Challenges of delineation of hypopharyngeal tumors
PO-1199
Abstract
Challenges of delineation of hypopharyngeal tumors
Authors: Ellen Rylander1, Gabriella Alexandersson von Döbeln2, Eva Onjukka3, Sara Jonmarker Jaraj4, Mattias Hedman5
1Karolinska University Hospital, Karolinska Comprehensive Cancer Center, Stockholm, Sweden; 2Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Stockholm, Sweden; 3Karolinska University Hospital, Department of Medical Radiation Physics and Nuclear Medicine, Stockholm, Sweden; 4Karolinska University Hospital, Department of Neuroradiology, Stockholm, Sweden; 5Karolinska University Hospital, Department of Radiation Oncology, Stockholm, Sweden
Show Affiliations
Hide Affiliations
Purpose or Objective
Delineation of hypopharyngeal tumors has traditionally been carried out by a radiation oncologist at our institution. We hypothesized that radiologist consultation can improve the accuracy of delineation.
Material and Methods
54 patients were included in a retrospective single-center study of all patients with hypopharyngeal cancer treated with definitive radiotherapy with or without concomitant and/or induction chemotherapy between 2009 and 2015.
Blinded for the original delineation of the gross tumor volume (GTV) and the clinical target volume (CTV) a radiation oncologist and a head and neck radiologist defined new GTVs with guidance from diagnostic radiology. New CTVs were defined by the oncologist and peer reviewed by a second radiation oncologist using current guidelines. Qualitative and quantitative analyses comparing the original and new target delineations were performed. The qualitative measure consisted of a four grade scale while the quantitative measures considered were sensitivity and positive predictive value, using the updated volumes as reference. The agreement between the quantitative- and qualitative measures, respectively, was assessed in a Spearman correlation analysis.
Results
The median volume of all new targets decreased after re-delineation (primary GTV (GTVp) from 17.4 to 9.2 cc, lymph node GTV (GTVn) from 11.0 to 9.8 cc and CTV from 203.7 to 93.8 cc). In the overlap analyses the mean positive predictive values +/-SD were 0.53 +/-0.24 (GTVp) and 0.61 +/-0.30 (GTVn) meaning that 53% and 61% of the GTVs in the original delineation consisted of the updated GTVs. This indicates a large overestimation of the original GTV. The mean sensitivity values +/- SD were 0.73 +/-0.19 (GTVp) and 0.63 +/-0.24 (GTVn) which means that 73% and 63% of the updated GTVs were included in the original delineation. Qualitatively, 21 (39%) and 10 (19%) of the original GTVp and GTVn, respectively, were considered acceptable. The sensitivity score for GTVp correlated with the qualitative measure, but the other quantitative measures did not correlate with the qualitative.
Conclusion
Incorporating radiological expertise in the delineation of hypopharyngeal tumors may reduce the risk of overestimating the GTV and the CTV and thereby irradiation of healthy tissues. Furthermore, it might reduce the risk of missing the target.