Stereotactic ablative radiotherapy for non-small cell lung cancer: rationale and outcomes

Stereotactic ablative radiotherapy (SABR), also known in older reports as stereotactic body radiation therapy, represents an evolving and expanding radiation treatment option for many forms of local malignancy, from primary tumors to metastatic and recurrent disease. It involves the precise delivery of higher doses of external-beam radiation per treatment over a shortened treatment course compared with traditional regimens. SABR has become the standard of care for patients with medically inoperable early-stage non-small cell lung cancer (NSCLC) and is becoming a more viable option for surgical candidates with early-stage primary NSCLCs who prefer noninvasive modalities of treatment. Although SABR is being used for the treatment of primary and metastatic disease in many sites of the body, such as the central nervous system, liver, pancreas, spine metastases, and isolated nodal disease in the mediastinum and abdomen, this article focuses on treatment of NSCLC in the thorax. Specifically, this review provides the rationale, evidence, and indications for treating early-stage lung cancers with SABR.

RTOG 0618: Stereotactic body radiation therapy (SBRT) to treat operable early-stage lung cancer patients

7523

Background: The Radiation Therapy Oncology Group (RTOG) protocol 0618 was a phase II trial utilizing SBRT to treat early stage non-small cell lung cancer in operable patients (pts). Methods: All pts were deemed operable by a thoracic surgeon utilizing specific criteria. Pts with biopsy proven peripheral T1-T3, N0, M0 tumors were eligible. The prescription dose was 18 Gy X 3 fractions delivered in 1½-2 weeks. The primary endpoint was 2-year primary tumor control (PTC, avoidance of in-field (INF) and marginal failure (MF)) with overall and progression free survival (OS, PFS), adverse events (AE), local (LF), regional (RF), and distant failure (DF) as secondary endpoints. Early surgical salvage was directed as part of protocol design in the event of LF after SBRT. Results: The study opened December 2007 and closed May 2010 after accruing a total of 33 pts. Of 26 evaluable pts, 23 had T1, and 3 had T2 tumors. Median age was 72 years. Median FEV1, DLCO at enrollment were 72%, 68% predicted, respectively. 4 pts (16%) had SBRT related grade 3 AEs while 0 had grade 4-5 AEs. Median follow-up was 25 months. 2 pts have been scored with INF (11.7 and 12.4 months post SBRT) and 1 with MF (32.5 months post SBRT) giving an estimated 2-year primary tumor failure rate of 7.7% (95% CI: 0.0%, 18.1%). 2-year estimates of LF (primary tumor plus involved lobe failure), RF, and DF are 19.2% (95% CI: 3.7%, 34.7%), 11.7% (95% CI: 0.0%, 24.5%), and 15.4% (95% CI: 1.2%, 29.6%), respectively. Only one patient was eligible for attempted surgical salvage and underwent lobectomy 1.2 years post SBRT complicated by a grade 4 cardiac arrhythmia. 2-year estimates of PFS and OS are 65.4% (95% CI: 44.0%, 80.3%) and 84.4% (95% CI: 63.7%, 93.9%), respectively. Conclusions: SBRT given appears to be associated with a high rate of PTC, moderate treatment related morbidity, and infrequent need for surgical salvage in operable early stage lung cancer pts with peripheral lesions. These results support ongoing enrollment into the ACOSOG Z4099-RTOG 1021 trial comparing SBRT to sublobar resection in high risk operable pts. The project was supported by RTOG grant U10 CA21661, CCOP grant U10 CA37422, and ATC U24 CA81647 from the National Cancer Institute. Clinical trial information: NCT00551369.

A phase II trial of second-line erlotinib in combination with stereotactic body radiation therapy (SBRT) for patients with metastatic non-small cell lung cancer (NSCLC)

8074

Background: Stage IV NSCLC patients who progress through first-line therapy have poor progression-free survival (PFS) and overall survival (OS), most commonly failing in existing sites of gross disease after systemic therapy. Cytoreduction with SBRT may aid systemic agents in prolonging survival. We decided to test this hypothesis in a multi-institutional phase II study with SBRT and erlotinib. Methods: Stage IV NSCLC patients with ≤ 6 sites of extracranial disease who failed first-line systemic therapy were eligible to receive SBRT to all sites of clinically apparent disease, utilizing equipotent fractionation schemes based on location of disease and risk of toxicity to critical normal structures, and erlotinib given daily (150 mg OD) until disease progression. Frequent SBRT fractionation schemes used included 33 Gy in 11 Gy fractions and 40 Gy in 8 Gy fractions. Safety and clinical endpoints were evaluated. Results: 23 patients (12 M: 11 F) with a median age of 67 (56-86) were enrolled in this trial with median follow-up of 14.7 months. All patients progressed through platinum-based chemotherapy, 14 with paclitaxel and 7 with pemetrexed as part of the doublet regimen. 20/23 patients received SBRT to 3 or fewer sites. Lung parenchyma and mediastinal lymph nodes represented most common sites of irradiation. Median PFS was 10.7 months and median OS was 20.8 months.A majority of patients progressed in new sites with only 4 patients failing locally. Most distant failures manifested in the liver. Only one grade 3 toxicity, pneumonitis, was radiation-related. The trial commenced before molecular profiling became standard; 5/10 patient tumors tested, however, had EGFR alterations by IHC/FISH, 0/10 were positive for an EGFR mutation. Conclusions: Use of SBRT with erlotinib for unselected stage IV NSCLC patients as a second-line therapy was well tolerated and resulted in significant PFS and OS, substantially greater than historical values for patients who only received second-line systemic agents. Debulking gross disease with local therapy results in a median PFS of nearly a year with patients relapsing most commonly in new rather than existing sites. Clinical trial information: NCT00547105.

