Is reseeding from the primary a plausible cause of node failure?

Area of Science:

• Oncology
• Radiation Oncology
• Head and Neck Cancers

Background:

• Previous analyses excluded patients with node recurrence linked to primary failure or low radiotherapy doses (<55 Gy).
• This exclusion significantly reduced the observed rate of node failures, potentially skewing results.

Purpose of the Study:

• To re-evaluate nodal failure in oropharyngeal and pharyngolaryngeal squamous cell carcinomas by including all patients.
• To determine factors influencing nodal failure and the impact of excluding low-dose treatments.

Main Methods:

• Analysis of 1251 patients with node-positive oropharyngeal and pharyngolaryngeal squamous cell carcinomas treated with external radiotherapy.
• Inclusion of all patients, regardless of primary failure association or received dose, for comprehensive analysis.

Main Results:

• When all patients were included, nodal failure probability increased with larger nodes, T4 primaries, lower nodal doses, contralateral metastases, and nodal fixation.
• A significant dose-control relationship was lost when low-dose treatments (<55 Gy) were excluded.
• 60% of node recurrences associated with primary failure occurred within one month post-irradiation, suggesting they were not from primary tumor reseeding.

Conclusions:

• The majority of nodal failures are unlikely to originate from primary tumor reseeding and should be included in local-control analyses.
• Excluding palliative, low-dose treatments hinders the understanding of dose-response relationships in radiotherapy for head and neck cancers.