Fractionated stereotactic radiosurgery for 50 patients with recurrent or residual nasopharyngeal carcinoma

Salvage treatments for locally recurrent nasopharyngeal cancer: Systematic review and meta-analysis

The present study aimed to evaluate the effectiveness and safety of various salvage treatments to treat locally recurrent nasopharyngeal carcinoma (IrNPC). A comprehensive search was conducted to gather relevant research publications on salvage treatment for IrNPC. Specifically, 2-, 3-, and 5-year overall survival were the primary outcome. A total of 89 studies with 101 cohorts were collected. Endoscopic nasopharyngectomy was found to be associated with a significantly improved 5-year OS compared with CRT (p = 0.027) and IMRT (p = 0.016). Moreover, based on recurrence T classification, the 2-, 3-, and 5-year OS were similar across different treatments. Endoscopic nasopharyngectomy was associated with a significant reduction in treatment-related complications (grade ≥ 3) compared with IMRT (p < 0.001) and open nasopharyngectomy (p = 0.028). Endoscopic nasopharyngectomy may provide comparable treatment outcomes to re-irradiation, while offering a better safety profile for selective patients with resectable IrNPC.

Recurrent Nasopharyngeal Cancer: Critical Review of Local Treatment Options Including Recommendations during the COVID-19 Pandemic

Simple Summary

Options for the curative treatment of locally recurrent nasopharyngeal carcinoma include surgery or re-irradiation. Both approaches have been scientifically explored, yet there is no consensus on the indication or definitive preference of the above two salvage treatments. The aim of this review is to summarize the current evidence on the local treatment of recurrent nasopharyngeal carcinoma. The feasibility, safety, and efficacy of salvage surgery and radical re-irradiation are discussed. Recommendations on treatment modifications during the coronavirus disease 2019 pandemic are included as well.

Abstract

Recurrent nasopharyngeal carcinoma represents an extremely challenging therapeutic situation. Given the vulnerability of the already pretreated neurological structures surrounding the nasopharynx, any potential salvage retreatment option bears a significant risk of severe complications that result in high treatment-related morbidity, quality of life deterioration, and even mortality. Yet, with careful patient selection, long-term survival may be achieved after local retreatment in a subgroup of patients with local or regional relapse of nasopharyngeal cancer. Early detection of the recurrence represents the key to therapeutic success, and in the case of early stage disease, several curative treatment options can be offered to the patient, albeit with minimal support in prospective clinical data. In this article, an up-to-date review of published evidence on modern surgical and radiation therapy treatment options is summarized, including currently recommended treatment modifications of both therapeutic approaches during the coronavirus disease 2019 pandemic.

Gamma Knife Radiosurgery Using Co-Registration with PET-CT and MRI for Recurrent Nasopharyngeal Carcinoma with Previous Radiotherapy : A Single Center 14-Year Experience

Objective

We retrospectively evaluated the efficacy of Gamma Knife radiosurgery (GKS) for recurrent nasopharyngeal carcinoma (NPC) in patients who previously underwent radiotherapy, and analyzed the treatment outcomes over 14 years.

Methods

Ten patients with recurrent NPC who had previously received radiotherapy underwent stereotactic radiosurgery using a Gamma Knife^® (Elekta Inc, Atlanta, GA, USA) between 2005 and 2018. The median target volume was 8.2 cm³ (range, 1.7–17.8), and the median radiation dose to the target was 18 Gy (range, 12–30). The median follow-up period was 18 months (range, 6–76 months). Overall and local failure-free survival rates were determined using the Kaplan-Meier method.

Results

The NPCs recurred at the primary cancer site in seven patients (70%), as distant brain metastasis in two (20%), and as an extension into brain in one (10%). The recurrent tumors in seven of the 10 patients (70%) were found on the routine follow-up imaging studies. Two patients presented with headache and one with facial pain. Local failure after GKS occurred in five patients (50%) : two of whom died eight and 6 months after GKS, respectively. No adverse radiation effects were noted after GKS. The 1- and 3-year overall survival rates after GKS were 90% and 77%, respectively. The local failure-free survival rates at 6 months, 1 year, and 3 years after GKS were 80%, 48%, and 32%, respectively. The median interval from GKS to local failure was 8 months (range, 6–12). Univariate analysis revealed that using co-registration with positron emission tomography-computed tomography (PET-CT) and magnetic resonance imaging (MRI) was associated with a lower local failure rate of recurrent NPC (p=0.027).

Conclusion

GKS is an acceptable salvage treatment option for patients with recurrent NPC who previously received radiation therapy. PET-CT and MRI co-registration for dose planning can help achieve local control of recurrent NPC.

Stereotactic body radiotherapy for recurrent head and neck cancer: A critical review

The management of patients with recurrent head and neck cancers remains a challenging clinical dilemma. Concerns over toxicity with re-irradiation have limited its use in the clinical setting. Stereotactic Body Radiation Therapy (SBRT) has emerged as a highly conformal and precise type of radiotherapy and has the advantage of sparing normal tissue. Although SBRT is an attractive treatment modality, its use in the clinic is limited, given the technically challenging nature of the procedure. In this review, we attempt to provide a comprehensive overview of the role of re-irradiation in patients with recurrent head and neck cancers, with particular attention to the advent of SBRT and its use with systemic therapies such as cetuximab. In the second portion of this review, we present our systematic review of published experiences with SBRT in recurrent head and neck cancers in an attempt to provide data on response rates (RR), overall survival and toxicity. © 2016 Wiley Periodicals, Inc. Head Neck 39: 595-601, 2017.

Image-Guided Radiosurgery of Head and Neck Cancers

OBJECTIVES: Radiosurgery precisely delivers a single high dose or a few fractionated doses of radiation to a localized tumor via the stereotactic approach. Some head and neck sites are suitable for radiosurgery since there is minimal or no organ motion. The clinical studies were carried out to determine the accuracy of stereotactic radiosurgery and to demonstrate the effectiveness of radiosurgery in head and neck cancers.

MATERIALS AND METHODS: Thirteen patients were treated with either single-dose or fractionated radio-surgery to the tumor. All patients except one with cancer of the lip had received prior treatments including surgery, radiotherapy, and chemotherapy for the primary cancers. The dose ranged 12 to 18 Gy for single-dose radiosurgery and 30 Gy in 5 or 6 fractions twice a week for fractionated radiosurgery. Tumor localization was achieved via the stereotactic approach.

RESULTS: Accuracy of radiosurgery was within 1.5 mm. Despite the recurrent disease from previous heavy treatments, 9 patients (70%) showed a significant response (complete or >50% tumor reduction) to radiosurgery, and 3 patients had stable disease. Complete tumor response was achieved in 6 patients. All patients had excellent pain relief with functional and cosmetic preservation. There was no acute and subacute radiation toxicity detected clinically during the minimal follow-up of 6 months.

