Search

Incidence of oropharyngeal squamous cell carcinoma (OPSCC) is increasing globally and the human papillomavirus (HPV) has been linked to this increase. This study aimed to present a comprehensive overview of OPSCC trends in incidence rates by age group and investigate differences in risk factors profile. Netherlands Cancer Registry data from 1989-2018 were analyzed to calculate the annual percentage change (APC) over European standardized incidence rates by gender and age group using joinpoint regression software. Smoking, alcohol drinking and HPV-status were available for 2015-2018. During 1989-2018, 13 048 cases of OPSCC were reported with a male-to-female ratio of 2.1:1. The overall incidence rate increased by 5.4% (APC) annually from 1989 to 1996 but slowed thereafter by 1.2%. Significant declines were found in patients of 35-44 years (APCs -3.7%). Adults aged 45-59 years displayed significant increases from 1989 to 2001, followed by a significant decline. In patients >= 60 years, the incidence rates increased overall, with APC for women being consistently higher than men. The data on HPV status was available for 69% of the patients, of whom 47% were HPV+. Smoking and alcohol consumption were more prevalent, that is 75 and 76 % respectively. The declining trends of OPSCC for Dutch people aged 35-44 years from 1989 to 2018 and for those aged 45-59 years from 2002 onwards are inconsistent to trends reported elsewhere in the developed countries. The prevalence of smoking and drinking alcohol was quite high in all age groups, whereas the proportion of HPV-positivity was relatively low.

Background In this feasibility study we aimed to evaluate the value of previously reported molecular tumor biomarkers associated with lymph node metastasis in oral squamous cell carcinoma (OSCC) to optimize neck strategy selection criteria.Methods The association between expression of cortactin, cyclin D1, FADD, RAB25, and S100A9 and sentinel lymph node status was evaluated in a series of 87 (cT1-2N0) patients with OSCC treated with primary resection and SLNB procedure.Results Tumor infiltration depth and tumor pattern of invasion were independent prognostic markers for SLN status, while none of the tumor makers showed a better prognostic value to replace SLNB as neck staging technique in the total cohort. However, in the subgroup of patients with pT1N0 OSCC, cortactin expression (OR 16.0, 95%CI 2.0-127.9) was associated with SLN classification.Conclusions Expression of cortactin is a promising immunohistochemical tumor marker to identify patients at low risk that may not benefit from SLNB or END.

Introduction: Life expectancy is rising and consequently also the number of older patients with head and neck cancer. Different treatment regimens are often applied for older patients. The aim of this study is to investigate how treatment patterns and survival rates have changed over the past 20 years in older patients with head and neck squamous cell carcinoma (HNSCC). Materials: Patient and tumour characteristics, treatment and 5-year survival data from the Netherlands Cancer Registry of patients aged >60 years diagnosed with HNSCC in 1990-1995 and 2010-2015 were compared using chi-square test and relative survival analysis.Results: Data of 14,114 patients were analyzed. Oral cavity cancer treatment did not change over time, while survival improved from 54% to 58% (p 1/4 0.03). Oropharyngeal and hypopharyngeal cancer treatment shifted towards non-surgical, with survival improving from 31% to 51% (p < 0.01) and 26% to 34% (p < 0.01), respectively. Laryngeal cancer treatment changed towards surgery in stage I and non-surgical treatment in stage III and IV disease. Survival in laryngeal cancer stage I remained stable and favorable at a relative survival rate of around 90%. Survival non-significantly changed from 54% to 49% for stage III disease and from 37% to 33% for disease.Conclusion: Relative survival increased for all head and neck cancer sites in older patients, except for laryngeal cancer. For oropharyngeal, hypopharyngeal and advanced laryngeal cancer, a shift towards non-surgical treatment modalities was observed.(c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license

OBJECTIVE: Head and neck squamous cell carcinomas (HNSCC) are rapidly developing tumours, and substantial delay in treatment initiation is associated with decreased overall survival. The effect of delay on health-related quality of life (HRQOL) is unknown. The aim of this study was to assess the impact of delay on QOL and overall survival.METHODS: Patients with mucosal HNSCC were prospectively included. HRQOL and 2-year overall survival were analysed using linear mixed-model analyses and cox regression, respectively. Delay was defined as care pathway interval (CPI) of ≥30 days between first consultation and treatment initiation.RESULTS: Median CPI was 39 days for the 173 patients included. A trend towards higher HRQOL-scores (indicating better HRQOL) during 2-year follow-up for patients with delay in treatment initiation was visible in the adjusted models (HRQOL summary score-β: 2.62, 95% CI: 0.57-4.67, p = 0.012). Factors associated with decreased overall survival were moderate comorbidities (HR: 5.10, 95% CI: 1.65-15.76, p = 0.005) and stage-IV tumours (HR: 12.37, 95% CI: 2.81-54.39, p = 0.001). Delay was not associated with worse overall survival.CONCLUSION: Timely treatment initiation is challenging, especially for patients with advanced tumours and initial radiotherapy treatment. Encountering delay in treatment initiation did not result in clinically relevant differences in HRQOL-scores or decreased overall survival during 2-year follow-up.

