Cell kinetics as a predictive factor in node-positive breast cancer treated with adjuvant hormone therapy

Cell proliferation of the primary tumor predicts ipsilateral axillary node disease in elderly breast cancer patients

The present study investigated whether tumor markers such as cell proliferation and steroid receptor status, which have been shown to have relevance for important endpoints (relapse-free and overall survival), can also predict axillary disease in elderly patients with breast cancer. We evaluated 351 consecutive elderly women with breast cancer ≥70 years of age with estrogen receptor (ER)‑positive tumors with no palpable axillary nodes, for whom information on cell proliferation determined by the 3H-thymidine labeling index (TLI) and progesterone receptor (PgR) was available. Patients underwent quadrantectomy (70.1%) or quadrantectomy plus radiotherapy (29.9%) without axillary node dissection, followed by adjuvant tamoxifen for at least 2 years. Univariable (cumulative incidence curves) and multivariable analyses (Fine and Gray models) were carried out. After a median follow-up of 16 years, ipsilateral axillary relapse was not related to PgR status but was strongly associated with tumor cell proliferation in both small (pT1) and large (pT2-4b) tumors. Axillary relapse cumulative incidence increased from 1% in patients with low-TLI (≤3%), PgR-positive and pT1 tumors to a maximum of 20% in patients with high-TLI, PgR-negative and pT2-4b tumors. Tumor cell proliferation, determined by TLI at primary surgery, is an important predictor of axillary relapse in elderly ER-positive breast cancer patients and could help to identify patients who should undergo axillary surgery.

A New TNM Classification for Breast Cancer to Meet the Demands of the Present and the Challenges of the Future

In this article we will describe our proposed changes to the breast cancer tumor node metastasis (TNM) classification which, while retaining TNM structure to ensure backwards compatibility, will render it more useful and better able to accommodate future developments. We propose changing T to specify exact tumor size (a tumor of pathological diameter 1.7 cm would be pT1.7); changing N to specify the number of metastatic lymph nodes over the total number removed (e.g., pN5/21); adding suffixes to M to indicate metastatic site; removing in situ neoplasms from the classification, since they are not carcinomas and are incapable of metastasizing; and removing the terms ‘infiltrating’ and ‘invasive’ since they are redundant. Finally, we would include hormone receptor, HER2, and other biological indicators of prognosis, as they are verified, in a placeholder system appended to the TNM. These proposals shift the emphasis from the quantity of tumor present to the quality of the cancer.

Is the thymidine labeling index a good prognostic marker in breast cancer?

Background

The aim of the present study was to determine the prognostic relevance of thymidine labeling index (TLI) in patients with breast cancer.

Methods

TLI of the primary tumor was measured in 268 patients at the time of the surgical biopsy by an in vitro method.

Results

Fifty-four patients had stage I disease, and 138 patients had stage II disease, and 76 patients had stage III disease. One hundred-four patients were found to have low TLI-index (<3%), and 164 patients had high TLI-index (≥3%). The median follow-up was 71.5 months (range, 6–138 months). The 5-year overall survival (OS) and disease free survival (DFS) rates was 84% and 74%, respectively. Lymph node involvement, tumor size more than 2 cm, high nuclear grade and estrogen receptor negativity were found to be associated with poorer DFS and OS rates. On subgroup analysis, however, the 5-year OS rate was significantly higher in the low TLI-group than in the high TLI-group in patients with stage I disease (100% vs 76%, p = 0.05).

Conclusion

Our findings suggest that the prognostic significance of TLI appears to be limited to early breast cancer that might help to distinguish patients who need more aggressive adjuvant treatment.

Pathology parameters and adjuvant tamoxifen response in a randomised premenopausal breast cancer trial

BACKGROUND

Subgroups of breast cancer that have an impaired response to endocrine treatment, despite hormone receptor positivity, are still poorly defined. Breast cancer can be subdivided according to standard pathological parameters including histological type, grade, and assessment of proliferation. These parameters are the net result of combinations of genetic alterations effecting tumour behaviour and could potentially reflect subtypes that respond differently to endocrine treatment.

AIMS

To investigate the usefulness of these parameters as predictors of the response to tamoxifen in premenopausal women with breast cancer.

MATERIALS/METHODS

Clinically established pathological parameters were assessed and related to the tamoxifen response in 500 available tumour specimens from 564 premenopausal patients with breast cancer randomised to either two years of tamoxifen or no treatment with 14 years of follow up. Proliferation was further evaluated by immunohistochemical Ki-67 expression.

