Active surveillance for clinical complete responders after chemoradiotherapy for oesophageal squamous cell carcinoma.

BACKGROUND: Guidelines on the treatment of oesophageal squamous cell carcinoma (SCC) recommend neoadjuvant chemoradiotherapy plus surgery or definitive chemoradiotherapy. The aim of this study was to evaluate the outcome of patients with a cCR after chemoradiotherapy who underwent active surveillance. METHODS: Patients with oesophageal SCC who were treated with chemoradiotherapy between January 2016 and June 2022 were identified from an institutional database. Survival and recurrence of patients with a cCR who underwent active surveillance were compared with those of patients who underwent planned surgery. Survival was calculated according to the Kaplan-Meier method and compared between groups using the log rank test. RESULTS: The 37 patients who underwent active surveillance were older and tumours were more often located in the middle/upper-third of the oesophagus than in the surgery group of 57 patients. Median follow-up was 28.1 (i.q.r. 17.2-47.1) months for the active surveillance group and 20 (12.9-39.1) months for the surgery group. Overall survival was comparable between the two groups, with 3-year survival rates of 50 (95% c.i. 31 to 67) and 59 (40 to 73)% for the active surveillance and surgery groups respectively (P = 0.55). Three-year progression-free survival for patients who underwent active surveillance was better than in the surgery group: 70 (43 to 85) versus 58 (40 to 72)% (P = 0.02). Overall and progression-free survival was comparable between patients in the active surveillance group and 23 patients in the surgery group who had a pCR (ypT0 N0). The overall recurrence rate was comparable between the groups: 7 of 37 (19.4%) in active surveillance group versus 16 of 49 (32.6%) in surgery group (P = 0.26). Locoregional recurrence was noted more often in the active surveillance group and systemic recurrence in the surgery group. CONCLUSION: Active surveillance is feasible and safe for patients with oesophageal SCC who have a cCR after chemoradiotherapy.

Codon-specific KRAS mutations predict survival benefit of trifluridine/tipiracil in metastatic colorectal cancer.

Genomics has greatly improved how patients with cancer are being treated; however, clinical-grade genomic biomarkers for chemotherapies are currently lacking. Using whole-genome analysis of 37 patients with metastatic colorectal cancer (mCRC) treated with the chemotherapy trifluridine/tipiracil (FTD/TPI), we identified KRAS codon G12 (KRASG12) mutations as a potential biomarker of resistance. Next, we collected real-world data of 960 patients with mCRC receiving FTD/TPI and validated that KRASG12 mutations were significantly associated with poor survival, also in analyses restricted to the RAS/RAF mutant subgroup. We next analyzed the data of the global, double-blind, placebo-controlled, phase 3 RECOURSE trial (n = 800 patients) and found that KRASG12 mutations (n = 279) were predictive biomarkers for reduced overall survival (OS) benefit of FTD/TPI versus placebo (unadjusted interaction P = 0.0031, adjusted interaction P = 0.015). For patients with KRASG12 mutations in the RECOURSE trial, OS was not prolonged with FTD/TPI versus placebo (n = 279; hazard ratio (HR) = 0.97; 95% confidence interval (CI) = 0.73-1.20; P = 0.85). In contrast, patients with KRASG13 mutant tumors showed significantly improved OS with FTD/TPI versus placebo (n = 60; HR = 0.29; 95% CI = 0.15-0.55; P < 0.001). In isogenic cell lines and patient-derived organoids, KRASG12 mutations were associated with increased resistance to FTD-based genotoxicity. In conclusion, these data show that KRASG12 mutations are biomarkers for reduced OS benefit of FTD/TPI treatment, with potential implications for approximately 28% of patients with mCRC under consideration for treatment with FTD/TPI. Furthermore, our data suggest that genomics-based precision medicine may be possible for a subset of chemotherapies.

Treatment of EGJ Cancer within or outside Clinical Trials: Does the Setting Matter? A Monocentric Prospective Observational Study.