Background In the Netherlands, differentiated thyroid cancer (DTC) is treated surgically in three different hospital types, including university, teaching, and non- teaching peripheral hospitals. This study evaluates postoperative complications and referral patterns in patients with DTC in the northern region of the Netherlands to gain an understanding on how to improve management implementation. Methods Data from 567 patients diagnosed between 1989 and 2009 were obtained from the Netherlands Cancer Registry and were supplemented with information from hospital digital information systems and patient records from 15 hospitals: 1 university, 3 teaching, and 11 peripheral hospitals. Surgically treated patients with a histologically proven DTC derived from the original pathology reports were included. Results Surgical treatment could be performed in a single procedure in 234 patients (41.3%), but several surgeries were needed in the remaining 333 patients (58.7%). Recurrent laryngeal nerve (RLN) palsy occurred after all types of thyroid surgical procedures, but mostly after initial (hemi)thyroidectomy and reoperations. RLN was temporary in 3.2% of the nerves at risk and persistent in 1.8%. Temporary hypocalcemia developed in 13.7% of patients, and persistent hypocalcemia occurred in 4.8%. Patients were mainly referred to the university hospital from a non-teaching (40.7%, 48/118) or teaching hospital (11.1%, 16/144); however, 80% of patients were not referred. Conclusions The complication rate and number of multiple surgeries support the efforts in optimizing clinical management in thyroid cancer. Careful considerations prior to initial surgical treatment by early discussion in telemedicine-based regional tumor boards could possibly prevent reoperations and potentially diminish complications.

Purpose Cognitive symptoms are reported to affect cancer survivors’ functioning at work. However, little is known about the type of cancer treatment and cognitive symptoms in working cancer survivors. We examined the longitudinal association between type of cancer treatment and cognitive symptoms in cancer survivors post return to work, and whether the course of cognitive symptoms over 18 months differed per type of cancer treatment. Methods Data from the Dutch longitudinal “Work-Life after Cancer” study were used. The study population consisted of 330 working cancer survivors who completed questionnaires at baseline, and 6, 12, and 18 months follow-up. Cognitive symptoms were assessed with the cognitive symptom checklist-work and linked with cancer treatment data from the Netherlands Cancer Registry. Data were analyzed using generalized estimating equations. Results Cancer survivors who received chemotherapy reported comparable memory symptom levels (b: − 2.3; 95% CI = − 7.1, 2.5) to those receiving locoregional treatment. Executive function symptom levels (b: − 4.1; 95% CI = − 7.8, − 0.4) were significantly lower for cancer survivors who received chemotherapy, compared with those receiving locoregional treatment. In cancer survivors who received other systemic therapy, memory (b: 0.4; 95% CI = 0.1, 0.7) and executive function symptom levels (b: 0.4; 95% CI = 0.0, 0.7) increased over time. In cancer survivors who received chemotherapy and locoregional treatment, memory and executive function symptom scores were persistent during the first 18 months after return to work. Conclusions The contradictory finding that cancer patients receiving chemotherapy report fewer cognitive symptoms warrants further research. Implications for Cancer Survivors Working cancer survivors may have cognitive symptom management needs irrespective of the type of cancer treatment they received.

Objective Head and neck squamous cell carcinomas (HNSCC) are relatively fast-growing tumours, and delay of treatment is associated with tumour progression and adverse outcomes. The aim of this study is to identify determinants of delay in a head and neck oncology centre.Methods This cohort study with prospectively collected data investigated associations between patient (including geriatric assessment at first consultation), tumour and treatment characteristics and treatment delay. Two quality indicator intervals assessing value-based healthcare were studied: care pathway interval (CPI, interval between first visit in an HNOC and treatment initiation) and time-to-treatment initiation (TTI, interval between histopathological confirmation of HNSCC and treatment initiation), using regression analyses.Results Stage-IV tumours and initial radiotherapy were independent predictors of delay in CPI. Initial radiotherapy was associated with delay in TTI. Overall, 37% of the patients started treatment within 30 days after first consultation (67% in case of initial surgical treatment and 11.5% if treated with (chemo)radiation, p Conclusion The majority of HNSCC patients encounter delay in treatment initiation, specifically in patients with advanced-stage tumours or when radiotherapy is indicated.