RESULTS

Oestrogen receptor positive ductal carcinomas responded as expected to tamoxifen, whereas the difference in recurrence free survival between control and tamoxifen treated patients was less apparent in the relatively few lobular carcinomas. For histological grade, there was no obvious difference in treatment response between the groups. The relation between proliferation and tamoxifen response seemed to be more complex, with a clear response in tumours with high and low proliferation, whereas tumours with intermediate proliferation defined by Ki-67 responded more poorly.

CONCLUSIONS

Clinically established pathology parameters seem to mirror the endocrine treatment response and could potentially be valuable in future treatment decisions for patients with breast cancer.

Prognostic value of proliferation in invasive breast cancer: a review

Breast cancer is the leading cause of death among solid tumours in women, and its incidence is increasing in the West. Adjuvant chemotherapy and hormonal treatment improve survival but have potentially serious side effects, and are costly. Because adjuvant treatment should be given to high risk patients only, and traditional prognostic factors (lymph node status, tumour size) are insufficiently accurate, better predictors of high risk and treatment response are needed. Invasive breast cancer metastasises haematogenously very early on, so many breast cancer prognosticators are directly or indirectly related to proliferation. Although studies evaluating the role of individual proliferation regulating genes have greatly increased our knowledge of this complex process, the functional end result-cells dividing-has remained the most important prognostic factor. This article reviews the prognostic value of different proliferation assays in invasive breast cancer, and concludes that increased proliferation correlates strongly with poor prognosis, irrespective of the methodology used. Mitosis counting provides the most reproducible and independent prognostic value, and Ki67/MIB1 labelling and cyclin A index are promising alternatives that need methodological fine tuning.

Relationship between the thymidine labeling and Ki-67 proliferative indices in 126 breast cancer patients

Proliferative activity has been proposed as a prognostic and predictive marker for breast cancer; Ki-67 is one of the most frequently used markers to assess proliferative activity. In the current study, Ki-67 immunoreactivity was comparatively assessed, even in terms prognostic relevance, with 3H-thymidine labeling index as a reference standard for proliferation in 126 patients with stage I and II breast cancer. There was a significant but weak correlation between Ki-67 values and the 3H-thymidine labeling index (r = 0.19, P = 0.03). Analysis of variance showed that the mean 3H-thymidine labeling index values were not statistically different in terms of pathologic size (T1, T2. T3, T4), number of pathologically positive axillary nodes (neg, pos 1-3, pos > 3), and grading classes (1, 2, 3), but significantly and inversely correlated with estrogen receptor status (P = 0.033) and progesterone receptor status (P = 0.08). The Ki-67 values significantly correlated with N status (P = 0.041), estrogen receptor status (P < 0.001), progesterone receptor status (P < 0.001), and grading (P < 0.001). The median follow-up was 37 months. In terms of prognosis, Ki-67 was associated significantly with overall survival (P = 0.01) and marginally with disease-free survival (P = 0.095). A significant difference in prognosis was found for both disease-free survival (P = 0.024) and overall survival (P = 0.040) when a 3H-thymidine labeling index cut-off of 6.5% was used (P = 0.024). The results suggest that, although both are indicators of proliferative activity, 3H-thymidine labeling index and Ki-67 seem to identify breast cancers with different phenotypes.

Prognostic and predictive role of proliferation indices in adjuvant therapy of breast cancer

In breast cancer, proliferative activity represents one of the biologic processes most thoroughly investigated for its association with tumor progression. In addition to the mitotic activity component of pathologic grading systems, several proliferation indices have provided independent information on prognosis and response to specific treatments in large retrospective studies. Recently, results from treatment protocols prospectively planned to test the clinical utility of proliferative activity have indicated that tumor cell proliferation markers identify two subsets among patients with lymph node-negative cancers: 1) those at a very low risk of relapse and 2) those who will benefit from regimens including antimetabolites. Future efforts should compare the prognostic accuracy of different proliferation markers, confirm preliminary evidence of a relationship between proliferation and response to specific systemic treatments, and standardize assay techniques to facilitate their transfer to general oncology practice.

