Recognized causes of hypocobalaminaemia in dogs include dietary deficiency, exocrine pancreatic insufficiency and infiltrative or inflammatory disease of the distal small intestine. We hypothesized that low serum cobalamin concentrations in dogs with lymphoma may reflect intestinal involvement, and may negatively influence patient survival.

Serum cobalamin concentrations were measured by an automated chemiluminescence assay in 58 dogs newly diagnosed with multicentric lymphoma, prior to the initiation of chemotherapy. In all cases, the diagnosis was established by cytological or histopathological examination of affected tissues. In addition, all dogs underwent staging, and were categorized based on WHO standards. Survival times for patients undergoing treatment with a VELCAP protocol were calculated from the day of diagnosis, and the end point of the study was established at 60 days.

Median serum cobalamin concentration was 401 ng/L with a range of <150 ng/L (lower limit of the working range of the assay) to 1813 ng/L. Results of <150 ng/L were assumed to be 149 ng/L for statistical purposes. Of the 58 dogs, 9 (16%) had serum cobalamin concentrations below the established normal range of 252-908 ng/ L. Survival data for these individuals was compared to dogs with serum cobalamin >252 ng/L.

All of the hypocobalaminaemic patients underwent chemotherapy, but only 3 (33%) reached the study end-point of 60 days. Of the six dogs (67%) that died or were euthanized before the end-point, the average survival time was 23 days. Survival data was available for 43 dogs with serum cobalamin concentration >252 ng/L before starting chemotherapy. Of these, 40 (91%) reached the end-point, while 4 (9%) died before the study completion date (P<0.001).

These findings indicate that although hypocobalaminaemia is uncommon in dogs with lymphoma, a subnormal serum cobalamin concentration does appear to predict a poor response. Most likely, this is due to infiltration of the small intestine (stage V lymphoma), but alternatively, a subnormal serum cobalamin concentration may directly impact patient response to treatment. Whether or not cobalamin supplementation has an impact on treatment outcome remains to be determined. These results would suggest that serum cobalamin concentrations should be measured in dogs diagnosed with multicentric lymphoma.