Prognostic factors for outcomes after whole-brain irradiation of brain metastases from relatively radioresistant tumors: a retrospective analysis

<p>Abstract</p> <p>Background</p> <p>This study investigated potential prognostic factors in patients treated with whole-brain irradiation (WBI) alone for brain metastases from relatively radioresistant tumors such as malignant melanoma, renal cell carcinoma, and colorectal cancer. Additionally, a potential benefit from escalating the radiation dose was investigated.</p> <p>Methods</p> <p>Data from 220 patients were retrospectively analyzed for overall survival and local control. Nine potential prognostic factors were evaluated: tumor type, WBI schedule, age, gender, Karnofsky performance score, number of brain metastases, extracerebral metastases, interval from diagnosis of cancer to WBI, and recursive partitioning analysis (RPA) class.</p> <p>Results</p> <p>Survival rates at 6 and 12 months were 32% and 19%, respectively. In the multivariate analysis, WBI doses >30 Gy (p = 0.038), KPS ≥70 (p < 0.001), only 1-3 brain metastases (p = 0.007), no extracerebral metastases (p < 0.001), and RPA class 1 (p < 0.001) were associated with improved survival. Local control rates at 6 and 12 months were 37% and 15%, respectively. In the multivariate analyses, KPS ≥70 (p < 0.001), only 1-3 brain metastases (p < 0.001), and RPA class 1 (p < 0.001) were associated with improved local control. In RPA class 3 patients, survival rates at 6 months were 10% (35 of 39 patients) after 10 × 3 Gy and 9% (2 of 23 patients) after greater doses, respectively (p = 0.98).</p> <p>Conclusions</p> <p>Improved outcomes were associated with WBI doses >30 Gy, better performance status, fewer brain metastases, lack of extracerebral metastases, and lower RPA class. Patients receiving WBI alone appear to benefit from WBI doses >30 Gy. However, such a benefit is limited to RPA class 1 or 2 patients.</p

Intercenter validation of a knowledge based model for automated planning of volumetric modulated arc therapy for prostate cancer. The experience of the German RapidPlan Consortium.

To evaluate the performance of a model-based optimisation process for volumetric modulated arc therapy applied to prostate cancer in a multicentric cooperative group. The RapidPlan (RP) knowledge-based engine was tested for the planning of Volumetric modulated arc therapy with RapidArc on prostate cancer patients. The study was conducted in the frame of the German RapidPlan Consortium (GRC).43 patients from one institute of the GRC were used to build and train a RP model. This was further shared with all members of the GRC plus an external site from a different country to increase the heterogeneity of the patient's sampling. An in silico multicentric validation of the model was performed at planning level by comparing RP against reference plans optimized according to institutional procedures. A total of 60 patients from 7 institutes were used.On average, the automated RP based plans resulted fully consistent with the manually optimised set with a modest tendency to improvement in the medium-to-high dose region. A per-site stratification allowed to identify different patterns of performance of the model with some organs at risk resulting better spared with the manual or with the automated approach but in all cases the RP data fulfilled the clinical acceptability requirements. Discrepancies in the performance were due to different contouring protocols or to different emphasis put in the optimization of the manual cases.The multicentric validation demonstrated that it was possible to satisfactorily optimize with the knowledge based model patients from all participating centres. In the presence of possibly significant differences in the contouring protocols, the automated plans, though acceptable and fulfilling the benchmark goals, might benefit from further fine tuning of the constraints. The study demonstrates that, at least for the case of prostate cancer patients, it is possibile to share models among different clinical institutes in a cooperative framework

Summary of the analysis of the volume differences for PTV, bladder and rectum among the seven centres participating to the study.

<p>The dashed line represents the average value over the cohort. PTV and rectum distributions resulted significantly different among the groups while this did not occurred for the bladder.</p

constraints and objectives as defined in the RapidPlan model.

<p>constraints and objectives as defined in the RapidPlan model.</p

Distribution of the dose volume histograms of each structure used for the model definition from the 43 patients used for the training.

<p>Outlined one typical example with the bands showing the prediction variance inherited from the training cohort.</p

Summary of the DVH analysis for the various OARs.

<p>Summary of the DVH analysis for the various OARs.</p

Dose volume histograms per target volume and organ at risk averaged per each participating centre.

<p>The graphs shows the significant variation in the level of sparing of all OARs corresponding to different contouring and optimization strategies. The variance is substantially consistent between RP and CL plans.</p

Average dose volume histograms for the entire cohort of 60 patients comparing RapidPlan based (RP) vs. manually optimized (CL) plans.

<p>The solid (dashed) lines are the averages for the CL (RP) data while the inter-patient variability at 1.5 standard deviation is represented by the dotted lines. On average the RP plans proved to be moderately better than the CL plans in the mean to high dose range.</p

The comparison of the average dose volume histograms for the target volumes and the organs at risk between RP plans optimised for 6 or 15 MV photon beams.

<p>The comparison of the average dose volume histograms for the target volumes and the organs at risk between RP plans optimised for 6 or 15 MV photon beams.</p