Radiotherapy is intriguing as it not only eliminates tumor cells but also triggers a response from cytotoxic T cells, which attack the tumor. Thus, radiotherapy and immunotherapy are being combined... Show moreRadiotherapy is intriguing as it not only eliminates tumor cells but also triggers a response from cytotoxic T cells, which attack the tumor. Thus, radiotherapy and immunotherapy are being combined in clinical studies, although their success has been limited. We used mouse tumor models to understand how radiotherapy induces T cell priming and subsequent anti-tumor immunity. In a model resembling lymphocyte-depleted cancer, we identified obstacles to systemic radiotherapy-induced T cell responses and proposed interventions to overcome them. Additionally, we explored strategies to counter local T cell suppression in the tumor microenvironment. In poorly immunogenic tumors, radiotherapy can provoke a T cell response, but this is counteracted by the generation of immunosuppressive Tregs. Combining radiotherapy with checkpoint immunotherapy, despite its success in humans, unexpectedly amplified the Treg response, further hindering cytotoxic T-cell activity. Our findings suggest this immunotherapy may not benefit these cancers. We discovered that molecules like CD80 and CD86, capable of stimulating T cells via the CD28 receptor, have distinct roles in promoting cytotoxic and Treg cells. Blocking CD86 enhanced cytotoxic T cell responses post-radiotherapy, leading to tumor rejection. Our study elucidates how tumor characteristics shape T-cell responses, how radiotherapy can evoke both favorable and unfavorable responses, and how targeted antibody immunotherapy can influence this interplay. Show less
This thesis focuses on treatment outcomes of high risk endometrial cancer and corresponding patients’ and clinicians’ preferences regarding adjuvant treatment decisions; molecular studies on the... Show moreThis thesis focuses on treatment outcomes of high risk endometrial cancer and corresponding patients’ and clinicians’ preferences regarding adjuvant treatment decisions; molecular studies on the etiology of mismatch repair deficiency (MMRd) in intermediate and high risk endometrial cancer; and the combination of immunotherapy and PARP inhibition for the treatment of recurrent or metastatic endometrial cancer.The overall aims of this thesis were:• To evaluate health-related quality of life up to 5 years after chemoradiotherapy compared with pelvic radiotherapy alone in the adjuvant treatment of high risk endometrial cancer in the PORTEC-3 trial;• To investigate the preferences of patients and clinicians regarding the benefit-risk trade-off of the addition of chemotherapy to adjuvant pelvic radiotherapy;• To investigate the prevalence and prognosis of Lynch syndrome-associated endometrial cancer among MMRd endometrial cancers;• To evaluate the role of combined checkpoint inhibition and PARP inhibition in women with metastatic or recurrent endometrial cancer in terms of progression-free survival and toxicity in the DOMEC trial. Show less
For part I population-based data from the national cancer registries of Belgium, the Netherlands, Norway, and Sweden was used. In all countries, the use of chemotherapy increased with stage and... Show moreFor part I population-based data from the national cancer registries of Belgium, the Netherlands, Norway, and Sweden was used. In all countries, the use of chemotherapy increased with stage and decreased with age. Also, 30-day and one-year excess mortality decreased over the years for colon and rectal cancer. After surviving the first postoperative year, the survival of surgically treated older patients aligned with their younger counterparts, except for patients with stage III disease. Part II describes the results of the analyses of the RAPIDO trial. DRTF decreased from 30% in the standard-care group to 24% in the experimental group at 3 years after randomisation, mainly due to a decrease in DM, which is probably due to better compliance preoperatively and perhaps due the earlier treatment of micrometastases in the treatment process. Although patients with DM in the experimental group had worse survival compared to patients in the standard-care group, the cumulative probability of overall survival remained comparable for both treatment groups. If the patients with a complete response can be identified during reassessment after neoadjuvant therapy, surgery may be omitted, a W&W after a cCR with an appropriate follow-up has no additional oncological risk in young patients compared to older patients (part III). This opens the door for potential organ preservation. Show less
