Phase 1 Clinical Trial of Stereotactic Body Radiation Therapy Concomitant With Neoadjuvant Chemotherapy for Breast Cancer

Robotic stereotactic radioablation of breast tumors: Influence of beam size on the absorbed dose distributions

Robotic stereotactic radioablation (RSR) therapy for breast tumors has been shown to be an effective treatment strategy when applied concomitantly with chemotherapy, with the purpose of reducing the tumor volume thus making it more amenable for breast conserving surgery. In this paper we used Monte Carlo simulation within a realistic patient model to determine the influence that the variation in beam collimation radius has on the resultant absorbed dose distributions for this type of treatment. Separate optimized plans were obtained for treatments using 300 circular beams with radii of 0.5 cm, 0.75 cm, 1.0 cm and 1.5 cm. Cumulative dose volume histograms were obtained for the gross, clinical and planning target volumes as well as for eight organs and structures at risk. Target coverage improves as the collimator size is increased, at the expense of increasing the volume of healthy tissue receiving mid-level absorbed doses. Interestingly, it is found that the maximum dose imparted to the skin is highly dependent on collimator size, while the dosimetry of other structures, such as both the ipsilateral and contralateral lung tissue are basically unaffected by a change in beam size.

Preoperative Single-Fraction Partial Breast Radiation Therapy: A Novel Phase 1, Dose-Escalation Protocol With Radiation Response Biomarkers

PURPOSE

Women with biologically favorable early-stage breast cancer are increasingly treated with accelerated partial breast radiation (PBI). However, treatment-related morbidities have been linked to the large postoperative treatment volumes required for external beam PBI. Relative to external beam delivery, alternative PBI techniques require equipment that is not universally available. To address these issues, we designed a phase 1 trial utilizing widely available technology to 1) evaluate the safety of a single radiation treatment delivered preoperatively to the small-volume, intact breast tumor and 2) identify imaging and genomic markers of radiation response.

METHODS AND MATERIALS

Women aged ≥55 years with clinically node-negative, estrogen receptor-positive, and/or progesterone receptor-positive HER2-, T1 invasive carcinomas, or low- to intermediate-grade in situ disease ≤2 cm were enrolled (n=32). Intensity modulated radiation therapy was used to deliver 15 Gy (n=8), 18 Gy (n=8), or 21 Gy (n=16) to the tumor with a 1.5-cm margin. Lumpectomy was performed within 10 days. Paired pre- and postradiation magnetic resonance images and patient tumor samples were analyzed.

RESULTS

No dose-limiting toxicity was observed. At a median follow-up of 23 months, there have been no recurrences. Physician-rated cosmetic outcomes were good/excellent, and chronic toxicities were grade 1 to 2 (fibrosis, hyperpigmentation) in patients receiving preoperative radiation only. Evidence of dose-dependent changes in vascular permeability, cell density, and expression of genes regulating immunity and cell death were seen in response to radiation.

CONCLUSIONS

Preoperative single-dose radiation therapy to intact breast tumors is well tolerated. Radiation response is marked by early indicators of cell death in this biologically favorable patient cohort. This study represents a first step toward a novel partial breast radiation approach. Preoperative radiation should be tested in future clinical trials because it has the potential to challenge the current treatment paradigm and provide a path forward to identify radiation response biomarkers.

Emerging applications of stereotactic body radiotherapy

Stereotactic body radiotherapy (SBRT) has been used extensively in patients with lung, liver and spinal tumors, and the treatment outcomes are very favorable. For certain conditions such as medically inoperable stage I non-small-cell lung cancer, liver and lung oligometastases, primary liver cancer and spinal metastases, SBRT is regarded as one of the standard therapies. In the recent years, the use of SBRT has been extended to other disease conditions and sites such as recurrent head and neck cancer, renal cell carcinoma, prostate cancer, adrenal metastasis, pancreatic cancer, gynecological malignancies, spinal cord compression, breast cancer, and stage II-III non-small-cell lung cancer. Preliminary data in the literature show promising results but the follow-up intervals are short for most studies. This paper will provide an overview of these emerging applications.

