Potential and pitfalls of sentinel node detection in breast cancer

The last decade has seen the development of a minimally invasive technique to identify representative nodes--sentinel nodes--that reflect the tumor status of nodes in the axillary lymphatic basin draining a primary breast carcinoma. Sentinel lymph node dissection (SLND), originally developed as an alternative to elective complete lymph node dissection in patients with primary cutaneous melanoma, has been applied successfully to the management of patients with breast cancer. SLND holds promise as a staging technique to replace formal level I and II axillary lymph node dissection in selected patients with breast carcinoma, thus avoiding an unnecessary procedure that has no role in many patients with tumor-free axillae. Under way are two large randomized trials examining the role of SLND for the management of patients with invasive breast carcinoma. Even when tumor is detected in the sentinel node, a focused examination of this node may indicate whether or not completion axillary lymph node dissection is necessary. However, although SLND has great potential, its successful widespread use requires more stringent definition of the sentinel node and standardized guidelines for lymphatic mapping. Each institution must carefully assess the accuracy and consistency of results obtained by its multidisciplinary SLND team.

Pathologic features associated with nonsentinel lymph node metastases in patients with metastatic breast carcinoma in a sentinel lymph node

BACKGROUND

To the authors' knowledge it has not yet been determined which patients with primary breast carcinoma and an axillary sentinel lymph node (SN) metastasis have additional metastases in nonsentinel lymph nodes.

METHODS

Pathologic features of the primary breast carcinoma and its SN metastasis were examined in 194 patients and correlated with the tumor status of the non-SNs in the same axillary basin. Two-level cytokeratin immunohistochemistry was applied to the SNs and to non-SNs of cases that were negative by standard hematoxylin and eosin examination.

RESULTS

Lymph node staging based on SN findings, size of the primary tumor, and presence of peritumoral lymphatic vascular invasion (LVI) were associated with non-SN metastasis. The majority (63%) of the 101 patients with SN macrometastases had non-SN metastases. Extranodal hilar tissue invasion in conjunction with SN involvement also was strongly associated with non-SN metastasis (P = 0.0001) but was present in only 65% of patients (35 of 54 patients) with non-SN macrometastases. Approximately 26% of patients (24 of 93 patients) with SN micrometastases (</= 2.0 mm) had non-SN metastases; among these patients only primary tumor size and peritumoral LVI were correlated with non-SN metastasis.

CONCLUSIONS

Detailed pathologic examination of the primary tumor and its SN metastasis may increase precision in the selection of patients for further axillary surgery or radiation therapy.

Gangliosides as targets for immunotherapy for pancreatic adenocarcinoma

BACKGROUND

Pancreatic adenocarcinoma cells express gangliosides and sialyl Lewis (sLe) antigens. It is not known whether these carbohydrate antigens can be targeted by immunotherapy. The authors measured the expression of GM(2) and sLe antigens on the surface of pancreatic carcinoma cells and the serum levels of total gangliosides, GM(2), and antiganglioside antibodies in patients with pancreatic carcinoma.

METHODS

Cell surface GM(2) and sLe antigens were measured by cell suspension enzyme linked immunoadsorbent assay (ELISA) in four pancreatic carcinoma cell lines. Sera from 20 pancreatic carcinoma patients and 20 age- and gender-matched healthy volunteers were analyzed for antiganglioside and anti-sLe immunoglobulin (Ig) M titers by ELISA. Serum levels of total gangliosides and GM(2) also were measured.