Isolated central nervous system progression on Crizotinib: an Achilles heel of non-small cell lung cancer with EML4-ALK translocation?

Advanced non-small lung cancer (NSCLC) remains almost uniformly lethal with marginal long-term survival despite efforts to target specific oncogenic addiction pathways that may drive these tumors with small molecularly targeted agents and biologics. The EML4-ALK fusion gene encodes a chimeric tyrosine kinase that activates the Ras signaling pathway, and this fusion protein is found in approximately 5% of NSCLC. Targeting EML4-ALK with Crizotinib in this subset of NSCLC has documented therapeutic efficacy, but the vast majority of patients eventually develop recurrent disease that is often refractory to further treatments. We present the clinicopathologic features of three patients with metastatic NSCLC harboring the EML4-ALK translocation that developed isolated central nervous system (CNS) metastases in the presence of good disease control elsewhere in the body. These cases suggest a differential response of NSCLC to Crizotinib in the brain in comparison to other sites of disease, and are consistent with a previous report of poor CNS penetration of Crizotinib. Results of ongoing clinical trials will clarify whether the CNS is a major sanctuary site for EML4-ALK positive NSCLC being treated with Crizotinib. While understanding molecular mechanisms of resistance is critical to overcome therapeutic resistance, understanding physiologic mechanisms of resistance through analyzing anatomic patterns of failure may be equally crucial to improve long-term survival for patients with EML4-ALK translocation positive NSCLC.

Cost-effectiveness analysis of stereotactic body radiation therapy versus intensity-modulated radiation therapy: an emerging initial radiation treatment option for organ-confined prostate cancer

PURPOSE

The purpose of this study is to compare the cost-effectiveness of two external beam radiation therapy techniques for treatment of low- to intermediate-risk prostate cancer: stereotactic body radiation therapy (SBRT) and intensity-modulated radiation therapy (IMRT).

MATERIALS AND METHODS

A Markov decision analysis model with probabilistic sensitivity analysis was designed with the various disease states of a 70-year-old patient with organ-confined prostate cancer to evaluate the cost-effectiveness of two external beam radiation treatment options.

RESULTS

The Monte Carlo simulation revealed that the mean cost and quality-adjusted life-years (QALYs) for SBRT and IMRT were $22,152 and 7.9 years and $35,431 and 7.9 years, respectively. The sensitivity analysis revealed that if the SBRT cohort experienced a decrease in quality of life of 4% or a decrease in efficacy of 6%, then SBRT would no longer dominate IMRT in cost-effectiveness. In fact, with these relaxed assumptions for SBRT, the incremental cost-effectiveness ratio of IMRT met the societal willingness to pay threshold of $50,000 per QALY.

CONCLUSION

Compared with IMRT, SBRT for low- to intermediate-risk prostate cancer has great potential cost savings for our health care system payers and may improve access to radiation, increase patient convenience, and boost quality of life for patients. Our model suggests that the incremental cost-effectiveness ratio of IMRT compared with SBRT is highly sensitive to quality-of-life outcomes, which should be adequately and comparably measured in current and future prostate SBRT studies.

Cost-effectiveness analysis of SBRT versus IMRT: an emerging initial radiation treatment option for organ-confined prostate cancer

OBJECTIVES

The purpose of this study is to compare the cost-effectiveness of 2 external beam radiation therapy techniques for treatment of lowto intermediate-risk prostate cancer: stereotactic body radiation therapy (SBRT) and intensitymodulated radiation therapy (IMRT).

MATERIALS AND METHODS

A Markov decision analysis model with probabilistic sensitivity analysis was designed with the various disease states of a 70-year-old patient with organ-confined prostate cancer to evaluate the cost-effectiveness of 2 external beam radiation treatment options.

RESULTS

The Monte Carlo simulation revealed that the mean cost and quality-adjusted life-years (QALYs) for SBRT and IMRT were $22,152 and 7.9 years and $35,431 and 7.9 years, respectively. The sensitivity analysis revealed that if the SBRT cohort experienced a decrease in quality of life of 4% or a decrease in efficacy of 6%, then SBRT would no longer dominate IMRT in cost-effectiveness. In fact, with these relaxed assumptions for SBRT, the incremental cost-effectiveness ratio of IMRT met the societal willingness to pay threshold of $50,000 per QALY.

CONCLUSIONS

Compared with IMRT, SBRT for lowto intermediate-risk prostate cancer has great potential cost savings for our healthcare system payers and may improve access to radiation, increase patient convenience, and boost quality of life for patients. Our model suggests that the incremental cost-effectiveness ratio of IMRT compared with SBRT is highly sensitive to quality-oflife outcomes, which should be adequately and comparably measured in current and future prostate SBRT studies.

Intraduodenal sarcoma recurrence of retroperitoneal origin: an unusual cause for a duodenal obstruction

Soft tissue sarcomas are uncommon tumors, and intraduodenal soft tissue sarcoma manifestation is even more rare. Only three cases of intraduodenal sarcomas have been reported in the literature thus far. Here, we report a case of an intraduodenal recurrence of a retroperitoneal sarcoma causing bowel obstruction. This unusual recurrence pattern likely relates to the patient’s previous resection and radiation treatment, and highlights the benefits, limitations and follow-up strategies after multimodality treatment.

