Significant variability in 10-year cumulative radiation exposure incurred on different surveillance regimens after surgery for pT1 renal cancers: yet another reason to standardize protocols?

Role of F-18 FDG PET/CT in the follow-up of asymptomatic renal cell carcinoma patients for postoperative surveillance: based on conditional survival analysis

PURPOSE

This study investigated the clinical usefulness of F-18 fluorodeoxylucose (FDG) positron emission tomography/computed tomography (PET/CT) for postoperative surveillance in the RCC patients in terms of detectability of recurrence and radiation exposure.

METHODS

Three-hundred-and-forty- three RCC patients who underwent surgery and postoperative surveillance were retrospectively included. Conditional recurrent free survival (CRFS) was investigated and diagnostic performance of conventional imaging (CI) which include abdominopelvic CT or/and chest CT was compared to the FDG PET/CT.

RESULTS

At a median follow-up of 4.3 years (0.5-13.0 years), thirty-nine patients (11.4%) developed recurrence. CRFS of the patients increased over time with greater increment in advanced stage. The sensitivity, specificity, positive-predictive value, negative-predictive value, and accuracy of FDG PET/CT were 92.3%, 97%, 80%, 99.0%, and 96.5% in detecting recurrence, while those values for CI were 89.7%, 97.7%, 83.3%, 98.7%, and 96.8%, respectively. There were no significant differences in these values between FDG PET/CT and CI (McNemar test, p = 0.581). The average radiation dose from FDG PET/CT was around 16.9 ± 3.08 mSv at each follow-up time point. For early stage patients, the average radiation dose from CI was around 26.5 ± 8.57 mSv at each follow-up time point, while this was about 33.0 ± 9.76 mSv for advanced stage patients.

CONCLUSION

FDG PET/CT exhibited good diagnostic performance in asymptomatic RCC patients after surgery, of a level comparable to that of CI, but with a lower radiation dose.

CT-guided cryoablation of renal cancer: radiation burden and the associated risk of secondary cancer from procedural- and follow-up imaging

OBJECTIVES

To estimate radiation dose and the associated risk of secondary cancer risk related to percutaneous cryoablation (PCA) and follow-up imaging in a cohort of patients treated for small renal masses (SRMs).

METHODS

A total of 149 patients underwent PCA for a SRM at our institution. Based on CT dose reports, we calculated the mean effective dose for a CT-guided PCA procedure and post-ablative follow-up CT. Applying follow-up recommendations by a multidisciplinary expert panel, we calculated the total radiation dose for the PCA procedure and the CT surveillance program corresponding to a minimal and preferable follow-up regime (5-year vs 10-year). Estimates of the lifetime attributable cancer risk for different age groups were calculated based on the cumulative effective dose based on the latest BEIR VII report.

RESULTS

Total dose for the PCA treatment and follow-up CTs amounted to 174 and 294 mSv for a minimal and preferable protocol, respectively. Follow-up CTs accounted for the majority of the total effective dose for the minimal and preferable protocol (89% vs 94%). CT fluoroscopy contributed only to a limited amount of the total radiation dose for the minimal and preferable protocol (1.8% vs 1.1%). A 70-year-old male undergoing PCA treatment has a lifetime attributable cancer risk of 0.8% (1 in 131) when completing the preferable follow-up protocol. The same regimen in a 30-year-old female results in a lifetime attributable risk of cancer of 3.4% (1 in 29).

CONCLUSION

Radiation dose and the associated risk of secondary cancer are high for patients with SRMs undergoing PCA and post-ablative follow-up imaging in particular in younger patients. Radiation exposure in the PCA procedure itself accounts for only a limited amount of the total radiation. Radiologists and clinicians must strive to implement radiation dose saving measures especially with respect to the follow-up regime.

[Follow-up of renal cell carcinoma in a nonmetastatic stage]

Postoperative follow-up care after curative surgery or ablative treatment is the standard of care in patients with nonmetastatic renal cell carcinoma. The goal is to identify and treat postoperative complications and local recurrences early on. Follow-up investigations and their relevance are widely acknowledged and validated and patients undergoing follow-up seem to benefit from a longer survival in nonmetastatic renal cell carcinoma. Hence there is no consensus on a standardized follow-up strategy. The most disputed question is around the frequency of the investigations and the duration of the follow-up. Without an evidence-based follow-up protocol, urologists should carry out an individualized, potentially lifelong follow-up regimen, which also includes the patients' needs and perspectives.

Toward a Framework for Benefit-Risk Assessment in Diagnostic Imaging: Identifying Scenario-specific Criteria

RATIONALE AND OBJECTIVES

Diagnostic imaging has many effects and there is no common definition of value in diagnostic radiology. As benefit-risk trade-offs are rarely made explicit, it is not clear which framework is used in clinical guideline development. We describe initial steps toward the creation of a benefit-risk framework for diagnostic radiology.

