"True" versus "apparent" stage I epithelial ovarian cancer: value of frozen section analysis

Intraoperative frozen section analysis for the diagnosis of early stage ovarian cancer in suspicious pelvic masses

BACKGROUND

Women with suspected early-stage ovarian cancer need surgical staging which involves taking samples from areas within the abdominal cavity and retroperitoneal lymph nodes in order to inform further treatment. One potential strategy is to surgically stage all women with suspicious ovarian masses, without any histological information during surgery. This avoids incomplete staging, but puts more women at risk of potential surgical over-treatment.A second strategy is to perform a two-stage procedure to remove the pelvic mass and subject it to paraffin sectioning, which involves formal tissue fixing with formalin and paraffin embedding, prior to ultrathin sectioning and multiple site sampling of the tumour. Surgeons may then base further surgical staging on this histology, reducing the rate of over-treatment, but conferring additional surgical and anaesthetic morbidity.A third strategy is to perform a rapid histological analysis on the ovarian mass during surgery, known as 'frozen section'. Tissues are snap frozen to allow fine tissue sections to be cut and basic histochemical staining to be performed. Surgeons can perform or avoid the full surgical staging procedure depending on the results. However, this is a relatively crude test compared to paraffin sections, which take many hours to perform. With frozen section there is therefore a risk of misdiagnosing malignancy and understaging women subsequently found to have a presumed early-stage malignancy (false negative), or overstaging women without a malignancy (false positive). Therefore it is important to evaluate the accuracy and usefulness of adding frozen section to the clinical decision-making process.

OBJECTIVES

To assess the diagnostic test accuracy of frozen section (index test) to diagnose histopathological ovarian cancer in women with suspicious pelvic masses as verified by paraffin section (reference standard).

SEARCH METHODS

We searched MEDLINE (January 1946 to January 2015), EMBASE (January 1980 to January 2015) and relevant Cochrane registers.

SELECTION CRITERIA

Studies that used frozen section for intraoperative diagnosis of ovarian masses suspicious of malignancy, provided there was sufficient data to construct 2 x 2 tables. We excluded articles without an available English translation.

DATA COLLECTION AND ANALYSIS

Authors independently assessed the methodological quality of included studies using the Quality Assessment of Diagnostic Accuracy Studies tool (QUADAS-2) domains: patient selection, index test, reference standard, flow and timing. Data extraction converted 3 x 3 tables of per patient results presented in articles into 2 x 2 tables, for two index test thresholds.

MAIN RESULTS

All studies were retrospective, and the majority reported consecutive sampling of cases. Sensitivity and specificity results were available from 38 studies involving 11,181 participants (3200 with invasive cancer, 1055 with borderline tumours and 6926 with benign tumours, determined by paraffin section as the reference standard). The median prevalence of malignancy was 29% (interquartile range (IQR) 23% to 36%, range 11% to 63%). We assessed test performance using two thresholds for the frozen section test. Firstly, we used a test threshold for frozen sections, defining positive test results as invasive cancer and negative test results as borderline and benign tumours. The average sensitivity was 90.0% (95% confidence interval (CI) 87.6% to 92.0%; with most studies typically reporting range of 71% to 100%), and average specificity was 99.5% (95% CI 99.2% to 99.7%; range 96% to 100%).Similarly, we analysed sensitivity and specificity using a second threshold for frozen section, where both invasive cancer and borderline tumours were considered test positive and benign cases were classified as negative. Average sensitivity was 96.5% (95% CI 95.5% to 97.3%; typical range 83% to 100%), and average specificity was 89.5% (95% CI 86.6% to 91.9%; typical range 58% to 99%).Results were available from the same 38 studies, including the subset of 3953 participants with a frozen section result of either borderline or invasive cancer, based on final diagnosis of malignancy. Studies with small numbers of disease-negative cases (borderline cases) had more variation in estimates of specificity. Average sensitivity was 94.0% (95% CI 92.0% to 95.5%; range 73% to 100%), and average specificity was 95.8% (95% CI 92.4% to 97.8%; typical range 81% to 100%).Our additional analyses showed that, if the frozen section showed a benign or invasive cancer, the final diagnosis would remain the same in, on average, 94% and 99% of cases, respectively.In cases where the frozen section diagnosis was a borderline tumour, on average 21% of the final diagnoses would turn out to be invasive cancer.In three studies, the same pathologist interpreted the index and reference standard tests, potentially causing bias. No studies reported blinding pathologists to index test results when reporting paraffin sections.In heterogeneity analyses, there were no statistically significant differences between studies with pathologists of different levels of expertise.