Dosimetric and motion analysis of margin-intensive therapy by stereotactic ablative radiotherapy for resectable pancreatic cancer

Background

The retroperitoneal margin is a common site of positive surgical margins in patients with resectable pancreatic cancer. Preoperative margin-intensive therapy (MIT) involves delivery of a single high dose of ablative radiotherapy (30 Gy) focused on this surgically inaccessible margin, utilizing stereotactic techniques in an effort to reduce local failure following surgery. In this study, we investigated the motion of regional organs at risk (OAR) utilizing 4DCT, evaluated the dosimetric effects of abdominal compression (AC) to reduce regional motion, and compared various planning techniques to optimize MIT.

Methods

10 patients were evaluated with 4DCT scans. All 10 patients had scans using AC and seven of the 10 patients had scans both with and without AC. The peak respiratory abdominal organ and major vessel centroid excursion was measured. A "sub-GTV" region was defined by a radiation oncologist and surgical oncologist encompassing the retroperitoneal margin typically lateral and posterior to the superior mesenteric artery (SMA), and a 3-5 mm margin was added to constitute the PTV. Identical 3D non-coplanar SABR (3DSABR) plans were designed for the average compression and non-compression scans. Compression scans were planned with 3DSABR, coplanar IMRT (IMRT), and Cyberknife (CK) planning techniques. Dose volume analysis was undertaken for various endpoints, comparing OAR doses with and without AC and for different planning methods.

Results

The mean PTV size was 20.2 cm³. Regional vessel motion of the SMA, celiac trunk, and renal vessels was small (< 5 mm) and not significantly impacted by AC. Mean pancreatic motion was > 5 mm, so AC has been used in all patients enrolled thus far. AC did not significantly increase OAR dose including the stomach and traverse colon. There were several statistically significant differences in the doses to OARs as a function of the type of planning modality used.

Conclusions

AC does not significantly reduce the limited motion of structures in close proximity to the MIT target and does not significantly increase the dose to OARs that can be displaced by the compression plate. The treatment planning techniques evaluated in this study have different advantages with no clearly superior method in our analysis. Dose to adjacent vessels may be reduced with 3DSABR or IMRT techniques, while conformality is increased with IMRT or CK.

Phosphorus-32 therapy for cystic craniopharyngiomas

BACKGROUND AND PURPOSE

To examine control rates for predominantly cystic craniopharyngiomas treated with intracavitary phosphorus-32 (P-32).

MATERIAL AND METHODS

22 patients with predominantly cystic craniopharyngiomas were treated at Indiana University between October 1997 and December 2006. Nineteen patients with follow-up of at least 6 months were evaluated. The median patient age was 11 years, median cyst volume was 9 ml, a median dose of 300 Gy was prescribed to the cyst wall, and median follow-up was 62 months.

RESULTS

Overall cyst control rate after the initial P-32 treatment was 67%. Complete tumor control after P-32 was 42%. Kaplan-Meier 1-, 3-, and 5-year initial freedom-from-progression rates were 68%, 49%, and 31%, respectively. Following salvage therapy, the Kaplan-Meier 1-, 3-, and 5-year ultimate freedom-from-progression rates were 95%, 95%, and 86%, respectively. All patients were alive at the last follow-up. Visual function was stable or improved in 81% when compared prior to P-32 therapy. Pituitary function remained stable in 74% of patients following P-32 therapy.

CONCLUSIONS

Intracystic P-32 can be an effective and tolerable treatment for controlling cystic components of craniopharyngiomas as a primary treatment or after prior therapies, but frequently allows for progression of solid tumor components. Disease progression in the form of solid tumor progression, re-accumulation of cystic fluid, or development of new cysts may require further radiotherapy or surgical intervention for optimal long-term disease control.

Stereotactic body radiation therapy for oligometastases

There are data in the literature to suggest the presence of an oligometastatic state, and local aggressive therapy of the oligometastases may improve outcomes including survival. Stereotactic body radiation therapy has emerged as one of the local therapy options for oligometastases in various body sites, most commonly in the lung and the liver. Retrospective studies and clinical trials have demonstrated promising results with the use of stereotactic body radiation therapy for oligometastases. However, most of the studies have relatively short follow-up intervals. Longer follow-up is necessary to better define the role of stereotactic body radiation therapy in the management of patients with oligometastases. Given the high propensity for distant progression, the combination of novel systemic therapy and stereotactic body radiation therapy is to be explored.

Stereotactic body radiation therapy (SBRT) for genitourinary malignancies

Stereotactic body radiation therapy (SBRT) is a novel treatment modality in radiation oncology that delivers a very high dose of radiation to the tumor target with high precision using single or a small number of fractions. SBRT is the result of technological advances in patient/tumor immobilization, image guidance, and treatment planning and delivery. This modality is safe and effective in both early stage primary cancer and oligometastases. Compared to the use of stereotactic radiosurgery for other tumor sites, SBRT is slow to be adopted in the management of genitourinary malignancies. There are now emerging data that show the safety and efficacy of this treatment modality in genitourinary (GU) malignancies especially in prostate cancer and renal cell carcinoma. Preclinical data, clinical experience, and challenges are reviewed and discussed.