CONCLUSION: Image-guided radiosurgery is effective in achieving the local tumor control and pain relief. Radiosurgery provided excellent functional and cosmetic preservation with minimal complication. The results indicate the potential of radiosurgery in the treatment of recurrent and selected primary head and neck cancers. (Otolaryngol Head Neck Surg 2004;130:690-7.)

A triplet chemotherapy regimen of cisplatin, fluorouracil and paclitaxel for locoregionally recurrent nasopharyngeal carcinoma cases contraindicated for re-irradiation/surgery

OBJECTIVE

Salvage treatment for locoregionally recurrent nasopharyngeal carcinoma remains a significant challenge. The present study was conducted to evaluate the efficacy, toxicity and prognostic factors of a triplet chemotherapy regimen involving cisplatin, fluorouracil and paclitaxel (TPF) for locoregionally recurrent nasopharyngeal carcinoma (NPC) cases contraindicated for re-irradiation/surgery.

METHODS

Patients with locoregionally recurrent NPC unsuitable for re-irradiation/surgery were treated with TPF therapy. The chemotherapy drugs were administered as follows: 135 mg/m(2) paclitaxel on day 1, 25 mg/m(2)/day cisplatin on days 1-3, followed by continuously infused intravenous fluorouracil for 120 h at a variable dosage from 600 to 800 mg/m(2)/day, depending on prior radiation.

RESULTS

Twenty-seven patients were enrolled. The overall response was 66.7%. The median progression-free survival (PFS) and overall survival (OS) were 8.5 and 27.2 months, respectively. Toxicity was mild to moderate. Neutropenia and leukopenia were the primary grade 3-4 chemotherapy toxicities. 6 patients who regained the potential for re-radiotherapy or surgery showed significantly better outcomes than those treated with chemotherapy alone (median PFS: 20.8 vs. 7.1 months, P = 0.005; median OS: 54.2 vs. 20.6 months, P = 0.021).

CONCLUSION

TPF triplet chemotherapy showed a high response rate for locoregionally recurrent NPC with an acceptable toxicity profile.

Frameless Stereotactic Radiosurgery for Recurrent Head and Neck Carcinoma

The aim of this study was to assess the feasibility and toxicity of stereotactic radiosurgery (CK-SRS) using the CyberKnife® Frameless Radiosurgery System (Accuray Inc., Sunnyvale, CA) in the management of recurrent squamous cell carcinoma of the head and neck region (SCCHN). Between November 2001 and February 2004, 22 patients with recurrent, previously irradiated SCCHN were treated with CK-SRS. The following endpoints were assessed post-CK-SRS: local control (LC), cause-specific survival (CSS), overall survival (OS), symptom relief, and acute and late toxicity. Kaplan-Meier survival analyses were used to estimate the LC, CSS, and OS rates. Clinical symptoms were graded as “improved,” “stable,” or “progressed” after CK-SRS. Acute and late toxicity were graded according to the National Cancer Institute Common Toxicity Criteria (CTC) scale, version 2.0. Seventeen patients were followed until their death. The median follow-up in the remaining five patients was 19 months (range 11–40 months). The median survival time for the entire cohort was 12 months from the time of CK-SRS. The 2-year LC, CSS, and OS rates were 26%, 26%, and 22%, respectively. After CK-SRS, symptoms were improved or stable in all but one patient who reported increasing pain. The treatment was well tolerated, with one case each of Grade 2 and 3 mucositis. There were no acute Grade 4 or 5 CTC toxicities. There were no late toxicities in this cohort. Frameless stereotactic radiosurgery for recurrent SCCHN is feasible and safe in the setting of high doses of prior irradiation. The majority of patients experienced palliation of disease without excess toxicity.

Stereotactic ablative radiosurgery for locally advanced or recurrent skull base malignancies with prior external beam radiation therapy

PURPOSE

Stereotactic ablative radiotherapy (SABR) is an attractive modality to treat malignancies invading the skull base as it can deliver a highly conformal dose with minimal toxicity. However, variation exists in the prescribed dose and fractionation. The purpose of our study is to examine the local control, survival, and toxicities in SABR for the treatment of previously irradiated malignant skull base tumors.

MATERIALS AND METHODS

A total of 31 patients and 40 locally advanced or recurrent head and neck malignancies involving the skull base treated with a common SABR regimen, which delivers a radiation dose of 44 Gy in 5 fractions from January 1st, 2004 to December 31st, 2013, were retrospectively reviewed. The local control rate (LC), progression-free survival rate, overall survival (OS) rate, and toxicities were reported.

RESULTS

The median follow-up time of all patients was 11.4 months (range: 0.6-67.2 months). The median tumor volume was 27 cm(3) (range: 2.4-205 cm(3)). All patients received prior external beam radiation therapy with a median radiation dose of 64 Gy (range: 24-75.6 Gy) delivered in 12-42 fractions. Twenty patients had surgeries prior to SABR. Nineteen patients received chemotherapy. Specifically, eight patients received concurrent cetuximab (Erbitux™) with SABR. The median time-to-progression (TTP) was 3.3 months (range: 0-16.9 months). For the 29 patients (93.5%) who died, the median time from the end of first SABR to death was 10.3 months (range: 0.5-41.4 months). The estimated 1-year OS rate was 35%. The estimated 2-year OS rate was 12%. Treatment was well-tolerated without grade 4 or 5 treatment-related toxicities.

CONCLUSION

Stereotactic ablative radiotherapy has been shown to achieve low toxicities in locally advanced or recurrent, previously irradiated head and neck malignancies invading the skull base.

Current treatment options for local residual nasopharyngeal carcinoma

OPINION STATEMENT

Local residual disease occurs in 7-13 % after primary treatment for nasopharyngeal carcinoma (NPC). To prevent tumor progression and/or distant metastasis, treatment is indicated. Biopsy is the "gold standard" for diagnosing residual disease. Because late histological regression frequently is seen after primary treatment for NPC, biopsy should be performed when imaging or endoscopy is suspicious at 10 weeks. Different modalities can be used in the treatment of local residual disease. Interestingly, the treatment of residual disease has better outcomes than treatment of recurrent disease. For early-stage disease (rT1-2), treatment results and survival rates are very good and comparable to patients who had a complete response after the first treatment. Surgery (endoscopic or open), brachytherapy (interstitial or intracavitary), external or stereotactic beam radiotherapy, or photodynamic therapy all have very good and comparable response rates. Choice should depend on the extension of disease, feasibility of the treatment, and doctor's and patient's preferences and experience, as well as the risks of the adverse events. For the more extended tumors, choice of treatment is more difficult, because complete response rates are poorer and severe side effects are not uncommon. The results of external beam reirradiation and stereotactic radiotherapy are better than brachytherapy for T3-4 tumors. Photodynamic therapy resulted in good palliative responses in a few patients with extensive disease. Also, chemotherapeutics or the Epstein-Barr virus targeted therapies can be used when curative intent treatment is not feasible anymore. However, their advantage in isolated local failure has not been well described yet. Because residual disease often is a problem in countries with a high incidence of NPC and limited radiotherapeutic and surgical facilities, it should be understood that most of the above mentioned therapeutic modalities (radiotherapy and surgery) will not be readily available. More research with controlled, randomized trials are needed to find realistic treatment options for residual disease.

