Patient Outcomes after Reirradiation of Small Skull Base Tumors using Stereotactic Body Radiotherapy, Intensity Modulated Radiotherapy, or Proton Therapy

Reirradiation for Locally Recurrent Head and Neck Cancer: State-of-the-Art and Future Directions

Reirradiation of the head and neck presents one of the most complex and challenging scenarios faced by (for) clinicians due to the narrow therapeutic window. Its use is increasing in clinical practice, often guided by empirical and pragmatic approaches due to the limited availability of high-level evidence from randomized clinical trials. Successful reirradiation requires a precise balance between tumor control probability (TCP) and normal tissue complication probability (NTCP). Advances in radiation technologies, including intensity-modulated radiation therapy (IMRT), proton beam therapy (PBT), and stereotactic body radiation therapy (SBRT), have enabled more precise high-dose delivery, potentially improving dose distribution and reducing severe toxicity. This review explores current state-of-the-art approaches to reirradiating recurrent head and neck cancer, focusing on modern reirradiation techniques and critically assessing the literature on their clinical application, integration with systemic therapy, and future directions. It also addresses key practical challenges related to patient selection and toxicity/risk management, offering a comprehensive overview of the evolving treatment landscape and highlighting some of the most complex issues clinicians face in reirradiation.

Advanced External Beam Stereotactic Radiotherapy for Skull Base Reirradiation

BACKGROUND/OBJECTIVES

Stereotactic body radiation therapy (SBRT) for skull base reirradiation is particularly challenging, as patients have already received substantial radiation doses to the region, and nearby normal organs may have approached their tolerance limit from prior treatments. In this study, we reviewed the characteristics and capabilities of four advanced external beam radiation delivery systems and four modern treatment planning systems and evaluated the treatment plan quality of each technique using skull base reirradiation patient cases.

METHODS

SBRT plans were generated for sixteen skull base reirradiation patients using four modalities: the GK plan for the Elekta Leksell Gamma Knife Perfexion/ICON, the CyberKnife (CK) plan for the Accuray CyberKnife, the intensity-modulated proton therapy (IMPT) plan for the Hitachi ProBeat-FR proton therapy machine, and the volumetric-modulated arc therapy (VMAT) plan for the Varian TrueBeam STx. These plans were evaluated and compared using two novel gradient indices in addition to traditional dosimetry metrics for targets and organs at risk (OARs). The steepest border gradient quantified the percent prescription dose fall-off per millimeter at the boundary between the target and adjacent critical structures. This gradient index highlighted the system's ability to spare nearby critical OARs. The volume gradient assessed the extent of dose spread outside the target toward the patient's body.

RESULTS

All plans achieved comparable target coverage and conformity, while IMPT and VMAT demonstrated significantly better uniformity. The GK plans exhibited the highest border gradient, up to 20.9%/mm, followed by small-spot-size IMPT plans and CK plans. Additionally, IMPT plans showed the benefit of reduced dose spread in low-dose regions and the lowest maximum and mean doses to the brainstem and carotid artery.

CONCLUSIONS

The advanced external beam radiotherapy modalities evaluated in this study are well-suited for SBRT in skull base reirradiation, which demands precise targeting of tumors with highly conformal doses and steep dose gradients to protect nearby normal structures.

Proton Beam Therapy in the Reirradiation Setting of Brain and Base of Skull Tumour Recurrences

The therapeutic management of local tumour recurrence after a first course of radical radiotherapy is always complex. Surgery and reirradiation carry increased morbidity due to radiation-induced tissue changes. Proton beam therapy (PBT) might be advantageous in the reirradiation setting, thanks to its distinct physical characteristics. Here we systematically reviewed the use of PBT in the management of recurrent central nervous system (CNS) and base of skull (BoS) tumours, as published in the literature. The research question was framed following the Population, Intervention, Comparison and Outcomes (PICO) criteria: the population of the study was cancer patients with local disease recurrence in the CNS or BoS; the intervention was radiation treatment with PBT; the outcomes of the study focused on the clinical outcomes of PBT in the reirradiation setting of local tumour recurrences of the CNS or BoS. The identification stage resulted in 222 records in Embase and 79 in Medline as of March 2023. Sixty-eight duplicates were excluded at this stage and 56 were excluded after screening as not relevant, not in English or not full-text articles. Twelve full-text articles were included in the review and are presented according to the site of disease, namely BoS, brain or both brain and BoS. This review showed that reirradiation of brain/BoS tumour recurrences with PBT can provide good local control with acceptable toxicity rates. However, reirradiation of tumour recurrences in the CNS or BoS setting needs to consider several factors that can increase the risk of toxicities. Therefore, patient selection is crucial. Randomised evidence is needed to select the best radiation modality in this group of patients.

