Tumor-dose-rate variations during robotic radiosurgery of oligo and multiple brain metastases

Prediction of complete response after neoadjuvant chemotherapy for invasive breast cancers: The utility of shear wave elastography and superb microvascular imaging in pretreatment breast ultrasound

PURPOSE

To investigate whether multiparametric parameters of pretreatment breast ultrasound (US) and clinicopathologic factors are associated with pathologic complete response (pCR) after neoadjuvant chemotherapy (NAC) for breast cancer.

METHODS

Between November 2018 and September 2022, 88 patients who underwent NAC and subsequent surgery were included in this study (median age, 55 years; interquartile range [IQR], 45, 59.3). Multiparametric breast US including grayscale, shear wave elastography (SWE) and superb microvascular imaging (SMI) of pathologically proven invasive breast cancers were retrospectively reviewed. Clinicopathological and multiparametric parameters of breast US, including size, SWEmax, SWEratio and vascular index on SMI (SMIVI) were compared between the groups. Univariate and multivariate logistic regression analyses were performed to determine factors predicting pCR after NAC. AUROC curve analysis was performed to determine the predictors' optimal cut-off values and diagnostic performance.

RESULTS

The pCR group (n = 24) showed a significantly smaller tumor size, lower SWEmax, higher Ki-67 index, higher hormone receptor negativity and negative axillary lymph node metastasis compared to the non-pCR group (n = 64). Multivariate regression analysis showed that SWEmax (adjusted odds ratio[aOR] = 0.956, 95 % confidence interval [CI] = 0.919-0.994, P = 0.025) and Ki-67 index (aOR = 1.083, 95 % CI = 1.012-1.159, P = 0.021) were independently associated with pathologically complete response. The optimal cut-off values for predicting pCR were 27.5 % for Ki-67 with an AUC of 0.743 and 134.8 kPa for SWEmax with an AUC of 0.779. A combination model including clinical factors and SWEmax showed the best diagnostic performance with an AUC of 0.876.

CONCLUSION

A higher Ki-67 index and lower SWEmax measured on pretreatment breast US were independently associated with pCR in invasive breast cancer after NAC.

Impact of prescription isodose level and collimator selection on dose homogeneity and plan quality in robotic radiosurgery

Purpose

In stereotactic radiosurgery (SRS), prescription isodoses and resulting dose homogeneities vary widely across different platforms and clinical entities. Our goal was to investigate the physical limitations of generating dose distributions with an intended level of homogeneity in robotic SRS.

Methods

Treatment plans for non-isocentric irradiation of 4 spherical phantom targets (volume 0.27–7.70 ml) and 4 clinical targets (volume 0.50–5.70 ml) were calculated using Sequential (phantom) or VOLO^TM (clinical) optimizers (Accuray, Sunnyvale, CA, USA). Dose conformity, volume of 12 Gy isodose (V12Gy) as a measure for dose gradient, and treatment time were recorded for different prescribed isodose levels (PILs) and collimator settings. In addition, isocentric irradiation of phantom targets was examined, with dose homogeneity modified by using different collimator sizes.

Results

Dose conformity was generally high (nCI ≤ 1.25) and varied little with PIL. For all targets and collimator sets, V12Gy was highest for PIL ≥ 80% and lowest for PIL ≤ 65%. The impact of PIL on V12Gy was highest for isocentric irradiation and lowest for clinical targets (VOLO^TM optimization). The variability of V12Gy as a function of collimator selection was significantly higher than that of PIL. V12Gy and treatment time were negatively correlated. Plans utilizing a single collimator with a diameter in the range of 70–80% of the target diameter were fastest, but showed the strongest dependence on PIL.

Conclusion

Inhomogeneous dose distributions with PIL ≤ 70% can be used to minimize dose to normal tissue. PIL ≥ 90% is associated with a marked and significant increase in off-target dose exposure. Careful selection of collimators during planning is even more important.

Supplementary Information

The online version of this article (10.1007/s00066-021-01872-4) contains supplementary material, which is available to authorized users.

MRI characteristics in treatment for cerebral melanoma metastasis using stereotactic radiosurgery and concomitant checkpoint inhibitors or targeted therapeutics

Introduction

Combination therapy for melanoma brain metastases (MM) using stereotactic radiosurgery (SRS) and immune checkpoint-inhibition (ICI) or targeted therapy (TT) is currently of high interest. In this collective, time evolution and incidence of imaging findings indicative of pseudoprogression is sparsely researched. We therefore investigated time-course of MRI characteristics in these patients.

Methods

Data were obtained retrospectively from 27 patients (12 female, 15 male; mean 61 years, total of 169 MMs). Single lesion volumes, total MM burden and edema volumes were analyzed at baseline and follow-up MRIs in 2 months intervals after SRS up to 24 months. The occurrence of intralesional hemorrhages was recorded.

Results

17 patients (80 MM) received ICI, 8 (62 MM) TT and 2 (27 MM) ICI + TT concomitantly to SRS. MM-localization was frontal (n = 89), temporal (n = 23), parietal (n = 20), occipital (n = 10), basal ganglia/thalamus/insula (n = 10) and cerebellar (n = 10). A volumetric progression of MM 2–4 months after SRS was observed in combined treatment with ICI (p = 0.028) and ICI + TT (p = 0.043), whereas MMs treated with TT showed an early volumetric regression (p = 0.004). Edema volumes moderately correlated with total MM volumes (r = 0.57; p < 0.0001). Volumetric behavior did not differ significantly over time regarding lesions’ initial sizes or localizations. No significant differences between groups were observed regarding rates of post-SRS intralesional hemorrhages.

Conclusion

Reversible volumetric increases in terms of pseudoprogression are observed 2–4 months after SRS in patients with MM concomitantly treated with ICI and ICI + TT, rarely after TT. Edema volumes mirror total MM volumes. Medical treatment type does not significantly affect rates of intralesional hemorrhage.