Stereotactic body radiation therapy (stereotactic ablative radiotherapy) for stage I non-small cell lung cancer--updates of radiobiology, techniques, and clinical outcomes

Stereotactic body radiation therapy (SBRT), also known as stereotactic ablative radiotherapy (SABR), has emerged as one of the standard treatment options for stage I non-small cell lung cancer (NSCLC), mainly in medically inoperable patients. Its use has also been explored in operable patients. A large body of experience, either from retrospective studies or clinical trials, has been accumulated over the years and more is known about the radiobiology, cancer biology, technical aspects, clinical outcomes, and toxicities of SBRT. This article provides updates of these aspects of SBRT for stage I NSCLC.

A study on the dosimetric accuracy of treatment planning for stereotactic body radiation therapy of lung cancer using average and maximum intensity projection images

PURPOSE

To assess the accuracy of current stereotactic body radiation therapy (SBRT) lung treatment planning methodologies on irregular breathing patterns, we have performed a systematic dosimetric evaluation in phantoms by utilizing maximum intensity projection (MIP) and average (AVG) images generated from four dimensional computed tomography (4DCT).

METHODS

A custom built programmable lung phantom was used to simulate tumor motions due to various breathing patterns of patients. 4DCT scans were obtained in helical mode, and reconstructed AVG and MIP datasets were imported into the Pinnacle 8.0 h treatment planning system. SBRT plans were generated and executed, and delivered doses were measured by radiochromic film for analysis.

RESULTS

For targets moving regularly or irregularly within a small range (7.0+/-1.8 mm, n=6), we observed good agreement between the measured and computed dose distributions. However, for targets moving irregularly with a larger range (20.8+/-2.6 mm, n=4), the measured isodose lines were found to be shifted relative to the planned distribution, resulting in an under-dosing (over 10%) in a portion of the PTV. We further observed that the discrepancy between planned and measured dose distribution is due to the inaccurate representation of irregular target motion in the MIP images generated from 4DCT.

CONCLUSIONS

Caution should be used when planning from 4DCT images in the presence of large and irregular target motion. The inaccuracy inherent in 4DCT MIP and AVG images can be mitigated through the application of methodologies to reduce respiratory motion, such as abdominal compression, and through the use of volumetric image guidance (e.g., cone beam CT-CBCT) to assure precise targeting with minimal shifts.

A pilot trial of serial 18F-fluorodeoxyglucose positron emission tomography in patients with medically inoperable stage I non-small-cell lung cancer treated with hypofractionated stereotactic body radiotherapy

PURPOSE

Routine assessment was made of tumor metabolic activity as measured by 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in Stage I non-small-cell lung cancer (NSCLC). This report describes PET correlates prospectively collected after stereotactic body radiotherapy (SBRT) for patients with medically inoperable NSCLC.

METHODS AND MATERIALS

14 consecutive patients with medically inoperable Stage I NSCLC were enrolled. All patients received SBRT to 60-66 Gy in three fractions. Patients underwent serial planned FDG-PET/computed tomography fusion imaging before SBRT and at 2, 26, and 52 weeks after SBRT.

RESULTS

With median follow-up of 30.2 months, no patients experienced local failure. One patient developed regional failure, 1 developed distant failure, and 1 developed a second primary. The median tumor maximum standardized uptake value (SUV(max)) before SBRT was 8.70. The median SUV(max) values at 2, 26, and 52 weeks after SBRT were 6.04, 2.80, and 3.58, respectively. Patients with low pre-SBRT SUV were more likely to experience initial 2-week rises in SUV, whereas patients with high pre-SBRT SUV commonly had SUV declines 2 weeks after treatment (p = 0.036). Six of 13 patients had primary tumor SUV(max) >3.5 at 12 months after SBRT but remained without evidence of local disease failure on further follow-up.

CONCLUSIONS

A substantial proportion of patients may have moderately elevated FDG-PET SUV(max) at 12 months without evidence of local failure on further follow-up. Thus, slightly elevated PET SUV(max) should not be considered a surrogate for local treatment failure. Our data do not support routine serial FDG-PET/computed tomography for follow-up of patients receiving SBRT for Stage I NSCLC.

Stereotactic body radiation therapy: a novel treatment modality

Stereotactic body radiation therapy (SBRT) involves the delivery of a small number of ultra-high doses of radiation to a target volume using very advanced technology and has emerged as a novel treatment modality for cancer. The role of SBRT is most important at two cancer stages-in early primary cancer and in oligometastatic disease. This modality has been used in the treatment of early-stage non-small-cell lung cancer, prostate cancer, renal-cell carcinoma, and liver cancer, and in the treatment of oligometastases in the lung, liver, and spine. A large body of evidence on the use of SBRT for the treatment of primary and metastatic tumors in various sites has accumulated over the past 10-15 years, and efficacy and safety have been demonstrated. Several prospective clinical trials of SBRT for various sites have been conducted, and several other trials are currently being planned. The results of these clinical trials will better define the role of SBRT in cancer management. This article will review the radiobiologic, technical, and clinical aspects of SBRT.

