Tumour-related changes in natural killer cell activity in melanoma patients. Influence of stage of disease, tumour thickness and age of patients.

The influence of tumour growth on the natural killer (NK) activity of melanoma patients was examined by analysis of NK activity in 51Cr release assays before and at intervals after surgical removal of localized melanoma. In patients with Stage I and II melanoma, removal of the tumour was associated with changes in the level of NK activity which were not detected in patients who had surgery for skin graft after previous removal of the primary melanoma. The changes in NK activity after removal of melanoma were however different in patients with Stage I compared to Stage II melanoma. In the former, NK activity which appeared specifically directed toward melanoma cells was maximal 2-4 weeks after removal of the tumour and then decreased to normal levels. The NK activity after surgery was directly related to the thickness of the tumour. In patients with Stage II melanoma, NK activity did not increase but fell to low levels after removal of the tumour. The level of NK activity in these patients was not related to the thickness of their primary melanoma. In patients with Stage I and II melanoma the NK activity against melanoma cells showed a significant increase with age. The reason for the different sequence of changes in NK activity after removal of melanoma in the two patient groups is unknown. It is suggested however that the differences observed in patients with Stage II melanoma may reflect differences in the tumour or host response which contributed to the spread of the tumour to regional lymph nodes in these patients.