Factors associated with success of the extreme drug resistance assay in primary breast cancer specimens

The extreme drug resistance (EDR) assay has not been widely studied in the setting of non-metastatic breast cancer. We evaluated the feasibility of performing the assay in 144 primary breast tumor specimens from two institutions by determining the rate of successful tumor culture for assays, number of drugs evaluated per assay, and time from tumor biopsy to receipt of results. We also sought to determine factors that are associated with assay success. An exploratory analysis was performed to detect possible associations between estrogen receptor (ER), progesterone receptor (PR) and HER2/NEU over-expression and extreme drug resistance demonstrated by the assay for specific chemotherapeutic agents. Of 144 tumor specimens submitted, tumor was successfully cultured for assay in 101(70%) of cases. A median of five drugs was evaluated per assay (range 2-9). Results were obtained in a median of 8 days (range 2-29). Young age, high tumor grade, PR negativity, and higher tumor submission weight were predictive for a successful assay. EDR was observed in 7-15% of tumors to doxorubicin, cyclophosphamide, 5-fluorouracil (5FU) and mitoxantrone, but EDR to paclitaxel was observed in 35%. Extreme drug resistance to 5-FU was associated with negative ER and PR status. There was a trend toward association between EDR to paclitaxel and HER2/NEU over-expression. The EDR assay may be successfully performed in the majority of tumors, and assay results are available in a timely fashion such that adjuvant treatment drug selection could be guided by results. These results may be helpful for designing possible future trials that evaluate the assay's role in adjuvant chemotherapy selection.

Comparison between different cell kinetic variables in human breast cancer

Cell kinetics holds a prominent role among biological factors in predicting clinical outcome and response to treatment in neoplastic patients. Different cell kinetic variables are often considered as valid alternatives to each other, but the limited size of case series analysed in several studies and the lack of simultaneous determinations of all the variables on the same tumours do not justify this conclusion. In the present study, the correlation between [3H]thymidine labelling index ([3H]dT LI), flow cytometric S phase cell fraction (FCM-S) and Ki-67 immunoreactivity (Ki-67/MIB-1) was verified and the type of correlation with the most important clinical, pathological and biological patient and tumour characteristics was investigated in a very large series of breast cancer patients. Ki-67/MIB-1, FCM-S and [3H]dT LI were determined in 609, 526 and 485 patients, respectively, and all three cell proliferation indices were evaluated in parallel on the same tumour in a series of 330 breast cancer patients. All the cell kinetic determinations were performed within the context of National Quality Control Programmes. Very poor correlation coefficients (ranging from 0.37 to 0.18) were observed between the different cell kinetic variables determined in parallel on the same series of breast cancers. Moreover, Ki-67/MIB-1 and FCM-S showed a significant relationship with histological type, grade and tumour size, whereas statistically significant correlations were not observed for [3H]dT LI. In conclusion, the results show that the different cell kinetic variables provide different biological information and cannot be considered as alternatives to each other.

Biomarker prediction of clinical outcome in operable breast cancer patients treated with tamoxifen

The predictivity of tumour size, oestrogen (ER) and progesterone (PgR) receptors, 3H-thymidine labelling index (TLI), c-erbB-2 and p27kip1 expression on clinical outcome was analysed on a consecutive series of 118 postmenopausal patients with ER-positive, node-positive tumours. All patients were treated with surgery +/- radiotherapy and adjuvant tamoxifen (30 mg/day) for at least 2 years. TLI, ER, c-erbB-2 and p27kip1 were generally unrelated to each other. PgR was directly related to ER and inversely to c-erbB-2. Tumour size was inversely related to both c-erbB-2 and p27kip1 expression. At a median follow-up of 75 months, 5-year relapse-free survival was significantly lower for patients with very rapidly proliferating (HR = 2.61, 95% CI = 1.34-5.08), PgR negative (HR = 2.76, 95% CI = 1.43-5.33) or relatively low ER content (HR = 2.20, 95% CI = 1.14-4.25) tumours than for patients with tumours expressing the opposite biological profiles. Overall survival was also significantly different as a function of TLI (HR = 3.47, 95% CI = 1.52-7.93) and PgR (HR = 2.27, 95% CI = 1.00-5.15). TLI and PgR maintained an independent relevance in multivariate analysis and together were capable of identifying subgroups of patients at significantly different risk of relapse and death.