AIMS: In the 8th edition of the American Joint Committee on Cancer (AJCC) TNM staging Manual, tumor infiltration depth and extranodal extension are added to the pathological classification for oral squamous cell carcinoma. Currently available 8th TNM validation studies are lacking patients with conservative neck treatment, while changes in the classification especially affect patients with small tumors. This study's aim was to determine the potential impact of the changes within the 8th edition pTNM classification on the prognosis and treatment strategy of oral squamous cell carcinoma in a well-defined series of pT1-T2 patients with a long-term follow-up.METHODS AND RESULTS: 211 first primary pT1-T2 oral squamous cell carcinoma patients, with surgical resection as primary treatment were analyzed retrospectively. 173 patients received a neck dissection and 38 patients had a frequent clinical neck assessment. Long-term follow-up (median: 64 months) and reassessed tumor infiltration depth were available. Classification according to the 8th edition criteria resulted in 36% total upstaging with the T classification and 16% with N classification. T3 restaged patients (n=30, 14%) had lower 5-year disease specific survival rates compared to T2 staged patients (81% versus 67%, p = 0.042). Postoperative (chemo)radiotherapy could have been considered in another 7 (3%) patients based on the 8th edition criteria.CONCLUSIONS: Addition of tumor infiltration depth and extranodal extension within the 8th TNM classification leads to the identification of oral squamous cell carcinoma patients with a worse prognosis who might benefit from an improved postoperative treatment strategy. This article is protected by copyright. All rights reserved.

Objective 18F FDG-PET is superior to other imaging techniques in revealing residual laryngeal cancer after radiotherapy. Unfortunately, its specificity is low, due to FDG uptake in inflammation and in anaerobic conditions. PET imaging with the amino acid-based radiopharmaceutical C11-methionine (MET) should be less influenced by post-radiation conditions. The aim of this study was to investigate the potential of MET in diagnosing recurrent laryngeal cancer after radiotherapy as compared to 18F-FDG. Methods Forty-eight patients with a clinical suspicion of local residual disease at least 3 months after completion of radiotherapy or chemoradiotherapy for a T2-4 laryngeal carcinoma, along with an indication for direct laryngoscopy, were included. They received MET-PET and FDG-PET prior to the direct laryngoscopy. One senior nuclear medicine physician assessed both the FDG-PET and MET-PET images visually for the degree of abnormal uptake. The gold standard was a biopsy-proven recurrence 12 months after PET. The nuclear physician had no access to the medical charts and was blinded to the results of the other PET. Sensitivity, specificity and positive and negative predictive value were calculated. Results The sensitivity of FDG was 77.3% and the specificity 56.0% after the conservative reading, with these values equalling 54.5% and 76.0% for MET. The positive predictive value of FDG was 60.7% and the negative predictive value 73.7%. The PPV of MET was 66.7%, and the NPV was 65.5%. The McNemar test within diseased (sensitivity comparison) shows a p-value of 0.125, and the McNemar test within non-diseased (specificity comparison) shows a P-value of 0.180. Conclusion MET-PET is not superior to FDG-PET in terms of identifying recurrent laryngeal cancer.

Purpose Distant metastasis (DM) in patients with head and neck squamous cell carcinoma (HNSCC) is uncommon, but strongly deteriorates prognosis. Controversy exists regarding age as a predictor for the presence and development of DM. The aim of this study was to investigate age and other predictors for DM in HNSCC patients. Methods From 1413 patients diagnosed with a primary HNSCC between 1999 and 2010 in a tertiary referral centre, patient, disease and pathological characteristics were extracted from patient files. Uni- and multivariable Cox regression analyses were performed to identify risk factors for DM as primary outcome. Results DM occurred in 131 (9.3%) patients, of which 27 (1.9%) were diagnosed simultaneously with the primary tumour, 27 (1.9%) were diagnosed synchronous, and 77 (5.4%) were diagnosed metachronous. The most common site of DM was lung (51.1%), followed by bone (19.1%) and liver (11.5%). Multivariable analysis identified male gender (HR = 1.95, 95% CI 1.23–3.10) hypopharyngeal tumours (HR = 3.28, 95% CI 1.75–6.14), advanced T-stage (HR = 1.61, 95% CI 1.09–2.38), poor differentiation grade (HR = 2.49, 95% CI 1.07–5.78), regional lymph node metastasis (HR = 5.35, 95% CI 3.25–8.79) and extranodal extension of regional lymph nodes metastasis (HR = 3.06, 95% CI 1.39–6.72) as independent prognostic factors for the presence or development of DM. No relation with age was found. Conclusion Age is not related to the presence or development of DM. This study emphasizes the importance of screening for DM, especially in males, patients with hypopharyngeal tumours, advanced T-stage, histopathological poor differentiation grade, regional lymph node metastasis and extranodal extension.