A simple strategy to decrease fatal carotid blowout syndrome after stereotactic body reirradiaton for recurrent head and neck cancers

BACKGROUND

This study aimed to compare the therapeutic outcomes and fatal carotid blow out syndrome (CBOS) incidence rates between two different stereotactic body radiotherapy (SBRT) protocols.

METHODS

The study included 75 patients with inoperable locally recurrent head and neck cancer treated with SBRT in our department between June 2007 and March 2011. The first 43 patients were treated sequentially (group I). Then our SBRT protocol was changed due to the high rate of CBOS, and the following 32 patients were treated every other day in a prospective institutional protocol (group II).

RESULTS

Median overall survival in group I and group II was 11 months and 23 months, respectively (P = 0.006). We observed 11 cases of CBOS. Only 1 of 7 patients (14%) with CBOS survived in group I, whereas 2 of 4 patients (50%) in group II remain alive. CBOS free median overall survivals were 9 months, and 23 months in group I and group II respectively (P = 0.002). The median radiation dose received by the carotid artery in patients with CBOS was 36.5 Gy (range: 34-42.8 Gy), versus 34.7 Gy (range: 0-44 Gy) in the patients that didn't have CBOS (P = 0.15). CBOS did not occur in any of the patients with a maximum carotid artery radiation dose <34 Gy.

CONCLUSIONS

Every other day SBRT protocol for re-irradiation of recurrent head and neck cancer is promising in terms of decreasing the incidence of fatal CBOS.

Fractionated stereotactic radiotherapy for 136 patients with locally residual nasopharyngeal carcinoma

Background

To evaluate the efficacy and toxicity of fractionated stereotactic radiotherapy (FSRT) in patients with residual nasopharyngeal carcinoma (NPC).

Methods

From January 2000 to December 2009, 136 NPC patients with residual lesions after primary radiotherapy (RT) were treated by FSRT. The total dose of primary RT was 68.0-78.0 Gy (median, 70.0 Gy). The median time from the primary RT to FSRT was 24.5 days. Tumor volumes for FSRT ranged from 0.60 to 77.13 cm3 (median, 13.45 cm3). The total FSRT doses were 8.0-32.0Gy (median, 19.5 Gy) with 2.0-10.0 Gy per fraction.

Results

Five-year local failure-free survival (LFFS), freedom from distant metastasis (FFDM), overall survival (OS), and disease free survival (DFS) rates for all patients were 92.5%, 77.0%, 76.2%, and 73.6%, respectively. No statistical significant differences were found in LFFS, DFS and OS in patients with stage I/II versus stage III/ IV diseases. Nineteen patients exhibited late toxicity. T stage at diagnosis was a significant prognostic factor for OS and DFS. Age was a prognostic factor for OS.

Conclusion

FSRT after external beam radiotherapy provides excellent local control for patients with residual NPC. The incidence of severe late toxicity is low and acceptable. Further investigation of optimal fractionation regimens will facilitate reduction of long-term complications.

Frequency, outcome and prognostic factors of carotid blowout syndrome after hypofractionated re-irradiation of head and neck cancer using CyberKnife: a multi-institutional study

PURPOSE

Re-irradiation has attracted attention as a potential therapy for recurrent head and neck tumors. However, carotid blowout syndrome (CBS) has become a serious complication of re-irradiation because of the associated life-threatening toxicity. Determining of the characteristics of CBS is important. We conducted a multi-institutional study.

METHODS AND PATIENTS

Head and neck carcinoma patients (n=381) were treated with 484 re-irradiation sessions at 7 Japanese CyberKnife institutions between 2000 and 2010.

RESULTS

Of these, 32 (8.4%) developed CBS, which proved fatal that median survival time after CBS onset was 0.1 month, and the 1-year survival rate was 37.5%. The median duration between re-irradiation and CBS onset was 5 months (range, 0-69 months). Elder age, skin invasion, and necrosis/infection were identified as statistically significant risk factors after CBS by univariate analysis. The presence of skin invasion at the time of treatment found only in postoperative case, is identified as only statistically significant prognostic factor after CBS in multivariate analysis. The 1-year survival rate for the group without skin invasion was 42%, whereas no patient with skin invasion survived more than 4 months (0% at 1 year, p=0.0049).

CONCLUSIONS

Careful attention should be paid to the occurrence of CBS if the tumor is located adjacent to the carotid artery. The presence of skin invasion at CBS onset is ominous sign of lethal consequences.

Stereotactic Body Radiotherapy (SBRT) for primary and recurrent head and neck tumors

Stereotactic Body Radiotherapy (SBRT) is increasingly used to treat a variety of head and neck tumors as a result of its highly conformal dose distributions and stereotactic spatial accuracy in delivery. Our experience and other previous reports have shown that SBRT is technically feasible, well-tolerated and compares favorably to other alternatives of salvage therapy in the management of patients with recurrent and/or previously irradiated head and neck cancers. Furthermore, it has the advantage of a shorter treatment schedule, greater compliance, and safe delivery in the outpatient setting. This affords an opportunity to introduce SBRT as a definitive treatment in select patients. This review presents an overview of the use of SBRT for managing head and neck tumors by highlighting the existing indications and the expanding role of SBRT in managing these patients.

Reirradiation of head and neck cancer focusing on hypofractionated stereotactic body radiation therapy

Reirradiation is a feasible option for patients who do not otherwise have treatment options available. Depending on the location and extent of the tumor, reirradiation may be accomplished with external beam radiotherapy, brachytherapy, radiosurgery, or intensity modulated radiation therapy (IMRT). Although there has been limited experience with hypofractionated stereotactic radiotherapy (hSRT), it may have the potential for curative or palliative treatment due to its advanced precision technology, particularly for limited small lesion. On the other hand, severe late adverse reactions are anticipated with reirradiation than with initial radiation therapy. The risk of severe late complications has been reported to be 20- 40% and is related to prior radiotherapy dose, primary site, retreatment radiotherapy dose, treatment volume, and technique. Early researchers have observed lethal bleeding in such patients up to a rate of 14%. Recently, similar rate of 10-15% was observed for fatal bleeding with use of modern hSRT like in case of carotid blowout syndrome. To determine the feasibility and efficacy of reirradiation using modern technology, we reviewed the pertinent literature. The potentially lethal side effects should be kept in mind when reirradiation by hSRT is considered for treatment, and efforts should be made to minimize the risk in any future investigations.