Harnessing progress in radiotherapy for global cancer control

The pace of technological innovation over the past three decades has transformed the field of radiotherapy into one of the most technologically intense disciplines in medicine. However, the global barriers to access this highly effective treatment are complex and extend beyond technological limitations. Here, we review the technological advancement and current status of radiotherapy and discuss the efforts of the global radiation oncology community to formulate a more integrative 'diagonal approach' in which the agendas of science-driven advances in individual outcomes and the sociotechnological task of global cancer control can be aligned to bring the benefit of this proven therapy to patients with cancer everywhere.

A Prospective Study of Conventionally Fractionated Dose Constraints for Reirradiation of Primary Brain Tumors in Adults

PURPOSE

Dose constraints for reirradiation of recurrent primary brain tumors are not well-established. This study was conducted to prospectively evaluate composite dose constraints for conventionally fractionated brain reirradiation.

METHODS AND MATERIALS

A single-institution, prospective study of adults with previously irradiated, recurrent brain tumors was performed. For 95% of patients, electronic dosimetry records from the first course of radiation (RT1) were obtained and deformed onto the simulation computed tomography for the second course of radiation (RT2). Conventionally fractionated treatment plans for RT2 were developed that met protocol-assigned dose constraints for RT2 alone and the composite dose of RT1 + RT2. Prospective composite dose constraints were based on histology, interval since RT1, and concurrent bevacizumab. Patients were followed with magnetic resonance imaging including spectroscopy and perfusion studies. Primary endpoint was the rate of symptomatic brain necrosis at 6 months after RT2.

RESULTS

Patients were enrolled from March 2017 to May 2018; 20 were evaluable. Eighteen had glioma, 1 had atypical choroid plexus papilloma, and 1 had hemangiopericytoma. Nineteen patients were treated with volumetric modulated arc therapy, and one was treated with protons. Median RT1 dose was 57 Gy (range, 50-60 Gy). Median RT1-RT2 interval was 49 months (range, 9-141 months). Median RT2 dose was 42.4 Gy (range, 36-60 Gy). Median planning target volume was 186 cc (range, 8-468 cc). Nineteen of 20 patients (95%) were free of grade 3+ central nervous system necrosis. One patient had grade 3+ necrosis 2 months after RT2; the patient recovered fully and lived another 18 months until dying of disease progression. Median overall survival from RT2 start for all patients was 13.3 months (95% credible interval, 6.3-20.7); for patients with glioblastoma, 11.5 months (95% credible interval, 6.1-20.1).

CONCLUSIONS

Brain reirradiation can be safely performed with conventionally fractionated regimens tailored to previous dose distributions. The prospective composite dose constraints described here are a starting point for future studies of conventionally fractionated reirradiation.

Impact of salvage surgery for recurrent sinonasal cancers with skull base and intracranial involvement

OBJECTIVE

Patients with recurrent sinonasal cancers (RSNCs) often present with extensive involvement of the skull base and exhibit high rates of subsequent recurrence and death after therapy. The impact of salvage surgery and margin status on progression-free survival (PFS) and overall survival (OS) has yet to be demonstrated. The goal of this study was to determine whether skull base resection with negative margins has an impact on outcomes in the recurrent setting.