Prognostic significance of biologic markers in node-negative breast cancer patients: a prospective study

It is generally thought that future advances in the treatment and cure of breast cancer patients will be made possible through a deeper understanding of tumor biology and an improved capability to define the prognosis of each single patient. This will lead to the formulation of new, more selective, and patient-tailored therapies. It is therefore important, when studying potential prognostic factors, to follow methodologic requirements and guidelines which involve the carrying out of prospective studies as confirmatory steps. Repeatedly or recently investigated prognostic markers (tumor size, menopausal status, ER, PgR, 3H thymidine labeling index, c-erbB-2 and p27 expression) were evaluated on a series of 286 prospectively recruited node negative breast cancer patients who underwent loco-regional treatment alone and were closely followed. The individual and relative prognostic contribution of each variable with respect to other factors, as well as their ability to identify node negative patients at risk, were assessed by univariate and multivariate analysis. At a five-year follow-up, only tumor size (p = 0.021) and TLI (p = 0.016) individually proved to be significant prognostic indicators of relapse-free survival. Conversely, p27 expression was not related to RFS and c-erbB-2 expression appeared to have only a short-term effect on patient prognosis. TLI and tumor size, tested in multivariate analysis along with ER and menopausal status, maintained their independent prognostic relevance. The study, performed on a large series of node-negative patients given loco-regional treatment alone, for the first time prospectively recruited, showed the prognostic relevance of TLI and its independence from other clinico-pathologic and biologic factors over a five-year period.

The prognostic value of proliferation indices: a study with in vivo bromodeoxyuridine and Ki-67

Proliferation indices are intended to help patients and clinicians make treatment decisions. We have previously demonstrated that a proliferation index based on in vivo labeling of S-phase cells with bromodeoxyuridine (BrdUrd) correlates with Ki-67 labeling index (LI). We now compare the prognostic value of these indices. With written consent, we gave 129 women with biopsy confirmed breast cancer 200 mg/M2 BrdUrd during 30 min immediately preceding surgery. We used IU-4 anti BrdUrd antibody to count the immunohistochemical labeling index (LI) of DNA-incorporated BrdUrd in 2,000 cells and MIB-1 to count Ki-67 (118 cases). Patients received standard surgical and adjuvant treatment. No patients were lost to follow-up and patients were followed a minimum of 2 (median 5.1) years. We compared survival and recurrence in tumors with high vs low labeling indices. We found that women in the low BrdUrd LI group had better disease free survival (92% vs 67% 5-yr DFS p = 0.001) and overall survival (94% vs 70% 5-yr OS, p = 0.0001) than those with a high LI. In comparison, a low Ki-67 index predicted better OS (87% vs 80% 5-yr OS, p = 0.020) and a trend for better DFS (84% vs 72% DFS p = 0.055). The apparent superiority of BrdUrd LI over Ki-67 LI is likely due to chance (p = 0.18). In multivariate survival analyses we found that BrdUrd LI proliferative index significantly improves prediction of DFS or OS even when node status, age or tumor size is in the model. We conclude that markers of proliferation are useful adjuncts in predicting patient prognosis.

Biomarkers and outcome after tamoxifen treatment in node-positive breast cancers from elderly women

The predictive role of tumour proliferative rate and expression of p53, bcl-2 and bax proteins, alone and in association with tumour size, nodal involvement and oestrogen receptors (ER), was analysed on 145 elderly patients (> or =70 years of age) with histologically assessed node-positive breast cancers treated with radical or conservative surgery plus radiotherapy followed by adjuvant tamoxifen for at least 1 year. The 7-year probability of relapse was significantly higher for patients with tumours rapidly proliferating (hazard ratio (HR) = 2.0, P = 0.01), overexpressing p53 (HR = 4.4, P = 0.0001), weakly or not exhibiting bcl-2 (HR = 1.9, P = 0.02), without ERs (HR = 3.4, P = 0.0001) or with > or = 4 positive lymph nodes (HR = 2.3, P = 0.003) than for patients with tumours expressing the opposite patho-biological profile. Conversely, tumour size and bax expression failed to influence relapse-free survival. Adjustment for the duration of tamoxifen treatment did not change these findings. Oestrogen receptors, cell proliferation, p53 accumulation and bcl-2 expression were also predictive for overall survival. Within ER-positive tumours, cell proliferation, p53 accumulation, bcl-2 expression and lymph node involvement provided significant and independent information for relapse and, in association, identified subgroups of patients with relapse probabilities of 20% (low-risk group, exhibiting only one unfavourable factor) to 90% (high-risk group, exhibiting three unfavourable factors). Such data could represent the initial framework for a biologically tailored therapy even for elderly patients and highlight the importance of a patho-biological characterization of their breast cancers.