Current treatment options for recurrent nasopharyngeal cancer

Loco-regional control rate of nasopharyngeal carcinoma (NPC) has improved significantly in the past decade. However, local recurrence still represents a major cause of mortality and morbidity in advanced stages, and management of local failure remains a challenging issue in NPC. The best salvage treatment for local recurrent NPC remains to be determined. The options include brachytherapy, external radiotherapy, stereotactic radiosurgery, and nasopharyngectomy, either alone or in different combinations. In this article we will discuss the different options for salvage of locally recurrent NPC. Retreatment of locally recurrent NPC using radiotherapy, alone or in combination with other treatment modalities, as well as surgery, can result in long-term local control and survival in a substantial proportion of patients. For small-volume recurrent tumors (T1–T2) treated with external radiotherapy, brachytherapy or stereotactic radiosurgery, comparable results to those obtained with surgery have been reported. In contrast, treatment results of advanced-stage locally recurrent NPC are generally more satisfactory with surgery (with or without postoperative radiotherapy) than with reirradiation.

Salvage reirradiaton with stereotactic body radiotherapy for locally recurrent head-and-neck tumors

PURPOSE

In this study, we present our results of reirradiation of locally recurrent head-and-neck cancer with image-guided, fractionated, frameless stereotactic body radiotherapy technique.

METHODS AND MATERIALS

From July 2007 to February 2009, 46 patients were treated using the CyberKnife (Accuray, Sunnyvale, CA) at the Department of Radiation Oncology, Hacettepe University, Ankara, Turkey. All patients had recurrent, unresectable, and previously irradiated head-and-neck cancer. The most prominent site was the nasopharynx (32.6%), and the most common histopathology was epidermoid carcinoma. The planning target volume was defined as the gross tumor volume identified on magnetic resonance imaging and computed tomography. There were 22 female and 24 male patients. Median age was 53 years (range, 19-87 years). The median tumor dose with stereotactic body radiotherapy was 30 Gy (range, 18-35 Gy) in a median of five (range, one to five) fractions.

RESULTS

Of 37 patients whose response to therapy was evaluated, 10 patients (27%) had complete tumor regression, 11 (29.8%) had partial response, and 10 (27%) had stable disease. Ultimate local disease control was achieved in 31 patients (83.8%). The overall survival was 11.93 months in median (ranged, 11.4-17.4 months), and the median progression free survival was 10.5 months. One-year progression-free survival and overall survival were 41% and 46%, respectively. Grade II or greater long-term complications were observed in 6 (13.3%) patients. On follow-up, 8 (17.3%) patients had carotid blow-out syndrome, and 7 (15.2%) patients died of bleeding from carotid arteries. We discovered that this fatal syndrome occurred only in patients with tumor surrounding carotid arteries and carotid arteries receiving all prescribed dose.

CONCLUSIONS

Stereotactic body radiotherapy is an appealing treatment option for patients with recurrent head-and-neck cancer previously treated with radiation to high doses. Good local control with considerable 1-year survival is achieved with a relatively high rate of morbidity and related mortality.

Current management strategy of nasopharyngeal carcinoma

Nasopharyngeal carcinoma is an unique head and neck cancer. It is common among the southern Chinese and is closely associated with the Epstein Barr virus (EBV). To diagnose the disease in its early stage is infrequent as the symptoms are usually trivial and patients only present in late stages. Testing the blood for elevated EBV DNA has now become a screening test for the high risk group of patients, aiming to diagnose the disease in its early stages. Imaging studies, positron emission tomography scans in addition to clinical examination provide information on the extent of the disease. The confirmation of the disease still depends on endoscopic examination and biopsy. Radiotherapy with or without chemotherapy has been the primary treatment modality. The application of intensity modulated radiotherapy and the use of concomitant chemoradiation have improved the control of nasopharyngeal carcinoma together with the reduction of long term side effects. The early detection of residual or recurrence tumor in the neck or at the primary site has allowed delivery of salvage treatment. The choice of the optimal surgical salvage, either for neck disease or primary tumor depends on the extent of the residual or recurrent disease. The outcome of these patients have improved with the application of the appropriate surgical salvage.

Fractionated stereotactic radiosurgery for reirradiation of head-and-neck cancer

PURPOSE

Stereotactic radiosurgery (SRS) is an appealing treatment option after previous radiotherapy because of its precision, conformality, and reduced treatment duration. We report our experience with reirradiation using fractionated SRS for head-and-neck cancer.

METHODS AND MATERIALS

From 2002 to 2008, 65 patients received SRS to the oropharynx (n = 13), hypopharynx (n = 8), nasopharynx (n = 7), paranasal sinus (n = 7), neck (n = 7), and other sites (n = 23). Thirty-eight patients were treated definitively and 27 patients with metastatic disease and/or untreated local disease were treated palliatively. Nine patients underwent complete macroscopic resection before SRS. Thirty-three patients received concurrent chemoradiation. The median initial radiation dose was 67 Gy, and the median reirradiation SRS dose was 30 Gy (21-35 Gy) in 2-5 fractions.

RESULTS

Median follow-up for surviving patients was 16 months. Fifty-six patients were evaluable for response: 30 (54%) had complete, 15 (27%) had partial, and 11 (20%) had no response. Median overall survival (OS) for all patients was 12 months. For definitively treated patients, the 2-year OS and locoregional control (LRC) rates were 41% and 30%, respectively. Multivariate analysis demonstrated that higher total dose, surgical resection, and nasopharynx site were significantly associated with improved LRC; surgical resection and nonsquamous histology were associated with improved OS. Seven patients (11%) experienced severe reirradiation-related toxicity, including one treatment-attributed death.

CONCLUSION

SRS reirradiation for head-and-neck cancer is feasible. This study demonstrates encouraging response rates with acceptable toxicity. Fractionated SRS reirradiation with concurrent chemotherapy in select patients warrants further study.

