Evaluation of adjuvant doxorubicin-based chemotherapy for the treatment of feline mammary carcinoma.

Feline mammary carcinomas (FMC) are locally invasive and highly metastatic tumors. Because of the high metastatic potential, patients often are treated with adjuvant doxorubicin-based chemotherapy, but little data exist to evaluate the effect of this strategy. Adjuvant doxorubicin-based chemotherapy improves outcome for FMC compared with surgery alone. Cats with naturally occurring, biopsy-confirmed FMC treated with either surgery alone (Sx) or with surgery plus adjuvant doxorubicin-based chemotherapy (Sx + Chemo). Retrospective cohort study. Clinical data were collected and compared to identify differences between groups. Outcome results were determined and compared. Prognostic factors for disease-free survival (DFS) and overall survival were evaluated. Seventy-three cats were evaluated, of which 37 were in the Sx group and 36 in the Sx + Chemo group. No differences in clinical data were found between Sx and Sx + Chemo groups. Median DFS times for the Sx and Sx + Chemo groups were 372 and 676 days, respectively (P = .15) and median survival times (ST) were 1,406 and 848 days, respectively (P = .78). For cats that underwent a unilateral radical mastectomy, ST was significantly longer for the Sx + Chemo compared with the Sx group (1,998 versus 414 days, respectively; P = .03). This study did not find a benefit to adjuvant doxorubicin-based chemotherapy in cats with FMC. Additional studies are required to determine whether patient subgroups with negative prognostic factors may benefit from adjuvant chemotherapy.