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Clinical Outcome of Patients with Lymph NodeNegative Breast Carcinoma who have Sentinel Lymph Node Micrometastases Detected by Immunohistochemistry Anees Chagpar, M.D., M.Sc.1 Lavinia P. Middleton, M.D.2 Aysegul A. Sahin, M.D.2 Funda Meric-Bernstam, M.D.1 Henry M. Kuerer, M.D., Ph.D.1 Barry W. Feig, M.D.1 Merrick I. Ross, M.D.1 Frederick C. Ames, M.D.1 S. Eva Singletary, M.D.1 Thomas A. Buchholz, M.D.3 Vincente Valero, M.D.4 Kelly K. Hunt, M.D.1 1
Department of Surgical Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.
2
Department of Pathology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.
3
Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.
4
Department of Medical Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas. Presented in part at the 39th Annual Meeting of the American Society of Clinical Oncology, Chicago, Illinois, May 30 through June 3, 2003. Supported in part by the Susan G. Komen Breast Cancer Foundation. The authors are grateful to Stephanie Deming for her critical reading of the article. Address for reprints: Kelly K. Hunt, M.D., Professor of Surgery, Chief, Surgical Breast Section, Department of Surgical Oncology, Unit 444, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030; Fax: (713) 792-4689; E-mail:
[email protected] Received November 15, 2004; accepted December 3, 2004.
BACKGROUND. The ideal pathologic assessment of sentinel lymph nodes (SLNs) in patients with breast carcinoma remains controversial. The authors evaluated how detailed assessment of SLNs using immunohistochemistry (IHC) and serial sectioning would affect treatment decisions and outcomes in patients with breast carcinoma who had negative SLNs on standard hematoxylin and eosin staining.
METHODS. The SLNs from patients who were treated between June 1998 and June, 1999 and who had negative lymph node status determined by hematoxylin and eosin staining (n ⫽ 84 patients) were evaluated further with serial sectioning and cytokeratin IHC. Patients were offered adjuvant therapy based on primary tumor factors. RESULTS. The median patient age was 57 years, and the median tumor size was 1.2 cm. At a median follow-up of 40.2 months, 81 patients (96%) were alive with no evidence of disease, 1 patient was alive with disease, 1 patient had died of disease, and 1 patient had died of other causes. Fifteen patients (18%) had micrometastases identified on IHC. Of the total 84 patients, information regarding adjuvant therapy was not available for 5 patients. Of the remaining 79 patients, 10 patients (13%) were not offered adjuvant chemotherapy but had positive SLN status determined by IHC. SLN status based on IHC evaluation did not correlate with age (P ⫽ 0.077), tumor size (P ⫽ 0.717), grade (P ⫽ 0.148), estrogen receptor status (P ⫽ 1.000), or lymphovascular invasion (P ⫽ 0.274). Furthermore, IHC-detected positive SLN status did not correlate with distant metastasis (P ⫽ 0.372) or overall or distant metastasis-free survival (P ⫽ 0.543 and P ⫽ 0.540, respectively). CONCLUSIONS. Although the finding of SLN micrometastases by IHC may change management in ⬎ 12% of patients, preliminary results suggested that such micrometastases do not affect outcomes significantly. Cancer 2005;103:1581– 6. © 2005 American Cancer Society. KEYWORDS: Breast carcinoma, sentinel lymph node, immunohistochemistry, micrometastases, survival.
I
t is well accepted that, in patients with breast carcinoma, the status of the axillary lymph nodes is the most accurate predictor of prognosis.1 Axillary lymph node dissection, however, is associated with significant morbidity and is unnecessary for women who have proven lymph node-negative disease.2 The technique of sentinel lymph node (SLN) dissection has gained popularity, because it offers the ability to assess the first draining lymph node for the presence of metastatic disease, thereby permitting accurate staging of patients while sparing those without evidence of metastasis a full axillary lymph node dissection.3,4
© 2005 American Cancer Society DOI 10.1002/cncr.20934 Published online 3 March 2005 in Wiley InterScience (www.interscience.wiley.com).
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Because the SLNs have been deemed the lymph nodes most likely to contain metastases if metastases are present, pathologists have employed a variety of techniques to study these lymph nodes with more scrutiny.5 The adoption of serial sectioning and immunohistochemistry (IHC) in the assessment of SLNs has led to the increased finding of micrometastatic disease and “upstaging” of patients who were classified previously with negative lymph node status on the basis of standard hematoxylin and eosin (H&E) staining. The impact of this reclassification on the ultimate outcome of these patients, however, remains unclear.6 The objective of the current study was to determine how the more rigorous study of SLNs with serial sectioning and IHC would affect the adjuvant treatment of patients and their outcome in terms of survival and development of metastatic disease.