Emerging applications of stereotactic radiotherapy in head and neck cancer

Advances in the management of locally advanced head and neck cancer (HNC) have been focused on treatment intensification, including concomitant chemoradiotherapy, biological agents, and combining surgery with chemoradiotherapy. Despite these improvements, locoregional recurrence still constitutes the main pattern of treatment failure. As improvements in radiotherapy delivery and image-guided therapy have come to fruition, the principles of stereotactic radiosurgery are now being applied to extracranial sites, leading to stereotactic body radiotherapy. This article focuses on the emerging evidence for the use of stereotactic body radiotherapy for treatment of HNC as a boost after conventional external-beam radiotherapy, and also as reirradiation in recurrent or second primary HNC.

Fractionated stereotactic radiotherapy in residual or recurrent nasopharyngeal carcinoma

The aim of this study was to evaluate results of fractionated stereotactic radiotherapy (FSRT) in patients with residual or recurrent nasopharyngeal carcinoma (NPC) in terms of local progression-free (LPFS) and overall survival (OS) rate and complications after treatment. There were 32 residual or recurrent NPC patients treated with FSRT using linac-based radiosurgery system. Time from the previous radiotherapy to FSRT was 1-165 months (median, 15). Two patients were treated for the second and one for the third recurrence. Thirteen patients (40.6%) also received chemotherapy with FSRT. Tumor volume ranged from 6.2-215 cc (median, 44.4). Average FSRT dose was 17-59.4 Gy (median, 34.6) in 4-25 fractions (median,6) in 1-5.5 weeks (median, 3). Median follow-up time was 25.5(3-67) months. LPFS rate at 1 and 3 years after FSRT was 67.8% and 37.9%. OS rate at 1 and 3 years was 89.7% and 71.2%. If all patients who had tumor progression with no further follow-up were assumed dead, the OS rate at 1 and 3 years would be 75.0% and 37.9%. Univariate analysis showed better local tumor control in patients with tumor volume </=100 cc (p=0.04) or in those without chemotherapy (p=0.0005). Only chemotherapy retained significance in multivariate analysis (hazard ratio 5.47, 95%CI 1.86-16.04). Eight patients (25%) had complications after FSRT, all grade 2-3 except 1 grade 4 with complete recovery.

Comparison of single versus fractionated dose of stereotactic radiotherapy for salvaging local failures of nasopharyngeal carcinoma: a matched-cohort analysis

BACKGROUND

Local failure is an important cause of morbidity and mortality in nasopharyngeal carcinoma (NPC). Although surgery or brachytherapy may be feasible in selected cases, most patients with local failure require external beam re-irradiation. Stereotactic radiation using single or multiple fractions have been employed in re-irradiation of NPC, but the optimal fractionation scheme and dose are not clear.

METHODS

Records of 125 NPC patients who received salvage stereotactic radiation were reviewed. A matched-pair design was used to select patients with similar prognostic factors who received stereotactic re-irradiation using single fraction (SRS) or multiple fractions (SRM). Eighty-six patients were selected with equal number in SRS and SRM groups. All patients were individually matched for failure type (persistent or recurrent), rT stage (rT1-2 or rT3-4), and tumor volume (< or = 5 cc, >5-10 cc, or >10 cc). Median dose was 12.5 Gy in single fraction by SRS, and 34 Gy in 2-6 fractions by SRM.

RESULTS

Local control rate was better in SRM group although overall survival rates were similar. One- and 3-year local failure-free rates were 70% and 51% in SRS group compared with 91% and 83% in SRM group (p = 0.003). One- and 3-year overall survival rates were 98% and 66% in SRS group compared with 78% and 61% in SRM group (p = 0.31). The differences in local control were mainly observed in recurrent or rT2-4 disease. Incidence of severe late complications was 33% in SRS group vs. 21% in SRM group, including brain necrosis (16% vs. 12%) and hemorrhage (5% vs. 2%).

CONCLUSION

Our study showed that SRM was superior to SRS in salvaging local failures of NPC, especially in the treatment of recurrent and rT2-4 disease. In patient with local failure of NPC suitable for stereotactic re-irradiation, use of fractionated treatment is preferred.

Fractionated stereotactic radiotherapy as reirradiation for locally recurrent head and neck cancer

PURPOSE

We report early preliminary experience with CyberKnife radiosurgery (RS) as salvage treatment for locally recurrent head and neck cancer (HNC).

METHODS AND MATERIALS

Between March 2004 and August 2006, 36 patients (44 sites) were treated with CyberKnife RS as reirradiation for locally recurrent HNC. Treatment sites were as follows: nasopharynx (8), maxillary sinus (8), neck lymph nodes (8), skull base (7), nasal cavity (4), retropharyngeal lymph nodes (3), orbit (2), and others (4). Total doses administered were 18-40 Gy (median, 30 Gy) in 3 to 5 fractions to the 65%-85% isodose line for 3-5 consecutive days. Previous external radiation dose ranged from 39.6 to 134.4 Gy (median, 70.2 Gy). Gross tumor volume ranged from 0.2 to 114.9 cm(3) (median, 22.6 cm(3)). Median follow-up was 17.3 months.

RESULTS

Thirty-five of 44 sites were evaluated for response. Fifteen (42.9%) sites achieved complete response, 13 sites (37.1%) achieved a partial response, 3 (8.6%) sites maintained stable disease, and 4 sites (11.4%) showed tumor progression. Grade III acute complications were noted in 13 patients. Late complications were observed in three patients (1 bone necrosis, 2 soft tissue necrosis) during follow-up.

CONCLUSION

These preliminary results suggest that fractionated stereotactic radiosurgery is an effective treatment modality as a salvage treatment with good short-term local control. The early overall response rate is encouraging. However, more experience and a longer follow-up are necessary to determine the role of fractionated stereotactic radiosurgery as a salvage treatment of locally recurrent HNC and to define long-term complications.

Chemoradiotherapy for locally recurrent nasopharyngeal carcinoma: treatment outcome and prognostic factors

OBJECTIVE

To evaluate the treatment outcome of patients with locally recurrent nasopharyngeal carcinoma (NPC) treated with re-irradiation and chemotherapy.

METHODS

Between 1991 and 2004, 36 patients with locally recurrent NPC received re-irradiation and chemotherapy. The median re-irradiation dose was 37.9 Gy; the median total dose of prior irradiation and re-irradiation was 104.4 Gy. The outcome is studied retrospectively and also evaluated the prognostic factors and toxicities.

RESULTS

With a median follow-up of 40 months, 3-year overall survival (OS) was 58.3% and 3-year progression-free survival (PFS) was 25.0%. Patients aged <50 and of early stage at recurrence had a significantly better OS and PFS. Over Grade 3 of late toxicities were seen in patients received a total dose of >110 Gy.

CONCLUSIONS

Age and stage at recurrence were identified as prognostic factors for OS and PFS. Patients received external beam radiation therapy at a total dose of more than 110 Gy should be careful for severe late toxicities, and it is thought to be the optimal dose for recurrent tumor.

