the whole sub-region of the neck containing the sentinel lymph node(s) or the node(s) only should be defined as target volume.

Moreover, the dose used nowadays for elective nodal irradiation, i.e. 50 Gy in fractions of 2 Gy or biologically equivalent, dates back from the 70's. Many arguments (a.o. our better capacity to stage the neck with 3D imaging and the use of concomitant chemotherapy in the majority of node-positive HNSCC) are in favour of dose de-escalation. A multicentric randomized study performed in 100 HNSCC recently showed that the elective dose could be reduced to 40 Gy in fractions of 2 Gy or biologically equivalent, helping to reduce the risk of late dysphagia at 6 months post-radiotherapy. Confirmatory studies need to be performed on larger groups of patients.

The primary aim is to evaluate contralateral regional control (cRC) rate at 2 years in head and neck squamous cell carcinomas (HNSCC) of the oral cavity, oropharynx, larynx or hypopharynx with positive nodes on only one side of the neck and no distant metastasis treated by (chemo)radiotherapy applying a dose- and/or volume de-escalation.