MATERIALS AND METHODS The medical records of women who underwent SLN dissection at The University of Texas M. D. Anderson Cancer Center between June 1998 and June 1999, who did not receive neoadjuvant chemotherapy, and who had negative SLN status according to routine H&E staining of bivalved lymph nodes were reviewed. In total, 84 patients met these criteria. The SLNs from each of these patients were subjected to further examination using serial sectioning and IHC for cytokeratin. Each lymph node was sectioned perpendicular to the long axis at 2-mm to 4-mm intervals. Each section was processed into a paraffin embedded block, which was then sectioned serially at 4-m to 5-m intervals. Ten slides were made of each block, and pancytokeratin immunoperoxidase staining was performed using 2 of these slides. The other eight slides obtained from the serial sectioning were subjected to further study with H&E staining. The presence or absence of metastases was recorded after this more careful examination. All patients had been classified initially with negative lymph node status and were offered adjuvant therapy on the basis of their initial primary tumor characteristics. Data were collected based on a retrospective review of patients’ medical records approved by The University of Texas M. D. Anderson Cancer Center’s Institutional Review Board. Information recorded included patient demographics, tumor characteristics, adjuvant therapy, and outcome in terms of progression to distant metastasis and overall and distant metastasis-free survival. An analysis of factors that potentially had a correlation with the presence of micrometastases on further examination of the SLNs was performed using likelihood ratio tests for discrete variables and Mann–Whitney U tests for continuous
TABLE 1 Primary Tumor Features Feature Tumor size ⱕ 2 cm ⬎ 2 cm and ⱕ 5 cm Histologic subtype Infiltrating ductal carcinoma Infiltrating lobular carcinoma Other Gradea 1 2 3 Estrogen receptor statusb Positive Negative Progesterone receptor statusb Positive Negative Lymphovascular invasionc Absent Present
No. of patients (%)
75 (89.3) 9 (10.7) 77 (91.7) 4 (4.8) 3 (3.6) 8 (9.5) 39 (46.4) 35 (41.7) 52 (61.9) 26 (31.0) 51 (60.7) 27 (32.1) 75 (89.3) 2 (2.4)
a
Nuclear grade was not specified in 2 patients (2%). Estrogen receptor status was not recorded in 6 patients (7%), and progesterone receptor status was not documented in 6 patients (7%). c Lymphovascular invasion was not specified in 7 patients (8%). b
variables. Survival analyses were performed for overall and distant metastasis-free survival using the method of Kaplan and Meier. Comparisons for survival were made using log-rank analysis. All statistical analyses were performed using SPSS software (version 10.1; SPSS, Inc., Chicago, IL).
RESULTS Patient Demographics The median patient age at initial diagnosis of breast carcinoma was 57 ⫾ 13 years (range, 26 – 84 years). Sixty-three patients (75%) were white, 9 patients (11%) were Hispanic, 8 patients (9%) were African American, and the remaining 4 patients (5%) were of unspecified ethnicity.
Primary Tumor Characteristics Primary tumor characteristics of the patients in the study are shown in Table 1. The median tumor size was 1.20 cm, with a standard deviation of 0.71 cm (range, 0.2– 4.0 cm). Forty-nine patients (58%) had carcinoma of the left breast, and 35 patients (42%) had carcinoma of the right breast. Seventy-two patients (86%) underwent breast-conserving surgery, and 12 patients (14%) underwent mastectomy.
IHC-Detected Micrometastases/Chagpar et al.
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SLN Characteristics Sixty-two patients (74%) had preoperative lymphoscintigraphy to map the location of the SLN. In 42 of these patients (68%), drainage was to the axilla. In 9 patients (14%), drainage was to both the axilla and the internal mammary lymph nodes. In 11 patients (18%), no drainage was demonstrated on lymphoscintigraphy. SLN mapping was performed with radioactive colloid and/or blue dye, depending on the surgeon’s preference. The median number of SLNs harvested was 2 (range, 1–10 SLNs). The median size of the largest SLN was 2.0 cm (range, 0.6 – 4.5 cm). The median counts per minute for the hottest lymph node was 1107 (range, 0 – 6502 counts per minute).