Local surgical, ablative, and radiation treatment of metastases

Because local therapies directed toward a specific tumor mass are known to be effective for treating early-stage cancers, it should be no surprise that there has been considerable historical experience using local therapies for metastatic disease. In more recent years, increasing interest in the use of local therapy for metastases likely has arisen from improvements in systemic therapy. In the absence of effective systemic therapies, such local treatments were often considered futile given both the difficulty in eliminating all sites of identifiable metastatic disease as well as realities regarding the rapid natural history of uncontrolled tumor dissemination. However, with a higher likelihood of patients surviving longer after effective systemic therapy, even if not cured, the goal of the eradication of residual metastases via potent local therapies can be rationalized. However, this rationalization should be evidence-based so as to avoid harming patients for no established benefit. Although surgical metastectomy remains the most common and first-line standard among local therapies, nonsurgical alternatives, including thermal ablation and stereotactic body radiotherapy, have become increasingly popular because they are generally less invasive than surgery and have demonstrated considerable promise in eradicating macroscopic tumor. Rather than eliminating the need for local therapies, improvements in systemic therapies appear to be increasing the prudent utilization of modern local therapies in patients presenting with more advanced cancer.

Gamma knife stereotactic radiosurgery for low-grade astrocytomas

Patients with low-grade astrocytoma (LGA; 8 pilocytic astrocytomas, 2 subependymal giant cell astrocytomas, 2 fibrillary astrocytomas) were selected for treatment with gamma knife stereotactic radiosurgery (GKSRS) based on having a demarcated appearance on CT or MRI and the possibility of dose sparing of adjacent eloquent structures. A median dose of 13 Gy was prescribed to the 50% isodose line, which covered the gross tumor. The median patient age was 17.4 years. The median target volume was 4.4 cm(3). With a median follow-up of 48.2 months, 4-year tumor control and overall survival were 77 and 83%, respectively. Only 2 patients experienced symptomatic treatment-related toxicity. GKSRS can provide local control in cases of unresectable or recurrent LGA with a low incidence of side effects in carefully selected patients.

Endocrine response after gamma knife-based stereotactic radiosurgery for secretory pituitary adenoma

PURPOSE

To examine treatment outcomes of Gamma Knife-based stereotactic radiosurgery (GK-based SRS) for secretory pituitary adenomas.

MATERIALS AND METHODS

25 patients were treated with GK-based SRS for secretory pituitary adenomas with >or=12 months of follow-up.

RESULTS

For prolactinomas, 2 of 4 patients (50%) showed normalization of serum prolactin at a mean time of 18 months. One of 4 had a >or=50% decrease but still abnormal prolactin levels. For adrenocorticotrophic hormone-secreting tumors, 6 of 12 patients (50%) showed normalization of their endocrine levels at a median of 10 months. An additional 2 (17%) had a >or=50% decrease. For growth hormone-secreting tumors, 4 of 9 patients (44%) showed normalization of endocrine levels at a median time of 30 months. Two patients (22%) had >or=50% lower but abnormal endocrine levels.

CONCLUSION

GK-based SRS provides a reasonable rate of endocrine normalization of secretory pituitary adenoma. The time to endocrine response is shorter than reported for fractionated external beam radiotherapy. There is a low risk of optic neuropathy.

Role of stereotactic radiosurgery and fractionated stereotactic radiotherapy in pediatric brain tumors

Brain tumors are the most common solid tumor in childhood. Surgery and/or fractionated radiotherapy are conventional treatment modalities. Stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT) are advanced radiation therapy techniques that have been frequently used in adults with brain tumors but they are less frequently used in pediatric patients. SRS and FSRT can potentially add to the armamentarium against brain tumors in children. This article will review the role of SRS and FSRT in the management of pediatric brain tumors.

Brain metastasis from non-seminomatous germ cell tumor of the testis

Brain metastasis occurs rarely in patients with testicular cancer in the modern era where cisplatin-based chemotherapy regimens are used. The occurrence of brain metastasis can be synchronous or metachronous (with or without concurrent systemic disease). Long-term survival can be achieved in some patients. The vast majority of testicular cancer cases with brain metastasis reported in the literature involve nonseminomatous germ cell tumor and this subtype will be the focus of this review. This article reviews the literature of the diagnosis and management of brain metastasis from nonseminomatous germ cell tumor of the testis.

Successful treatment of a skull base malignant rhabdoid tumor with surgery, chemotherapy and gamma Knife-based stereotactic radiosurgery in a young child

Most childhood rhabdoid tumors occur in the kidney or central nervous system but they can occur in other sites and they usually run an aggressive clinical course. We report a case of an 8-month-old boy with a right temporal bone rhabdoid tumor treated with surgery, chemotherapy and Gamma Knife-based stereotactic radiosurgery. The patient remained alive after 61 months and repeat magnetic resonance imaging (MRI) of the brain showed no evidence of recurrence. There were no obvious endocrine deficits or growth abnormalities at last follow-up. Gamma Knife-based stereotactic radiosurgery may have a role in the management of very young children with skull base tumors.

The North American experience with stereotactic body radiation therapy in non-small cell lung cancer

INTRODUCTION

In North America, the majority of prospective investigation using stereotactic body radiation therapy (SBRT) for thoracic targets has been carried out treating medically inoperable patients with non-small cell lung cancer.

METHODS

Because SBRT involves constructing very compact high-dose volumes within the lung for targeting cancer deposits, tumor position must be accurately assessed throughout the respiratory cycle. Measures to account for this motion, either by tracking (chasing), gating, or inhibition (breath hold and abdominal compression) must be used to avoid large margins of error that would expose uninvolved normal tissues. Sophisticated image guidance and related treatment delivery technology have been used primarily for the purpose of targeting the tumor with as low a radiation dose to the surrounding normal tissue as possible.