During recent decades, many studies have been performed in patients with early glottic cancer, which provide new insight into the two main treatment modalities, TOLMS and radiotherapy, and their... Show moreDuring recent decades, many studies have been performed in patients with early glottic cancer, which provide new insight into the two main treatment modalities, TOLMS and radiotherapy, and their outcomes. The aim of this thesis was: (i) What is the role of TOLMS in T2 glottic carcinoma in the Netherlands? (ii) Should more patients with T2 glottic carcinoma be treated with TOLMS? Within this thesis, we found that (i) the laryngeal preservation rate for T2 glottic carcinoma is higher after primary treatment with TOLMS than after primary treatment with radiotherapy; (ii) that the binary use (yes/no) for the involvement of the anterior commissure (AC) as a prognostic factor leads to inconsistent results, whereas studies with a more detailed classification of the AC show that there is a significant impact on oncological outcomes; (iii) that vertical involvement of the AC on imaging has a significant impact on local control not only in patients treated with TOLMS but also in patients receiving primary radiotherapy; and (iv) that patient with T2 glottic carcinoma treated with radiotherapy reported good long-term functional outcomes, although patients with tumors infiltrating the vocal fold muscle show a trend toward a higher degree of voice handicap than patients with tumor with only superficial spread. Show less
Adapting a radiotherapy treatment plan to the daily anatomy is a crucial task to ensure adequate irradiation of the target without unnecessary exposure of healthy tissue.This adaptation can be... Show moreAdapting a radiotherapy treatment plan to the daily anatomy is a crucial task to ensure adequate irradiation of the target without unnecessary exposure of healthy tissue.This adaptation can be performed by automatically generating contours of the daily anatomy together with fast re-optimization of the treatment plan. These measurescan compensate for the daily variation and ensure the delivery of the prescribed dose distribution at small margins and high robustness settings. In this thesis, we focused on developing a deep learning-based methodology for automatic contouring for real-time adaptive radiotherapy either guided by CT or MR imaging modalities Show less
The studies in this thesis contribute to more accurate risk assessment and prognosis prediction for DCIS and to better response evaluation of IBC treatment.For the Ductal Carcinoma In Situ (DCIS)... Show moreThe studies in this thesis contribute to more accurate risk assessment and prognosis prediction for DCIS and to better response evaluation of IBC treatment.For the Ductal Carcinoma In Situ (DCIS) studies, unbiased cohorts were used within the international Grand Challenge PRECISION consortium, funded by Cancer Research UK and KWF Dutch Cancer Society. DCIS is graded as low-, intermediate-, or high-grade depending on how abnormal the DCIS-cells look like. However, we showed that pathologists often disagree on grade. To overcome this limitation, we found that almost all DCIS scored as non-high-grade by the majority of pathologists express the estrogen receptor (ER) and are negative for the growth factor receptor HER2, whereas high-grade DCIS is mixed in expression for ER and HER2. We also provided insights in the recurrence risks of DCIS after treatment. See also https://cancergrandchallenges.org/teams/precision.The studies on Invasive Breast Cancer (IBC) were performed on a hospital-based cohort. We found for example substantial variation in tumour response evaluation for HER2-positive IBC after pre-operative chemotherapy due to different guidelines used. For accurate outcome analysis, reducing such variation is mandatory. Therefore, we are working on reaching international consensus of response evaluation. Show less
The recent FLAME trial has demonstrated improved local control of intermediate to high-risk prostate cancer after focal dose escalation of the visible tumor. To visualize the tumor, MRI... Show moreThe recent FLAME trial has demonstrated improved local control of intermediate to high-risk prostate cancer after focal dose escalation of the visible tumor. To visualize the tumor, MRI examinations were taken in which prostate tissue characteristics were visualized. Since this treatment strategy improves the clinical outcome of the patient, a technical analysis of the FLAME dataset is useful for the further optimization of focal dose escalation strategies.Delineation of the prostate tumor appeared to be performed differently in the participating radiotherapy departments. Considering the impact on the realized tumor dose, this analysis demonstrated the need for guidelines of tumor delineation on MRI. Due to the complex nature of the treatment plans, in addition a prediction model was developed, which identified patients for which a higher tumor dose could be planned.The application of MRI was also investigated for ‘dose painting by numbers’, in which MRI values are translated to prescription dose without interference of manual tumor delineations. Dose prescription based on MRI appeared robust to daily patient variations, a prerequisite for further development of ‘dose painting by numbers’. However, because of the absence of significant tumor changes during the treatment course, MRI was considered not suitable for early adaptive treatment. Show less
This thesis sought to obtain a better understanding of the composition of the immune microenvironment in NSCLC and how to modulate this tumor immune microenvironment by RT to induce amplified... Show moreThis thesis sought to obtain a better understanding of the composition of the immune microenvironment in NSCLC and how to modulate this tumor immune microenvironment by RT to induce amplified antitumor immune responses to ICIs in advanced NSCLC patients. In the first part of this thesis, a multiangular approach of a combination of protein and mRNA expression with clinicopathological characteristics in a large cohort of early stage, resected NSCLC samples will be discussed. The second part focusses on the immune modulating effects of RT, in particular when combined with immunotherapy treatment in metastatic NSCLC. Show less