Airway surgery in pediatric patients is challenging with regard to balancing surgical exposure with ventilation requirements, as during the procedure the airway must be shared between laryngologist and anesthetist. For endoscopic laryngeal surgery, different methods of ventilation are used, among others jet ventilation via a specifically adapted suspension laryngoscope using a dual jet stream(Supraglottic Superimposed High Frequency Jet ventilation, SSHFJV) (1).High BMI and a history of pulmonary pathology proved to be factors contributing to failing of SSHFJV in adult patients (2). However, factors influencing the failure of SSHFJV in pediatric patients have never been described yet.

Background: To determine time of onset and risk of hypothyroidism after total laryngectomy (TL) with and without (hemi)thyroidectomy in relation to treatment regimen, that is, preoperative radiotherapy (RT-TL), postoperative radiotherapy (TL-RT), and postoperative re-irradiation (RT-TL-RT). Methods: Retrospective review of 128 patients treated by RT-TL (51 patients), TL-RT (55 patients), and RT-TL-RT (22 patients). Risk of hypothyroidism was determined by multivariable Cox regression analysis and euthyroid survival was calculated using Kaplan-Meier method. Results: Hypothyroidism developed in 69 (54%) patients. The median onset of hypothyroidism was later (P

Contains fulltext : 200394.pdf (Publisher’s version ) (Closed access) BACKGROUND: Long-term trends of sinonasal cancer in The Netherlands have been investigated with particular attention on adenocarcinoma for which wood or leather dust is a well-known risk factor. METHODS: All 4345 patients (1989-2014) registered in the Netherlands Cancer Registry were included. Standardized 3-year moving incidence rates per 1 000 000/person-years, and estimated annual percentage change (EAPC) were calculated. RESULTS: Forty-seven percent of the patients had squamous cell carcinoma (SCC), 12% had lymphoma, and 12% had adenocarcinoma. Sixty-one percent of the tumors were located in the nasal cavity, 22% in the maxillary, and 11% in the ethmoidal sinus. Male incidence decreased to 11.5/1 000 000 due to less SCC (EAPC -0.9%; 95% confidence interval [CI] -1.6 to 0.3) and adenocarcinoma (EAPC -4.3%; 95% CI -5.5 to 3.1). Female incidence increased to 7/1 000 000 (EAPC +2.0%; 95% CI +1.1 to +3.0) due to more SCC (EAPC +2.2%; 95% CI +1.0 to +3.5), whereas adenocarcinoma remained stable (0.6/1 000 000; EAPC +1.1%; 95% CI -6.0 to +8.7). Tumors of the nasal cavity increased in women (EAPC +3.3%; 95% CI +2.0 to 4.7). CONCLUSION: The decrease of male sinonasal adenocarcinoma may be the result of preventive measures combined with less workers in high-risk occupations. 01 november 2018

Background: Monitoring and effectively improving oncologic integrated care requires dashboard information based on quality registrations. The dashboard includes evidence-based quality indicators (QIs) that measure quality of care. This study aimed to assess the quality of current integrated head and neck cancer care with QIs, the variation between Dutch hospitals, and the influence of patient and hospital characteristics. Methods: Previously, 39 QIs were developed with input from medical specialists, allied health professionals, and patients' perspectives. QI scores were calculated with data from 1,667 curatively treated patients in 8 hospitals. QIs with a sample size of >400 patients were included to calculate reliable QI scores. We used multilevel analysis to explain the variation. Results: Current care varied from 29% for the QI about a case manager being present to discuss the treatment plan to 100% for the QI about the availability of a treatment plan. Variation between hospitals was small for the QI about patients discussed in multidisciplinary team meetings (adherence: 95%, range 88%-98%), but large for the QI about malnutrition screening (adherence: 50%, range 2%-100%). Higher QI scores were associated with lower performance status, advanced tumor stage, and tumor in the oral cavity or oropharynx at the patient level, and with more curatively treated patients (volume) at hospital level. Conclusions: Although the quality registration was only recently launched, it already visualizes hospital variation in current care. Four determinants were found to be influential: tumor stage, performance status, tumor site, and volume. More data are needed to assure stable results for use in quality improvement.