RESULTS

Phase I dose escalation trials have been carried out in North America to achieve potent tumorcidal dose levels capable of eradicating tumors with high likelihood. These studies indicate a clear dose-response relationship for tumor control with escalating dose of SBRT. While late toxicity requires further careful assessment, acute and subacute toxicity are generally acceptable. Radiographic and local tissue effects consistent with bronchial or vascular damage and downstream collapse with fibrosis are common. While such radiographic changes are most often asymptomatic, more frequent and sometimes debilitating toxicity has been observed for patients with tumors near the central airways.

CONCLUSIONS

Prospective trials using SBRT in North America have been able to identify potent tolerant dose levels and confirm their efficacy in patients with medically inoperable disease. Although mechanisms of this injury remain elusive, ongoing prospective trials offer the hope of finding the ideal application for SBRT in treating pulmonary targets.

Stereotactic body radiation therapy in multiple organ sites

INTRODUCTION

Stereotactic body radiation therapy (SBRT) uses advanced technology to deliver a potent ablative dose to deep-seated tumors in the lung, liver, spine, pancreas, kidney, and prostate.

METHODS

SBRT involves constructing very compact high-dose volumes in and about the tumor. Tumor position must be accurately assessed throughout treatment, especially for tumors that move with respiration. Sophisticated image guidance and related treatment delivery technologies have developed to account for such motion and efficiently deliver high daily dose. All this serves to allow the delivery of ablative dose fractionation to the target capable of both disrupting tumor mitosis and cellular function.

RESULTS

Prospective phase I dose-escalation trials have been carried out to reach potent tumoricidal dose levels capable of eradicating tumors with high likelihood. These studies indicate a clear dose-response relationship for tumor control with escalating dose of SBRT. Prospective phase II studies have been reported from several continents consistently showing very high levels of local tumor control. Although late toxicity requires further careful assessment, acute and subacute toxicities are generally acceptable. Patterns of toxicity, both clinical and radiographic, are distinct from those observed with conventionally fractionated radiotherapy as a result of the unique biologic response to ablative fractionation.

CONCLUSION

Prospective trials using SBRT have confirmed the efficacy of treatment in a variety of patient populations. Although mechanisms of ablative-dose injury remain elusive, ongoing prospective trials offer the hope of finding the ideal application for SBRT in the treatment arsenal.

FDG-PET and stereotactic body radiotherapy (SBRT) for stage I non-small-cell lung cancer

PURPOSE

To investigate the utility of positron emission tomography (PET) in patients treated with stereotactic body radiotherapy (SBRT) for stage I non-small-cell lung cancer (NSCLC) on prospective institutional trials.

PATIENTS AND METHODS

Fifty-eight patients with medically inoperable stage I NSCLC who participated in prospective phase I and II trials of SBRT, had >or=2 years of follow-up, and received FDG-PET imaging are the focus of this evaluation. Fifty-seven of 58 patients received pre-SBRT FDG-PET to confirm stage I status. All patients received stereotactic body frame immobilization and treatment with 7-10 photon beams. SBRT total doses ranged from 24 to 72Gy in three fractions. No elective nodal irradiation was undertaken. Regular follow-up with planned CT imaging was performed on all patients. Post-SBRT FDG-PET was not mandated by protocol and was typically ordered upon concern for disease recurrence. Thirty-eight post-SBRT PET studies were performed in 28 patients at a median 17.3 months following SBRT.

RESULTS

With a median follow-up of 42.5 months, the 3-year actuarial overall survival and local control for this select subset of our SBRT experience were 48.9% and 74.8%, respectively. Pre-SBRT FDG-PET SUV did not predict 3-year overall survival or local control. Fourteen of 57 patients eventually failed in nodal stations by CT and/or PET. Isolated first site of failure was nodal in 6 patients (10%). Out of 28 patients with post-SBRT PET, 4 (14%) had delayed PET imaging (22-26 months after SBRT) showing moderate hypermetabolic activity (SUV 2.5-5.07), but no evidence of local, nodal, or distant recurrence by clinical examination and conventional imaging performed 20-26 months following these concerning PET findings.

CONCLUSIONS

Isolated nodal recurrence following PET-staged I NSCLC treated with SBRT is uncommon. Moderate post-SBRT PET hypermetabolic activity may persist 2 years following treatment without definite evidence of recurrence. Further study is needed to confirm these results in larger populations with longer follow-up.

Interim analysis of a prospective phase I/II trial of SBRT for liver metastases

Stereotactic Body Radiation Therapy (SBRT) is a potent means of systemic cytoreductive therapy for selected patients with metastatic cancer. We here report an interim analysis of a prospective Phase I/II study of SBRT for liver metastases. Eligible patients with liver metastases met these criteria: (1) maximum tumor diameter < 6 cm; (2) < or =3 discrete lesions; (3) treatment planning confirmed > or = 700 cm3 of normal liver receives < or =15 Gy. The gross tumor volume (GTV) was expanded 5-10 mm to yield the planning target volume, which received 60 Gy in 3 fractions of SBRT over 3-14 days in the Phase II component of the trial. As of July, 2006, 36 patients have been enrolled: 18 in Phase I, 18 in Phase II. The median age was 58 years (range 27-91); the M:F ratio was 20:16. The most common primary sites were lung (n = 10), colorectal (n = 9), and breast (n = 4). Among 21 pts with > or = 6 months post-SBRT follow-up (median 19 months, range 6-29), one instance of SBRT-related grade 3 toxicity occurred in subcutaneous tissue superficial to the liver. No grade IV toxicity occurred. For 28 discrete lesions treated (median GTV 14 cm3, range 1-98) the 18 month actuarial local control estimate is 93%. This interim analysis indicates that a very high rate of durable in-field tumor control can be safely achieved with SBRT to 1-3 liver lesions as administered in this protocol, to a prescription dose of 60 Gy in 3 fractions.

