The clinical relevance of various methods of classifying ipsilateral breast tumour recurrence as either true local recurrence or new primary.

PURPOSE: Describes the relevance of -various classification methods for ipsilateral breast tumour recurrence (IBTR) as either true recurrence (TR) or new primary (NP) on both disease-specific survival (DSS) and distant metastasis-free survival (DMFS). METHOD: Two hundred and thirty-four of 4359 women undergoing breast-conserving therapy experienced IBTR. We compared the impact of four known classification methods and two newly created classification methods. RESULTS: For three of the methods, a better DSS was observed for NP compared to TR with the hazard ratio (HR) ranging from 0.5 to 0.6. The new Twente method classification, comprising all classification criteria of three known methods, and the new Morphology method, using only morphological criteria, had the best HR and confidence interval with a HR 0.5 (95% CI 0.2-1.0) and a HR 0.5 (95% CI 0.3-1.1), respectively. For DMFS, the HR for NP compared to TR ranged from 0.6 to 0.9 for all six methods. The new Morphology method and the Twente method noted the best HR and confidence intervals with a HR 0.6 (95% CI 0.3-1.1) and a HR 0.6 (95% CI 0.4-1.2), respectively. CONCLUSION: IBTR classified as TR or NP has a prognostic value for both DSS and DMFS, but depends on the classification method used. Developing and validating a generally accepted form of classification are imperative for using TR and NP in clinical practice.

Clinical relevance of the timing of radiotherapy after breast-conserving surgery : Results of a large, single-centre, population-based cohort study.

PURPOSE: To investigate the effect of the timing of radiation therapy after breast-conserving surgery in relation to distant metastasis-free survival and disease-specific survival. METHODS: The analysis was performed in relation to 4189 women all undergoing breast-conserving therapy (BCT). Three groups were defined with respect to lymph node status and the use of adjuvant systemic therapy (AST). Patients were categorized into time intervals: < 37 days, 37-53 days, 54-112 days and > 112 days. RESULTS: For women without lymph node metastases and with favourable characteristics aged > 55 years, an improved treatment efficacy was noted when starting radiotherapy with a time interval of < 37 days. The same was observed for women with lymph nodes metastases receiving AST aged ≤ 50 years. Finally, for women aged > 50 years with negative lymph node status but with unfavourable characteristics and receiving AST, an improved treatment efficacy was noted when starting radiotherapy after a time interval of ≥ 37 days. CONCLUSION: The results of our study further support the hypothesis that the timing of radiotherapy may have an impact on treatment efficacy and that further studies (preferably randomized trials) are indicated.

Internal mammary and medial supraclavicular lymph node chain irradiation in stage I-III breast cancer (EORTC 22922/10925): 15-year results of a randomised, phase 3 trial.

BACKGROUND: 10-year results from several studies showed improved disease-free survival and distant metastasis-free survival, reduced breast cancer-related mortality, and variable effects on overall survival with the addition of partial or comprehensive regional lymph node irradiation after surgery in patients with breast cancer. We present the scheduled 15-year analysis of the European Organisation for Research and Treatment of Cancer (EORTC) 22922/10925 trial, which aims to investigate the impact on overall survival of elective internal mammary and medial supraclavicular (IM-MS) irradiation. METHODS: EORTC 22922/10925, a randomised, phase 3 trial done across 46 radiation oncology departments from 13 countries, included women up to 75 years of age with unilateral, histologically confirmed, stage I-III breast adenocarcinoma with involved axillary nodes or a central or medially located primary tumour. Surgery consisted of mastectomy or breast-conserving surgery and axillary staging. Patients were randomly assigned (1:1) centrally using minimisation to receive IM-MS irradiation at 50 Gy in 25 fractions (IM-MS irradiation group) or no IM-MS irradiation (control group). Stratification was done for institution, menopausal status, site of the primary tumour within the breast, type of breast and axillary surgery, and pathological T and N stage. Patients and investigators were not masked to treatment allocation. The primary endpoint was overall survival analysed according to the intention-to-treat principle. Secondary endpoints were disease-free survival, distant metastasis-free survival, breast cancer mortality, any breast cancer recurrence, and cause of death. Follow-up is ongoing for 20 years after randomisation. This study is registered with ClinicalTrials.gov, NCT00002851. FINDINGS: Between Aug 5, 1996, and Jan 13, 2004, we enrolled 4004 patients, of whom 2002 were randomly assigned to the IM-MS irradiation group and 2002 to the no IM-MS irradiation group. At a median follow-up of 15·7 years (IQR 14·0-17·6), 554 (27·7%) patients in the IM-MS irradiation group and 569 (28·4%) patients in the control group had died. Overall survival was 73·1% (95% CI 71·0-75·2) in the IM-MS irradiation group and 70·9% (68·6-72·9) in the control group (HR 0·95 [95% CI 0·84-1·06], p=0·36). Any breast cancer recurrence (24·5% [95% CI 22·5-26·6] vs 27·1% [25·1-29·2]; HR 0·87 [95% CI 0·77-0·98], p=0·024) and breast cancer mortality (16·0% [14·3-17·7] vs 19·8% [18·0-21·7]; 0·81 [0·70-0·94], p=0·0055) were lower in the IM-MS irradiation group than in the control group. No significant differences in the IM-MS irradiation group versus the control group were seen for disease-free survival (60·8% [95% CI 58·4-63·2] vs 59·9% [57·5-62·2]; HR 0·93 [95% CI 0·84-1·03], p=0·18), or distant metastasis-free survival (70·0% [67·7-72·2] vs 68·2% [65·9-70·3]; 0·93 [0·83-1·04], p=0·18). Causes of death between groups were similar. INTERPRETATION: The 15-year results show a significant reduction of breast cancer mortality and any breast cancer recurrence by IM-MS irradiation in stage I-III breast cancer. However, this is not converted to improved overall survival. FUNDING: US National Cancer Institute, Ligue Nationale contre le Cancer, and KWF Kankerbestrijding.

