For the segmentation task, the ground truth is based on human annotations of GTVp and GTVn. The contours were manually delineated by an annotator and cross checked by another. Precise contouring guidelines were elaborated to ensure the unification of all annotations. However, it is important to note that the delineation made according to guidelines can lead to a discrepancy between the TNM staging and the presence of GTVn. For instance, it can happen that a patient has an N-stage of 0 but still has contoured GTVns.
Primary tumor delineation guidelines (GTVp)
Oropharyngeal lesions are contoured on PET/CT using information from PET and unenhanced CT acquisitions. The contouring includes the entire edges of the morphologic anomaly as depicted on unenhanced CT (mainly visualized as a mass effect) and the corresponding hypermetabolic volume, using PET acquisition, unenhanced CT and PET/CT fusion visualizations based on automatic co-registration.
The contouring excludes the hypermetabolic activity projecting outside the physical limits of the lesion (for example in the lumen of the airway or on the bony structures with no morphologic evidence of local invasion).
Standardized nomenclature according to AAPM TG-263: GTVp.
Check clinical nodal category to make sure nearby FDG-avid and/or enlarged lymph nodes (e.g. submandibular, high level II, and retropharyngeal) are excluded. In case of tonsillar fossa or base of tongue fullness/enlargement without corresponding FDG avidity, clinical data was reviewed to rule out pre-radiation tonsillectomy or extensive biopsy. If so, the case was excluded.
When more than one volume (rare): GTVt1, GTVt2, …
When none (5% of cases [Kennel et al. 2019]), no region should be created.
Metastatic lymph nodes delineation guidelines (GTVn)
Lymph nodes are contoured on PET/CT using information from PET and unenhanced CT acquisitions. The contouring includes the entire edges of the morphologic lymphadenopathy as depicted on unenhanced CT and the corresponding hypermetabolic volume, using PET acquisition, unenhanced CT and PET/CT fusion visualizations based on automatic co-registration for all cervical lymph node levels .
Standardized nomenclature for lymph node *ROI: GTVn.
The contouring excludes the hypermetabolic activity projecting outside the physical limits of the lesion (for example on the bordering bony, muscular or vascular structures).
When more than one: GTVn01, GTVn02, ... or all contours in a single label GTVn
When none, no region should be created.
Limit on size and SUV:
Pathologically confirmed OR SUV>2.5 OR diameter >=1cm, irrespective of the number of nodes.
Separation of GTVns:
If several GTVns are “merged”/”touch”: keep one structure with all of them.
GTVn and GTVp must be separated.
For the outcome prediction task, the selected clinical endpoint is Recurrence-Free Survival (RFS), defined as time without any recurrence, censoring all others, including deaths. In particular, local, regional, and distant mets are events and all others are censored. Time to event, defined in days, starts with the end of radiation therapy.
All patients get curative treatment and live with no cancer till recurrence. This differs from the HECKTOR 2021 edition, where Progression Free Survival (PFS) was used. PFS is more relevant to treatment of metastatic disease since the National Cancer Institute (NCI) definition of PFS is the length of time during and after the treatment that a patient lives with the disease but it does not get worse (i.e. regression or stable disease). Therefore, we decided to target RFS in this HECKTOR 2022 edition.