Planned neck dissection following radiation treatment for head and neck malignancy

Correlation of tumour and treatment characteristics to dose received by cochlea in volumetric arc therapy

PURPOSE

This is a radiation field simulation study using CT images designed to see the cochlear dosimetry and its correlation with tumour and treatment characteristics during radiotherapy for head and neck cancers (HNC) for identifying the factors associated with a higher dose delivered to the cochlea.

METHODS

From 2018 to 2020, 80 patients with HNC underwent volumetric arc therapy (VMAT) to a dose of 66-70 Gy at 2 Gy per fraction with bilateral cochlea contoured for VMAT optimization as an organ at risk. Minimum, mean and maximum planned radiation dose to the cochlea based on tumour and treatment characteristics and dose-volume histogram variables of VMAT plans were analysed.

RESULTS

Mean (standard deviation, SD) cochlear volume was 0.14 (0.06) cm³ with maximum and mean planned doses of 10.3 (SD = 11.6) Gy and 8.5 (SD = 9.8) Gy, respectively. We found a statistically significant correlation between mean dose received by bilateral cochlea (P-0.000, r_right-0.84, r_left-0.78, r_midline-0.92). Tumours of the paranasal sinuses, and the parotids and more advanced T stages were associated with a higher mean dose to cochlea but was not significant statistically. The dose received by the 95% target nodal volume (D_95%) showed a significant correlation with the cochlear mean dose (P-0.000, r_right-0.85, r_left-0.77, r_midline-0.93) CONCLUSION: With VMAT we have achieved a better sparing of cochlea. The mean dose to the cochlea of one side significantly differed from the other side in patients with lateralized cancers. D_95% of nodal volume also showed a significant correlation with the cochlear mean dose.

Less may be more: nodal treatment in neck positive head neck cancer patients

Ongoing debates about the need and extent of planned neck dissection (PND), and required nodal radiation doses volumes lead to this evaluation. Aim was to assess nodal control after definitive intensity modulated radiation therapy (IMRT ± systemic therapy) followed by PND in our head neck cancer cohort with advanced nodal disease. Between 01/2005 and 12/2013, 99 squamous cell cancer HNC patients with pre-therapeutic nodal metastasis ≥3 cm were treated with definitive IMRT followed by PND. In addition, outcome in 103 patients with nodal relapse after IMRT and observation only (no-PND cohort) were analyzed. Prior to PND, PET-CT, fine needle aspirations, ultrasound and palpation were assessed regarding its predictive value. Patterns of nodal relapse were assessed in patients with isolated neck failure after definitive IMRT alone. 70/99 (70 %) PND specimens showed histopathological complete response (hCR), which translated into statistically significantly superior survival compared with partial response (hPR) with 4-year overall survival, disease specific survival and nodal control rates of 90/83/96 vs 67/60/78 % (p = 0.002/0.001/0.003). 1/99 patient developed isolated subsequent nodal disease. 64/2147 removed nodes contained viable tumor (3 %). Predictive information of the performed diagnostic investigations was not reliable. 17/70 hCR patients showed true negative findings in available three to four investigations (0/29 hPR). 27/103 no-PND patients developed isolated neck disease (26 %) with successful salvage in 21/24 [88 %, or 21/27 (78 %)]. Nearly all failures occurred in the prior nodal gross tumor volume area. A more restrictive approach regarding PND and/or nodal IMRT dose-volumes may be justified.