The Mitotic Activity Index in combination with Her2neu: a strong prognosticator in breast cancer.

PURPOSE: The aim of this study is to evaluate the prognostic value of the Mitotic Activity Index (MAI) in combination with the human epidermal growth factor receptor (Her2) for distant metastases-free survival (DMFS) and disease-specific survival (DSS) in breast cancer and compare it with the immunohistochemically (IHC) profile types. METHODS: Analyses were based on 2.923 breast-conserving breast cancer specimens with known MAI, Her2 status, and hormone receptor status, resulting in 2.678 Her2MAI combinations, MAI ≤ 12/Her2negative, MAI > 12/Her2negative, MAI > 12/Her2positive, and MAI ≤ 12/Her2positive, and 2.560 IHC profile types, luminal A, luminal B, triple negative, and non-luminal Her2positive. RESULTS: For DMFS, the MAI > 12/Her2negative combination showed a significantly worse outcome in multivariate analyses compared to the MAI ≤ 12/Her2negative combination. None of the IHC profile types showed significantly different outcomes for DMFS and DSS as compared to luminal A. We performed a separate analysis on age and lymph node status. The significance of MAI > 12/Her2negative seems to be limited to women ≤ 55 years for both DMFS and DSS. However, with respect to DSS, this seems to be limited to node negative cases. The IHC profile types for DSS, luminal B showed a significantly worse outcome for women > 55 years compared to that for luminal A, although it showed rather wide confidence interval. CONCLUSION: The MAI > 12/Her2negative combination seems to be a strong prognosticator for DMFS and DSS, particularly for women ≤ 55 years. However, none of the IHC profile types seems to be a prognosticator in breast cancer.

An actualised population-based study on the use of radiotherapy in breast cancer patients in the Netherlands.

The utilization rate of RT increased from 64.4% in 2011 to 70.3% in 2015. After BCS and mastectomy, 97.3% and 26.1% of the patients received RT, respectively. For patients undergoing BCS and mastectomy, lower age and ER + tumours were associated with higher RT utilisation rates. After mastectomy, also larger tumour sizes, lymph node involvement, grade-2 and 3 tumours and diagnosis in more recent years were associated with higher RT use.

Internal Mammary and Medial Supraclavicular Irradiation in Breast Cancer.