INTRODUCTION: RCTs support neoadjuvant chemoradiotherapy (nCRT) followed by surgery in locally advanced esophago-gastric junction (LA-EGJ) adenocarcinoma. However, RCTs are performed in highly controlled settings with limited representativeness of real-life patients (RLS). The aim of the study was to compare the outcomes in RLS and clinical trial settings. METHODS: The outcomes of RLS, which comprised 125 patients consequently treated for LA-EGJ adenocarcinoma between 2012 and 2017, were compared with the phase II trial (PIIS), performed on 65 patients from 2003 to 2011. RESULTS: About half of RLS (51.2%) were treated with nCRT according to VR protocol, 20.8% with standard CRT according to CROSS/Al-Sarraf, 20% with chemotherapy (CT) alone. pCR was 36.8%, 28.6%, and 9.1% after VR protocol, standard CRT, and CT, respectively (p = 0.082), while 3-year overall survival (OS) was 58.6% (95% CI 43.2-71.1%), 32.8% (14.6-52.4%), and 44.8% (21.3-65.9%), respectively (p = 0.030). With respect to PIIS, RLS had a higher proportion of cN+ (94% vs. 54%; p < 0.001) and a lower proportion of pCR after CT/CRT (23% vs. 39%; p = 0.041). Three-year OS was slightly higher, although not significantly, in PIIS (58.9%, 45.1-70.2%) than RLS (47.9%, 37.4-57.7%) and nearly identical to 3-year OS in RLS treated with VR protocol. CONCLUSION: Real-life patients with EGJ adenocarcinoma have more advanced cancer at baseline, lower pathologic response to neoadjuvant treatment than patients enrolled in clinical trials, but similar survival.

Pressurized intraperitoneal aerosol chemotherapy (PIPAC) in multimodal therapy for patients with oligometastatic peritoneal gastric cancer: a randomized multicenter phase III trial PIPAC VEROne.

Objectives: Peritoneal carcinomatosis is the most frequent site of metastases in patients with gastric cancer. Current standard treatment is palliative systemic chemotherapy with very poor prognosis. Cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC) resulted in long-term benefits in selected patients. Among patients with peritoneal carcinomatosis, a distinctive subset is oligometastatic disease which is characterized by low metastatic burden. Pressurized intraperitoneal aerosol chemotherapy (PIPAC) is a recent technique of intraperitoneal chemotherapy used in combination with systemic chemotherapy with promising results. Methods: PIPAC VER-One is a prospective, randomized, multicenter phase III clinical trial that aims to evaluate the effectiveness of the use of PIPAC in combination with systemic chemotherapy in patients with gastric cancer and synchronous positive peritoneal cytology and/or limited peritoneal metastases (peritoneal cancer index [PCI] ≤6). Patients will be randomized into two arms: arm A (control) treated with standard systemic chemotherapy and arm B (experimental) treated with a bidirectional scheme including PIPAC and systemic chemotherapy. Results: Primary endpoint is the secondary resectability rate. Secondary endpoints are: overall survival (OS), pregression-free survival (PFS), disease-free survival (DFS), histological response assessed both on primary tumor and peritoneal lesions, quality of life (QoL), complication rate (CTCAE v5), and incremental cost-effectiveness ratios (ICER). Conclusions: The role of PIPAC in multimodal treatment for oligometastatic gastric cancer will be investigated in this trial.

Pretreatment Primary Tumor Stage is a Risk Factor for Recurrence in Patients with Esophageal Squamous Cell Carcinoma Who Achieve Pathological Complete Response After Neoadjuvant Chemoradiotherapy.

BACKGROUND: Although pathological complete response (pCR) after multimodal treatment for esophageal cancer is associated to the best prognosis, recurrence may occur in 20-40% of cases. The present study investigated the recurrence pattern and predictive factors of recurrence after pCR in patients with esophageal cancer. METHODS: In this study, 427 patients received preoperative treatment for either esophageal squamous cell carcinoma (SCC) or adenocarcinoma at Verona University Hospital between 2000 and 2018. Of these, 145 patients (34%) achieved a pCR. Long-term prognosis, recurrence pattern, and risk factors for relapse in pCR patients were analysed. RESULTS: During a median follow-up of 52 months, 37 relapses (25.5%) occurred, mostly at distant level (n = 28). Nearly all locoregional relapses (8/9) were detected in SCC cases. The 5-year overall survival and cancer-related survival were 71.7% (95% confidence interval [CI] 62.6-78.9%) and 77.5% (95% CI 68.5-84.2%) respectively. Male sex, higher body mass index, and cT4 were significant risk factors for recurrence at univariate analysis. The multivariate analysis confirmed the role of cT4 as predictor of recurrence only in SCCs. CONCLUSIONS: Esophageal cancer recurs in about one-fourth of pCR cases. A fair number of local recurrences occurs in SCCs, but the main problem is the systemic disease control. According to our analysis, SCCs patients with cT4 stage have an increased risk to recur, so they should be managed differently by a personalized approach in terms of adjuvant treatment and follow-up.