Dosimetric comparison of preoperative single-fraction partial breast radiotherapy techniques: 3D CRT, noncoplanar IMRT, coplanar IMRT, and VMAT

The purpose of this study was to compare dosimetric parameters of treatment plans among four techniques for preoperative single‐fraction partial breast radiotherapy in order to select an optimal treatment technique. The techniques evaluated were noncoplanar 3D conformal radiation therapy (3D CRT), noncoplanar intensity‐modulated radiation therapy (IMRTNC), coplanar IMRT (IMRTCO), and volumetric‐modulated arc therapy (VMAT). The planning CT scans of 16 patients in the prone position were used in this study, with the single‐fraction prescription doses of 15 Gy for the first eight patients and 18 Gy for the remaining eight patients. Six (6) MV photon beams were designed to avoid the heart and contralateral breast. Optimization for IMRT and VMAT was performed to reduce the dose to the skin and normal breast. All plans were normalized such that 100% of the prescribed dose covered greater than 95% of the clinical target volume (CTV) consisting of gross tumor volume (GTV) plus 1.5 cm margin. Mean homogeneity index (HI) was the lowest (1.05±0.02) for 3D CRT and the highest (1.11±0.04) for VMAT. Mean conformity index (CI) was the lowest (1.42±0.32) for IMRTNC and the highest (1.60±0.32) for VMAT. Mean of the maximum point dose to skin was the lowest (73.7±11.5%) for IMRTNC and the highest (86.5±6.68%) for 3D CRT. IMRTCO showed very similar HI, CI, and maximum skin dose to IMRTNC (differences<1%). The estimated mean treatment delivery time, excluding the time spent for patient positioning and imaging, was 7.0±1.0,8.3±1.1,9.7±1.0, and 11.0±1.5min for VMAT,IMRTCO,IMRTNC and 3D CRT, respectively. In comparison of all four techniques for preoperative single‐fraction partial breast radiotherapy, we can conclude that noncoplanar or coplanar IMRT were optimal in this study as IMRT plans provided homogeneous and conformal target coverage, skin sparing, and relatively short treatment delivery time.

PACS numbers: 81.40.Wx, 87.55.D‐

Stereotactic radiation therapy of renal cancer inferior vena cava tumor thrombus

Renal Cell Carcinoma (RCC) is a common malignancy world-wide that is rising in incidence. Up to 10% of RCC patients present with inferior vena cava (IVC) tumor thrombus (IVC-TT). Although surgery is the only treatment with proven efficacy for IVC-TT, the surgical management of advanced (level III and IV) IVC-TT is difficult with high morbidity and mortality, and offers a poor survival outcome. Currently, there are no treatment options in the setting of recurrent or unresectable RCC IVC-TT. Even though RCC may be resistant to conventionally fractionated radiation therapy, hypofractionated radiation has shown excellent control rates for both primary and metastatic RCC. We report our experience treating 2 RCC patients with Level IV IVC-TT -one recurrent and the other unresectable-with stereotactic ablative radiation therapy (SABR). The first patient is a 75-year-old gentleman with a level IV RCC IVC-TT who presented 9 months after his radical nephrectomy and thrombectomy with a growing level IV IVC-TT that became refractory to 4 targeted agents. He received SABR of 50Gy in 5 fractions and at 2-year follow-up is doing well with a significant decrease in the enhancement and size of the IVC-TT. The second patient is an 83-year-old gentleman who presented with metastatic RCC and level IV IVC-TT but was not a surgical candidate. After progression on temsirolimus, he received SABR of 36Gy in 4 fractions to his IVC-TT and survived 18 months post-SABR. Both patients improved symptomatically and did not experience any acute or late treatment-related toxicity. Their survival of 24 months and 18 months are comparable to the reported median survival of 20 months in patients with level IV IVC-TT that underwent surgical resection. Therefore, SABR can be a potentially safe treatment option in the unresectable setting for RCC patients with IVC-TT and should be further evaluated in prospective trials.

Current challenges and future perspectives of radiotherapy for locally advanced breast cancer

PURPOSE OF REVIEW

To discuss current issues in the field of radiation oncology for locally advanced breast cancer (LABC).