BackgroundTo improve quality of care, centralisation of cancer services in high-volume centres has been stimulated. Studies linking specialisation and high (surgical) volumes to better outcomes already appeared in the 1990's. However, actual centralisation was a difficult process in many countries. In this study, factors influencing the centralisation of cancer services in the Netherlands were determined.Material and methodsCentralisation patterns were studied for three types of cancer that are known to benefit from high surgical caseloads: oesophagus-, pancreas- and bladder cancer. The Netherlands Cancer Registry provided data on tumour and treatment characteristics from 2000-2013 for respectively 8037,4747 and 6362 patients receiving surgery. By plotting timelines of centralisation of cancer surgery, relations with the appearance of (inter)national scientific evidence, actions of medical specialist societies, specific regulation and other important factors on the degree of centralisation were ascertained.ResultsFor oesophagus and pancreas cancer, a gradual increase in centralisation of surgery is seen from 2005 and 2006 onwards following (inter)national scientific evidence. Centralisation steps for bladder cancer surgery can be seen in 2010 and 2013 anticipating on the publication of norms by the professional society. The most influential stimulus seems to have been regulations on minimum volumes.ConclusionScientific evidence on the relationship between volume and outcome lead to the start of centralisation of surgical cancer care in the Netherlands. Once a body of evidence has been established on organisational change that influences professional practice, in addition some form of regulation is needed to ensure widespread implementation.

Hypopharynx cancer has the worst prognosis of all head and neck squamous cell cancers. Since the 1990s, a treatment shift has appeared from a total laryngectomy towards organ preservation therapies. Large randomized trials evaluating treatment strategies for hypopharynx cancer, however, remain scarce, and frequently this malignancy is evaluated together with larynx cancer. Therefore, our aim was to determine trends in incidence, treatment and survival of hypopharynx cancer. We performed a population-based cohort study including all patients diagnosed with T1–T4 hypopharynx cancer between 1991 and 2010 in the Netherlands. Patients were recorded by the national cancer registry database and verified by a national pathology database. 2999 patients were identified. The incidence increased significantly with 4.1% per year until 1997 and decreased non-significantly afterwards. For women, the incidence increased with 1.7% per year during the entire study period. Total laryngectomy as primary treatment significantly decreased, whereas radiotherapy and chemoradiation increased. The 5-year overall survival significantly increased from 28% in 1991–2000 to 34% in 2001–2010. Overall survival for T3 was equal for total laryngectomy and (chemo)radiotherapy, but for T4-patients the survival was significantly better after primary total laryngectomy (± adjuvant radiotherapy). This large population-based study demonstrates a shift in treatment preference towards organ preservation therapies. The 5-year overall survival increased significantly in the second decade. The assumed equivalence of organ preservation and laryngectomy may require reconsideration for T4 disease. Electronic supplementary material The online version of this article (doi:10.1007/s00405-017-4766-6) contains supplementary material, which is available to authorized users.

Background: Audit and feedback on professional practice and health care outcomes are the most often used interventions to change behaviour of professionals and improve quality of health care. However, limited information is available regarding preferred feedback for patients, professionals and health insurers.Objective: Investigate the (differences in) preferences of receiving feedback between stakeholders, using the Dutch Head and Neck Audit as an example.Methods: A total of 37 patients, medical specialists, allied health professionals and health insurers were interviewed using semi-structured interviews. Questions focussed on: Why, On what aspects and How do you prefer to receive feedback on professional practice and health care outcomes?Results: All stakeholders mentioned that feedback can improve health care by creating awareness, enabling self-reflection and reflection on peers or colleagues, and by benchmarking to others. Patients prefer feedback on the actual professional practice that matches the health care received, whereas medical specialists and health insurers are interested mainly in health care outcomes. All stakeholders largely prefer a bar graph. Patients prefer a pie chart for patient-reported outcomes and experiences, while Kaplan-Meier survival curves are preferred by medical specialists. Feedback should be simple with firstly an overview, and 1-4 times a year sent by e-mail. Finally, patients and health professionals are cautious with regard to transparency of audit data.Conclusions: This exploratory study shows how feedback preferences differ between stakeholders. Therefore, tailored reports are recommended. Using this information, effects of audit and feedback can be improved by adapting the feedback format and contents to the preferences of stakeholders.

