Exfoliative tumor clearance following radiotherapy estimated by comparing radioresponse between primary esophageal cancer and its lymph node metastasis.

Background/aims: We estimated the capacity for exfoliative mechanical clearance which could occur in shrinkage of esophageal tumors following radiotherapy; both mechanical clearance and phagocytotic biological clearance of another clearance mechanism could participate in primary diseases located on outer tissue surfaces, whereas only biological clearance can participate in lymph node metastases surrounded by normal tissues which prevent mechanical clearance.

Methodology: Twenty-one patients with primary esophageal cancer and lymph node metastasis both treated by radiotherapy with the same dose were reviewed. The extent of tumor shrinkage was estimated by measuring the size on computed tomography scans before and after radiotherapy. The capacity for biological clearance plus mechanical clearance (primary disease) or biological clearance alone (lymph node metastasis) was defined as the slope of a tumor shrinkage curve. The capacity for mechanical clearance was estimated by intra-patient subtraction.

Results: Extent of tumor shrinkage was consistently greater in primary disease than in lymph node metastasis for each patient, showing significant correlation in extent of shrinkage between them. The capacity was smaller for mechanical clearance than for biological clearance as a whole, showing no correlation between them.

Conclusions: Mechanical clearance is highly likely to participate extra in the shrinkage of tumors located on outer tissue surfaces; therefore, these tumors will normally respond more highly than parenchymal tumors.