BACKGROUND: The effect of internal mammary and medial supraclavicular lymph-node irradiation (regional nodal irradiation) added to whole-breast or thoracic-wall irradiation after surgery on survival among women with early-stage breast cancer is unknown. METHODS: We randomly assigned women who had a centrally or medially located primary tumor, irrespective of axillary involvement, or an externally located tumor with axillary involvement to undergo either whole-breast or thoracic-wall irradiation in addition to regional nodal irradiation (nodal-irradiation group) or whole-breast or thoracic-wall irradiation alone (control group). The primary end point was overall survival. Secondary end points were the rates of disease-free survival, survival free from distant disease, and death from breast cancer. RESULTS: Between 1996 and 2004, a total of 4004 patients underwent randomization. The majority of patients (76.1%) underwent breast-conserving surgery. After mastectomy, 73.4% of the patients in both groups underwent chest-wall irradiation. Nearly all patients with node-positive disease (99.0%) and 66.3% of patients with node-negative disease received adjuvant systemic treatment. At a median follow-up of 10.9 years, 811 patients had died. At 10 years, overall survival was 82.3% in the nodal-irradiation group and 80.7% in the control group (hazard ratio for death with nodal irradiation, 0.87; 95% confidence interval [CI], 0.76 to 1.00; P=0.06). The rate of disease-free survival was 72.1% in the nodal-irradiation group and 69.1% in the control group (hazard ratio for disease progression or death, 0.89; 95% CI, 0.80 to 1.00; P=0.04), the rate of distant disease-free survival was 78.0% versus 75.0% (hazard ratio, 0.86; 95% CI, 0.76 to 0.98; P=0.02), and breast-cancer mortality was 12.5% versus 14.4% (hazard ratio, 0.82; 95% CI, 0.70 to 0.97; P=0.02). Acute side effects of regional nodal irradiation were modest. CONCLUSIONS: In patients with early-stage breast cancer, irradiation of the regional nodes had a marginal effect on overall survival. Disease-free survival and distant disease-free survival were improved, and breast-cancer mortality was reduced. (Funded by Fonds Cancer; ClinicalTrials.gov number, NCT00002851.).

Breast MRI increases the number of mastectomies for ductal cancers, but decreases them for lobular cancers.

PURPOSE: In this retrospective population-based cohort study, we analyzed breast MRI use and its impact on type of surgery, surgical margin involvement, and the diagnosis of contralateral breast cancer. METHODS: All Dutch patients with cT1-4N0-3M0 breast cancer diagnosed in 2011-2013 and treated with primary surgery were eligible for inclusion. Using multivariable analyses, we analyzed in different categories whether MRI use was related to surgery type, margin involvement, and diagnosis of contralateral breast cancer (CBC). RESULTS: MRI was performed in 10,740 out of 36,050 patients (29.8%). Patients with invasive ductal cancer undergoing MRI were more likely to undergo primary mastectomy than those without MRI (OR 1.30, 95% confidence interval (CI) 1.22-1.39, p < 0.0001). Patients with invasive lobular cancer undergoing MRI were less likely to undergo primary mastectomy than those without MRI (OR 0.86, 95% CI 0.76-0.99, p = 0.0303). A significantly lower risk of positive surgical margins after breast-conserving surgery was only seen in patients with lobular cancer who had undergone MRI as compared to those without MRI (OR 0.59, 95% CI 0.44-0.79, p = 0.0003) and, consequently, a lower risk of secondary mastectomy (OR 0.61, 95% CI 0.42-0.88, p = 0.0088). Patients who underwent MRI were almost four times more likely to be diagnosed with CBC (OR 3.55, 95% CI 3.01-4.17, p < 0.0001). CONCLUSIONS: Breast MRI use was associated with a reduced number of mastectomies and less positive surgical margins in invasive lobular cancer, but with an increased number of mastectomies in ductal cancers. Breast MRI use was associated with a fourfold higher incidence of CBC.

Single dose IOERT versus whole breast irradiation : Cosmetic results in breast-conserving therapy.

BACKGROUND: Scarce data are available about the cosmetic result of single dose intraoperative electron radiotherapy (IOERT) in breast-conserving radiotherapy. METHODS AND MATERIALS: We included 71 breast cancer patients. Breast-conserving surgery and sentinel node procedure had started almost 3 years earlier. Subsequently, 26 patients were treated with IOERT and 45 patients received postoperative whole breast irradiation (WBI). For both groups we determined seven dimensionless asymmetry features. We compared the subjectively and the objectively derived cosmetic scores with each other. RESULTS: For four asymmetry features we noted significantly smaller differences for patients treated with IOERT when compared to those treated with WBI: relative breast contour difference, relative breast area difference and relative breast overlap difference. After correcting for excision volume a significant difference was noticed also for relative lower breast contour. For the IOERT group the cosmetic scores "excellent or good" as determined by each patient and one physician were 88 and 96 %, respectively. When the overall cosmetic scores for patients treated with IOERT and WBI were compared to those of the objectively derived scores, there was a fair level of agreement. CONCLUSION: For patients treated with IOERT we noted less asymmetry and high rates of "good or excellent" subjectively derived cosmetic scores. The level of agreement between the subjectively and the objectively derived cosmetic scores was limited. Due to the small sample size and the design of the study no definitive conclusions can be drawn.

