Dosimetric Comparison of Conventional Radiotherapy, Volumetric Modulated Arc Therapy, and Proton Beam Therapy for Palliation of Thoracic Spine Metastases Secondary to Breast or Prostate Cancer.

The aim of this planning study was to compare the dosimetric outcomes of Volumetric Modulated Arc Therapy (VMAT), Proton Beam Therapy (PBT), and conventional External Beam Radiation Therapy (cEBRT) in the treatment of thoracic spinal metastases originating from breast or prostate cancer. Our study utilized data from 30 different treatment plans and evaluated target coverage and doses to vital organs at risk (OARs), such as the spinal cord, heart, esophagus, and lungs. The results showed that VMAT and PBT achieved superior target coverage and significantly lower doses to the spinal cord compared to cEBRT (target: median PTVD95%: 75.2 for cEBRT vs. 92.9 and 91.7 for VMAT (p < 0.001) and PBT (p < 0.001), respectively; spinal cord: median Dmax%: 105.1 for cEBRT vs. 100.4 and 103.6 for VMAT (p < 0.001) and PBT (p = 0.002), respectively). Specifically, VMAT was notable for its superior target coverage and PBT for significantly lower doses to heart, lungs, and esophagus. However, VMAT resulted in higher lung doses, indicating potential trade-offs among different techniques. The study demonstrated the relative advantages of VMAT and PBT over traditional RT in the palliative treatment of spinal metastases using conventional fractionation. These findings underscore the potential of VMAT and PBT to improve dosimetric outcomes, suggesting that they may be more suitable for certain patient groups for whom the sparing of specific OARs is especially important.

Estimated Risk of Radiation-Induced Cancer after Thymoma Treatments with Proton- or X-ray Beams.

We compared the calculated risks of radiation-induced secondary malignant neoplasms (SMNs) for patients treated for thymic tumors with 3D-CRT, IMRT, or single-field uniform dose (SFUD) proton beam therapy (PBT) using the pencil beam scanning (PBS) technique. A cancer-induction model based on the organ equivalent dose (OED) concept was used. For twelve patients, treated with 3D-CRT for thymic tumors, alternative IMRT and SFUD plans were retrospectively prepared. The resulting DVHs for organs at risk (OARs) were extracted and used to estimate the risk of SMNs. The OED was calculated using a mechanistic model for carcinoma induction. Two limit cases were considered; the linear-exponential model, in which the repopulation/repair of the cells is neglected, and the plateau model, in which full repopulation/repair of the irradiated cells is assumed. The calculated risks for SMNs for the different radiation modalities and dose-relation models were used to calculate relative risks, which were compared pairwise. The risks for developing SMNs were reduced for all OARs, and for both dose-relation models, if SFUD was used, compared to 3D-CRT and IMRT. In conclusion, PBS shows a potential benefit to reduce the risk of SMNs compared to 3D-CRT and IMRT in the treatment of thymic tumors.

An in silico planning study comparing doses and estimated risk of toxicity in 3D-CRT, IMRT and proton beam therapy of patients with thymic tumours.

PURPOSE: To compare the dose distributions produced in patients (pts) treated for thymic tumours with spot-scanning proton beam therapy (PBT) implemented with single-field uniform dose (SFUD), intensity-modulated radiation therapy (IMRT) and three-dimensional conformal photon-beam based radiotherapy (3D-CRT). METHODS: Twelve pts, treated with 3D-CRT, were included. Alternative IMRT and SFUD plans were constructed. The IMRT plans were created using a setup with beams incident from 5 to 6 different angles. For the SFUD plans, a field-specific planning target volume (PTV) was created for each patient and a clinical target volume (CTV)-based robust optimization was performed. A robustness evaluation was performed for the CTV for all SFUD plans. A dosimetric evaluation was conducted for the doses to the CTV and organs at risk (OARs) for all plans. The normal tissue complication probability (NTCP), for different endpoints, was calculated using the Lyman-Kutcher-Burman (LKB)-model and compared between plans. RESULTS: SFUD was associated with significantly lower mean doses to the oesophagus, the heart, the left anterior descending coronary artery (LAD), lungs and breasts compared to 3D-CRT and IMRT. The maximum dose given to the spinal cord was significantly lower with SFUD. The risks for pneumonitis, esophagitis and myelopathy were significantly reduced in the SFUD plans. CONCLUSIONS: The present study showed dosimetric advantages of using scanned-beam PBT for the treatment of thymic tumours, as compared to 3D-CRT and IMRT, especially in regard to lower doses to the oesophagus and lungs. The risk of toxicity was reduced with SFUD.

ROC curves and evaluation of radiation-induced pulmonary toxicity in breast cancer.