Radiotherapy treatments need adequate quality control (QC) to ensure a correct delivery of the prescribed dose to the target area. One of the most extended safety nets for treatments in... Show moreRadiotherapy treatments need adequate quality control (QC) to ensure a correct delivery of the prescribed dose to the target area. One of the most extended safety nets for treatments in conventional radiotherapy machines is in-vivo EPID dosimetry, which uses the dose acquired by an Electronic Portal Imaging Device (EPID) during treatment to accurately reconstruct the dose as it was delivered to the patient.We developed a method to validate radiotherapy treatments delivered on a novel system: the Unity MR-Linac. This machine, which combines a radiation source (linac) and an imaging device (MRI), will help to irradiate tumors more accurately by means of a new range of techniques only available thanks to the image guidance of the MRI during irradiation. The verification of such treatments can be performed by using images of the delivered beam captured by an EPID situated opposite to the radiation source, behind the cryostat of the MRI scanner. This project focuses on the adaptation of an already existing algorithm used with conventional linacs to the new physics and design characteristics of the Unity MR-linac. The main challenge for this adaptation is the presence of the MRI scanner between the patient and the EPID, acting as a secondary source of scatter and as an attenuation medium for the beam. Show less
Approximately 15–20% of women with endometrial cancer have high-risk disease features and are at increased risk of distant metastases. Standard treatment after surgery is pelvic radiotherapy to... Show moreApproximately 15–20% of women with endometrial cancer have high-risk disease features and are at increased risk of distant metastases. Standard treatment after surgery is pelvic radiotherapy to reduce the risk of recurrence. In the international PORTEC-3 trial we have investigated the added value of adjuvant chemotherapy during and after radiotherapy in terms of efficacy, toxicity and quality of life. It was found that both overall and recurrence-free survival were significantly improved with the addition of chemotherapy to radiotherapy, especially for women with more advanced disease (stage 3) or with serous histological type. This comes however at the expense of increased and more serious toxicity and an impaired quality of life during and in the first 6 months after treatment. About 25% of women treated with chemotherapy still reported tingling and numbness of hands and/or feet at 2 years after treatment. It is therefore important to discuss the benefits and costs of the addition of chemotherapy in shared decision making, for which the results discussed in this thesis provide valuable information. Currently molecular analysis of the PORTEC-3 tissue samples is done to evaluate which patients benefit most from added chemotherapy. Show less
Prostate cancer (PCa) is frequently treated with radiotherapy. However, depending on the aggressiveness of the disease, the risk of recurrence can be up to 35% within five years of the initial... Show moreProstate cancer (PCa) is frequently treated with radiotherapy. However, depending on the aggressiveness of the disease, the risk of recurrence can be up to 35% within five years of the initial treatment. Patients with localised recurrent PCa are candidates for curative (i.e. salvage) treatment. To overcome the toxicity associated with whole-gland approaches, focal salvage treatments target the index lesion while sparing the surrounding tissue. The studies described in this thesis elaborate on the use of quantitative multi-parametric MRI (mp-MRI) for the detection and localisation of locally recurrent PCa after radiotherapy. Pre-treatment radiomic imaging features were found to have potential to improve recurrence-risk prediction models for high-risk PCa patients treated with radiotherapy. In this thesis, the mp-MRI properties of irradiated benign tissue and recurrent tumour were characterised, with access to pathological samples. These findings can be used as a foundation to establish guidelines (which are currently absent) on how to assess and score MRI scans after radiotherapy. Improving radiological knowledge in the recurrent setting can lead to improved staging and result in better patient selection for salvage treatments. Lastly, this thesis provides evidence on how best to define the region to target, leading to a refinement of focal salvage strategies. Show less