18F-FDG PET/CT Metrics Are Correlated to the Pathological Response in Esophageal Cancer Patients Treated With Induction Chemotherapy Followed by Neoadjuvant Chemo-Radiotherapy.

BACKGROUND AND OBJECTIVE: The aim of this study was to assess the ability of Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (18F-FDG PET/CT) to provide functional information useful in predicting pathological response to an intensive neoadjuvant chemo-radiotherapy (nCRT) protocol for both esophageal squamous cell carcinoma (SCC) and adenocarcinoma (ADC) patients. MATERIAL AND METHODS: Esophageal carcinoma (EC) patients, treated in our Center between 2014 and 2018, were retrospectively reviewed. The nCRT protocol schedule consisted of an induction phase of weekly administered docetaxel, cisplatin, and 5-fluorouracil (TCF) for 3 weeks, followed by a concomitant phase of weekly TCF for 5 weeks with concurrent radiotherapy (50-50.4 Gy in 25-28 fractions). Three 18F-FDG PET/CT scans were performed: before (PET1) and after (PET2) induction chemotherapy (IC), and prior to surgery (PET3). Correlation between PET parameters [maximum and mean standardized uptake value (SUVmax and SUVmean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG)], radiomic features and tumor regression grade (TGR) was investigated. RESULTS: Fifty-four patients (35 ADC, 19 SCC; 48 cT3/4; 52 cN+) were eligible for the analysis. Pathological response to nCRT was classified as major (TRG1-2, 41/54, 75.9%) or non-response (TRG3-4, 13/54, 24.1%). A major response was statistically correlated with SCC subtype (p = 0.02) and smaller tumor length (p = 0.03). MTV and TLG measured prior to IC (PET1) were correlated to TRG1-2 response (p = 0.02 and p = 0.02, respectively). After IC (PET2), SUVmean and TLG correlated with major response (p = 0.03 and p = 0.04, respectively). No significance was detected when relative changes of metabolic parameters between PET1 and PET2 were evaluated. At textural quantitative analysis, three independent radiomic features extracted from PET1 images ([JointEnergy and InverseDifferenceNormalized of GLCM and LowGrayLevelZoneEmphasis of GLSZM) were statistically correlated with major response (p < 0.0002). CONCLUSIONS: 18F-FDG PET/CT traditional metrics and textural features seem to predict pathologic response (TRG) in EC patients treated with induction chemotherapy followed by neoadjuvant chemo-radiotherapy. Further investigations are necessary in order to obtain a reliable predictive model to be used in the clinical practice.

Long-Term Outcomes of Induction Chemotherapy Followed by Chemo-Radiotherapy as Intensive Neoadjuvant Protocol in Patients with Esophageal Cancer.

BACKGROUND: A phase II intensive neoadjuvant chemo-radiotherapy (nCRT) protocol for esophageal cancer (EC) was previously tested at our Center with promising results. We here present an observational study to evaluate the efficacy of the protocol also in "real life" patients. METHODS: We retrospectively reviewed 122 ECs (45.1% squamous cell (SCC) and 54.9% adenocarcinoma (ADC)) treated with induction docetaxel, cisplatin, and 5-fluorouracil (TCF), followed by concomitant TCF and radiotherapy (50-50.4 Gy/25-28 fractions), between 2008 and 2017. Primary endpoints were overall survival (OS), event-free survival (EFS) and pathological complete response (pCR). RESULTS: With a median follow-up of 62.1 months (95% CI 50-67.6 months), 5-year OS and EFS rates were 54.8% (95% CI 44.7-63.9) and 42.7% (95% CI 33.1-51.9), respectively. A pCR was observed in 71.1% of SCC and 37.1% of ADC patients (p = 0.001). At multivariate analysis, ypN+ was a significant prognostic factor for OS (Hazard Ratios (HR) 4.39 [95% CI 2.36-8.18]; p < 0.0001), while pCR was a strong predictor of EFS (HR 0.38 [95% CI 0.22-0.67]; p < 0.0001). CONCLUSIONS: The nCRT protocol achieved considerable long-term survival and pCR rates also in "real life" patients. Further research is necessary to evaluate this protocol in a watch-and-wait approach.