Outcome of Fractionated Stereotactic Radiotherapy for 90 Patients With Locally Persistent and Recurrent Nasopharyngeal Carcinoma

PURPOSE

Local recurrence remains one of the major causes of failure in nasopharyngeal carcinoma (NPC). Stereotactic radiosurgery and fractionated stereotactic radiation therapy (FSRT) have recently evolved as a salvage option of NPC. This study was conducted to review the treatment outcome after FSRT for NPC.

METHODS AND MATERIALS

Between September 1999 and December 2005, 90 patients with persistent (Group 1: n = 34, relapse within 6 months of RT) or recurrent (Group 2: n = 56, relapse beyond 6 months) NPC received FSRT using multiple noncoplanar arcs of 8-MV photon to the target. Median FSRT dose was 18 Gy in three fractions (Group 1) or 48 Gy in six fractions (Group 2). Median follow-up was 20.3 months.

RESULTS

Complete response rate after FSRT was 66% for Group 1 and 63% for Group 2. One-, 2-, and 3-year disease-specific survival (DSS) and progression-free survival (PFS) rates for all patients were 82.6%, 74.8%, 57.5%, and 72.9%, 60.4%, 54.5%, respectively. Three-year local failure-free survival, DSS, and PFS rates were 89.4%, 80.7%, and 72.3% for Group 1, and 75.1%, 45.9%, and 42.9% for Group 2, respectively. Multivariate analysis showed that recurrent disease and large tumor volume were independent factors that predicted poorer DSS and PFS. Seventeen patients developed late complications, including 2 with fatal hemorrhage.

CONCLUSIONS

Our results indicate that FSRT is effective for patients with persistent and recurrent NPC. Compared with reported results of radiosurgery, FSRT provides satisfactory tumor control and survival with a lower risk of complications and it may be a better treatment for local failures of NPC.

Stereotactic Radiosurgery Versus Gold Grain Implantation in Salvaging Local Failures of Nasopharyngeal Carcinoma

BACKGROUND

Limited local failure of nasopharyngeal carcinoma (NPC) can often be salvaged by reirradiation using different techniques. Both gold grain implantation (GGI) and stereotactic radiosurgery (SRS) have been used as salvage treatment of NPC but the relative efficacy of these two treatments is not known.

METHODS AND MATERIALS

A total of 74 patients with local NPC failure were included in this retrospective analysis. Of these patients, 37 underwent SRS (median dose, 12.5 Gy) and 37 split-palatal GGI at a dose of 60 Gy. The two groups were individually matched for prognostic factors, except for tumor volume. The median follow-up was 42 months.

RESULTS

Local control was better in the GGI group. The 3-year local failure-free rate was 77.9% for the GGI group compared with 68.3% for the SRS group. However, the difference was not statistically significant (p = 0.098). In the subgroup with a tumor volume of <or=5 cm3, the 3-year local failure-free rates were similar, with 79.3% in the GGI group and 72.4% in the SRS group. Neuroendocrine complications were more common in the SRS group, and headache and fistula were more common in the GGI group.

CONCLUSION

Stereotactic radiosurgery and GGI are both effective salvage treatment for NPC. In patients with limited local failure, both yielded comparable high tumor control rates.

Experience in fractionated stereotactic body radiation therapy boost for newly diagnosed nasopharyngeal carcinoma

PURPOSE

Radiotherapy is the most effective treatment for nasopharyngeal carcinoma (NPC). The aim of this study is to evaluate the efficacy and toxicity of fractionated stereotactic body radiation therapy (SBRT) boost for NPC.

METHODS AND MATERIALS

Sixty-four patients with newly diagnosed, nonmetastatic NPC were treated with conventional radiotherapy 64.8-68.4 Gy followed by fractionated SBRT boost 12-15 Gy between January 2002 and July 2004. Most patients (72%) presented with Stage III-IV disease. Fifty-two patients also received cisplatin-based concurrent (38) or neoadjuvant (14) chemotherapy. The major endpoints were local control, overall survival, and complications.

RESULTS

All patients finished the planned dose of radiotherapy. After a median follow-up of 31 months (range, 22-54), 15 patients developed tumor recurrences--3 in the nasopharynx, 4 in the neck, 5 in distant sites, 1 in both nasopharynx and neck, 2 in the neck and a distant site. The 3-year actuarial rate of local control was 93.1%, regional control 91.4%, freedom from distant metastasis 90.3%, and overall survival 84.9%, respectively. There were no Grade 4 acute or chronic radiation-related complications.

CONCLUSIONS

Fractionated SBRT boost for NPC is technically feasible and provides good local control without any severe complications.

Predictive factors of tumor control and survival after radiosurgery for local failures of nasopharyngeal carcinoma

BACKGROUND

Stereotactic radiosurgery has been employed as a salvage treatment of local failures of nasopharyngeal carcinoma (NPC). To identify patients that would benefit from radiosurgery, we reviewed our data with emphasis on factors that predicted treatment outcome.

PATIENTS AND METHODS

A total of 48 patients with local failures of NPC were treated by stereotactic radiosurgery between March 1996 and February 2005. Radiosurgery was administered using a modified linear accelerator with single or multiple isocenters to deliver a median dose of 12.5 Gy to the target periphery. Median follow-up was 54 months.

RESULTS

Five-year local failure-free probability after radiosurgery was 47.2% and 5-year overall survival rate was 46.9%. Neuroendocrine complications occurred in 27% of patients but there were no treatment-related deaths. Time interval from primary radiotherapy, retreatment T stage, prior local failures and tumor volume were significant predictive factors of local control and/or survival whereas age was of marginal significance in predicting survival. A radiosurgery prognostic scoring system was designed based on these predictive factors. Five-year local failure-free probabilities in patients with good, intermediate and poor prognostic scores were 100%, 42.5%, and 9.6%. The corresponding five-year overall survival rates were 100%, 51.1%, and 0%.

CONCLUSION

Important factors that predicted tumor control and survival after radiosurgery were identified. Patients with good prognostic score should be treated by radiosurgery in view of the excellent results. Patients with intermediate prognostic score may also be treated by radiosurgery but those with poor prognostic score should receive other salvage treatments.

Dose Escalation of Three-dimensional Conformal Radiotherapy for Locally Recurrent Nasopharyngeal Carcinoma: A Prospective Randomised Study

AIMS

To investigate prospectively the feasibility and efficacy of dose escalation using three-dimensional conformal radiotherapy (3D-CRT) boost technique for locally recurrent nasopharyngeal carcinoma (NPC) in a randomised study.