RESULTS

All cell lines expressed GM(2) and sLe antigens. When compared with age- and gender-matched volunteers, patients had significantly higher serum levels of total gangliosides (25.6 +/- 9.0 mg/dL vs. 15.6 +/- 2.7 mg/dL; P < 0.001), GM(2) (0.278 +/- 0.415 mg/dL vs. 0.013 +/- 0.018 mg/dL; P = 0.02), ELISA units of anti-GM(2) IgM antibody (368 +/- 95 vs. 155 +/- 25; P = 0.04) and anti-GD(1b) IgM antibody (351 +/- 91 vs. 138 +/- 26; P = 0.03), but not anti-sLe(x) IgM (1389 +/- 345 vs. 1081 +/- 224; P = 0.46) or anti-sLe(a) IgM antibody (1097 +/- 253 vs. 1200 +/- 315; P = 0.80). Patients with unresectable tumors had higher serum levels of total gangliosides compared with patients with resectable tumors, and a serum level > 25 mg/dL was found to correlate significantly with poor overall survival (P < 0.02).

CONCLUSIONS

Increased serum levels of total gangliosides and GM(2) may reflect shedding or release of gangliosides from the surface of tumor cells. Production of IgM antibody against GM(2) and GD(1b) indicates that these gangliosides are immunogenic antigens that may be potential targets for effective active immunotherapy.

Sentinel node metastasis in patients with breast carcinoma accurately predicts immunohistochemically detectable nonsentinel node metastasis

BACKGROUND

Sentinel lymphadenectomy is highly accurate for identifying axillary metastasis from a primary breast carcinoma. Nonsentinel axillary lymph nodes (NSNs) are unlikely to contain tumor cells if the axillary sentinel node (SN) is tumor free. We previously showed that the size of the primary tumor and the size of its SN metastasis predict the risk of NSN tumor involvement detected by hematoxylin and eosin staining. This study used immunohistochemical staining (IHC) to determine the likelihood of NSN axillary metastasis in the presence of SN metastasis.

METHODS

Between 1991 and 1997, axillary lymphadenectomy was performed in 156 women (157 axillary basins) who had primary breast carcinoma with SN metastasis. By hematoxylin and eosin staining, we identified NSN metastasis in 55 axillae (35%). IHC was then used to re-examine all NSNs (1827 lymph nodes) from the remaining 102 axillae. The incidence of IHC-detected NSN involvement was analyzed with respect to clinical and tumor characteristics.

RESULTS

By using IHC, we identified NSN metastasis in 15 (14.7%) of the 102 axillae. By multivariate analysis, the size of the SN metastasis (P = .0001) and the size of the primary tumor (P = .038) were the only independent variables predicting NSN metastasis determined by using either hematoxylin and eosin staining or IHC. Only the number of SN metastases (1 vs. >1) was a significant (P = .04) predictor of IHC-detected NSN metastasis.

CONCLUSIONS

Use of IHC increases the likelihood of detection of NSN metastasis, and the risk of IHC-detected metastasis increases with the size of the SN metastasis and the size of the primary tumor. If SN involvement is micrometastatic (< or =2 mm) or detected by using IHC, tumor cells are unlikely to be found in other axillary lymph nodes in patients with a small primary tumor. The clinical significance of micrometastatic disease in lymph nodes is controversial, and a prospective randomized study is necessary to resolve this important issue.

Do all patients with sentinel node metastasis from breast carcinoma need complete axillary node dissection?

OBJECTIVE

To determine the likelihood of nonsentinel axillary metastasis in the presence of sentinel node metastasis from a primary breast carcinoma.

SUMMARY BACKGROUND DATA

Sentinel lymphadenectomy is a highly accurate technique for identifying axillary metastasis from a primary breast carcinoma. Our group has shown that nonsentinel axillary lymph nodes are unlikely to contain tumor cells if the axillary sentinel node is tumor-free, but as yet no study has examined the risk of nonsentinel nodal involvement when the sentinel node contains tumor cells.

METHODS

Between 1991 and 1997, axillary lymphadenectomy was performed in 157 women with a tumor-involved sentinel node. Fifty-three axillae (33.5%) had at least one tumor-involved nonsentinel node. The authors analyzed the incidence of nonsentinel node involvement according to clinical and tumor characteristics.