MATERIALS AND METHODS

We performed a literature search and an online survey of physicians to identify and collect benefit-risk criteria (BRC) relevant to diagnostic imaging tests. We operationalized a process for selection of BRC with the use of four clinical use case scenarios that vary by diagnostic alternatives and clinical indication. Respondent BRC selections were compared across clinical scenarios and between radiologists and nonradiologists.

RESULTS

Thirty-six BRC were identified and organized into three domains: (1) those that account for differences attributable only to the test or device (n = 17); (2) those that account for clinical management and provider experiences (n = 12); and (3) those that capture patient experience (n = 7). Forty-eight survey participants selected 22 criteria from the initial list in the survey (9-11 per case). Engaging ordering physicians increased the number of criteria selected in each of the four clinical scenarios presented. We developed a process for standardizing selection of BRC in guideline development.

CONCLUSION

These results suggest that a process relying on elements of comparative effectiveness and the use of standardized BRC may ensure consistent examination of differences among alternatives by way of making explicit implicit trade-offs that otherwise enter the decision-making space and detract from consistency and transparency. These findings also highlight the need for multidisciplinary teams that include input from ordering physicians.

Patterns of surveillance imaging after nephrectomy in the Medicare population

OBJECTIVES

To characterize patterns of imaging surveillance after nephrectomy in a population-based cohort of older patients with kidney cancer.

PATIENTS AND METHODS

Using the Surveillance, Epidemiology and End Results (SEER)-Medicare database, we identified patients aged ≥ 66 years who underwent partial or radical nephrectomy for localized kidney cancer diagnosed between 2000 and 2009. Primary outcomes were chest imaging (X-ray or computed tomography [CT]) and abdominal imaging (CT, MRI or ultrasonography) in Medicare claims from 4 to 36 months after surgery. We estimated the frequency of imaging in three time periods (postoperative months 4-12, 13-24, 25-36), stratified by tumour stage. Repeated-measures logistic regression was used to identify the patient and disease characteristics associated with imaging.

RESULTS

Rates of chest imaging were 65-80%, with chest X-ray surpassing CT in each time period. Rates of abdominal imaging were 58-76%, and cross-sectional imaging was more common than ultrasonography in each time period. Use of cross-sectional chest and abdominal imaging increased over time, while the use of chest X-ray decreased (P < 0.01). Ultrasonography use remained stable for patients with T1 and T2 disease, but the rate of use decreased in patients with T3 disease (P < 0.05). Rates of chest and abdominal imaging increased with tumour stage (P < 0.001).

CONCLUSIONS

Patterns of imaging suggest possible overuse in patients at low risk of recurrence and underuse in those at greater risk. New surveillance imaging guidelines may reduce unwarranted variability and promote risk-based, cost-effective management after nephrectomy.

Comparison of Renal Cell Carcinoma Surveillance Guidelines: Competing Trade-Offs

PURPOSE

We estimated the differences in intensity, cost, radiation exposure and cancer control of published surveillance guidelines screening for secondary renal cell carcinoma in patients treated with partial nephrectomy.

MATERIALS AND METHODS

We developed a Monte Carlo simulation model to contrast the existing guidelines in terms of cost, radiation exposure and cancer control. Model inputs were extrapolated from the existing literature. Surveillance guidelines were analyzed from the AUA, CUA, EAU and NCCN®. Risk stratification among patients treated with partial nephrectomy was based on tumor characteristics.

RESULTS

Expected costs during the 5 years after partial nephrectomy were $587 (CUA), $1,076 (AUA), $1,705 (EAU) and $1,768 (NCCN) for low risk patients, and $903 (CUA), $2,525 (EAU) and $3,904 (AUA and NCCN) for high risk patients. Radiation exposure ranged from 31.41 mSv (CUA) to 104.34 mSv (NCCN) for low risk patients and 46.88 mSv (CUA) to 231.61 mSv (AUA and NCCN) for high risk patients. The EAU and CUA guidelines led to the diagnosis of the highest percentage of low risk patients (more than 95%) while all guidelines diagnosed more than 92% of high risk patients with recurrence.

CONCLUSIONS

Renal cell carcinoma surveillance guidelines differ greatly in terms of intensity, cost and radiation exposure. It is important for clinicians to adopt standardized surveillance strategies that limit unnecessary cost and radiation exposure without compromising cancer control.

Low yield of surveillance imaging after surgery for T1 kidney cancer

PURPOSE

To examine the mode of relapse detection and subsequent treatment after partial or radical nephrectomy in patients with low-risk (pT1, N0, Nx) kidney cancer.