Treatment choice in elderly pharyngeal cancer patient is disputed. This study was aimed to asses association of co-morbidity, complications and survival in different treatment modalities of pharyngeal cancer patients.Retrospective analysis of pharyngeal cancer patients, diagnosed between 1997 and 2007 in a tertiary referral hospital was performed. Patients 75 years and older (n = 42), were matched with two control patients 64 years and younger (n = 84). Co-morbidity (ACE-27), treatment related complications and survival data were assessed and analyzed.Frequency of co-morbidity was similar in both age groups, although discarding alcohol abuse resulted in higher incidence of co-morbidity in the elderly group. Complication rate was not significantly different. In a multivariate analysis only stage found to be a significant predictor of complications. Survival estimates adjusted to sex, age and birth cohort revealed co-morbidity to be a significant predictor for survival in elderly and young patients.No evidence has been found to treat elderly pharyngeal cancer patients differently than younger ones. Treatment related complications are not predicted by co-morbidities in young and elderly patients; however survival is predicted by comorbidity. Therefore thorough pre-treatment evaluation and care necessary in the elderly population. (C) 2011 Elsevier Ltd. All rights reserved.

Dietary energy restriction may protect against cancer. In parts of The Netherlands, mostly in larger cities, periods of chronically impaired nutrition and even severe famine (Hunger Winter 1944-1945) existed during the 1930s and World War II (1940-1945). We studied the association between energy restriction during childhood and early adulthood on the risk of ovarian cancer later in life. In 1986, the Netherlands Cohort Study was initiated. A self-administered questionnaire on dietary habits and other cancer risk factors was completed by 62,573 women aged 55-69 years at baseline. Follow-up for cancer was established by record linkage to the Netherlands Cancer Registry. After 16.3 years of follow-up, 364 invasive epithelial ovarian cancer cases and 2220 subcohort members (sampled from the total cohort directly after baseline) with complete information confounders were available for case-cohort analyses. In multivariable analysis, ovarian cancer risk was lower for participants with an unemployed father during the 1930s (Hazard Ratio (HR), 0.70; 95% Confidence Interval (CI), 0.47-1.06) compared to participants with an employed father as well as for participants living in a city during World War II (HR, 0.69; 95% CI, 0.54-0.90) compared to participants living in the country-side. Residence in a Western City during the famine (Hunger Winter) was not associated with a decreased risk. Our results show a relation between proxy variables for modest energy restriction over a longer period of time during childhood or early adulthood and a reduced ovarian cancer risk.

Background Treatment variation is an important issue in health care provision. An external peer review programme for multidisciplinary cancer care was introduced in 1994 in the Netherlands to improve the multidisciplinary organisation of cancer care in hospitals. So far the clinical impact of external quality assessment programmes such as external peer review and accreditation remains unclear. Our objective was to examine the degree of variation in treatment patterns and the possible effect of external peer review for multidisciplinary cancer care for breast cancer patients. Methods Patients with breast cancer were included from 23 hospitals from two ‘intervention regions’ with the longest experience with the programme and 7 hospitals that never participated (control group). Data on tumour and treatment characteristics were retrieved from the Netherlands Cancer Registry. Treatment modalities investigated were: the completeness of breast conserving therapy, introduction of the sentinel node biopsy, radiotherapy after breast conserving surgery for ductal carcinoma in situ (DCIS), adjuvant radiotherapy for locally advanced breast cancer (T3/M0 or any T,N2-3/M0), adjuvant chemotherapy for early stage breast cancer (T1-2/N+/M0) and neo-adjuvant chemotherapy for T4/M0 breast cancer. Hospitals from the two intervention regions were dichotomised based on their implementation proportion (IP) of recommendations from the final reports of each peer review (high IP vs. low IP). This was regarded as a measure of how well a hospital participated in the programme. Results 63,516 female breast cancer patients were included (1990-2010). Variation in treatment patterns was observed between the intervention regions and control group. Multidisciplinary treatment patterns were not consistently better for patients from hospitals with a high IP. Conclusions There is no relationship between the external peer review programme for multidisciplinary cancer care and multidisciplinary treatment patterns for breast cancer patients. Regional factors seem to exert a stronger effect on treatment patterns than hospital participation in external peer review. Electronic supplementary material The online version of this article (doi:10.1186/1471-2407-14-596) contains supplementary material, which is available to authorized users.