# Combining radiological and radiation oncology expertise in the delineation of hypopharyngeal tumours: potential effects on treatment volumes and patterns of failure

## TL;DR

Working together, radiologists and oncologists can more accurately define cancer volumes for treatment, potentially reducing side effects.

## Contribution

The study shows that radiologists improve tumor volume delineation in hypopharyngeal cancer radiotherapy planning.

## Key findings

- Gross tumor volume (GTV) decreased by 47% with radiologist involvement.
- Only 39% of original GTV and 19% of lymph node GTV were considered acceptable.
- 3-year and 5-year locoregional progression-free survival rates were 75.5% and 66.6%.

## Abstract

•A collaboration between a radiologist and a radiation oncologist is feasible when delineating tumour and target volumes.•There is a reduction of GTV volumes when a radiologist is included in defining the target for hypopharyngeal cancers.•A low concordance between the original and the new GTVp and GTVn, indicates a significant impact of the radiologist.

A collaboration between a radiologist and a radiation oncologist is feasible when delineating tumour and target volumes.

There is a reduction of GTV volumes when a radiologist is included in defining the target for hypopharyngeal cancers.

A low concordance between the original and the new GTVp and GTVn, indicates a significant impact of the radiologist.

Target definition is one of the greatest uncertainties in the radiotherapy process. We aimed to investigate whether a radiologist specialized in head and neck can improve the target definition of hypopharyngeal cancers.

We retrospectively identified 54 patients with hypopharyngeal cancer who received curative-intent radiotherapy between 2009–2015. New target structures were defined incorporating head and neck radiology expertise and updated delineation guidelines. The new structures were subsequently compared both quantitively and qualitatively to the original delineations. Loco-regional failures were analyzed in relation to radiotherapy dose and target volumes.

There was a significant reduction in gross tumour volume (GTV) for the primary tumour, decreasing from 14.4 to 9.2 cm3 (−47 %), and in clinical target volume (CTV), decreasing from 203.7 to 93.8 cm3 (−54 %). Mean quantitative values indicated a large overestimation of the original GTV (Dice Coefficient 0.58 ± 0.2 SD, Jaccard index 0.44 ± 0.19 SD, Positive predictive value 0.53 ± 0.24 SD). Only 39 % of the original primary tumour GTV and 19 % of the original lymph node GTV were assessed as acceptable. Twelve patients (22 %) had a locoregional recurrence. In relation to both the original radiation dose and the updated dose distribution, nine recurrences were classified as in field, two as marginal, and one could not be evaluated. The 3-year and 5-year locoregional progression free survival (PFS) was 75.5 % and 66.6 % respectively.

Incorporating radiological expertise in the delineation of hypopharyngeal tumours leads to large changes in tumour volumes and possibly a decrease in radiation volumes which may lead to reduced side effects.