PURPOSE: To study clinical, radiologic, and physiologic pulmonary toxicity in 128 women after adjuvant radiotherapy (RT) for breast cancer in relation to dosimetric factors. METHODS AND MATERIAL: The patients underwent pulmonary function testing before and 5 months post-RT. Similarly, computer tomography of the chest was repeated 4 months post-RT and changes were scored with a semiquantitative system. Clinical symptoms were registered and scored according to Common Toxicity Criteria. All patients underwent three-dimensional dose planning, and the ipsilateral lung volume receiving > or = 13 Gy (V13), V20, and V30 were calculated. Multiple logistic or regression analyses were used for multivariate modeling. The relation between the dosimetric factors and side effects was also analyzed with receiver operating characteristic (ROC) curves. RESULTS: V20 was, according to multivariate modeling, the most important variable for the occurrence of the three studied side effects (p < 0.01). Age was also related to symptomatic and radiologic pneumonitis. Reduced pre-RT functional level was more common in patients developing symptomatic toxicity. The ROC areas for symptomatic pneumonitis in relation to V13, V20, and V30 were 0.69, 0.69, and 0.67, and for radiologic pneumonitis 0.85, 0.85, and 0.81. CONCLUSIONS: Our results support the use of three-dimensional planning aimed at minimizing the percent of incidentally irradiated lung volume to reduce pulmonary toxicity. Age was also correlated with post-RT side effects. According to ROC analysis, V20 could well predict the risk for radiologic pneumonitis for the studied semiquantitative model.

Quantitative assessment of lung density changes after 3-D radiotherapy for breast cancer.

Our aim was to reduce the rates of clinical and radiological pneumonitis in local-regional radiotherapy (RT) for breast cancer compared to a previous treatment series by applying a pre-planned lung dose volume constraint. 3-D dose planning was performed in 66 women with the aim of not exceeding an ipsilateral V20 of 30%. The patients were followed for short-term signs/symptoms of post-RT pneumonitis and radiological changes on chest CT 4 months after RT. Radiological abnormalities were scored with a CT-adapted modification of a semi-quantitative classification system originally proposed by Arriagada which accounts for severity and affected lung regions. The abnormal subvolumes were contoured and the mean doses were calculated. Three cases of mild and one case of moderate symptomatic pneumonitis were diagnosed. The mean V20 was higher in symptomatic than in unaffected patients, 29% vs. 24% (p =0.04). Mild/moderate radiological changes were frequently observed on CT in regions with average doses >30 Gy. According to multivariate modeling, a trend for association was found between the studied dosimetric factors V13, V20, V30 and mean lung dose, and moderate-severe changes on CT but not with patient specific covariates, e.g. chemotherapy or tamoxifen exposure. 3-D planned local-regional RT with a preplanned lung dose volume constraint of V20 <30% resulted in few cases of moderate symptomatic pneumonitis. Mild/moderate radiological changes were still detectable on CT in subvolumes receiving doses >30 Gy. Long-term follow-up for evaluation of possible late morbidity is warranted.

Efficacy of systemic therapy in advanced pancreatic carcinoma.

With a worldwide incidence of more than 200,000 cases and almost as many deaths, pancreatic carcinoma (PC) remains one of the leading causes of cancer deaths, especially in the Western world. Due to the late onset of symptoms, almost all patients suffer from disseminated disease at the time of diagnosis and only a minority will ever be candidates for radical surgery. Only about one tenth of the operated patients remain disease free. For these reasons, development of effective palliative systemic therapy is important. Almost a decade ago, gemcitabine replaced 5-Fu as the gold standard in systemic treatment of advanced PC. Since then, a number of trials have investigated the potential additional effect of several cytotoxic or targeted agents in combination with gemcitabine. As shown in this review, nearly all these trials have proved disappointing. This review provides an overview of the results of current phase III trials of gemcitabine based systemic therapy. Furthermore, we discuss the role of systemic therapy compared to BSC only and the potential future role of targeted therapies.

Capecitabine as third line therapy in patients with advanced colorectal cancer.

This study sought to determine whether third line therapy with capecitabine (cap.) could provide any clinical benefit in patients with advanced colorectal cancer who have progressed on 5-Fu combination therapy with both irinotecan and oxaliplatin. Twenty patients who were pretreated with and had progressed on irinotecan+Nordic FLv (5-Fu/leukovorin) and oxaliplatin+c.i. 5-Fu/leukovorin were studied. Cap. was administered at 1000-1250 mg/m2 bid d1-14 q 3 w. Time to progression (TTP) (either radiological or clinical) and overall survival (OS) were estimated with the Kaplan-Meier actuarial method. The median number of administered cap. courses was four. No radiological or biochemical responses were observed. Three patients were classified as having stable disease at three months. Two of these patients had, however, minor radiological progression and a =100% increase in CEA compared to base line. Seventeen patients were classified as having progressive disease during the first three months period. Median TTP and OS were 2.8 months and 6.1 months, respectively. A response rate of =15% for third line cap. in metastatic CRC can be ruled out. Median PFS was limited in the study population. This observation and the few cases with SD at three months, lead us to believe that little or no clinical benefit can be expected from single drug cap. in patients with irinotecan- and oxaliplatin-combination resistant advanced colorectal cancer.