Long-term effects of first degree family history of breast cancer in young women: Recurrences and bilateral breast cancer.

BACKGROUND: The aim of this study is to analyze the impact of first degree relative (FDR) of young breast cancer patients. METHODS: Data were used from our prospective population-based cohort study which started in 1983. The family history (FH) was registered with regard to FDR: the presence or absence of invasive breast cancer in none vs. one or more FDRs at any age. RESULTS: A total of 1109 women, ≤50 years with 1128 breast conserving treatments was seen. The incidence of FDR was 17.0% for one FDR and 3.2% ≥2 FDR. The three groups, none, 1 or ≥2 FDR, were comparable. The local failure rate is comparable for all three groups. Women with a positive FH and metachronous bilateral breast cancer (MBBC) showed a lower local failure (HR 0.2; 95% CI 0.05-0.8). A positive FH was an independent predictor for a better disease-specific survival (HR 0.6; 95% CI 0.4-0.9). CONCLUSION: A positive FH, based on FDR implies a better prognosis in relation to survival for young women treated with BCT. In contrast to no FH for FDR, MBBC in women with a positive FH was not associated with an increased risk of local recurrence.

Whole-breast irradiation with or without a boost for patients treated with breast-conserving surgery for early breast cancer: 20-year follow-up of a randomised phase 3 trial.

BACKGROUND: Since the introduction of breast-conserving treatment, various radiation doses after lumpectomy have been used. In a phase 3 randomised controlled trial, we investigated the effect of a radiation boost of 16 Gy on overall survival, local control, and fibrosis for patients with stage I and II breast cancer who underwent breast-conserving treatment compared with patients who received no boost. Here, we present the 20-year follow-up results. METHODS: Patients with microscopically complete excision for invasive disease followed by whole-breast irradiation of 50 Gy in 5 weeks were centrally randomised (1:1) with a minimisation algorithm to receive 16 Gy boost or no boost, with minimisation for age, menopausal status, presence of extensive ductal carcinoma in situ, clinical tumour size, nodal status, and institution. Neither patients nor investigators were masked to treatment allocation. The primary endpoint was overall survival in the intention-to-treat population. The trial is registered with ClinicalTrials.gov, number NCT02295033. FINDINGS: Between May 24, 1989, and June 25, 1996, 2657 patients were randomly assigned to receive no radiation boost and 2661 patients randomly assigned to receive a radiation boost. Median follow-up was 17.2 years (IQR 13.0-19.0). 20-year overall survival was 59.7% (99% CI 56.3-63.0) in the boost group versus 61.1% (57.6-64.3) in the no boost group, hazard ratio (HR) 1.05 (99% CI 0.92-1.19, p=0.323). Ipsilateral breast tumour recurrence was the first treatment failure for 354 patients (13%) in the no boost group versus 237 patients (9%) in the boost group, HR 0.65 (99% CI 0.52-0.81, p<0.0001). The 20-year cumulative incidence of ipsilatelal breast tumour recurrence was 16.4% (99% CI 14.1-18.8) in the no boost group versus 12.0% (9.8-14.4) in the boost group. Mastectomies as first salvage treatment for ipsilateral breast tumour recurrence occurred in 279 (79%) of 354 patients in the no boost group versus 178 (75%) of 237 in the boost group. The cumulative incidence of severe fibrosis at 20 years was 1.8% (99% CI 1.1-2.5) in the no boost group versus 5.2% (99% CI 3.9-6.4) in the boost group (p<0.0001). INTERPRETATION: A radiation boost after whole-breast irradiation has no effect on long-term overall survival, but can improve local control, with the largest absolute benefit in young patients, although it increases the risk of moderate to severe fibrosis. The extra radiation dose can be avoided in most patients older than age 60 years. FUNDING: Fonds Cancer, Belgium.

The prognostic relevance of the mitotic activity index in axillary lymph node-negative breast cancer.

The aim of the present study is to look at the mitotic activity index (MAI) as a prognostic factor in a prospective population-based cohort of lymph node-negative invasive breast cancer patients. Analyses were based on 2,048 breast-conserving therapies in 1,971 patients, node-negative, and without any form of adjuvant systemic therapy with long-term follow-up. The 15-year distant metastases-free survival (DMFS) for women ≤55 years was 88.3 % for low MAI values (≤12) versus 73.4 % for high MAI values (>12); (HR 2.8; 95 % CI 1.8-4.4; p < 0.001). Multivariate analyses for DMFS showed significance for MAI. For MAI and Bloom-Richardson grading, by performing a likelihood ratio test, we showed the statistical significance for both. For women >55-years, the MAI was not an independent significant factor. We also confirmed the above findings for disease-specific survival. When multi-gene assays are not available, the MAI remains a robust prognostic marker in women younger than 55 years of age with early node-negative breast cancer.