RESULTS

Only two variables had a significant impact on the likelihood of nonsentinel node metastasis: the size of the sentinel node metastasis and the size of the primary tumor. The rate of nonsentinel node involvement was 7% when the sentinel node had a micrometastasis (< or =2 mm), compared with 55% when the sentinel node had a macrometastasis (>2 mm). In addition, the rate of nonsentinel node tumor involvement increased with the size of the primary tumor.

CONCLUSIONS

If a primary breast tumor is small and if sentinel node involvement is micrometastatic, then tumor cells are unlikely to be found in other axillary lymph nodes. This suggests that axillary lymph node dissection may not be necessary in patients with sentinel node micrometastases from T1/T2 lesions, or in patients with sentinel node metastases from T1a lesions.

Caloric restriction causes secretagogue specific changes of gastric acid secretion in rats

The purpose of this study was to examine the effects of short-term caloric restriction (CR) for 4, 8 and 16 weeks on gastric acid secretion in rats. CR rats fed 60% of normal food intake for 4, 8 or 16 weeks and then prepared with gastric fistulas. Histamine- and carbachol-stimulated gastric acid secretion were significantly (P < 0.05) decreased after more than 4 weeks and 8 weeks of caloric restriction, respectively. In contrast, gastrin-stimulated acid secretion was unaffected by CR. The 1-h-integrated acid output to a submaximal dose of gastrin (40 micrograms.kg-1) was significantly higher than that of histamine (5 mg.kg-1) after 8 weeks of CR (63 +/- 13 and 27 +/- 4 microEq.h-1, respectively). Gastrin treatment (5 micrograms.kg-1.h-1) of CR rats restored the gastric acid responses to both histamine and carbachol. These results suggest that CR can selectively decrease the gastric acid responses to both histamine and carbachol by depletion of the endogenous tissue stores of gastrin. More importantly, these results indicate that under an in vivo gastrin-diminished condition, histamine is not the final secretagogue for gastric acid secretion.

Mechanisms of bombesin on growth of gastrinoma (PT) in vivo

The growth of the human gastrinoma model (PT) in athymic nude mice is stimulated by bombesin (BBS), an amphibian peptide homologous to both human gastrin-releasing peptide (GRP) and neuromedin B (NMB). The mechanism is not known, and a potent and specific GRP-R antagonist BIM26226, which has low affinity for NMB-R, was used in vivo in athymic nude mice bearing gastrinoma subcutaneously. Both the BBS and BIM26226 stimulated the growth of PT, and the growth stimulation was even greater when given together. RT-PCR study of gastrinoma revealed the presence of both GRP-R and NMB-R mRNA, but much more abundant NMB-R mRNA. We conclude that BBS-stimulated growth of gastrinoma involves both GRP-R and NMB-R, and our findings suggest that GRP-R mediates negative and NMB-R produces positive growth effects on gastrinoma.

Short-term caloric restriction augments age-related decreases in gastrin content and release

Aging is associated with significant structural and functional changes in the gastrointestinal tract. Gastrin, a hormone produced by G cells in the antrum of the stomach, stimulates proliferation of gastric mucosa; its synthesis appears to decrease with age. Life-long restriction of caloric intake is the only experimental manipulation that has been shown to retard aging processes in rats. The purpose of this study was to examine the effect of short-term caloric restriction (CR) on the production and release of the hormone gastrin with aging. Aging causes a fall in both fasting plasma levels of gastrin and antral content of gastrin in Fischer 344 rats; short-term CR appears to augment this age-related decrease. Steady state levels of antral gastrin mRNA were decreased with aging, and short-term CR resulted in an augmented decrease in aged, but not in young rats. Our findings indicate that gastrin release, synthesis and gene expression decrease with age. Restriction of the caloric intake for a short period (i.e. 8 weeks) augments this age-related decrease in antral gastrin and fasting plasma levels. Short-term CR appears to decrease the production of gastrin at the level of gene expression.

Caloric restriction increases the expression of heat shock protein in the gut

OBJECTIVE

The authors determined whether caloric restriction (CR) either acutely or chronically, alters heat shock protein 70 (hsp70) gene expression in the gut.