Gamma-knife-based stereotactic radiosurgery for uveal melanoma

Nineteen patients with uveal melanoma were treated with Gamma-Knife-based stereotactic radiosurgery (SRS). The radiation dose was 40 Gy prescribed to the 50% isodose line for all patients. The median follow-up was 40 months. The 3- and 5-year overall survival rates were 86 and 55%, respectively. The 3- and 5-year tumor control rates were both 94%. Six of the 19 treated patients (32%) developed distant metastasis 31-75 months after SRS. Out of the 19 patients treated with SRS, 2 had improved, 4 had stable and 13 had worse vision in the treated eye. Gamma-Knife-based SRS appears to provide excellent local control of uveal melanoma. The risk of distant metastasis is significant. Effective systemic therapy is to be explored to improve the treatment outcome of uveal melanoma.

Which MR imaging sequences are necessary in determining the need for radiation therapy for cord compression? A prospective study

BACKGROUND AND PURPOSE

To determine which MR imaging sequences are necessary to assess for spinal metastases.

METHODS

Hypothetical MR imaging interpretations and management plans were made prospectively for consecutive adult cases acquired retrospectively. Standardized MR imaging protocols were independently interpreted by 2 neuroradiologists. MR imaging protocol types varied: 1) T1-weighted images only; 2) T1-weighted and T2-weighted images; 3) T1-weighted and postcontrast T1-weighted images; and 4) T1- and T2-weighted images and postcontrast T1-weighted images. Hypothetical management plans were created by 2 radiation oncologists. Logit model was used to investigate the effect of MR imaging protocol type on the probability of recommending radiation therapy (RT). Mixed effect models were used to investigate whether median spinal level or total number of spinal levels of planned RT was associated with MR imaging protocol type.

RESULTS

Thirty-one subjects were evaluated, each with multiple scan interpretations. Logit model showed that neither MR imaging protocol type nor neuroradiologist reader affected the probability that the oncologist would recommend RT (all P > .50). Mixed models showed that neither ML nor NL was affected by MR imaging protocol type or by neuroradiologist reader (all P > .12).

CONCLUSION

Although MR imaging is known to be the most useful diagnostic test in suspected spinal cord compression, which particular MR images are necessary remain unclear. Compared with T1-weighted images alone, the additional use of T2-weighted and/or postcontrast T1-weighted sequences did not significantly affect the probability that RT would be recommended or the levels that would be chosen for RT in our study. Our data suggest that unenhanced T1-weighted images may be sufficient for evaluation of possible cord compression.

Gamma Knife Radiosurgery in the Treatment of Choroidal Neovascularization (Wet-Type Macular Degeneration)

We evaluated retrospectively our institutional experience in the treatment of macular degeneration with gamma knife radiosurgery (GKR). Treatment was delivered in a single shot of 12 Gy. Seven patients were treated between March of 1999 and May of 2000. The median duration of follow-up was 2.2 years. The majority of patients maintained stable visual acuity after treatment. Our series indicates that GKR may be useful as a salvage treatment for patients who have failed or are ineligible for other treatments for their macular degeneration. Further studies are needed to better define the role of GKR in the treatment of macular degeneration.

Extracranial Radiosurgery (Stereotactic Body Radiation Therapy) for Oligometastases

Extracranial radiosurgery, also known as stereotactic body radiation therapy (SBRT), is an increasingly used method of treatment of limited cancer metastases located in a variety of organs/sites including the spine, lungs, liver, and other areas in the abdomen and pelvis. The techniques used to perform SBRT were initially modeled after intracranial radiosurgery, although considerable evolution in technique and conduct has occurred for extracranial applications. Unlike intracranial radiosurgery, SBRT requires characterization and accounting for inherent organ movement including breathing motion. Potent dose hypofractionation schedules have been used with SBRT such that the treatment is generally both ablative and convenient. Because the treatment is severely damaging to tissues within and about the target, the volume of adjacent normal tissue must be strictly minimized to avoid toxic late effects. Outcomes in various sites show very high rates of local control with toxicity mostly related to tubular tissues like the airways and bowels. With proper conduct though, SBRT can be an extremely effective treatment option for oligometastases.

The role of Gamma Knife Radiosurgery in the management of unresectable gross disease or gross residual disease after surgery in ependymoma

PURPOSE/OBJECTIVE

To evaluate the efficacy and the toxicity of Gamma Knife (GK)-based stereotactic radiosurgery (SRS) in the management of gross disease in ependymoma.