Bone metastases of the long bones can cause pain and pathologic fractures. Local treatment consists of radiotherapy or surgical stabilisation. The most appropriate treatment depends on many factors... Show moreBone metastases of the long bones can cause pain and pathologic fractures. Local treatment consists of radiotherapy or surgical stabilisation. The most appropriate treatment depends on many factors, including the symptoms, the location and extent of the lesion, the wishes and expectations of the patient, and the expected remaining survival. Survival estimation of patients with symptomatic long bone metastases is crucial to prevent over- and undertreatment. This thesis aimed to develop a prognostic model for estimating survival in patients with cancer and symptomatic metastases of the long bones, evaluate current (surgical) treatment modalities and trends, and provide rationale for future prospective randomized trials. As a result, the OPTIModel was developed: an easy-to-use prognostic model that categorises patients into four clinically relevant survival categories based on only three variables (tumour type, Karnofsky Performance Score, visceral/brain metastases). To enable easy use of the model, an app was created (OPTIModel). Futhermore, this thesis shows that almost all treatments of pathologic fractures are based on expert opinion and small, retrospective cohorts, as opposed to large, prospective (randomized) trials, which is interesting in an era of evidence based medicine. This confirms the need of a prospective, multicenter cohort, which was designed and implemented accordingly. Show less
This thesis focuses on several aspects of quality of life in patients with painful bone metastases, treated with palliative radiotherapy within the randomized Dutch Bone Metastasis Study.The... Show moreThis thesis focuses on several aspects of quality of life in patients with painful bone metastases, treated with palliative radiotherapy within the randomized Dutch Bone Metastasis Study.The detailed course of quality of life after treatment was studied, as was the relation between a pain response and quality of life. Also prognostic factors predicting a pain response, psychological distress, side-effects and survival were studied. Show less
In this thesis, quantitative and qualitative evidence was gathered in an attempt to improve and extend the current sexual health care of gynaecological cancer survivors. Although surgery has a... Show moreIn this thesis, quantitative and qualitative evidence was gathered in an attempt to improve and extend the current sexual health care of gynaecological cancer survivors. Although surgery has a major impact on sexual functioning, vaginal changes and symptoms have been shown to be more profound after intensive radiotherapy. Therefore, the studies in this thesis were especially focused on gynaecological cancer survivors who received radiotherapy, and mainly concerned cervical cancer patients; a relatively young patient population often treated with intensive external-beam radiation therapy (EBRT) in combination concurrent chemotherapy, and intrauterine and vaginal brachytherapy (BT), although the results are equally relevant to other gynaecological cancer patients treated with EBRT with or without BT. In order to assess what type of patient education and/or support would be needed to minimise the impact of gynaecological cancer treatment on sexual functioning, and to improve the survivors’ sexual recovery we followed several approaches: assessment of survivors’ experience with sexual distress after treatment, and unmet needs for psychosexual counselling and support; it was explored how survivors and professionals could best deal with treatment-induced vaginal changes; and, partly based on the previous findings, a sexual rehabilitation intervention was developed and evaluated in a pilot study. Show less
In this thesis long-term effects and quality of life after treatment for rectal cancer are evaluated. Long-term data were assessed from the TME trial. In this trial 1530 Dutch patients with... Show moreIn this thesis long-term effects and quality of life after treatment for rectal cancer are evaluated. Long-term data were assessed from the TME trial. In this trial 1530 Dutch patients with rectal cancer were included between 1996 and 1999. These patients were randomly assigned to total mesorectal excision (TME) or to short-course preoperative radiotherapy (5x5 Gy) followed by TME surgery. Show less
Preclinical and clinical studies reveal that left-sided breast cancer radiotherapy is associated with an increased rate of major coronary events. Consequently, when irradiating women with left... Show morePreclinical and clinical studies reveal that left-sided breast cancer radiotherapy is associated with an increased rate of major coronary events. Consequently, when irradiating women with left-sided breast cancer, specific measures should be taken to decrease the heart dose as much as possible and to avoid radiation-induced coronary artery disease. This thesis focuses on several strategies to optimise the radiation treatment for patients with left-sided breast cancer. With respect to whole breast irradiation we concluded that: __ the routine use of MR images in addition to the CT scan, when delineating either the glandular breast tissue or the lumpectomy cavity, does not have added value. __ tangential IMRT technique combined with a breath-hold technique should be the treatment technique of choice for left-sided breast cancer. __ a breath-hold technique should and can be used in all left-sided breast cancer patients, regardless of age and breast size. __ breath-hold in left-sided whole breast radiotherapy results in a less pronounced increase of coronary calcium score and, hence, could result in less radiation-induced cardio vascular damage. Show less