SUMMARY BACKGROUND DATA

Caloric restriction prolongs the life span and delays age-related disease (e.g., cancer) in mammals; the mechanisms responsible for these effects are not known. Heat shock proteins are a group of stress-responsive genes of which the most prominent member is hsp70.

METHODS

In the first experiment, adult (4-month-old) rats (n = 3/group) were killed after a 48-hour fast or 6 and 24 hours after refeeding. In addition, three rats (controls) were killed without fasting or refeeding. The stomach was removed and RNA was extracted for hsp70 gene expression. In the second experiment, aged (22- to 26-month-old) rats were fed ad libitum (AL) or a CR diet (60% caloric intake of AL diet). Rats were killed, the stomach and duodenum were removed, and RNA was extracted for determination of hsp70 gene expression.

RESULTS

In the first experiment, hsp70 mRNA levels were increased approximately threefold in the stomach of rats fasted for 48 hours; levels decreased to control values by 6 and 24 hours after refeeding. In the second experiment, hsp70 mRNA levels were increased significantly in both the stomach and duodenum of aged CR rats compared with AL controls.

CONCLUSIONS

The authors have demonstrated that hsp70 mRNA levels are increased in the proximal gut of young and old rats, either acutely (with fasting) or with CR. Increased expression of the cytoprotective hsp70 gene in the gut may provide a possible cellular mechanism for the beneficial effects noted with CR.

Role of bombesin on gut mucosal growth

OBJECTIVE

The authors examined the effects of exogenous bombesin (BBS) on gut mucosal growth in chow-fed rats and the mucosal regeneration after gut atrophy brought about by feeding an elemental diet and after intestinal injury produced by methotrexate (MTX).

SUMMARY BACKGROUND DATA

Bombesin is one of many gastrointestinal peptides implicated in the regulation of gut mucosal growth. Although BBS is known to stimulate growth of normal pancreatic tissue, the trophic effect of BBS on gut mucosa is less clear and its exact role in gut mucosal regeneration and repair is not known.

METHODS

Rats were fed a regular chow diet (control) or an elemental diet plus either saline or BBS (10 micrograms/kg). In another experiment, rats fed a chow diet and treated with saline or BBS were given MTX (20 micrograms/kg) or a single intraperitoneal injection. In all experiments, small and large bowel mucosa and pancreas were removed and analyzed for BBS-mediated proliferation.

RESULTS

Bombesin produced significant mucosal proliferation of the small bowel at day 14, but not at day 7, in rats fed regular chow. In contrast, BBS treatment for 7 days produced significant proliferation in both the atrophic and injured gut mucosa of rats given elemental diet or MTX.

CONCLUSIONS

Bombesin may be an important enterotrophic factor for normal mucosal proliferation and may be clinically beneficial as an agent to restore or maintain gut mucosa during periods of atrophy or injury.

Bombesin stimulates mucosal growth in jejunal and ileal Thiry-Vella fistulas

OBJECTIVE

The authors determined whether the trophic effects of bombesin (BBS) on the small bowel mucosa are mediated by either nonluminal factors or endogenous luminal secretion.

SUMMARY BACKGROUND DATA

The gut hormone bombesin stimulates growth of small bowel mucosa. The mechanisms responsible for this trophic effect are not known.

METHODS

Rats underwent construction of a Thiry-Vella fistula (TVF) of either the jejunum or ileum. On postoperative day 10, the two groups were subdivided to receive either saline (control) or bombesin (10 micrograms/kg, subcutaneously, three times a day). After 14 days, rats were killed and the TVF was removed. The mucosa was scraped and weighed, and DNA and protein content was determined.

RESULTS

Bombesin significantly increased mucosal weight and DNA and protein content of both the jejunal and ileal TVF compared with the control rats.

CONCLUSIONS

Bombesin-mediated stimulation of small bowel mucosal growth is mediated by factors that are independent of luminal contents and pancreaticobiliary secretion. Bombesin may prove to be an important enterotrophic factor for gut mucosal proliferation.

