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1 Both authors: Department of Radiation Oncology, Stanford Hospital, Stanford University Medical Center, 300 Pasteur Dr., Stanford, CA 94305.
Received December 21, 2000;
accepted after revision March 8, 2001.
Address correspondence to M. C. Smitt.
Abstract
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SUBJECTS AND METHODS. From December 1998 to December 2000, 162 radiotherapy patients who were to be treated curatively underwent treatment planning CT scans on a helical scanner in the radiology department at Washington Hospital, Fremont, CA. All CT scans were prospectively interpreted relative to diagnoses, and reports were dictated for the medical records. The diagnostic reports and records on all patients were reviewed to determine the incidence of previously unknown benign or cancer-related findings, the impacts of such findings on treatment, and the need for additional radiologic studies or procedures on the basis of the CT interpretations.
RESULTS. Incidental benign findings were noted for 32 patients (20%). Potentially important benign findings were noted for three patients: two with aneurysms and one with a possible deep vein thrombosis. Potentially cancer-related findings were reported in 20 patients: a single liver lesion (four patients), multiple liver lesions (two patients), possible or probable lymphadenopathy (11 patients), abnormal soft tissue (one patient), a small-bowel obstruction (one patient), and a breast mass (one patient). After reviewing prior diagnostic studies and obtaining additional recommended studies, the physicians found that only three of the previously unknown findings required further investigation: two aneurysms, which did not require near-term treatment, and one metastatic neck node.
CONCLUSION. Routine diagnostic interpretation of radiotherapy planning scans resulted in few important medical findings and changed patient care for less than 1% of the patients.
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From December 1998 through December 2000, treatment planning CT scans obtained at Washington Hospital were prospectively interpreted by the Washington Hospital Radiology Group to diagnose any medically important benign or cancer-related conditions. During this period, 162 patients who received curative treatment underwent CT planning and became the subjects of this study. The indications for conformal therapy planning were consistent with established benefits and policies at Stanford University. The site and stage distributions for these patients are shown in Tables 1 and 2. Initial staging protocols were site-specific, in keeping with the National Comprehensive Cancer Network guidelines [2]. In particular, no breast and only four prostate patients underwent pretreatment CT or MR imaging, whereas all patients with other diagnoses had received routine cross-sectional imaging at presentation.
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All treatment planning CT scans were prospectively interpreted relative to diagnosis, and reports were dictated for the medical records. Any previous diagnostic CT reports and available medical records on all patients were reviewed and assessed to determine the incidence of previously unknown benign or cancer-related findings, impacts of such findings on treatment, and the need for additional radiologic studies or procedures on the basis of the treatment planning CT interpretations. Findings were classified as incidental benign findings if medical follow-up or further studies were not required, important benign findings if medical follow-up or studies were required, and cancer-related findings if the diagnostic report suggested possible unsuspected sites of carcinoma requiring medical follow-up or additional studies.
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Potential cancer-related findings were recorded in 20 patients (12%). These findings included a single liver lesion (n = 4), multiple liver lesions (n = 2), possible or probable lymphadenopathy (n = 11), abnormal soft tissue (n = 1), a small-bowel obstruction (n = 1), and a breast mass (n = 1). After clinical review, appropriate physical examination, and further radiologic studies, one patient was found to have a new metastatic deposit. This patient had apparently developed neck adenopathy in the interval between the initial consultation and simulation. CT findings led to a decision to perform a neck dissection before radiation. The findings for remaining patients were believed, on further investigation, to represent liver cysts, postoperative change or seroma, or vascular structures.
Diagnostic review of the treatment planning CT scans led to the performance of 10 additional radiologic studies or procedures. These included: contrast-enhanced CT (n = 4), liver sonography (n = 1), fine-needle aspiration (n = 1), MR imaging (n = 2), Doppler sonography (n = 1), and small-bowel series (n = 1). Most (n = 6) of these studies were ordered in breast cancer patients to evaluate multiple liver lesions or possible lymphadenopathy. Histologic diagnosis was pursued only when recommended by the diagnostic physicians after additional imaging studies. To date, no patient has had a recurrence in a nonbiopsied area identified by the treatment planning CT scans.