Predictors of Local Control for Stereotactic Ablative Radiotherapy (SAbR) in Pulmonary Oligometastases from Gastrointestinal Malignancies.

BACKGROUND/AIM: To assess predictors of local control (LC) for stereotactic ablative radiotherapy (SAbR) in pulmonary oligometastatic disease (OMD) from gastrointestinal (GI) malignancies. PATIENTS AND METHODS: Patients with pulmonary OMD treated with SAbR from January 2016 to December 2018 were included in this observational analysis. Primary endpoint was LC. Uni- and multivariate analyses to assess variable correlations were conducted. RESULTS: Thirty-seven patients and 59 lung metastases were evaluated. The delivered dose was 30-60 Gy in 3-8 fractions. After a median follow-up of 23.0 months (range=6.3-50.4 months), LC rate at 1/2 years was 89.7%/85.0%, and increased to 96.0%/91.0% for lesions treated with a biologically effective dose (BED10) ≥100 Gy (p=0.03). RECIST response at 6 months was predictive for LC (p=0.002). CONCLUSION: SAbR is an effective option for pulmonary OMD from GI malignancies. A BED10 ≥100 Gy and radiological response at 6 months can affect LC.

A phase II trial of the FGFR inhibitor pemigatinib in patients with metastatic esophageal-gastric junction/gastric cancer trastuzumab resistant: the FiGhTeR trial.

BACKGROUND: Prognosis of patients affected by metastatic esophageal-gastric junction (EGJ) or gastric cancer (GC) remains dismal. Trastuzumab, an anti-HER2 monoclonal antibody, is the only targeted agent approved for the first-line treatment of patients with HER2-overexpressing advanced EGJ or GC in combination with chemotherapy. However, patients invariably become resistant during this treatment. We recently identified the overexpression of fibroblast growth factor (FGF) receptor 3 (FGFR3) as a molecular mechanism responsible for trastuzumab resistance in GC models, providing the rationale for the inhibition of this receptor as a potential second-line strategy in this disease. Pemigatinib is a selective, potent, oral inhibitor of FGFR1, 2, and 3. METHODS: The FiGhTeR trial is a phase II, single-arm, open-label study to assess safety and activity of the FGFR inhibitor pemigatinib as second-line treatment strategy in metastatic EGJ/GC patients progressing under trastuzumab-containing therapies. The primary endpoint is the 12-week progression-free survival rate. Plasma and tumor tissue samples will be collected for translational research analyses at baseline, during treatment, and at progression on pemigatinib. DISCUSSION: Co-alterations in genes coding for different tyrosine-kinase receptors are emerging as relevant mechanisms of acquired resistance to anti-HER2 therapeutic strategies in GC. In particular, our group has recently identified that in GC models the overexpression of FGFR3 sustains the acquired resistance to trastuzumab. This trial aims to assess the safety, tolerability and activity of the FGFR inhibitor pemigatinib as a second-line treatment in metastatic EGJ/GC patients refractory to first-line trastuzumab-containing therapies. Furthermore, this study offers the opportunity to prospectively study mechanisms and pathways involved in trastuzumab resistance. PROTOCOL NUMBER: CRC2017_02. EUDRACT NUMBER: 2017-004522-14.

Organisational challenges, volumes of oncological activity and patients' perception during the severe acute respiratory syndrome coronavirus 2 epidemic.