RECENT FINDINGS

Large randomized studies involving nodal irradiation have recently been completed. The incremental benefit of treating the internal mammary nodes (IMNs) remains controversial. A randomized study specifically evaluating internal mammary node radiation (IMNR) failed to demonstrate significant benefit. A high impact, population-based study detected a proportional increase in major coronary events with increasing radiation dose. Advanced treatment techniques should be employed to reduce cardiac exposure. In patients with stage IV breast cancer (BCa), there is increasing evidence to suggest that locoregional treatments may improve overall survival (OS). Radiotherapy alone, without surgery, may provide equivalent local control and OS in patients with distant metastasis. High-dose stereotactic radiation regimens can be used to treat breast tumors with good local control rates in as few as three visits.BCa biomarkers are predictive of locoregional recurrence risk and should be used to guide radiotherapy in conjunction with standard staging. Clinically validated genetic profiling can measure tumor radiosensitivity and also help to predict normal tissue toxicity.

SUMMARY

We are entering an era of personalized radiotherapy for LABC. Radiation treatments must be tailored to each individual patient's risk and intrinsic tumor biology.

Intraoperative radiation therapy in early breast cancer using a linear accelerator outside of the operative suite: an "image-guided" approach

PURPOSE

To present local control, complications, and cosmetic outcomes of intraoperative radiation therapy (IORT) for early breast cancer, as well as technical aspects related to the use of a nondedicated linear accelerator.

METHODS AND MATERIALS

This prospective trial began in May of 2004. Eligibility criteria were biopsy-proven breast-infiltrating ductal carcinoma, age >40 years, tumor <3 cm, and cN0. Exclusion criteria were in situ or lobular types, multicentricity, skin invasion, any contraindication for surgery and/or radiation therapy, sentinel lymph node involvement, metastasis, or another malignancy. Patients underwent classic quadrantectomy with intraoperative sentinel lymph node and margins evaluation. If both free, the patient was transferred from operative suite to linear accelerator room, and IORT was delivered (21 Gy). Primary endpoint: local recurrence (LR); secondary endpoints: toxicities and aesthetics. Quality assurance involved using a customized shield for chest wall protection, applying procedures to minimize infection caused by patient transportation, and using portal films to check collimator-shield alignment.

RESULTS

A total of 152 patients were included, with at least 1 year follow-up. Median age (range) was 58.3 (40-85.4) years, and median follow-up time was 50.7 (12-110.5) months. The likelihood of 5-year local recurrence was 3.7%. There were 3 deaths, 2 of which were cancer related. The Kaplan-Meier 5-year actuarial estimates of overall, disease-free, and local recurrence-free survivals were 97.8%, 92.5%, and 96.3%, respectively. The overall incidences of acute and late toxicities were 12.5% and 29.6%, respectively. Excellent, good, fair, and bad cosmetic results were observed in 76.9%, 15.8%, 4.3%, and 2.8% of patients, respectively. Most treatments were performed with a 5-cm collimator, and in 39.8% of the patients the electron-beam energy used was ≥12 MeV. All patients underwent portal film evaluation, and the shielding was repositioned in 39.9% of cases. No infection or anesthesia complications were observed.

CONCLUSIONS

Local control with IORT was adequate, with low complication rates and good cosmetic outcomes. More than one-third of patients benefited from the "image-guidance" approach, and almost 40% benefited from the option of higher electron beam energies.

MRI and CT imaging for preoperative target volume delineation in breast-conserving therapy

BACKGROUND

Accurate tumor bed delineation after breast-conserving surgery is important. However, consistency among observers on standard postoperative radiotherapy planning CT is low and volumes can be large due to seroma formation. A preoperative delineation of the tumor might be more consistent. Therefore, the purpose of this study was to determine the consistency of preoperative target volume delineation on CT and MRI for breast-conserving radiotherapy.

METHODS

Tumors were delineated on preoperative contrast-enhanced (CE) CT and newly developed 3D CE-MR images, by four breast radiation oncologists. Clinical target volumes (CTVs) were created by addition of a 1.5 cm margin around the tumor, excluding skin and chest wall. Consistency in target volume delineation was expressed by the interobserver variability. Therefore, the conformity index (CI), center of mass distance (dCOM) and volumes were calculated. Tumor characteristics on CT and MRI were scored by an experienced breast radiologist.

