Assessment of influence of dose variation on the effectiveness and toxicity of cytostatic therapy of disseminated breast cancer

: Main indices of efficacy such as objective response and stabilization frequency, objective response median and survival rate were evaluated in 84 patients with disseminated breast cancer receiving different doses of cytostatics: high-dose chemotherapy (HDC) plus transplantation of peripheral blood stem cells, standard-dose (SDC), dose reduced by 20% (RDC20) or by 50% (RDC50). There was an inverse correlation between complete+partial response frequency, on the one hand, and dosage, on the other: highest dose--70% and lowest dose--11.1%. Objective response median in both groups was pretty close--8.5 +/- 5.5 and 5 +/- 0.4% months, respectively. The lowering of dose involved a higher risk of tumor progression from 15% after HDC, 46.6%--SDC and 44.4%--RDC20 to 61.1% after RDC50, with likelihood of objective response decreasing. Nether median nor mean survival rates depended on dosage, nor the difference was significant (p = 0.72). Hence, adequate dose proved to be an important factor, as far as treatment efficacy is concerned. Escalation to high dose was followed by an increase in objective response rates to 70%, SDC - 35.7%, RDC20--33.4% and RDC50--11.1%. Yet, nether dose escalation nor dose reduction involved significant variation in survival (p = 0.72).