BACKGROUND: On February 23rd, the 1st case of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection was diagnosed at the University Hospital Trust of Verona, Italy. On March 13th, the Oncology Section was converted into a 22-inpatient bed coronavirus disease (COVID) Unit, and we reshaped our organisation to face the SARS-CoV-2 epidemic, while maintaining oncological activities. METHODS: We tracked down (i) volumes of oncological activities (January 1st - March 31st, 2020 versus the same period of 2019), (ii) patients' and caregivers' perception and (iii) SARS-CoV-2 infection rate in oncology health professionals and SARS-CoV-2 infection-related hospital admissions of "active"' oncological patients. RESULTS: As compared with the same trimester in 2019, the overall reduction in total numbers of inpatient admissions, chemotherapy administrations and specialist visits in January-March 2020 was 8%, 6% and 3%, respectively; based on the weekly average of daily accesses, reduction in some of the oncological activities became statistically significant from week 11. The overall acceptance of adopted measures, as measured by targeted questionnaires administered to a sample of 241 outpatients, was high (>70%). Overall, 8 of 85 oncology health professionals tested positive for SARS-CoV-2 infection (all but one employed in the COVID Unit, no hospital admissions and no treatment required); among 471 patients admitted for SARS-CoV-2 infection, 7 had an "active"' oncological disease (2 died of infection-related complications). CONCLUSIONS: A slight, but statistically significant reduction in oncology activity was registered during the SARS-CoV-2 epidemic peak in Verona, Italy. Organisational and protective measures adopted appear to have contributed to keep infections in both oncological patients and health professionals to a minimum.

Clinical pathways in gastric cancer care.

The diagnostic-therapeutic pathways (DTPs) are emerging as useful instruments for clinical management of complex diseases as gastric cancer, whose treatment is challenging and requires a multidisciplinary approach. However, the DPTs of patients with gastric cancer are still not defined yet. The aim of this study was to define the optimal DPT to be applied for patients with gastric cancer in the Veneto region. Rather than defining the ideal DTPs a priori, we conducted a preliminary research by analyzing the differences in the actual DPTs for patients with gastric cancer among different hospitals (hub and spokes) in Veneto. Then, the final DPT was elaborated based on the current available best clinical evidences; however, also the areas of homogeneity among the actual DPTs of the included centers as well as the critical issues that had emerged by our preliminary analysis were taken into account for pathway design. High heterogeneity in actual DTPs of patients with gastric cancer was observed among the analyzed centres. Moreover, some of the major criticisms have been found at crucial points of the current pathways. Based on these data, a reference path that is applicable to the whole-regional health network was constructed. The reference DTP is focused on multidisciplinary team management of patients with gastric cancer. Clinical pathways are essential tools to properly manage complex diseases such as gastric cancer. As such, more efforts should be done to implement their use.

Para-aortic lymphadenectomy in surgery for gastric cancer: current indications and future perspectives.

Involvement of para-aortic nodes (PAN) has been detected at pathological examination in 10-25% of locally advanced gastric cancer. Based on these data of nodal diffusion, the lymphadenectomy of para-aortic stations would be desirable in locally advanced gastric cancer. However, the debate on the oncological benefit of para-aortic nodes dissection is still not solved. A review of the literature was performed and papers reporting either the rate of para-aortic nodal metastases or the long-term survival outcomes after D2+ para-aortic nodes dissection (PAND) or D3 lymphadenectomy were descriptively reported. The literature survey yielded 14 studies. Most of the papers show the outcome of series of advanced gastric cancer treated with surgery alone, while starting from 2012, 3 articles report the outcomes of D2 + PAND or D3 lymphadenectomy after preoperative chemotherapy. The rate of PAN metastases ranges between 8.5 and 28% in surgical series. Survival outcomes largely improved in series of patients treated with multimodal approach compared to those of surgery alone. In patients with clinically detected para-aortic nodal metastases, preoperative chemotherapy followed by PAND is indicated. More data are needed to clarify the indication to prophylactic PAND in the era of multimodal treatment, anyway super-extended lymphadenectomies have to be performed by experienced surgeons in dedicated centres.

Neoadjuvant therapy with weekly docetaxel and cisplatin, 5-fluorouracil continuous infusion, and concurrent radiotherapy in patients with locally advanced esophageal cancer produced a high percentage of long-lasting pathological complete response: a phase 2 study.