RESULTS

Preoperative tumor delineation resulted in a high interobserver agreement with a high median CI for the CTV, for both CT (0.80) and MRI (0.84). The tumor was missed on CT in 2/14 patients (14%). Leaving these 2 patients out of the analysis, CI was higher on MRI compared to CT for the GTV (p<0.001) while not for the CTV (CT (0.82) versus MRI (0.84), p=0.123). The dCOM did not differ between CT and MRI. The median CTV was 48 cm3 (range 28-137 cm3) on CT and 59 cm3 (range 30-153 cm3) on MRI (p<0.001). Tumor shapes and margins were rated as more irregular and spiculated on CE-MRI.

CONCLUSIONS

This study showed that preoperative target volume delineation resulted in small target volumes with a high consistency among observers. MRI appeared to be necessary for tumor detection and the visualization of irregularities and spiculations. Regarding the tumor delineation itself, no clinically relevant differences in interobserver variability were observed. These results will be used to study the potential for future MRI-guided and neoadjuvant radiotherapy.

TRIAL REGISTRATION

International Clinical Trials Registry Platform NTR3198.

Stereotactic body radiotherapy: a critical review for nonradiation oncologists

Stereotactic body radiotherapy (SBRT) involves the treatment of extracranial primary tumors or metastases with a few, high doses of ionizing radiation. In SBRT, tumor kill is maximized and dose to surrounding tissue is minimized, by precise and accurate delivery of multiple radiation beams to the target. This is particularly challenging, because extracranial lesions often move with respiration and are irregular in shape, requiring careful treatment planning and continual management of this motion and patient position during irradiation. This review presents the rationale, process workflow, and technology for the safe and effective administration of SBRT, as well as the indications, outcome, and limitations for this technique in the treatment of lung cancer, liver cancer, and metastatic disease.

The RSSearch™ Registry: patterns of care and outcomes research on patients treated with stereotactic radiosurgery and stereotactic body radiotherapy

BACKGROUND

The RSSearch™ Registry is a multi-institutional, observational, ongoing registry established to standardize data collection from patients treated with stereotactic radiosurgery (SRS) and/or stereotactic body radiotherapy (SBRT). This report describes the design, patient demographics, lesion characteristics, and SRS/SBRT treatment patterns in RSSearch™. Illustrative patient-related outcomes are also presented for two common treatment sites--brain metastases and liver metastases.

MATERIALS AND METHODS

Thirty-nine US centers participated in RSSearch™. Patients screened for SRS/SBRT were eligible to be enrolled. Descriptive analyses were performed to assess patient characteristics, physician treatment practices, and clinical outcomes. Kaplan-Meier analysis was used to determine overall survival (OS), local progression-free (LPFS), and distant disease-free survival (DDFS).

RESULTS

From January, 2008-January, 2013, 11,457 patients were enrolled. The median age was 67 years (range 7-100 years); 51% male and 49% female. Forty-six percent had no prior treatment, 22% had received chemotherapy, 19% radiation therapy and 17% surgery. There were 11,820 lesions from 65 treatment locations; 54% extracranial and 46% intracranial. The most common treatment locations were brain/cranial nerve/spinal cord, lung, prostate and liver. Metastatic lesions accounted for the majority of cases (41.6%), followed by primary malignant (32.9%), benign (10.9%), recurrent (9.4%), and functional diseases (4.3%). SRS/SBRT was used with a curative intent in 39.8% and palliative care in 44.8% of cases. The median dose for all lesions was 30 Gy (range < 1-96.7 Gy) delivered in a median number of 3 fractions. The median dose for lesions in the brain/cranial nerve/spinal cord, lung, liver, pancreas and prostate was 24, 54, 45, 29 and 36.25 Gy, respectively. In a subset analysis of 799 patients with 952 brain metastases, median OS was 8 months. For patients with a Karnofsky performance score (KPS) > 70, OS was 11 months vs. 4 months for KPS ≤ 70. Six-month and 12-month local control was 79% and 61%, respectively for patients with KPS ≤ 70, and 85% and 74%, respectively for patients with KPS > 70. In a second subset analysis including 174 patients with 204 liver metastases, median OS was 22 months. At 1-year, LPFS and DDFS rates were 74% and 53%, respectively.

LPFS CONCLUSION

This study demonstrates that collective patterns of care and outcomes research for SRS/SBRT can be performed and reported from data entered by users in a common database. The RSSearch™ dataset represents SRS/SBRT practices in a real world setting, providing a useful resource for expanding knowledge of SRS/SBRT treatment patterns and outcomes and generating robust hypotheses for randomized clinical studies.