AUTHORS' CONCLUSIONS

In a hypothetical population of 1000 patients (290 with cancer and 80 with a borderline tumour), if a frozen section positive test result for invasive cancer alone was used to diagnose cancer, on average 261 women would have a correct diagnosis of a cancer, and 706 women would be correctly diagnosed without a cancer. However, 4 women would be incorrectly diagnosed with a cancer (false positive), and 29 with a cancer would be missed (false negative).If a frozen section result of either an invasive cancer or a borderline tumour was used as a positive test to diagnose cancer, on average 280 women would be correctly diagnosed with a cancer and 635 would be correctly diagnosed without. However, 75 women would be incorrectly diagnosed with a cancer and 10 women with a cancer would be missed.The largest discordance is within the reporting of frozen section borderline tumours. Investigation into factors leading to discordance within centres and standardisation of criteria for reporting borderline tumours may help improve accuracy. Some centres may choose to perform surgical staging in women with frozen section diagnosis of a borderline ovarian tumour to reduce the number of false positives. In their interpretation of this review, readers should evaluate results from studies most typical of their population of patients.

Management of a suspicious adnexal mass: a clinical practice guideline

QUESTIONS

What is the optimal strategy for preoperative identification of the adnexal mass suspicious for ovarian cancer? What is the most appropriate surgical procedure for a woman who presents with an adnexal mass suspicious for malignancy?

PERSPECTIVES

In Canada in 2010, 2600 new cases of ovarian cancer were estimated to have been diagnosed, and of those patients, 1750 were estimated to have died, making ovarian cancer the 7th most prevalent form of cancer and the 5th leading cause of cancer death in Canadian women. Women with ovarian cancer typically have subtle, nonspecific symptoms such as abdominal pain, bloating, changes in bowel frequency, and urinary or pelvic symptoms, making early detection difficult. Thus, most ovarian cancer cases are diagnosed at an advanced stage, when the cancer has spread outside the pelvis. Because of late diagnosis, the 5-year relative survival ratio for ovarian cancer in Canada is only 40%. Unfortunately, because of the low positive predictive value of potential screening tests (cancer antigen 125 and ultrasonography), there is currently no screening strategy for ovarian cancer. The purpose of this document is to identify evidence that would inform optimal recommended protocols for the identification and surgical management of adnexal masses suspicious for malignancy.

OUTCOMES

Outcomes of interest for the identification question included sensitivity and specificity. Outcomes of interest for the surgical question included optimal surgery, overall survival, progression-free or disease-free survival, reduction in the number of surgeries, morbidity, adverse events, and quality of life.

METHODOLOGY

After a systematic review, a practice guideline containing clinical recommendations relevant to patients in Ontario was drafted. The practice guideline was reviewed and approved by the Gynecology Disease Site Group and the Report Approval Panel of the Program in Evidence-based Care. External review by Ontario practitioners was obtained through a survey, the results of which were incorporated into the practice guideline.

PRACTICE GUIDELINE

These recommendations apply to adult women presenting with a suspicious adnexal mass, either symptomatic or asymptomatic. IDENTIFICATION OF AN ADNEXAL MASS SUSPICIOUS FOR OVARIAN CANCER: Sonography (particularly 3-dimensional sonography), magnetic resonance imaging (mri), and computed tomography (ct) imaging are each recommended for differentiating malignant from benign ovarian masses. However, the working group offers the following further recommendations, based on their expert consensus opinion and a consideration of availability, access, and harm: Where technically feasible, transvaginal sonography should be the modality of first choice in patients with a suspicious isolated ovarian mass.To help clarify malignant potential in patients in whom ultrasonography may be unreliable, mri is the most appropriate test.In cases in which extra-ovarian disease is suspected or needs to be ruled out, ct is the most useful technique.Evaluation of an adnexal mass by Doppler technology alone is not recommended. Doppler technology should be combined with a morphology assessment.Ultrasonography-based morphology scoring systems can be used to differentiate benign from malignant adnexal masses. These scoring systems are based on specific ultrasound parameters, each with several scores base on determined features. All evaluated scoring systems were found to have an acceptable level of sensitivity and specificity; the choice of scoring system may therefore be made based on clinician preference.As a standalone modality, serum cancer antigen 125 is not recommended for distinguishing between benign and malignant adnexal masses.Frozen sections for the intraoperative diagnosis of a suspicious adnexal mass is recommended in settings in which availability and patient preference allow. SURGICAL PROCEDURES FOR AN ADNEXAL MASS SUSPICIOUS FOR MALIGNANCY: To improve survival, comprehensive surgical staging with lymphadenectomy is recommended for the surgical management of patients with early-stage ovarian cancer. Laparoscopy is a reasonable alternative to laparotomy, provided that appropriate surgery and staging can be done. The choice between laparoscopy and laparotomy should be based on patient and clinician preference. Discussion with a gynecologic oncologist is recommended. Fertility-preserving surgery is an acceptable alternative to more extensive surgery in patients with low-malignant-potential tumours and those with well-differentiated surgical stage i ovarian cancer. Discussion with a gynecologic oncologist is recommended.