MATERIALS AND METHODS

Thirty-six patients with locally recurrent NPC (>6 months interval from previous radical radiotherapy, no cervical lymph-node involvement and no distant metastasis) were enrolled. Treatment included conventional external-beam radiotherapy to 54 Gy, followed by a 3D-CRT boost to the gross tumour region. Patients were randomised to three boost dose levels: 16 Gy, 20 Gy and 24 Gy for groups I, II and III, respectively, with 12 patients in each group. All boost doses were delivered in 4-Gy fractions and 3 fractions per week. Median follow-up was 27 months (range 14-44 months).

RESULTS

Three-year, local-recurrence-free survival rate was significantly higher (72%) for the high-dose group III than for groups I and II (37% and 28%, respectively, P = 0.047). No significant difference was found in the 3-year overall survival rate among the three groups (72%, 59% and 82% for groups I, II and III, respectively). Three-year distant metastases rates were 17%, 0% and 18%, respectively. Skull-base invasion (P = 0.017) and pathology (P = 0.0006) correlated with overall survival. Treatment was well tolerated and no significant difference was observed among the three groups in acute and late toxicities (grade III toxicity is minimal: 17%, 17%, 0% of oral mucositis and 25%, 17%, 17% of nasopharyngeal mucositis in groups I, II, III, respectively, and 8% leukocytopenia only in group II; no grade IV toxicity occurred in any of the groups except for a fatal bleeding in group III).

CONCLUSIONS

Re-irradiation with high-dose 3D-CRT boost technique results in high local control rate and acceptable toxicity in patients with recurrent NPC. Dose escalation to the boost volume to 78 Gy (54 Gy + 24 Gy boost) results in improved recurrence-free survival compared with lower doses.

Stereotactic radiosurgery plus intracavitary irradiation in the salvage of nasopharyngeal carcinoma

BACKGROUND

We sought to assess the efficacy and complications of linear accelerator-based stereotactic radiosurgery (SRS) plus intracavitary irradiation (ICI) as salvage treatment for local persistent and recurrent nasopharyngeal carcinoma (NPC) after primary external beam radiotherapy (EBRT).

METHODS

Between July 1995 and June 2003, 36 patients (25 men and 11 women; median age, 48 years; range, 22-66 years) with local recurrent NPC confined to the nasopharynx (rT1) or limited extension to the parapharynx and nasal cavity (rT2) were treated with SRS plus ICI. Nineteen patients had rT1 and 17 had rT2 disease. Five patients (13.8%) had persistent disease, and 31 patients (86.1%) had recurrent disease using the definition of >4 months after the primary treatment as recurrent relapse. The median target volume was 36.3 cm(3) (range, 10.3-56.2 cm(3)) for the SRS treatment. All patients received 18 Gy to the 90% isodose line followed by two separate ICI 6 Gy each to 0.5 cm from the surface of the endotracheal balloon. Patients were assessed with serial nasoendoscopy and repeat scans (CT or MRI) at 3 months, and suspicious lesions were rebiopsied.

RESULTS

The median follow-up for surviving patients was 4.24 years (range, 0.73-8.81 years). Twenty-two of 36 (61%) patients were alive at the time of reporting. Twenty patients were free of disease, and two patients were alive with disease. Fourteen of 36 (39%) patients had died (five of distant metastases, six of local recurrences, two of both local disease and distant metastases, and one of unrelated cause). Patients with rT1 disease (median survival not reached) fared better that patients with rT2 disease (median survival, 4.6 years). The actuarial 5-year disease-free survival and overall survival (OS) were 57% (rT1 78%, rT2 39%) and 62% (rT1 80%, rT2 48%), respectively. The actuarial 5-year local control was 65% (rT1 82%, rT2 49%). The treatment was well tolerated with no significant acute complications. Sixteen patients (44%) had late complications, including palatal fibrosis in six patients (17%), trismus in seven patients (20%), cranial nerve palsies in seven patients (20%), temporal lobe necrosis in two patients (8%), and osteoradionecrosis of the skull base in six patients (17%). The complication-free survival rates at 2 and 5 years were 70% (95% confidence interval [CI], 56% to 87%) and 31% (95% CI, 17% to 56%), respectively. No patient died as a direct result of the late complication.

CONCLUSION

Although our series is small, the combination of SRS and ICI seems to be an effective salvage treatment for early-stage recurrent NPC. The OS of 62% at 5 years is very encouraging and favorable compared with reported reirradiation or surgical series. The late complications are considerable but expected because of the high doses of radiation previously delivered. The ideal dose fractionation for SRS and ICI is unknown and remains to be defined.

Reirradiation of nasopharyngeal carcinoma withintensity-modulated radiotherapy

BACKGROUND AND PURPOSE

To evaluate the treatment outcome in patients with locally recurrent nasopharyngeal carcinoma (NPC) treated with intensity-modulated radiation therapy (IMRT).

MATERIALS AND METHODS

Between October 2001 and May 2004, 31 patients with locally recurrent NPC received re-irradiation using IMRT. The rT classification distribution was 3 for rT1, 5 for rT2, 9 for rT3, and 14 for r T4. Median time from first course of radiotherapy to re-irradiation was 51 months. IMRT was performed using step-and-shoot method with nine 4-6 MV photon fields and median prescribed dose was 54 Gy (range: 50-60 Gy). Additional treatments included cisplatin-based induction chemotherapy in 68% and radiosurgery boost with a single dose which ranged from 8.5 to 12.5 Gy in 32%. Median follow-up time was 11 months.

RESULTS

After re irradiation, 58% of patients had complete regression of primary tumor. One-year loco-regional progression-free, distant metastasis-free and overall survival rates were 56, 90, and 63%, respectively. Significantly better 1-year local progression-free rate was observed in rT1-3 than r T4 tumor (100 vs. 35%). Grade 3 late toxicities, mostly ototoxicity/cranial neuropathy, occurred in six patients (19%). One-year actuarial rates of late toxicities were 70% for all grades and 25% for Grade 3.

CONCLUSION

Our preliminary results showed that good control of rT1-3 NPC can be achieved using IMRT with a dose between 50 and 60 Gy, whereas the outcome for r T4 tumor remained poor. Late toxicities were common but incidence of severe toxicities was relatively low.

Nasopharyngeal carcinoma

Incidence of nasopharyngeal carcinoma has remained high in endemic regions. Diagnosing the disease in the early stages requires a high index of clinical acumen and, although most cross-sectional imaging investigations show the tumour with precision, confirmation is dependent on histology. Epstein-Barr virus (EBV)-encoded RNA signal is present in all nasopharyngeal carcinoma cells, and early diagnosis of the disease is possible through the detection of raised antibodies against EBV. The quantity of EBV DNA detected in blood indicates the stage and prognosis of the disease. Radiotherapy with concomitant chemotherapy has increased survival, and improved techniques (such as intensity-modulated radiotherapy), early detection of recurrence, and application of appropriate surgical salvage procedures have contributed to improved therapeutic results. Screening of high-risk individuals in endemic regions together with developments in gene therapy and immunotherapy might further improve outcome.

