MRI and hybrid PET/CT for monitoring tumour metastasis in a metastatic breast cancer model in rabbit.

Objective: To study tumour growth and metastasis in a rabbit metastatic breast cancer (MBC) model and find the most sensitive screening modality in monitoring tumour metastasis.

Methods: The MBC model was established by injecting a VX2 tumour mass suspension into the mammary glands of 23 rabbits and was monitored by using physical examination, X-ray, MRI and hybrid PET/CT.

Results: Of all 23 rabbits, axillary lymph node metastasis was detected in 21 (91%) at day 33 after tumour inoculation, mediastinal node metastasis in five (22%) at day 42, abdominal node metastasis in two (9%) at day 48, lung metastasis in six (26%) at day 39, liver metastasis in three (13%) at day 48, and lumbar spine metastasis in one (4%) at day 51. Tumour invasion of pleura was found in one, stomach wall in one, and pleura and stomach concurrently in one rabbit. Sensitivity for detection of lymph node metastases was 78.6% (22/28) and 67.9% (19/28) with MRI and PET/CT, respectively; and sensitivity for detection of metastases in distant organs was 85.7% (12/14) and 71.4% (10/14), respectively.

Conclusions: The MBC model used here exhibits fast tumour growth and extensive metastasis in a relatively short period. Its metastatic pattern is quite similar to that of human MBC and hence could be potentially used as a model for testing imaging modalities and translational research, e.g., MBC management. MRI is superior to PET/CT in monitoring tumour metastasis.