METHODS

Retrospective study on 1404 patients treated with partial or radical nephrectomy for low-risk kidney cancer from the years 2000-2012. Scans for chest imaging (X-ray or CT) and abdominal imaging (CT, MRI, or ultrasound) are tabulated. For those patients with relapse, the site, mode of detection, and symptoms were recorded.

RESULTS

Twenty-one patients relapsed with a median follow-up of 4.1 years for patients who did not relapse. In 17 (81 %) patients, relapse was detected by imaging alone, while 4 (19 %) patients presented with symptoms. Of the patients who relapsed by imaging, 13 (76 %) were treated immediately, while 4 (24 %) continued observation. During the first 3 years of follow-up, 5762 imaging studies were performed to detect 8 relapses, with 6 patients receiving immediate treatment. The median number of imaging studies per patient per year for the first 3 years was 1.7 (interquartile range 1.0, 2.3) including 30 % CT, 3 % MRI, 36 % X-ray, and 31 % ultrasounds.

CONCLUSION

We found a low yield of surveillance imaging in the first 3 years for pT1 kidney cancer. Nearly 1000 imaging studies were performed to detect one relapse that required treatment. Further studies are needed to evaluate the clinical impact of imaging surveillance according to recent guidelines.

Radiation exposure from CT-guided ablation of renal masses: effects on life expectancy

OBJECTIVE. The purpose of this article is to project the effects of radiation exposure on life expectancy (LE) in patients who opt for CT-guided radiofrequency ablation (RFA) instead of surgery for renal cell carcinoma (RCC). MATERIALS AND METHODS. We developed a decision-analytic Markov model to compare LE losses attributable to radiation exposure in hypothetical 65-year-old patients who undergo CT-guided RFA versus surgery for small (≤ 4 cm) RCC. We incorporated mortality risks from RCC, radiation-induced cancers (for procedural and follow-up CT scans), and all other causes; institutional data informed the RFA procedural effective dose. Radiation-induced cancer risks were generated using an organ-specific approach. Effects of varying model parameters and of dose-reduction strategies were evaluated in sensitivity analysis. RESULTS. Cumulative RFA exposures (up to 305.2 mSv for one session plus surveillance) exceeded those from surgery (up to 87.2 mSv). In 65-year-old men, excess LE loss from radiation-induced cancers, comparing RFA to surgery, was 11.7 days (14.6 days for RFA vs 2.9 days for surgery). Results varied with sex and age; this difference increased to 14.6 days in 65-year-old women and to 21.5 days in 55-year-old men. Dose-reduction strategies that addressed follow-up rather than procedural exposure had a greater impact. In 65-year-old men, this difference decreased to 3.8 days if post-RFA follow-up scans were restricted to a single phase; even elimination of RFA procedural exposure could not achieve equivalent benefits. CONCLUSION. CT-guided RFA remains a safe alternative to surgery, but with decreasing age, the higher burden of radiation exposure merits explicit consideration. Dose-reduction strategies that target follow-up rather than procedural exposure will have a greater impact.

Current opinions on medical radiation: a survey of oncologists regarding radiation exposure and dose reduction in oncology patients

PURPOSE

The aim of this study was to evaluate oncologists' opinions about the use of ionizing radiation in medical imaging of oncology patients.

METHODS

An electronic survey was e-mailed to 2,725 oncologists at the top 50 National Cancer Institute-funded cancer centers. The survey focused on opinions on CT dose reduction in oncology patients and current philosophies behind long-term imaging in these patients.

RESULTS

The response rate was 15% (415 of 2,725). Eighty-two percent of respondents stated that their patients or families have expressed anxiety regarding radiation dose from medical imaging. Although fewer than half of oncologists (48%) did not know whether CT dose reduction techniques were used at their institutions, only 25% were concerned that small lesions may be missed with low-dose CT techniques. The majority of oncologists (63%) follow National Comprehensive Cancer Network guidelines for imaging follow-up, while the remainder follow other national guidelines such as those of the Children's Oncology Group, the American Society of Clinical Oncology, or clinical trials. Ninety percent of respondents believe that long-term surveillance in oncology patients is warranted, particularly in patients with breast cancer, melanoma, sarcoma, and pediatric malignancies. The majority of oncologists would consider the use of low-dose CT imaging in specific patient populations: (1) children and young women, (2) those with malignancies that do not routinely metastasize to the liver, and (3) patients undergoing surveillance imaging.

CONCLUSIONS

Cumulative radiation exposure is a concern for patients and oncologists. Among oncologists, there is support for long-term imaging surveillance despite lack of national guidelines.