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Hammersmith Hospital London W12 ONN, United Kingdom
In their article about positron emission tomography (PET) using FDG for recurrent ovarian cancer, Nakamoto et al. [1] have provided useful information on the technology's diagnostic and therapeutic efficacy. However, their report does not clarify the value of the test from the perspective of what has been called "patient outcome efficacy" [2]. In the setting interpreted by the authors as showing the most promising role for PET, namely, evidence of cancer recurrence on conventional criteria (group A), PET was, in retrospect, considered to have affected the treatment of five of 12 patients. To develop a case that such changes in treatment are of clinical value, it is also necessary to present data in terms of patient outcomes—principally, survival and quality of life. Unfortunately, the prognosis for patients with recurrent ovarian cancer has not improved in tandem with the technology available for its detection.
From an oncologist's perspective, the extent to which a change in timing of surgery for relapsed disease would justify the slight hazard, minor inconvenience, and substantial expense of a policy of routine PET scanning is not clear. It is insufficient to note that prognosis is improved by early detection of recurrence without offsetting the degree of improvement against the hazard and effort required to achieve that improvement. What is needed to answer these questions about clinical value are decision models and prospective clinical trials of PET-directed treatment. Most data on FDG PET that have appeared in the radiology literature thus far do not quantify clinical value in terms of patient outcomes and are better classified as reports of "diagnostic efficacy" [3]. These data are certainly valuable, but they are only part of the story. We are presently collaborating with the United Kingdom Medical Research Council Clinical Trials Unit to develop more direct measures of PET's patient outcome efficacy.
References
Johns Hopkins University Baltimore, MD 21287
Kyoto University Kyoto, Japan 606-8507
We thank Laking and Price for their thoughtful comments concerning the merits and shortcomings of our recent report on the use of FDG positron emission tomography (PET) to image patients with suspected recurrent ovarian cancer [1]. We agree that "patient outcome efficacy" should be discussed in terms of treatment of patients, and we understand the importance of such efficacy for the oncologist caring for this difficult group of patients.
Our report showed that FDG PET provides important information noninvasively. The measurement of metabolic activity cannot be obtained with conventional imaging modalities and, as we demonstrated, it does have an effect on patient treatment. We do not yet have sufficient data to discuss patient outcome in detail in terms of survival and quality of life or to establish decision models. Our long-term goal is to determine whether the information obtained by FDG PET can affect the clinical course of patients with ovarian cancer and improve their prognosis. We have recently started to follow up the patients who underwent FDG PET and determine their clinical course. In the future, we plan to carry out a prospective study. Our initial data in patients with advanced ovarian cancer indicate that recurrence is still possible even when PET findings are negative. Also, the negative PET results in patients with rising tumor markers suggest that this might be an indicator for a favorable chemotherapeutic response [2]. Our next step will be to clarify the long-term clinical significance of this modality by focusing on the relationship between the PET results and the patients' outcome. This step will include evaluation of the prognostic value of PET in patients with ovarian cancer. At the most recent annual meeting of the Society of Nuclear Medicine (June 2001), a number of articles were presented that indicated the prognostic value of FDG PET for various kinds of cancers. We anticipate that similar data will be forthcoming for ovarian cancer.
In summary, we foresee that FDG PET will have a growing influence on therapeutic treatment decisions, and that its use will improve the prognosis of patients over time. Our study showed that FDG PET does produce valuable data in patients with ovarian cancer and, as Laking and Price pointed out, well-controlled studies to prove the full merit of FDG PET in predicting patient outcome are extremely important.
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