Since its introduction more than a decade ago, intensity-modulated radiotherapy (IMRT) has spread to most radiotherapy departments worldwide for a wide range of indications. The technique has been rapidly implemented, despite an incomplete understanding of its advantages and weaknesses, the challenges of IMRT planning, delivery, and quality assurance, and the substantially increased cost compared with non-IMRT. Many publications discuss the theoretical advantages of IMRT dose distributions. However, the key question is whether the use of IMRT can be exploited to obtain a clinically relevant advantage over non-modulated external-beam radiation techniques. To investigate which level of evidence supports the routine use of IMRT for various disease sites, we did a review of clinical studies that reported on overall survival, disease-specific survival, quality of life, treatment-induced toxicity, or surrogate endpoints. This review shows evidence of reduced toxicity for various tumour sites by use of IMRT. The findings regarding local control and overall survival are generally inconclusive.
"reduction of the mlD could be achieved by reducing the treated volume. large margins are required to include inter-fractional motion, if patients are set up using external markers or by use of daily bone match . These margins may be reduced by implementation of daily soft tissue matching on the GTV. "
[Show abstract][Hide abstract] ABSTRACT: Background. Intensity-modulated radiotherapy (IMRT) in locally advanced non-small cell lung cancer (NSCLC) allows treatment of patients with large tumour volumes, but radiation pneumonitis (RP) remains a dose limiting complication. The incidence of severe RP using three-dimensional (3D) conformal radiotherapy, was previously reported to be 17%, with 2% lethal RP. The aim of this study was to monitor the incidence of RP following the introduction of IMRT.
Material and methods. IMRT was delivered using 4–8 beam arrangements and introduced in three phases. In phase I, 12 patients were treated using only one dose constraint (V20), in which the total lung volume receiving 20 Gy was limited to 40%. In phase II, 25 patients were treated with an additional dose constraint of mean lung dose (MLD) ≤ 20 Gy. In phase III, 50 patients were treated with an extra dose constraint (V5) in which the total lung volume receiving a dose of 5 Gy was ≤ 60%. RP was prospectively documented. The results of phase I & II (IMRT-1) were compared to those in phase III (IMRT-2).
Results. The median follow-up time was 17 months. The introduction of IMRT was associated with an increase in the incidence of RP in Phase I&II (IMRT-1) to 41%, six of 37 (16%) had grade 5 RP (IMRT-1). Introducing the dose constraint V5, led to a significant reduction in the lung volume receiving doses ≤ 20 Gy from 51 ± 2% to 41 ± 1% (p < 0.0001). Introducing V5 constraint did not decrease the incidence of severe (grade ≥ 3) RP, but significantly decreased the lethal pneumonitis to 4% (two of 50 patients), p = 0.05.
Conclusion. Introducing IMRT resulted in an increase in the incidence of severe and fatal RP, however a new dose constraint to the volume of lung receiving low doses reduced the incidence of lethal pneumonitis.
"As with PE, the adverse effects of RT can be divided into short term and long term effects. In addition to IC and ED, bowel problems (BP) such as abdominal pain, bloating and diarrhoea may develop . Local recurrence is a prerequisite for developing metastatic disease after initial treatment. "
[Show abstract][Hide abstract] ABSTRACT: There is an on-going debate about whether to perform surgery on early stage localised prostate cancer and risk the common long term side effects such as urinary incontinence and erectile dysfunction. Alternatively these patients could be closely monitored and treated only in case of disease progression (active surveillance). The aim of this paper is to develop a decision-analytic model comparing the cost-utility of active surveillance (AS) and radical prostatectomy (PE) for a cohort of 65 year old men with newly diagnosed low risk prostate cancer.
A Markov model comparing PE and AS over a lifetime horizon was programmed in TreeAge from a societal perspective. Comparative disease specific mortality was obtained from the Scandinavian Prostate Cancer Group trial. Direct costs were identified via national treatment guidelines and expert interviews covering in-patient, out-patient, medication, aids and remedies as well as out of pocket payments. Utility values were used as factor weights for age specific quality of life values of the German population. Uncertainty was assessed deterministically and probabilistically.
With quality adjustment, AS was the dominant strategy compared with initial treatment. In the base case, it was associated with an additional 0.04 quality adjusted life years (7.60 QALYs vs. 7.56 QALYs) and a cost reduction of [euro sign]6,883 per patient (2011 prices). Considering only life-years gained, PE was more effective with an incremental cost-effectiveness ratio of [euro sign]96,420/life year gained. Sensitivity analysis showed that the probability of developing metastases under AS, utility weights under AS are a major sources of uncertainty. A Monte Carlo simulation revealed that AS was more likely to be cost-effective even under very high willingness to pay thresholds.
AS is likely to be a cost-saving treatment strategy for some patients with early stage localised prostate cancer. However, cost-effectiveness is dependent on patients' valuation of health states. Better predictability of tumour progression and modified reimbursement practice would support widespread use of AS in the context of the German health care system. More research is necessary in order to reliably quantify the health benefits compared with initial treatment and account for patient preferences.
BMC Health Services Research 04/2014; 14(1):163. DOI:10.1186/1472-6963-14-163 · 1.71 Impact Factor
"Intensity-modulated radiotherapy (IMRT) can provide advantages compared to W-TF. In supine position IMRT using a tangential two-beam set-up (TF-IMRT) can improve dose homogeneity; however its ability to reduce high-dose regions to the underlying heart and lung tissue appear to be limited [4,5]. Supine multi-beam IMRT (MB-IMRT) may overcome those limitations often at cost of low- or intermediate-dose spread over the contralateral breast and ipsilateral thoracic region [6-10]. "
[Show abstract][Hide abstract] ABSTRACT: Early stage breast cancer patients are long-term survivors and finding techniques that may lower acute and late radiotherapy-induced toxicity is crucial. We compared dosimetry of wedged tangential fields (W-TF), tangential field intensity-modulated radiotherapy (TF-IMRT) and multi-beam IMRT (MB-IMRT) in prone and supine positions for whole-breast irradiation (WBI).
MB-IMRT, TF-IMRT and W-TF treatment plans in prone and supine positions were generated for 18 unselected breast cancer patients. The median prescription dose to the optimized planning target volume (PTVoptim) was 50 Gy in 25 fractions. Dose-volume parameters and indices of conformity were calculated for the PTVoptim and organs-at-risk.
Prone MB-IMRT achieved (p<0.01) the best dose homogeneity compared to WTF in the prone position and WTF and MB-IMRT in the supine position. Prone IMRT scored better for all dose indices. MB-IMRT lowered lung and heart dose (p<0.05) in supine position, however the lowest ipsilateral lung doses (p<0.001) were in prone position. In left-sided breast cancer patients population averages for heart sparing by radiation dose was better in prone position; though non-significant. For patients with a PTVoptim volume >=600 cc heart dose was consistently lower in prone position; while for patients with smaller breasts heart dose metrics were comparable or worse compared to supine MB-IMRT. Doses to the contralateral breast were similar regardless of position or technique. Dosimetry of prone MB-IMRT and prone TF-IMRT differed slightly.
MB-IMRT is the treatment of choice in supine position. Prone IMRT is superior to any supine treatment for right-sided breast cancer patients and left-sided breast cancer patients with larger breasts by obtaining better conformity indices, target dose distribution and sparing of the organs-at-risk. The influence of treatment techniques in prone position is less pronounced; moreover dosimetric differences between TF-IMRT and MB-IMRT are rather small.
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