TASK 1: Lesion Detection and Segmentation¶

The ground truth is based on human annotations of GTVp and GTVn for the segmentation task. The contours were manually delineated by an expert radiation oncologist and underwent quality control by a board of 4 experts (certified as both radiologists and/or nuclear medicine physicians) to ensure consistency across all datasets. Precise contouring guidelines were elaborated to ensure the unification of all annotations. In the HECKTOR 2025 edition, we will use a similar quality control methodology to ensure homogeneity and quality of contours across all centers.

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.

Special situations:

• 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.
• Clinical data was reviewed to rule out pre-radiation tonsillectomy or extensive biopsy in the case of the tonsillar fossa or base of tongue fullness/enlargement without corresponding FDG avidity. If so, the case was excluded.

ROI numbering:

• 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).

ROI numbering:

• 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.

TASK 2: Recurrence-Free Survival Prediction¶

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 metastases are events and all others are censored. Time to event, defined in days, starts with the end of radiation therapy.

All patients receive curative treatment and live with no cancer until recurrence. For the HECKTOR 2025 edition, this task is expanded by providing updated clinical information (especially improving completeness) and dose maps (+ dosimetry CT) of the radiotherapy planning as an added information channel to include in the prediction models, for an estimated subset of 650 patients.

TASK 3: HPV Status Diagnosis¶

For the diagnostic task (new in HECKTOR 2025), the selected endpoint is the HPV status (positive or negative). HPV status is highly clinically relevant as it is a major prognostic factor in oropharyngeal cancer. HPV-positive tumors generally have better outcomes than HPV-negative ones, which may lead to different treatment approaches.

The ground truth HPV status was determined through clinical testing (either p16 immunohistochemistry or HPV DNA testing) as documented in patient records. This task aims to develop models to predict HPV status from imaging and available clinical data, potentially avoiding invasive biopsy procedures.

The test set is estimated to consist of 80% HPV-positive cases and 20% HPV-negative cases, reflecting the current epidemiological distribution.

REFERENCES¶

[Kennel et al. 2019] Kennel T, et al. "Head and neck carcinoma of unknown primary", European Annals of Otorhinolaryngology, Head and Neck Diseases, 136(3): 185-192 (2019).