Background: Breast cancer is the most common invasive malignancy which occurs in women worldwide. The advent of neoadjuvant chemotherapy has radically changed the management of locally advanced breast cancer and a complete response is reported to significantly improve disease free survival. Traditionally, clinical response is assessed on basis of tumour size. In this study, an attempt was made to check whether tumour cellularity could be a better prognostic factor and also to check as to what impact the correlation of tumour size with cellularity had on the response assessment in locally advanced breast cancer patients.

Materials and Methods: Thirty seven patients with locally advanced breast cancer, who were treated by neoadjuvant chemotherapy during the period of December 2008 to May 2009, were selected for the study and from their case records, tumour size, clinical response and demographic details were gathered. Tumour cellularity was assessed prior to chemotherapy in core needle biopsy sections and it was matched with that seen in subsequent mastectomy specimens. Tumour size and cellularity were then correlated with the different treatment response groups and they were statistically analyzed by using the SPSS, version 13.0 software.

Results: After neoadjuvant chemotherapy, the tumour size and cellularity were found to be significantly reduced in breast carcinomas (p< 0.05, paired t-test). The relative changes in cellularity which were seen were highly variable between individual patients and different clinical response groups, particularly in the partial response and no response categories. The product of cellularity and size dramatically changed the distribution of residual tumour pathology, thus causing a shift towards a complete response.

Conclusion: The current study showed that the product of tumour size and cellularity may be a better prognostic indicator of clinical response in patients with neoadjuvant chemotherapy treated locally advanced breast cancer and that it would enable a new definition for clinical response in the future.