Lung metastases after curative or noncurative irradiation of microscopic primary melanomas

Sentinel lymph node metastasis in experimental melanoma: relationships among primary tumor size, lymphatic vessel diameter and 99mTc-labeled human serum albumin clearance

BACKGROUND

This study was designed to investigate the relationships among primary tumor size, lymphatic vessel diameters, the incidence of sentinel lymph node (SLN) metastasis and lymphatic clearance from murine footpad melanomas.

METHODS

Lymphatic clearance (LC) of [99mTc]HSA from the middle of the footpad of syngeneic C57BL/6 mice, with or without primary melanomas (sizes varying from 1 to 5 mm in anteroposterior diameter), was quantitated using a gamma scintillation detection system. Lymphatic vessel diameters (LD) were measured after injection of aniline blue dye into footpad tumors. The incidence of SLN, femoral lymph node (FLN), and lung metastases was recorded.

RESULTS

Metastasis to SLNs increased as tumor growth progressed (r = 0.976, p = 0.001), and there was a correlation between tumor size and both FLN (p = 0.041) and lung (p = 0.055) metastases. There was also a correlation between lymph node metastasis and LC (r = 0.83, p = 0.04) and LD (r = 0.84, p = 0.04).

CONCLUSIONS

These studies support the hypothesis that lymph flow and LD is increased in experimental murine melanomas and this relates to both primary tumor size and to lymphatic and hematogenous metastasis.

Spontaneous metastasis, proliferation characteristics and radiation sensitivity of fractionated irradiation recurrent and unirradiated human xenografts

PURPOSE

Do tumor cells which survive high dose fractionated irradiation exhibit modified metastasis activity, proliferation kinetics, and/or radiation sensitivity? To address this question experimentally, we have studied three recurrent human tumor xenograft systems.

METHODS AND MATERIALS

Three models were derived from a soft tissue sarcoma (HSTS26T), a colon adenocarcinoma (HCT15), and a glioblastoma (HGL21) which had recurred after 90 Gy, 109 Gy, or 77.4 Gy administered in 30 equal doses, respectively. Their production of spontaneous metastasis and cell proliferation characteristics were studied in early generation xenografts in SCID mice, and were compared to those in their previously unirradiated counterparts. As a control, we have also studied each tumor as a post-surgical recurrence. Specimens from the irradiated recurrent and their unirradiated primary tumors were cultured in vitro and their radiation sensitivity determined by clonogenic assay.

RESULTS

The three irradiated recurrent tumor systems retained the individual histological features of their unirradiated primary xenografts. A lower metastatic incidence was observed in two of the three irradiated recurrent tumor lines in comparison with their unirradiated control tumors and their surgical recurrent counterparts. No significant differences were found between the irradiated recurrent tumors and their unirradiated counterparts with respect to: volume doubling time, growth time, potential doubling time, mitotic index, PCNA index, and SF2 values.

CONCLUSIONS

High dose irradiation given in 30 fractions did not increase the metastatic activity in the three human tumor xenograft systems. Furthermore, the fractionated irradiation did not significantly change their proliferation characteristics and cellular radiation sensitivity.

Models of cell population in tumours and possibility of their application to optimization of radiotherapy

Two models of cell population in tumours are analyzed and used to explain some experiments on the influence of radiation on tumours. There is a proposal to remove disagreements between these models and experiments by the assumption that cells under the influence of a destructive factor may reduce their degree of differentiation.