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A few previous site-specific studies have examined the incidence of unsuspected comorbid disease discovered on diagnostic or treatment planning CT scans [8,9,10,11] (Table 5). Although a fair percentage of patients' scans do reveal some benign finding, only 1-10% reveal findings requiring medical follow-up or near-term treatment. The likelihood of relevant benign disease undoubtedly depends on characteristics of the studied patient population. Elderly patients and those with other risk factors for comorbid disease would be expected have a higher incidence. Among prostate cancer patients in the prior studies, 1-9% of their scans revealed medically important comorbid disease, primarily aneurysms. Second malignancies were also noted. Although the overall rate of medically important comorbid disease in our study was low, the rate among our prostate patients was 4%, consistent with other reports. Among our breast cancer patients, no benign findings that required treatment were found; a rate of less than 1% was reported in another study [11].
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Detecting additional foci of cancer on treatment planning scans has obvious importance in terms of prognosis and potential effects on treatment programs or radiotherapy field design. Prior studies showed a 3-7% [9, 11] incidence of unexpected cancer foci as compared with less than 1% in this study. However, these prior studies included patients with metastatic disease and higher numbers of patients with locally advanced disease. Looking only at patients receiving curative treatment in those studies, the incidence of new cancer findings was 4% and 2%, respectively [9, 11]. We did not routinely examine the results of diagnostic scan interpretation in patients who were not treated curatively because any such findings would be unlikely to affect overall patient outcomes. Histologic diagnosis of all CT findings was not obtained in this study, and the true frequency of pathologic findings could be higher. However, this study primarily addressed the likelihood of changes in clinical treatment with diagnostic interpretation using reasonable clinical judgment. To date, no patient has had a clinical recurrence in nonbiopsied areas.
Evaluating the impact of diagnostic interpretation of treatment planning scans requires recognition of the technical shortcomings of such scans. Radiotherapy planning scans may be obtained with markers or immobilization devices that create artifacts. Patient positioning may result in unusual fields of view. Optimal amounts of contrast media, whether IV or oral, are rarely administered in the radiotherapy department. For patients undergoing diagnsotic cross-sectional imaging as part of their routine staging workup, treatment scans obtained with such limitations seem unlikely to generate new findings. For patients who do not undergo routine diagnostic CT scans, planning scans could understimate findings or create ambiguous findings leading to unnecessary further studies. The review by Forman et al. [8] found that diagnostic CT scans for prostate staging led to 21 additional studies in 273 patients with prostate cancer. Diagnostic interpretation of planning scans in this study led to 10 additional studies in 162 patients. The most additional studies were performed in breast cancer patients, an occurrence that appeared to result from the lack of IV contrast medium in studies of the liver and the radiologist's lack of familiarity with the appearance of the postsurgical axilla and breast. More intensive staging of breast and prostate patients at presentation might decrease the likelihood of unexpected findings on radiotherapy treatment planning scans, but this procedure would not be consistent with current oncologic guidelines. Also, in current multimodality protocols, radiotherapy planning CT scans may be obtained long after initial staging, with the attendant possibility of new findings.
Significant benign or cancer-related findings were uncommon in this study, but radiation centers with a different distribution of disease sites, stages, or background patient comorbidities could encounter different results. Although such findings may be rare, they are not nonexistent. One study suggested that detailed review by the radiation oncologist could screen planning CT scans for significant findings [11]. Without a prospective comparison, it is unknown whether radiation oncology review can substitute for diagnostic expertise. In our breast cancer patients, we had a 53% incidence of incidental findings overall as compared with 11% in the previously cited study [11]. Alternatively, hard copies of CT scans could be selectively submitted for diagnostic review for patients for whom no pretreatment scan had been obtained or who had received interval therapy or had a long interval since the last scan. However, a funding mechanism for professional interpretation might need to be provided. Our center currently provides Medicare-equivalent reimbursement to the diagnostic group when other insurance coverage is not forthcoming (approximately 15-20% of these patients). Patients should perhaps be made aware through appropriate consent forms that treatment planning scans are not of diagnostic quality and will not be routinely reviewed by diagnostic radiologists. In addition to relevant benign findings in two patients and new metastatic disease in one, diagnostic expertise may have been useful in an additional 19 patients in whom IV contrast administration was needed for tumor delineation or for whom formal staging reevaluation was sought by the referring physician. It is unclear whether radiation oncologists currently have optimal knowledge or experience in terms of contrast medium reaction prophylaxis and treatment and contrast medium administration protocols. Such knowledge could, perhaps, be obtained by a coordination of policies with local diagnostic radiologists or by dissemination of appropriate professional guidelines. The indications for and use of contrast media in conformal therapy planning scans may increase.
In summary, diagnostic interpretation of radiotherapy planning scans in 162 patients treated curatively showed important benign disease in two patients and resulted in a change of planned cancer treatment in one patient (<1%).
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