Impact of hospital volume on breast cancer outcome: a population-based study in the Netherlands.

For low-volume tumours, high surgical hospital volume is associated with better survival. For high-volume tumours like breast cancer, this association is unclear. The aim of this study is to determine to what extent the yearly surgical hospital breast cancer volume is associated with overall survival. All patients, diagnosed with primary invasive non-metastatic breast cancer in the period 2001-2005, were selected from the Netherlands Cancer Registry. Hospitals were grouped by their annual volume of surgery for invasive breast cancer. Cox proportional hazard models were used including patient and tumour characteristics as covariates. Follow-up was completed until the 1st of February 2013. Primary endpoint was 10-year overall survival rate. In total, 58,982 patients with invasive non-metastatic breast cancer were diagnosed during the period 2001-2005. Hospitals were grouped by their (mean) annual surgical volume: <75 (n = 19), 75-99 (n = 30), 100-149 (n = 29), 150-199 (n = 9) and ≥200 (n = 14). The 10-year observed survival rates were 77, 81, 80, 82 and 82 %, respectively. After case-mix adjustment, patients in low-volume hospitals had a HR of 1.09 (<75 vs. ≥200; 95 % CI 1.03-1.15). Survival was significantly higher for lobular carcinoma and for diagnosis in the most recent year (2005). Being a male, having a higher age at diagnosis, a higher tumour grade, a larger tumour size, a higher number of positive lymph nodes, an earlier year of diagnosis and a lower SES resulted in a reduced survival and influenced death, all to a larger extent than surgical volume did. In the Netherlands, surgical hospital volume influences 10-year overall survival only marginally and far less than patient and tumour characteristics. No difference in survival was revealed for invasive non-metastatic breast cancer patients in hospitals with 75-99 operations per year compared with hospitals with over 200 operations per year.

Whole breast proton irradiation for maximal reduction of heart dose in breast cancer patients.

PURPOSE: In left-sided breast cancer radiotherapy, tangential intensity modulated radiotherapy combined with breath-hold enables a dose reduction to the heart and left anterior descending (LAD) coronary artery. Aim of this study was to investigate the added value of intensity modulated proton therapy (IMPT) with regard to decreasing the radiation dose to these structures. METHODS: In this comparative planning study, four treatment plans were generated in 20 patients: an IMPT plan and a tangential IMRT plan, both with breath-hold and free-breathing. At least 97 % of the target volume had to be covered by at least 95 % of the prescribed dose in all cases. Specifically with respect to the heart, the LAD, and the target volumes, we analyzed the maximum doses, the mean doses, and the volumes receiving 5-30 Gy. RESULTS: As compared to IMRT, IMPT resulted in significant dose reductions to the heart and LAD-region even without breath-hold. In the majority of the IMPT cases, a reduction to almost zero to the heart and LAD-region was obtained. IMPT treatment plans yielded the lowest dose to the lungs. CONCLUSIONS: With IMPT the dose to the heart and LAD-region could be significantly decreased compared to tangential IMRT with breath-hold. The clinical relevance should be assessed individually based on the baseline risk of cardiac complications in combination with the dose to organs at risk. However, as IMPT for breast cancer is currently not widely available, IMPT should be reserved for patients remaining at high risk for major coronary events.

Pseudo-progression after stereotactic radiotherapy of brain metastases: lesion analysis using MRI cine-loops.

Stereotactic radiotherapy (SRT) of brain metastasis can lead to lesion growth caused by radiation toxicity. The pathophysiology of this so-called pseudo-progression is poorly understood. The purpose of this study was to evaluate the use of MRI cine-loops for describing the consecutive events in this radiation induced lesion growth. Ten patients were selected from our department's database that had received SRT of brain metastases and had lesion growth caused by pseudo-progression as well as at least five follow-up MRI scans. Pre- and post SRT MRI scans were co-registered and cine-loops were made using post-gadolinium 3D T1 axial slices. The ten cine loops were discussed in a joint meeting of the authors. The use of cine-loops was superior to evaluation of separate MRI scans for interpretation of events after SRT. There was a typical lesion evolution pattern in all patients with varying time course. Initially regression of the metastases was observed, followed by an enlarging area of new contrast enhancement in the surrounding brain tissue. Analysis of consecutive MRI's using cine-loops may improve understanding of pseudo-progression. It probably represents a radiation effect in brain tissue surrounding the irradiated metastasis and not enlargement of the metastasis itself.