METHODS

A retrospective chart review of 47 patients who underwent surgery for RSNC with skull base invasion between November 1993 and June 2020 was conducted. The following variables were extracted from the clinical records: patient demographic characteristics (age and sex), tumor pathology, dural and orbital invasion, and prior radiation exposure and induction chemotherapy. Metastatic disease status, surgical approach, margin status, and history of postoperative chemotherapy and/or postoperative radiation therapy were noted. The primary and secondary outcomes were PFS and OS, respectively.

RESULTS

The cohort included 30 males (63.8%) and 17 females (36.2%), with a mean ± SD age of 54.8 ± 14.4 years. Thirty-five (74.5%) patients showed disease progression, and 29 (61.7%) patients died during the study period. The mean ± SD patient follow-up period was 61.8 ± 64.4 months. Dural invasion was associated with increased risk of death (HR 2.62, 95% CI 1.13-6.08). High-risk histopathology (HR 3.14, 95% CI 1.10-8.95) and induction chemotherapy (HR 2.32, 95% CI 1.07-5.06) were associated with increased odds of disease progression. When compared to patients with positive margins or gross-total resection with unknown margin status, those with negative margins had decreased odds of disease progression (HR 0.30, 95% CI 0.14-0.63) and death (HR 0.38, 95% CI 0.17-0.85).

CONCLUSIONS

RSNCs show high rates of subsequent disease progression and mortality. This study demonstrated that negative margins may be associated with improved PFS and OS in carefully selected patients who have undergone salvage surgery for RSNC.

Role of proton therapy in reirradiation and in the treatment of sarcomas

Reirradiation and irradiation of sarcoma is often difficult due to the frequent need for a high dose of radiation in order to increase tumor control. This can result in a greater risk of toxicity which can be mitigated with the use of proton therapy. The present review aims to summarize the role of proton therapy in these 2 clinical contexts.

A Systematic Review on Re-irradiation with Charged Particle Beam Therapy in the Management of Locally Recurrent Skull Base and Head and Neck Tumors

Purpose

To evaluate the clinical outcomes and treatment related toxicities of charged particle-based re-irradiation (reRT; protons and carbon ions) for the definitive management of recurrent or second primary skull base and head and neck tumors.

Materials and Methods

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were applied for the conduct of this systematic review. Published work in English language evaluating the role of definitive charged particle therapies in the clinical setting of reRT for recurrent or second primary skull base and head and neck tumors were eligible for this analysis.

Results

A total of 26 original studies (15 protons, 10 carbon ions, and 1 helium/neon studies) involving a total of 1,118 patients (437 with protons, 670 with carbon ions, and 11 with helium/neon) treated with curative-intent charged particle reRT were included in this systematic review. All studies were retrospective in nature, and the majority of them (n=23, 88 %) were reported as single institution experiences (87% for protons, and 90% for carbon ion-based studies). The median proton therapy reRT dose was 64.5 Gy (RBE 1.1) (range, 50.0 – 75.6 Gy ), while the median carbon ion reRT dose was 53.8 Gy (RBE 2.5 – 3.0) (range, 44.8 – 60 Gy ). Induction and/or concurrent chemotherapy was administered to 232 (53%) of the patients that received a course of proton reRT, and 122 (18%) for carbon ion reRT patients. ReRT with protons achieved 2-year local control rates ranging from 50% to 86%, and 41% to 92% for carbon ion reRT. The 2-year overall survival rates for proton and carbon ion reRT ranged from 33% to 80%, and 50% to 86% respectively. Late ≥ G3 toxicities ranged from 0% to 37%, with brain necrosis, ototoxicity, visual deficits, and bleeding as the most common complications. Grade 5 toxicities for all treated patients occurred in 1.4% (n= 16/1118) with fatal bleeding as the leading cause.

Conclusions

Based on current data, curative intent skull base and head and neck reRT with charged particle radiotherapy is feasible and safe in well-selected cases, associated with comparable or potentially improved local control and toxicity rates compared to historical reRT studies using photon radiotherapy. Prospective multi-institutional studies reporting oncologic outcomes, toxicity, and dosimetric treatment planning data are warranted to further validate these findings and to improve the understanding of the clinical benefits of charged particle radiotherapy in the reRT setting.