A systematic review of papers examining the use of intraoperative frozen section in predicting the final diagnosis of ovarian lesions

This systematic review assesses the accuracy of the frozen section classification of benign and borderline lesions or invasive carcinoma when compared with the final diagnosis on paraffin section. A Pubmed database search identified 18 retrospective cohort studies, published since 2005 that satisfied the criteria, on the critical appraisal sheet of the center for evidence-based medicine, The University of Oxford. The sensitivity, specificity, and negative and positive predictive values suggest that frozen section is more accurate at discriminating between benign lesions and invasive carcinoma than between benign and borderline or borderline lesions and invasive carcinoma and indicate a tendency to overcall benign tumors as borderline and borderline tumors as invasive malignancies. A narrative review of individual papers and abstracts suggests that this particular difficulty is encountered when dealing with clear cell carcinoma and mucinous lesions of all sorts. This may have greater importance in the future with the introduction of targeted chemotherapy requiring accurate typing to guide the use of genetic analysis. It would be beneficial if future researchers comparing the results of frozen section and paraffin sections presented their results in the context of preoperative assessment of the clinical and radiological findings or the intraoperative appearances of the tumor and abdominal cavity, which would allow the identification of those cases in which the frozen section allowed a refinement of the diagnoses made using these modalities.

Intra-operative frozen section analysis for suspected early-stage ovarian cancer: 11 years of Gateshead Cancer Centre experience

OBJECTIVE

In centres in which intra-operative frozen section (FS) analysis is not performed, 'apparent' early-stage ovarian cancer diagnosed after surgery on paraffin section may require further restaging laparotomy or adjuvant chemotherapy. Previous studies on FS analysis have reported high sensitivity, specificity and overall accuracy. The objective of this article is to present the largest published dataset on the accuracy of FS analysis over an 11-year period from a single institution.

DESIGN

Diagnostic test accuracy.

SETTING

Northern Gynaecological Oncology Centre and Department of Cellular Pathology, Gateshead, UK.

POPULATION

1439 intra-operative FS analyses performed between January 2000 and December 2010 for suspected ovarian cancer.

METHODS

Prospectively collected data on FS analysis were compared with gold standard paraffin section.

MAIN OUTCOME MEASURES

Sensitivity, specificity, likelihood ratios and post-test probability.

RESULTS

The overall sensitivity and specificity of FS analysis were 91.2% and 98.6%, respectively. Positive and negative likelihood ratios were 64.7% and 0.09%, respectively. The pre-test probability of an ovarian tumour being borderline or malignant was 45.8%. When FS analysis was reported to be positive, the post-test probability increased to 98% (confidence interval, 97-99%). Conversely, when FS analysis was reported to be negative, the post-test probability decreased to 7% (confidence interval, 6-9%). The majority of false test results were either borderline tumours or of mucinous differentiation.

CONCLUSIONS

Intra-operative FS analysis has excellent diagnostic test accuracy and assists gynaecological oncologists to perform the appropriate surgery in 95% of cases, thereby preventing the morbidity of surgical staging in benign cases and the morbidity of restaging procedures or chemotherapy in early-stage malignant tumours.

Importance of a specialized pathologist for the examination of frozen sections of adnexal masses

The aim of the present study was to examine the impact of a specialized pathologist on the accuracy of frozen section analysis for adnexal masses. We included women who underwent frozen section diagnosis for adnexal mass surgery. A specialized and a general pathologist read the sections. We calculated sensitivity, specificity, positive and negative predictive values, and accuracy for the whole series, as well as for the specialized and general pathologist groups. We included 325 patients; in 103 patients (31.7%), frozen section diagnosis was performed by the specialized and in 222 (68.3%), by the general pathologist. There was a significant difference in terms of correspondence between the specialized and the general pathologist groups (P= 0.024). We registered four overdiagnoses (both performed by the general pathologist [1.8% vs 0%]) and 56 underdiagnoses of which 14 (13.6%) were made by the specialized pathologist and 46 (20.7%) by the general pathologist. In 14 cases (4.3%), diagnosis could not be made on frozen section and was postponed to final histology for definitive diagnosis (1/103 [0.9%] for the specialized pathologist and 13/222 [5.8%] for the general pathologist). Our data confirm previous reports on the accuracy of frozen section analysis of adnexal masses and show a significant positive impact of the specialized pathologist as opposed to the general pathologist.