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Cancer screening trial to evaluate the efficacy of FDG-PET in healthy subjects: 2-year results of the Hamamatsu Medical Imaging Center study.

1025 Background: Positron emission tomography with 18F-fluorodeoxyglucose (FDG-PET) is increasingly used for cancer screening in Japan. Although it is not rare that cancers at early stages are incidentally found on FDG-PET in usual clinical practice, it is still unknown whether FDG-PET is an effective tool for early detection of cancer and decrease of cancer death. To evaluate the efficacy of FDG-PET in cancer screening, we started a prospective study 2 years ago.


METHODS
From Aug 26 2003 to July 22 2004, 1197 healthy volunteers aged 35 years or older (46.7±7.7y.o.) participated in our cancer screening trial. They are supposed to undergo screening tests annually for 5 years and will be followed for years. The screening tests included whole-body FDG-PET, chest and abdominal CT, brain and pelvic MRI, tumor markers (CEA, CA19-9, SCC, PSA, CA125), and fecal occult blood test. From July 26 2004 to July 22 2005, 1158 subjects of the 1197 underwent the second screening a year after the first one. We made contact with 39 other subjects who skipped the second screening to check the occurrence of cancers.


RESULTS
In the 2-year period, primary cancers occurred in 19 subjects. Fifteen cancers (6 thyroid, 3 breast, 2 prostate, 3 lung, 1 ectopic thymus in thyroid grand) were detected on the first year and one (prostate) on the second year by the screening. Ten of the 16 were at stage I. Three subjects with negative findings at the screening developed gastric lymphoma, gastric cancer and malignant lymphoma of the kidney, respectively, within a year after the screening. FDG-PET was positive in 10 of 15 cancers (6 thyroid, 2 breast, 1 prostate and 1 ectopic thymus) on the first year. No PET positive cancer was found on the second year. Sensitivity of the screening tests as a whole and FDG-PET alone for the first year was 78.9% and 52.6%, respectively. Positive and negative predictive values and specificity of FDG-PET were 11.0% (10/91), 99.2% (1097/1106), and 93.1% (1097/1178), respectively.


CONCLUSIONS
Cancer screening including FDG-PET showed reasonable accuracy and could detect a wide variety of cancers at early stages. This prospective study will clarify the details of efficacy and suitable interval of FDG-PET in cancer screening. No significant financial relationships to disclose.