Radiotherapy for nasopharyngeal carcinoma--transition from two-dimensional to three-dimensional methods

This review describes the clinical background that underlies the transition from two-dimensional to three-dimensional (3D) planning techniques in the treatment of nasopharyngeal cancer (NPC). A systematic search of the Medline was performed using 'nasopharyngeal carcinoma', 'radiotherapy', '3-dimensional conformal radiotherapy', 'stereotactic radiosurgery/radiotherapy' and 'intensity-modulated radiotherapy' as keywords. Citing evidence from the published literature and their own institutional experience, the authors critically examined the positive impact of 3D methods--with emphasis on intensity-modulated radiotherapy (IMRT)--on target coverage and geometric accuracy, sparing of normal organs, and dosimetric homogeneity. Potential problems related to the widespread practice of IMRT such as quality assurance, utilization of medical resources and the risk of developing radiation-induced secondary cancers were highlighted. Application of IMRT within the context of altered fractionation, dose escalation and concurrent chemotherapy were discussed. The article concluded with a suggested treatment approach and research direction for different stages of NPC.

Linear accelerator-based stereotactic radiosurgery for limited, locally persistent, and recurrent nasopharyngeal carcinoma: efficacy and complications

PURPOSE

To evaluate the efficacy and complication of linear accelerator-based stereotactic radiosurgery (SRS) when used as salvage treatment for early-stage persistent and recurrent nasopharyngeal carcinoma (NPC) after primary radiotherapy (RT).

MATERIALS AND METHODS

Between March 1998 and June 2001, 18 patients (15 men and 3 women; median age 46 years, range 32-84) with locally persistent or recurrent NPC confined to the nasopharynx (rT1) or with limited extension to the nasal fossa or parapharyngeal space (rT2) were treated by SRS. Thirteen patients had rT1 disease and 5 had rT2 disease. Most patients had disease not amenable to surgery or brachytherapy. All patients had undergone previous radical RT. Persistent disease was defined as tumor relapse within 4 months of completion of primary RT, and recurrence as tumor relapse beyond 4 months. Seven patients were treated for persistent disease, eight for a first recurrence, and three for a second recurrence. SRS was performed using multiple noncoplanar arcs of photons delivered to the target volume, which was defined by axial CT at a 3 mm thickness, supplemented by MRI in selected patients (67%). The median target volume was 5.3 cm(3) (range 2.2-16.9). The median SRS dose was 12.5 Gy (range 11-14) delivered to the 80% isodose line. All patients underwent serial nasopharyngoscopy and imaging after SRS. The median follow-up was 26 months (range 11-48).

RESULTS

After SRS, 16 (89%) of 18 patients had complete regression of tumor as assessed by nasopharyngoscopy and biopsy. Four patients with an initial complete response to SRS subsequently developed local relapse again, with one recurrence developing outside the target volume 8 months after SRS and three within the target volume at 6-26 months after SRS. Two patients with local disease controlled by SRS developed relapse in other sites (neck node and liver metastases). The actuarial 2-year local control rate after SRS was 72%. Patients treated for persistent disease had a better local control rate (100%; 7 of 7) than those treated for recurrent disease (46%; 5 of 11). Patients with rT1 disease also had a better outcome after SRS compared with those with rT2 disease, with a control rate of 77% (10 of 13) for rT1 disease and 40% (2 of 5) for rT2 disease. Treatments were well tolerated, with no acute side effects. One patient had radiologic evidence of temporal lobe necrosis, although the right temporal lobe had already received a high dose during prior RT. That patient also developed additional local recurrence and liver metastases and died. The actuarial 2-year survival rate was 86%.

CONCLUSIONS

Our preliminary results indicate that SRS is an effective treatment modality for persistent and recurrent early-stage NPC, with early control rates comparable to other salvage treatments such as brachytherapy and nasopharyngectomy. A modest SRS dose at 12.5 Gy also appears to be effective and is associated with minimal morbidities. More clinical experience and longer follow-up are needed to validate our results and to address fully the role of SRS in salvaging local failures of NPC.

Underdosage of the upper-airway mucosa for small fields as used in intensity-modulated radiation therapy: a comparison between radiochromic film measurements, Monte Carlo simulations, and collapsed cone convolution calculations

Head-and-neck tumors are often situated at an air-tissue interface what may result in an underdosage of part of the tumor in radiotherapy treatments using megavoltage photons, especially for small fields. In addition to effects of transient electronic disequilibrium, for these small fields, an increased lateral electron range in air will result in an important extra reduction of the central axis dose beyond the cavity. Therefore dose calculation algorithms need to model electron transport accurately. We simulated the trachea by a 2 cm diameter cylindrical air cavity with the rim situated 2 cm beneath the phantom surface. A 6 MV photon beam from an Elekta SLiplus linear accelerator, equipped with the standard multileaf collimator (MLC), was assessed. A 10 x 2 cm2 and a 10 x 1 cm2 field, both widthwise collimated by the MLC, were applied with their long side parallel to the cylinder axis. Central axis dose rebuild-up was studied. Radiochromic film measurements were performed in an in-house manufactured polystyrene phantom with the films oriented either along or perpendicular to the beam axis. Monte Carlo simulations were performed with BEAM and EGSnrc. Calculations were also performed using the pencil beam (PB) algorithm and the collapsed cone convolution (CCC) algorithm of Helax-TMS (MDS Nordion, Kanata, Cahada) version 6.0.2 and using the CCC algorithm of Pinnacle (ADAC Laboratories, Milpitas, CA, USA) version 4.2. A very good agreement between the film measurements and the Monte Carlo simulations was found. The CCC algorithms were not able to predict the interface dose accurately when lateral electronic disequilibrium occurs, but were shown to be a considerable improvement compared to the PB algorithm. The CCC algorithms overestimate the dose in the rebuild-up region. The interface dose was overestimated by a maximum of 31% or 54%, depending on the implementation of the CCC algorithm. At a depth of 1 mm, the maximum dose overestimation was 14% or 24%.

Fractionated stereotactic radiotherapy: a short review

Currently, optimally precise delivery of intracranial radiotherapy is possible with stereotactic radiosurgery and fractionated stereotactic radiotherapy. We present in this article a review of the underlying basic physical and radiobiological principles of fractionated stereotactic radiotherapy and review the clinical experience for ateriovenus malformations, pituitary adenomas, mengiomas, vestibular schwanomas, low grade astrocytomas, malignant gliomas, and brain metastases.