Pathologic Evaluation of SLNs Fifteen patients (18%) had micrometastatic disease identified on the basis of further evaluation of SLNs with serial sectioning and IHC. Figure 1 shows an SLN that was negative according to H&E staining; however, further sectioning and IHC showed that this SLN contained micrometastases. The median size of micrometastases found by serial sectioning and IHC was 0.5 mm (range, 0.1–2.5 mm). Only 1 SLN was identified that had a metastatic focus ⬎ 2 mm. Two patients had foci of metastases ⬍ 0.2 mm. The finding of micrometastases in these patients did not correlate with most traditional prognostic factors (Table 2). Neither age nor primary tumor size correlated with the status of the SLN (P ⫽ 0.077 and P ⫽ 0.717, respectively). Furthermore, there was no correlation between the finding of micrometastases and the size of the largest lymph node removed (P ⫽ 0.490), the maximal radioisotope count (P ⫽ 0.058), or the number of SLNs removed (P ⫽ 0.918).
Adjuvant Therapy Patients received adjuvant systemic therapy based on their primary tumor characteristics. Information regarding systemic therapy was not available for 5 patients (6%). Among the remaining 79 patients, 28 patients (35%) received adjuvant chemotherapy, and 45 patients (57%) received adjuvant hormone therapy. Thirteen patients (16%) received both chemotherapy and hormone therapy. Nineteen patients (24%) did not receive adjuvant systemic treatment. Among the 15 patients who had micrometastases identified on serial sectioning and IHC, 5 patients (33%) received adjuvant chemotherapy based on primary tumor features alone. It is interesting to note that, of these, 2 patients who had metastatic foci that measured ⬍ 0.2 mm received adjuvant chemotherapy
FIGURE 1. (A) This sentinel lymph node was negative for metastatic disease by hematoxylin and eosin staining. (B) It was found that the same sentinel lymph node had metastatic disease based on serial sectioning and immunohistochemistry for cytokeratin.
based on primary tumor features. One patient who had a micrometastatic focus that measured ⬎ 2 mm received hormone therapy but not adjuvant chemotherapy. The remaining 10 patients who were identified with micrometastases that measured 0.2–2.0 mm did not receive adjuvant chemotherapy. In our practice, these patients otherwise would have been offered chemotherapy, resulting in a potential change in man-
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TABLE 2 Correlation between Sentinel Lymph Node Status and Traditional Prognostic Variables SLN status: No. of patients (%)
Feature
Negative (n ⴝ 69)
Positive (n ⴝ 15)
P value
Grade 3a Lymphovascular invasion presentb ER negativec PR negativec
29 (43.3) 1 (1.6) 21 (33.3) 25 (39.7)
6 (40.0) 1 (7.7) 5 (33.3) 2 (13.3)
0.148 0.274 1.000 0.040
TABLE 3 Survival According to Sentinel Lymph Node Status Five-yr actuarial survival
SLN negative (mean ⴞ SD %)
SLN positive (%)
P value
Overall Distant-metastasis-free
95.7 ⫾ 3.0 95.6 ⫾ 3.1
100 100
0.543 0.540
SLN: sentinel lymph node; SD: standard deviation.
SLN: sentinel lymph node; ER: estrogen receptor; PR: progesterone receptor. a Nuclear grade was not specified in 2 patients (2.4%), both of whom had negative immunohistochemistry results. b Lymphovascular invasion was not specified in 7 patients (8.3%), including 5 patients with negative immunohistochemistry results and 2 patients with positive immunohistochemistry results. c Estrogen receptor status was not recorded in 6 (7.1%) patients, all of whom had negative immunohistochemistry results; and progesterone receptor status was not documented in 6 patients (7.1%), all of whom had negative immunohistochemistry results.
agement in 13% of patients if serial sectioning and IHC had been performed initially.
Follow-Up The median follow-up after the initial diagnosis of breast carcinoma was 40.2 months (range, 0.9 –54.2 months). At the time of last follow-up, 81 patients (96%) were alive with no evidence of disease, 1 patient was alive with disease, 1 patient had died of disease, and 1 patient had died of unrelated causes (cerebrovascular accident). Both the patient who was alive with disease and the patient who died of disease developed distant metastases (lung and brain, respectively). Both of these patients had negative SLN status according to serial sectioning and IHC results. There was no significant difference in the occurrence of distant metastases between the group of patients with negative lymph node status according to serial sectioning and IHC results and the group of patients who had micrometastatic disease (P ⫽ 0.372). Furthermore, there was no difference in overall or distant metastasis-free survival (Table 3).