In vivodosimetry in cancer patients undergoing intraoperative radiation therapy.

In vivodosimetry (IVD) is an important tool in external beam radiotherapy (EBRT) to detect major errors by assessing differences between expected and delivered dose and to record the received dose by individual patients. Also, in intraoperative radiation therapy (IORT), IVD is highly relevant to register the delivered dose. This is especially relevant in low-risk breast cancer patients since a high dose of IORT is delivered in a single fraction. In contrast to EBRT, online treatment planning based on intraoperative imaging is only under development for IORT. Up to date, two commercial treatment planning systems proposed intraoperative ultrasound or in-room cone-beam CT for real-time IORT planning. This makes IVD even more important because of the possibility for real-time treatment adaptation. Here, we summarize recent developments and applications of IVD methods for IORT in clinical practice, highlighting important contributions and identifying specific challenges such as a treatment planning system for IORT. HDR brachytherapy as a delivery technique was not considered. We add IVD for ultrahigh dose rate (FLASH) radiotherapy that promises to improve the treatment efficacy, when compared to conventional radiotherapy by limiting the rate of toxicity while maintaining similar tumour control probabilities. To date, FLASH IORT is not yet in clinical use.

Mapping the location of local and regional recurrences according to breast cancer surgery and radiation therapy: Results from EORTC 22922/10925.

The purpose of this study is to evaluate the influence of the extent of surgery and radiation therapy (RT) on the rates and sites of local (LR) and regional recurrences (RR) in the EORTC 22922/10925 trial. PATIENTS AND METHODS: All data were extracted from the trial's individual patients' case report forms (CRF) and analysed with a median follow-up of 15.7 years. Cumulative incidence curves were produced for LR and RR accounting for competing risks: an exploratory analysis of the effect of the extent of surgical and radiation treatments on LR rate was conducted using the Fine & Gray model accounting for competing risks and adjusted for baseline patient and disease characteristics. The significance level was set at 5%, 2-sided. Frequency tables were used to describe the spatial location of LR and RR. RESULTS: Out of 4004 patients included in the trial, 282 (7%) patients experienced LR and 165 (4.1%) RR, respectively. Cumulative incidence rate of LR at 15 years was lower after mastectomy (3.1%) compared to BCS + RT (7.3%) (F&G: HR (Hazard Ratio) = 0.421, 95%CI = 0.282-0.628, p-value < 0.0001). LR were similar up to 3 years for both mastectomy and BCS but continued to occur at a steady rate for BCS + RT, only. The spatial location of the recurrence was related to the locoregional therapy applied and the absolute gain of RT correlated to stage of disease and extent of surgery. CONCLUSIONS: The extent of locoregional therapies impacts significantly on LR and RR rates and spatial location.

Improved guideline compliance after a 3-year audit of multidisciplinary colorectal cancer care in the western part of the Netherlands.

BACKGROUND: From 2006 to 2008, an audit of the multidisciplinary diagnosis and treatment of colorectal cancer patients in the western part of the Netherlands was carried out. We evaluated whether compliance with guidelines had improved. METHODS: All patients with newly diagnosed and surgically treated colon (n = 1,667) and rectal cancer (n = 544) stage I-III were evaluated. Nine quality indicators were derived from the evidence-based guidelines. In order to compare hospital performances, hospital results were adjusted for casemix differences between hospitals. RESULTS: Colon cancer patients showed an increase in the examination of 10 or more lymph nodes (from 53% to 78%, P < 0.0001). For rectal cancer patients there was an increase in preoperative visualisation of the total colon (63-74%, P = 0.02), MRI (73-85%, P = 0.003), radiotherapy (from 82% to 93% for patients <75 years, P = 0.01) and examination of at least 10 lymph nodes (40-55%, P = 0.004). In 2006, standardised hospital performances differed widely for all quality indicators. Two years later, hospital performances for some quality indicators were more similar. CONCLUSIONS: After the feedback of benchmark information, compliance with guidelines for diagnosis and treatment of colorectal cancer patients improved, and differences between individual hospitals decreased. Although secular trends cannot be ruled out, it is highly likely that these results can be attributed to the audit.