Cancer odor in the blood of ovarian cancer patients: a retrospective study of detection by dogs during treatment, 3 and 6 months afterward

Background: In recent decades it has been noted that trained dogs can detect specific odor molecules emitted by cancer cells. We have shown that the same odor can also be detected in the patient's blood with high sensitivity and specificity by trained dogs. In the present study, we examined how the ability of dogs to detect this smell was affected by treatment to reduce tumor burden, including surgery and five courses of chemotherapy. Methods: In Series I, one drop of plasma from each of 42 ovarian cancer patients (taken between the fifth and sixth courses of chemotherapy) and 210 samples from healthy controls were examined by two trained dogs. All 42 patients in Series I had clinical complete responses, all except two had normal CA-125 values and all were declared healthy after primary treatment. In Series II, the dogs examined blood taken from a new subset of 10 patients at 3 and 6 months after the last (sixth) course of chemotherapy. Results: In Series I, the dogs showed high sensitivity (97%) and specificity (99%), for detecting viable cancer cells or molecular cancer markers in the patients' plasma. Indeed, 29 of 42 patients died within 5 years. In Series II, the dogs indicated positive samples from three of the 10 patients at both the 3- and 6-month follow-up. All three patients had recurrences, and two died 3-4 years after the end of treatment. This was one of the most important findings of this study. Seven patients were still alive in January 2013. Conclusions: Although our study was based on a limited number of selected patients, it clearly suggests that canine detection gave us a very good assessment of the prognosis of the study patients. Being able to detect a marker based on the specific cancer odor in the blood would enhance primary diagnosis and enable earlier relapse diagnosis, consequently increasing survival.