Surgical adjuvant chemotherapy: results with one short course with cyclophosphamide after mastectomy for breast cancer.
One single six-day course with cyclophosphamide (total dose 30 mg/kg) was given immediately after mastectomy to 507 breast cancer patients, with 519 randomized controls receiving no adjuvant chemotherapy. The control group now has 234 recurrences and 196 deaths, and the treatment group 175 recurrences and 146 deaths. The differences of 59 recurrences and 50 deaths in favour of the treatment group are significant with p values less than 0.001 and less than 0.01 respectively. The differences in recurrence rates increased gradually, reached 10.71% four years after mastectomy (p less than 0.001), and remained at the same level for another 6 years. The differences in death rates increased until 6 years after mastectomy, and was 10.48% after 10 years. With this pattern, the mechanism is probably not a delay in onset of clinical recurrences, but a definite reduction of recurrence rates due to tumoricidal chemotherapy. Prognostic factors or menstrual state had apparently no influence on the effect of this type of adjuvant chemotherapy. Side effects were of short duration and very moderate. Since there was a good effect in the prognostically most favourable groups of patients, treatment of such cases seems therefore also justified. The same chemotherapy course given 3 weeks after mastectomy seemed without effect.