Colorectal cancer is one of the most common cancers worldwide. Although there have been several improvements in screening, staging, and treatment in the past decades, survival differences remain.... Show moreColorectal cancer is one of the most common cancers worldwide. Although there have been several improvements in screening, staging, and treatment in the past decades, survival differences remain. For example among certain subgroups of patients, such as elderly patients and patients with comorbidities. Besides, inequalities in the quality of care between European countries remain. Quality control on surgery, radiotherapy, and pathology have been introduced in trials, followed by incorporation in the general care. Another option to incorporate improved quality of care is via an audit structure in which hospitals and clinicians can improve their results by learning from their own outcome statistics and those from colleagues treating a similar patient group. Although all these audit structures have achieved excellent results within countries, differences in outcome between European countries remain. A next step will b e to combine these national audits. The combined audit structure will provide a network in which __best practices__ can be compared and identified, including for certain subgroups, which has been initiated as European Registration of Cancer Care (EURECCA). To achieve optimal care for all patients, multidisciplinary care is the only way. By comparing multidisciplinary audit structures across countries, optimal treatment strategies within subgroups can be identified Show less
Pituitary insufficiency in the presence of a pituitary macroadenoma or after pituitary irradiation is frequently reported. In addition, pituitary insufficiency is increasingly reported after... Show morePituitary insufficiency in the presence of a pituitary macroadenoma or after pituitary irradiation is frequently reported. In addition, pituitary insufficiency is increasingly reported after traumatic head injuries. The correct evaluation and interpretation, however, of the pituitary axes, and consequently, the potential therapeutical consequences are a matter of controversies. The studies reported in this thesis aim to provide better insight into the complexity of different endocrine tests used for the evaluation of possible pituitary insufficiency and in the treatment of patients with pituitary insufficiency. Show less
The thesis is based on clinical research. Studies presented in the first part concentrate on the role of radiation therapy to reduce or to prevent (re)stenosis after percutaneous transluminal... Show moreThe thesis is based on clinical research. Studies presented in the first part concentrate on the role of radiation therapy to reduce or to prevent (re)stenosis after percutaneous transluminal angioplasty (PTA) and arteriovenous fistulas. After reviewing the concept, a multicenter study is reported in which the efficacy of endovascular brachytherapy (EBT) for prophylaxis of restenosis after femoropopliteal PTA is evaluated. Further, a randomised trial is discussed that assessed the presumed preventive effect of external beam radiation therapy on anastomotic intimal hyperplasia in prosthetic arteriovenous fistulas in patients with renal failure. The second part of this thesis focuses on stimulation of vascular growth in patients with severe limb ischemia who are without regular surgical or endovascular treatment options. After reviewing the concept, a clinical study evaluated feasibility and safety as well as efficacy of autologous cell therapy (bone marrow). The angiographic results of this study and hypotheses on the clinical usefulness of digital subtraction angiography in the assessment of the effects on possible inducement of collateral circulation after cell-based therapy are separately considered. In conclusion: The modest effect of vascular radiotherapy is too cumbersome for widespread clinical implementation. Cell therapy in vascular patients is promising. The mechanisms are not completely elucidated, but the ultimate success however will rest on its ability to demonstrate clinical efficacy. Show less
The general aim of this thesis is to determine and compare disease and voice outcome for T1 glottic carcinoma treated with radiotherapy or laser surgery. The findings show similar oncological and... Show moreThe general aim of this thesis is to determine and compare disease and voice outcome for T1 glottic carcinoma treated with radiotherapy or laser surgery. The findings show similar oncological and functional results for radiotherapy and laser surgery in __superficial midcord T1a glottic carcinoma__. This outcome supports the Dutch national guideline __Treatment of Laryngeal Carcinoma__ which was published during the life-time of this thesis. In this guideline laser surgery is labeled treatment of choice in these lesions because of the shorter treatment duration, lower costs and the possibility for repeated treatments and/or additional radiotherapy. For larger T1 lesions, our literature review concludes that more comparative data, especially on functional results, are needed before definite conclusions can be drawn as to the role of laser surgery in these lesions. These studies are now being perform ed in a collaboration between the Leiden University Medical Center and the Eramus Medical Center, Rotterdam. Show less
