Lymphocyte Depletion in Breast Cancer Patients Receiving Adjuvant Dose-Dense Chemotherapy.

Background: Dose-intense chemotherapy regimens are reportedly known to cause lymphocyte depletion. Increased incidence of pneumocystis carinii pneumonia (PCP) was reported in patients with diffuse large B-cell lymphoma treated with dose-dense CHOP plus rituximab. No studies have been conducted to date to assess the lymphocyte depletion in breast cancer patients receiving dose-dense chemotherapy. We retrospectively compared the lymphocyte recovery in breast cancer patients treated with dose-dense (q 2 weekly) doxorubicin/cyclophosphamide (AC) to those treated with AC in a non-dose-dense (q 3 weekly) method.

Methods: Newly diagnosed breast cancer patients treated at our institution between 2002 and 2006, with at least 4 cycles of AC in an adjuvant/neoadjuvant setting were analyzed. Complete blood count (CBC) with differential including white blood cells (WBC), hemoglobin (Hg), platelets, neutrophils, lymphocytes, monocytes, eosinophils and basophils were collected at baseline before the start of chemotherapy, before each ensuing cycle of chemotherapy and after the 4^th cycle of chemotherapy.

Results: A total of 103 patients were analyzed of which 50 patients were treated with dose-dense AC and 53 patients with non-dose-dense AC. After the 4^th cycle of chemotherapy, mean absolute lymphocyte count (ALC) was 780 ± 440/mm³ in the dose-dense group versus 950 ± 600/mm³ in the non-dose-dense group (p = .4617), mean Hg was 11.4 ± 1.2g/dL in the dose-dense group versus 12.2 ± 0.9g/dL in the non-dose-dense group, mean platelet count was 241 ± 85 x10⁹/L in the dose-dense group versus 391 ± 128 x10⁹/L in the non-dose-dense group. No opportunistic infections were noted in the dose-dense group.

Conclusions: These results demonstrate that dose-dense AC results in slightly increased lymphocyte depletion compared to non-dose-dense AC, not statistically significant. This didn’t result in any increased infectious complications. In both groups, baseline ALC was significantly positively related to ALC after the 4^th cycle of chemotherapy (p < 0.0001). Dose-dense AC did result in statistically significant platelet depletion.