Routinely available indicators of prognosis in breast cancer

Diagnosis coupled with prognostication is the challenge for and charge of the pathologist. In this time of rapidly developing basic knowledge and increasing sophistication in the evaluation of prognostic information, there has also been an important re-evaluation of the validity, reliability, and relevance of classic histopathology. Also, the precision of and criteria for evaluating tumor size and status of regional lymph nodes is under study. Our emphasis in this review is tissue pathology and further, its practical relevance to patient management. Histopathology remains the basis of diagnosis universally; the addition of other elements will increase precision of prediction, particularly of responsiveness to individual therapies. Histologic grade may be integrated to substratify high and low stage cases into prognostically more useful subsets. Histologic types also interact with size and nodal status to predict patients with excellent prognosis. Further refinement of these parameters may occur by analysis within clinical, pathologic, or therapeutic subsets.

Prognostic and predictive value of thymidine labelling index in breast cancer

In the last few decades, much effort has been directed towards identifying the phenotypic or functional aspect of tumor cells which can contribute to a biofunctional staging for improving the accuracy of pathologic staging used for identifying patients at different risk. Among known biologic factors, the proliferative capacity of the tumor cell population, a feature common to all tumors, has been widely investigated. Several approaches have been used to measure different aspects of the cell cycle. Among these, the thymidine labeling index (TLI) represents the fraction of cells in S-phase cell fraction and is based on the active incorporation of labelled thymidine into DNA. From basic studies conducted on several thousands of patients, the TLI of primary breast cancers appears closely related to steroid receptor status and generally unrelated to pathologic stage. Retrospective analyses performed on large series of patients treated with local regional therapy alone have consistently shown the relevance of TLI value to clinical aggressiveness in terms of relapse-free survival and overall survival. Moreover, TLI is a prognostic indicator which is independent of tumor size, steroid receptors, and p53 and bc12 protein expression, and which, together with patient age and tumor size, is able to identify patients at different risk of loco-regional or distant metastases. Recently, a direct relationship between TLI and response to polychemotherapy has been shown in patients with operable and advanced breast cancers. This finding, derived from retrospective and recently confirmed in prospective clinical studies, has led to the activation of cell kinetics based therapeutic protocols for patients with node-negative and one to three node-positive operable breast cancers.

Prognosis and prediction of response in breast cancer: the current role of the main biological markers

In the medical literature there are frequently conflicting reports on the utility of biological tumour markers available in the clinical management of breast cancer. In this review we analyse current information on the relationships between the most widely investigated breast cancer biological markers including oestrogen and progesterone receptors, p53, Bcl-2, c-erbB-2, cyclin expression, proliferative activity, DNA ploidy and the urokinase plasminogen activation system, as well as their relevance to prognosis and response to clinical treatment. By biological prognostic indicator, we mean a marker that correlates with survival and disease-free survival; the term predictor marker indicates a marker that is capable of predicting tumour sensitivity or resistance to various therapies. Similarly to other authors' experiences, our analysis suggests that oestrogen receptors are weak prognostic indicators and good predictors of response to endocrine therapy. Furthermore, there are consistent data suggesting that proliferation indices are good indicators of prognosis, and that they are directly related to response to chemotherapy and closely related to response to hormonotherapy. On the contrary, there is no evidence or conflicting data for all of the other biological markers. These should be considered in the context of randomized trials in order to precisely define their prognostic and predictive roles. p53 and c-erbB-2 seem to be the most promising factors, but their use in routine practice still needs validation.

Expression of p53, glutathione S-transferase-pi, and Bcl-2 proteins and benefit from adjuvant radiotherapy in breast cancer

BACKGROUND

In clinical breast cancer research, the utility of certain biomarkers as predictors of response to surgery, chemotherapy, or hormonal therapy has been studied intensively. Much less research has been done on the relevance of biologic predictors of response to radiotherapy, which represents an effective local-regional treatment for breast cancer.

PURPOSE

The utility of biomarkers involved in DNA damage repair (p53 protein), control of programmed cell death (p53 and Bcl-2 proteins), and cellular detoxification (glutathione S-transferase-pi [GST-pi] enzyme) in predicting local breast cancer recurrence was analyzed retrospectively in two cohorts of breast cancer patients. These patients had had no detectable metastases in the axillary lymph nodes (i.e., node-negative) or in distant sites and had had similar distributions of clinicopathologic and biologic prognostic features. They had been treated by conservative surgery alone (139 case patients) or by conservative surgery followed by adjuvant radiotherapy (496 case patients) during the period from 1984 through 1990.

