Background: Laboratory evidence suggests that many anticancer agents exert their effect by altering the ratio between apoptosis and cellular proliferation. The objective of this clinical study was to examine in vivo changes in apoptotic index (AI), Bcl-2 expression, proliferation (Ki-67 and S-phase fraction [SPF]), and ploidy as potential indicators of chemoresponsiveness.
Methods: Twenty-eight women with primary operable breast carcinoma received 2M (mitoxantrone 11 mg/m2, methotrexate 35 mg/m2 every 3 weeks) for 4 cycles before surgery/radiotherapy, and an additional 2 cycles were given after surgery. Clinical response was assessed after four cycles of treatment according to World Health Organization criteria. Changes in molecular markers were assessed from biopsies obtained by fine-needle aspiration performed before treatment, repeated after 24 and/or 72 hours (T1), and on Days 7 and 21 after the first cycle of chemotherapy. Flow cytometric analysis was used to assess SPF, ploidy, and AI (in situ DNA nick end labeling assay) whereas Ki-67 and Bcl-2 were evaluated by immunocytochemical analysis.
Results: The overall response rate was 61% (17 of 28 patients), with a 14% (4 of 28 patients) complete response rate. Patients with diploid carcinomas (P = 0.04) with high Ki-67 (P = 0.0001) and SPF (P = 0.09) were more likely to respond to treatment. Median AI increased by 3.4% with interquartile (IQ) range of 3.2 in responders, compared with only -0.1% (IQ range, 2.2) in nonresponders at T1 (P = 0.03). Median Ki-67 decreased by -12.0% (IQ range, 22.9) in responders and increased by 18.5% (IQ range, 15.1) in nonresponders on Day 21 (P = 0.003). Median Bcl-2 scores increased by 1.0 (IQ range, 4.0) in responders and were unchanged at 0.0 (IQ range, 0.5) in nonresponders (P = 0.08). Changes in SPF or ploidy were not significantly predictive of response.
Conclusions: The results of this preliminary study support evidence that chemotherapy may increase apoptosis, decrease Ki-67, and increase Bcl-2 expression in primary breast carcinomas that subsequently respond to therapy. Methodology allowing morphological confirmation of apoptosis would be advantageous.