We have focused on three aspects of
adjuvant chemotherapy applied to mice with one of the metastasizing
tumors:
Lewis lung carcinoma (LL) or mammary
carcinoma 2661 (M2661). The first aspect concerned the timing of
adjuvant chemotherapy. To investigate this,
tumor-bearing mice were treated postoperatively with
cyclophosphamide using a standard regimen. In M2661, adjuvant
therapy was marginally effective in contrast to the clearly significant results obtained in LL. Any delay in the initiation of adjuvant
therapy decreased the efficacy of the treatment. The effect of administering
chemotherapy before surgery was also studied; normally, marginally effective adjuvant
therapy was found to become effective when started preoperatively in M2661. In LL, effective adjuvant
therapy was found to become less effective when started preoperatively. The second aspect considered was the comparability between the increase in relapse-free survival time and the increase in cure rate as alternate goals of adjuvant
therapy. To study this, mice with small, medium, or large
residual tumor loads were subjected to surgery and subsequently treated with
cyclophosphamide. While the effect of adjuvant
therapy on the cure rate increased proportionally with decreasing
tumor load, the increase in lifespan in nonsurvivors was not related to
tumor load. The final aspect of study was the selection procedure for drugs to be applied in adjuvant treatment in our models. Taking the volume response of large
tumors as being predictive for the successful use of the same agent in adjuvant
therapy, we obtained both false-negative and false-positive results in our
tumor lines.