METHODS

The expression of the p53, GST-pi, and Bcl-2 proteins in the specimens of primary breast tumor obtained from these patients was determined by use of immunohistochemistry; cell proliferation activity and levels of steroid receptors were determined by use of a [3H]thymidine-labeling index assay and the dextran-coated charcoal technique, respectively. The median time of follow-up of patients was 6 years. In the analyses of patient outcomes, only local failures that presented as first events were considered.

RESULTS

After surgery alone, the risk of local recurrence at 6 years was higher for patients with tumors exhibiting elevated levels of p53 and GST-pi protein expression than for patients with low levels (hazard ratio [HR] = 3.1, 95% confidence interval [CI] = 1.3-7.7, two-sided P = .012; HR = 2.7, 95% CI = 1.1-6.4, two-sided P = .026, respectively). Weak or no observable expression of Bcl-2 protein was only suggestive of a higher frequency of local failures. Adjustment for patient age, tumor size, cell proliferation, and estrogen receptor status did not change these findings. Conversely, in the series of patients given conservative surgery followed by radiotherapy, there was no difference in local tumor recurrence between patients with tumors expressing or not expressing each of the three markers.

CONCLUSIONS

Our study provides indirect evidence of a benefit from radiation therapy in preventing local breast cancer relapse, particularly among node-negative patients with tumors that express elevated levels of the p53 or GST-pi proteins or that express little or no Bcl-2 protein.

Cell proliferation as a predictor of response to chemotherapy in metastatic breast cancer: a prospective study

Many biologic prognostic markers are available for patients with breast cancer, and considerable interest has been devoted to confirm preliminary evidence of their role as indicators of treatment response. It remains to be assessed whether such markers are predictors of response only to first-line or also to successive therapies. Proliferative activity, defined by the 3H-thymidine labeling index (TLI), was determined on the primary lesion from 76 patients at time of first diagnosis. At relapse, patients underwent chemotherapy as absolute (48 cases) or relative (28 cases) first-line treatment, and their clinical response was analyzed in relation to the TLI of the primary lesion. The objective clinical response was significantly higher for rapidly (47%; CL, 33-61%) than for slowly proliferating tumors (15%; CL, 1-29%). These findings held true also when adjusted for metastatic site, previous treatment, chemotherapy regimen administered, and hormone receptor status. However, the direct relation between cell proliferation and benefit from chemotherapy held true only when such a treatment was used as an absolute first-line approach. Cell proliferation of primary lesions represents a consistent indicator of response to chemotherapy over time. Previously administered regimens, at least hormone therapy, could alter the proliferation-related chemosensitivity profile of individual tumors.

Cell proliferation in 3,800 node-negative breast cancers: consistency over time of biological and clinical information provided by 3H-thymidine labelling index

For breast cancer, many prognostic markers that initially appeared promising have failed to maintain their clinical predictive value. Few reports have analyzed the consistency over time of biological and clinical information provided by biomarkers. Tumour cell proliferation has acquired relevance as an indicator of prognosis and of response to treatment. Since its clinical role has been investigated for some decades, cell proliferation represents an ideal marker for an over-time validation. In 3,800 node-negative breast cancers recruited between 1972 and 1991, the consistency of information provided by the 3H-thymidine labelling index (TLI), in terms of basic relations with other clinico-pathological and biological variables and clinical predictivity, was evaluated using a combined analysis of results previously published by our group for distinct series of patients. Clinical predictivity was analyzed on a subset of 2,067 patients given local-regional therapy until relapse and followed for a median time from 6 to 10 years. Over the entire period TLI maintained a weak direct relation with tumour size and an inverse strong relation with steroid receptors. An increase in TLI was observed for tumours in post-menopausal patients up to the mid 1980s. During 3 different accrual periods (1972-1983; 1984-1987; 1988-1991), TLI was a consistent and independent predictor of relapse-free time, distant metastasis and overall survival, regardless of its consideration as a continuous variable or with a cutoff value of 3%. The reproducibility of our results over time provides support to the consistency of the methodology used and of the biological and clinical information obtained when using TLI as an indicator of breast cancer cell proliferation.