Trophic response of gut and pancreas after ileojejunal transposition

OBJECTIVE

The authors determined whether ileojejunal transposition (IJT) stimulates the growth of the pancreas or the nontransposed segment of small intestine, and ascertained whether this trophic effect is altered by the location of transposed gut segment.

SUMMARY BACKGROUND DATA

Transposition of the ileum to the proximal small intestine stimulates a marked mucosal growth of the transposed ileal segment; the cellular mechanisms responsible for this adaptive hyperplasia are not known.

METHODS

The distal quarter of the small intestine (distal ileum) was transposed into the proximal (Type I), middle (Type II), or distal (Type III) portions of the remaining small intestine. On postoperative day 28, the pancreas and scraped mucosa from the segments of transposed ileum, proximal ileum, and duodenum were obtained, weighed, and examined for DNA and protein content.

RESULTS

All types of IJT increased mucosal weight and DNA content of the transposed ileum. Types I and II IJT produced a significant proliferation of the pancreas and mucosa of the duodenum and proximal ileum. The magnitude of proliferative increases was greatest in Type I IJT.

CONCLUSIONS

Ileojejunal transposition appears to be an excellent model to examine the mechanisms by which intestinal epithelial cells proliferate in response to luminal nutrients or humoral factors.

Bombesin improves survival from methotrexate-induced enterocolitis

OBJECTIVE

The authors determined whether bombesin could improve survival from methotrexate (MTX)-induced enterocolitis.

SUMMARY BACKGROUND DATA

Bombesin prevents gut mucosal atrophy, which is produced by feeding rats an elemental diet. Administration of MTX produces a lethal enterocolitis in rats fed an elemental diet.

METHODS

On treatment day 0, 60 rats were divided randomly into three groups and fed an elemental diet (Vivonex TEN, Sandoz, Minneapolis, MN) as the only source of nutrition. Groups were subdivided further to receive either saline or bombesin (10 micrograms/kg, subcutaneously, three times a day) beginning either on day 0 or day 14. Methotrexate (20 mg/kg, intraperitoneally) was given to all rats 14 days after the start of an elemental diet.

RESULTS

Bombesin prevented the mucosal atrophy in the ileum produced by the elemental diet and significantly decreased mortality in rats given MTX (whether given as a pretreatment or at the time of MTX administration).

CONCLUSION

Bombesin significantly improved survival in a lethal model of MTX-induced enterocolitis, possibly by maintaining gut mucosal structure. Administration of bombesin to patients receiving chemotherapy may be clinically useful in preventing the severe enterocolitis induced by various chemotherapeutic agents.

Change in endocrine pancreatic function in short-term diet restriction

Long-term diet restriction can retard the aging process. Lower sustained plasma glucose levels may be one of the key factors for prolongation of life. The purpose of this study was to determine the effects of short-term diet restriction on the endocrine pancreas in rats. One hundred 5-wk-old male Sprague-Dawley rats were fed ad libitum for 1 wk, and then 10 rats (5 fed, 5 fasted for 24 h) were killed. The remaining 90 rats were divided into two groups, either fed ad libitum or maintained on a restricted food intake (60% of control/day). At regular intervals after the start of food restriction, rats from each group were killed, and plasma and the pancreas were collected for measurements of glucose, insulin, and glucagon concentration and content. At the end of the study, isolated pancreatic perfusions were performed to examine dynamic insulin response to glucose. Throughout the study, plasma glucose and insulin levels were lower in fed rats from the diet-restricted group than in fed rats from the normally fed group. Furthermore, there were no differences in plasma glucose or insulin levels between fed and fasted rats in the diet-restricted group. Pancreatic perfusion showed that the second phase of insulin release was significantly lower in rats from the diet-restricted group than in rats from the normally fed group. Decreased content of spermine in the pancreas of the diet-restricted rats may correlate with a decreased second phase of insulin release. These findings may partly explain why lowered plasma insulin levels are observed in diet-restricted rats.