MATERIALS AND METHODS

Eight patients with 13 ependymomas were treated with GK-based SRS in our institution for gross disease. Five patients were treated for recurrent disease that developed after surgery and external beam radiotherapy (EBRT), two received SRS to the gross disease after surgery and EBRT, and one received SRS alone (in a 1.3 year old child). Median EBRT dose was 54.4 Gy (range 50-55.8 Gy). Median SRS dose was 14 Gy (range 12-20 Gy). Seven of eight (87.5%) patients had SRS to a single lesion and one of eight (12.5%) patients had treatment to six tumors in three different sessions.

RESULTS

The median follow up was 30.2 months (range 8-65.4 months). Out of the eight patients treated with SRS, six (75%) were alive, four (50%) were alive with no recurrence, two (25%) were alive with recurrence, and two (25%) died of recurrent disease. Both patients treated with SRS as a boost were alive and without recurrence. Out of the five patients who received SRS as salvage treatment, three (60%) were alive, two (40%) were alive without recurrence, two (40%) developed distant failure, and three (60%) had in-field control. Two patients who received SRS to their brainstem lesions developed symptoms related to radionecrosis and were successfully treated with steroid with good control of symptoms.

CONCLUSIONS

GK-based SRS appears to be a feasible and safe treatment modality for patients with ependymoma with unresectable gross disease or gross residual disease after surgery. SRS provides reasonable local control but out-of-field tumor progression remains an issue. For patients who receive SRS as a boost, the local control appears to be excellent.

Stereotactic Radiosurgery and Stereotactic Body Radiation Therapy: An Overview of Technical Considerations and Clinical Applications

SRS and SBRT have emerged as effective local treatment techniques for cranial and extracranial tumors, respectively. Clinical indications for SRS and SBRTcontinue to be redefined through ongoing clinical investigations. It will be especially interesting to investigate how SRS and SBRT might best be combined with new molecularly targeted systemic agents as the field of oncology progresses through the twenty-first century.

A phase I trial of stereotactic body radiation therapy (SBRT) for liver metastases

PURPOSE

To determine the maximum tolerated dose (MTD) of stereotactic body radiation therapy (SBRT) for liver metastases.

METHODS AND MATERIALS

A multicenter Phase I clinical trial was conducted. Eligible patients had one to three liver metastases, tumor diameter <6 cm, and adequate liver function. The first cohort received 36 Gy to the planning target volume (PTV) in three fractions (F). Subsequent cohorts received higher doses up to a chosen maximum of 60 Gy/3F. At least 700 mL of normal liver had to receive a total dose <15 Gy. Dose-limiting toxicity (DLT) included acute Grade 3 liver or intestinal toxicity or any acute Grade 4 toxicity. The MTD was exceeded if 2/6 patients in a cohort experienced DLT.

RESULTS

Eighteen patients were enrolled (10 male, 8 female): median age, 55 years (range, 26-83 years); most common primary site, colorectal (6 patients); median aggregate gross tumor volume, 18 ml (range, 3-98 ml). Four patients had multiple tumors. No patient experienced a DLT, and dose was escalated to 60 Gy/3F without reaching MTD.

CONCLUSIONS

Biologically potent doses of SBRT are well tolerated in patients with limited liver metastases. Results of this study form the basis for an ongoing Phase II SBRT study of 60 Gy over three fractions for liver metastases.

Stereotactic body radiation therapy of early-stage non-small-cell lung carcinoma: phase I study

PURPOSE

A Phase I dose escalation study of stereotactic body radiation therapy to assess toxicity and local control rates for patients with medically inoperable Stage I lung cancer.

METHODS AND MATERIALS

All patients had non-small-cell lung carcinoma, Stage T1a or T1b N0, M0. Patients were immobilized in a stereotactic body frame and treated in escalating doses of radiotherapy beginning at 24 Gy total (3 x 8 Gy fractions) using 7-10 beams. Cohorts were dose escalated by 6.0 Gy total with appropriate observation periods.

RESULTS

The maximum tolerated dose was not achieved in the T1 stratum (maximum dose = 60 Gy), but within the T2 stratum, the maximum tolerated dose was realized at 72 Gy for tumors larger than 5 cm. Dose-limiting toxicity included predominantly bronchitis, pericardial effusion, hypoxia, and pneumonitis. Local failure occurred in 4/19 T1 and 6/28 T2 patients. Nine local failures occurred at doses < or =16 Gy and only 1 at higher doses. Local failures occurred between 3 and 31 months from treatment. Within the T1 group, 5 patients had distant or regional recurrence as an isolated event, whereas 3 patients had both distant and regional recurrence. Within the T2 group, 2 patients had solitary regional recurrences, and the 4 patients who failed distantly also failed regionally.

CONCLUSIONS

Stereotactic body radiation therapy seems to be a safe, effective means of treating early-stage lung cancer in medically inoperable patients. Excellent local control was achieved at higher dose cohorts with apparent dose-limiting toxicities in patients with larger tumors.

Extracranial Stereotactic Radiation Delivery

Extracranial stereotactic radiation delivery, also known as stereotactic body radiation therapy (SBRT), involves delivering very potent doses of radiation to well-demarcated tumors in the neck, spine, chest, abdomen, and pelvis. Beyond just stereotactic targeting, it represents a formalism of treatment planning and conduct that facilitates the delivery of the most potent dose fractionation schedules ever considered in the field of radiation oncology. In doing so, it uses the most modern technologies to simultaneously hit the target and avoid normal innocent tissues. Clinical results already show that SBRT constitutes a new paradigm in cancer treatment that deserves careful implementation and assessment for the improvement in patient outcomes.