BACKGROUND: This phase 2 study was aimed at defining the pathological response rate of a neoadjuvant schedule including weekly docetaxel and cisplatin, continuous infusion (c.i.) of 5-fluorouracil (5-FU) and concomitant radiotherapy (RT) in untreated stage II-III adenocarcinoma and squamous cell carcinoma of mid-distal thoracic esophagus. METHODS: The schedule consisted of a first phase of chemotherapy alone and of a second phase of concurrent chemoradiation. Doses were as follows: docetaxel 35 mg/m(2) and cisplatin 25 mg/m(2) on days 1, 8, 15, 29, 36, 43, 50, and 57 plus 5-FU c.i. (180 mg/m(2) on days 1-21 and 150 mg/m(2) on days 29-63); RT (50 Gy) started at day 29. Surgery was planned 6 to 8 weeks after the completion of chemoradiation. RESULTS: A total of 74 patients were enrolled; pathological complete remission (pCR) was found in 47% (35 of 74) and near pCR (microfoci of tumor cells on the primary tumor without lymph nodal metastases) (pnCR) in 15% of the patients (11 of 74). Grade 3-4 neutropenia, nonhematological toxicity, and toxic deaths occurred in 13.5%, 32.4%, and 4% of the patients, respectively. Median follow-up was 55 months (range, 3-108 months). Median survival of all 74 patients was 55 months, whereas it was not reached in the pCR subset. The 3- and 5-year survival rates were, respectively, 83% and 77% for pCR, 73% and 44% for pnCR, and 21% and 14% for Residual Tumor subsets (P < .001). CONCLUSIONS: This study shows that 1) this intensive weekly schedule produced a high pathological response rate, 2) responders had high and long-term durable survival rates.

Pathological, biological and clinical characteristics, and surgical management, of elderly women with breast cancer.

For this retrospective study, we divided 3814 patients with invasive operable breast cancer into five groups based on their age at diagnosis. Univariate analysis showed that the elderly women had larger tumours with more axillary node involvement and lymphovascular invasion, more estrogen- and progesterone-positive tumours, lower grades and proliferative indices, and were less likely to be c-erbB2 positive. They were more likely to have been diagnosed in a symptomatic state and to have undergone mastectomy, and less likely to have undergone mammary reconstruction or axillary dissection, or to have a family history of breast cancer. The multinomial regression model showed that pT, pN, ER, PgR, the type of diagnosis, and a family history were independently associated with each other. The results of this study show that elderly women are more likely to have larger and more frequently N+ tumours, but these are biologically less aggressive and usually seem to receive less invasive surgical treatment.

Ifosfamide encephalopathy: a case report.

The aim of this short communication is to discuss the mechanism, modality and treatment of ifosfamide encephalopathy. We present the case of a 52-year-old woman treated with this alkylating agent who developed severe neurotoxicity. It was resolved with administration of Methylene blue, abundant intravenous hydration and interruption of ifosfamide.

Prognostic significance of laminin, laminin receptor, and bone marrow micrometastases in breast cancer patients: are these markers of aggressive behavior and metastatic potential?

Laminin is a basement membrane glycoprotein implicated in a large number of biologic activities of cancer progression, many of which are mediated by the presence of the laminin receptor (67LR) on the cell membrane. We studied the correlations of laminin and its receptor with standardized and new prognostic factors (including bone marrow micrometastases) in a series of 112 patients with operable breast cancers. Laminin-positive cells were detected in 60% of the tumors and 67LR-positive cells in 55%; both were present in 35% of the cases. No association was found between laminin or 67LR positivity and pathologic tumor size, pathologic nodal status, grading, Ki-67, estrogen receptor status, progesterone receptor status, or bone marrow micrometastases. The only statistically significant association was with menopausal status and age, with a higher percentage of 67LR-positive tumors among premenopausal and younger patients. The median follow-up was approximately 7 years. The prognosis of disease-free survival was similar in the laminin-positive and laminin-negative subjects but was significantly better in 67LR-negative patients; there were no significant differences in overall survival. The prognostic role of laminin and 67LR in disease-free survival and overall survival varied according to nodal status. In the absence of nodal involvement, the risk of relapse (and death) was greater in the patients who were positive for laminin, 67LR, or both than in those who were negative for laminin, 67LR, or both; in the case of 4 or more involved nodes, the prognostic role of laminin and 67LR was reversed. These results did not change after adjustment for age, menopausal status, tumor status, nodal status, grading, or bone marrow micrometastases.

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.