DISCUSSION With more rigorous pathologic analysis of SLNs, it is possible to find previously undetected foci of tumor cells. Other investigators have reported finding occult metastases in SLNs using serial sectioning and IHC in 4 –29% of patients.7–20 The current study and previous work from our institution concur, finding occult metastases in 18% of patients.21 In general, metastases found by IHC have been
small, with the majority measuring ⬍ 2 mm.7,10 –12,14 Two patients in our study had metastatic disease that measured ⬍ 0.2 mm, which would be classified as isolated tumor cells by the current American Joint Committee on Cancer staging system.22 The significance of such micrometastatic disease is uncertain, and it is not our practice to treat these patients as lymph node-positive. According to the National Institutes of Health consensus guidelines, patients with tumors that measure ⬎ 1.0 cm should be offered adjuvant therapy based on primary tumor characteristics alone.23 In the current study, 5 of 15 patients who had micrometastases identified by serial sectioning and IHC received adjuvant chemotherapy based on their primary tumor characteristics. Because it is our practice at The University of Texas M. D. Anderson Cancer Center also to offer chemotherapy to patients with micrometastatic disease (0.2–2.0 mm) in the regional lymph nodes, treatment may have been altered by the finding of such disease in 10 additional patients in the current study (13%). However, we did not find a significant difference in outcome in terms of survival or development of metastatic disease between patients with and without IHC-detected micrometastases. Although the number of patients in this study was small and the follow-up was relatively short, the current study should serve to call into question the impact of such minimal disease. Further investigation in this area is warranted, especially in this SLN era, when fewer lymph nodes are recovered at surgery and, thus, lymph nodes often are subjected to more scrutiny. Hansen et al. examined the John Wayne Cancer Center experience with 696 patients who had undergone SLN biopsy.24 Although those authors found a significant survival difference between patients who had macrometastases detected with H&E staining and patients with micrometastatic disease, they could not demonstrate any difference in disease-free or overall survival between patients who had micrometastases identified with IHC analysis and patients who had no lymph node involvement.24 Those results parallel the observations of the current study.
IHC-Detected Micrometastases/Chagpar et al. TABLE 4 Summary of Studies on the Impact of Microscopic Axillary Lymph Node Metastases on Survival
Study Bettelheim et al., 199026 Cote et al., 199931 Hainsworth et al., 199332 Trojani et al., 198733 McGuckin et al., 199528 Nasser et al., 199327 Friedman et al., 198829 Wilkinson et al., 198230
No. with negative lymph node status
Study method
Percent of patients with occult disease
Overall survival (% occult disease vs. % no occult disease)
921
SS
9
79 vs. 88
736 343
SS and IHC IHC
20 12
62 vs. 79a 70 vs. 85b
150
IHC
14
85 vs. 90c
208
SS and IHC
25
70 vs. 90d
159
SS and IHC
31
NS
456
SS
9
NS
525
SS
17
NS
SS: serial sectioning; IHC: immunohistochemistry; NS: not significant (P ⫽ 0.05). a For the subgroup of postmenopausal patients, not significant overall. b For the subgroup of patients with two or more lymph nodes involved, not significant overall. c For the subgroup of patients with ductal histology, not significant overall. d On univariate analysis; not significant on multivariate analysis.
Debate continues, however, regarding the impact of IHC-detected micrometastases on survival. Numerous studies have examined the impact on survival of stage migration secondary to more rigorous pathologic analysis in the setting of axillary lymph node dissection.25 Although some investigators found that the presence of micrometastases affected outcome negatively,26 others demonstrated no impact (Table 4).27–33 In a large study of 736 patients who underwent axillary lymph node dissection, the Ludwig group found that serial sectioning with H&E staining of 2 sections and 6 levels and IHC for 2 cytokeratin markers at 1 level significantly increased the detection rate of micrometastatic disease.30 Occult metastases were found in 52 patients (7%) and 148 patients (20%) by serial sectioning with H&E staining and by IHC, respectively.30 Occult disease detected by IHC was an independent predictor of disease recurrence, even after controlling for tumor grade, tumor size, estrogen receptor status, vascular invasion, and treatment.30 Regardless of the technique that was used to find occult disease, such disease was associated with significantly worse overall and disease-free survival in postmenopausal women.30 It is noteworthy that this was not the case for premenopausal women.30 A number of other studies similarly showed a survival benefit
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for a particular subgroup of patients.25,31,32 However, unlike ours, all of those studies were based on analysis of axillary lymph node dissection specimens (as opposed to SLN biopsy specimens), and there remains a paucity of data on the effect on survival of micrometastasis in SLNs. Further data on the relevance of micrometastatic disease in SLNs clearly are needed. The American College of Surgeons Oncology Group Z0010 trial, which was designed specifically to address this issue, completed accrual last year. That study should shed light on whether the use of serial sectioning, IHC, and molecular techniques, like reverse transcriptase-polymerase chain reaction analysis, to detect small foci or even single metastatic cells in SLNs, changes survival or has no real biologic significance.
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