Intensity-modulated radiation therapy for head and neck cancer

Long-term outcome of 18 F-fluorodeoxyglucose-positron emission tomography-guided dose painting for head and neck cancer: Matched case-control study

BACKGROUND

The purpose of this study was to report the long-term outcome of ¹⁸ F-fluorodeoxyglucose-positron emission tomography (¹⁸ F-FDG-PET)-guided dose painting for head and neck cancer in comparison to conventional intensity-modulated radiotherapy (IMRT) in a matched case-control study.

METHODS

Seventy-two patients with nonmetastatic head and neck cancer treated with dose painting were compared with 72 control patients matched on tumor site and T classification. Either ¹⁸ F-FDG-PET-guided dose painting by contour (DPBC) or voxel intensity-based dose painting by number (DPBN) was performed; control patients underwent standard IMRT. A total median dose to the dose-painted target was 70.2-85.9 Gy/30-32 fractions versus 69.1 Gy/32 fractions with conventional IMRT. In 31 patients, dose painting was adapted to per-treatment changes in the tumor and organs-at-risk (OAR).

RESULTS

Median follow-up in living dose-painting and control patients was 87.7 months (range 56.1-119.3) and 64.8 months (range 46.3-83.4), respectively. Five-year local control rates in the dose-painting patients were 82.3% against 73.6% in the control (P = .36); in patients treated to normalized isoeffective doses >91 Gy (NID2Gy) local control reached 85.7% at 5 years against 73.6% in the control group (P =.39). There was no difference in regional (P = .82) and distant control (P = .78). Five-year overall and disease-specific survival rates were 36.3% versus 38.1% (P = .50) and 56.5% versus 51.7% (P = .72), respectively. A half of the dose-painting patients developed acute grade ≥3 dysphagia (P = .004). Late grade 4 mucosal ulcers at the site of dose escalation in 9 of 72 patients was the most common severe toxicity with dose painting versus 3 of 72 patients with conventional IMRT (P = .11). Patients in the dose-painting group had increased rates of acute and late dysphagia (P = .004 and P = .005).

CONCLUSION

Dose-painting strategies can be used to increase dose to specific tumor subvolumes. Five-year local, regional, and distant control rates are comparable with patients treated with conventional IMRT. Volume and intensity of dose escalation should be further tailored, given the possible increase in severe acute and chronic toxicity. Adapting treatment and decreasing dose to the swallowing structures might contribute to lower toxicity rates when applied in smaller tumor volumes. Whether adaptive DPBN can significantly improve outcomes is currently being investigated in a novel clinical trial.

The management of head and neck tumors with high technology radiation therapy

Squamous cell carcinoma is responsible for 90% of the head and neck cancers affecting over 600,000 people worldwide. Radiation therapy, surgery and chemotherapy are the most important treatment modalities in head and neck squamous cell carcinoma. The aim of this review is to summarize the recent innovations in head and neck radiation therapy, which intends to appreciate the cutting-edge intensity-modulated radiation therapy strategies to mitigate long-term toxicities and evaluate promising technologies in the field as adaptive treatment, dose painting and proton therapy.

Intensity-modulated radiation therapy in head and neck cancers: an update

Intensity-modulated radiation therapy (IMRT), an advent of three-dimensional conformal radiotherapy (3D CRT), has excited the profession of radiation oncology more than any other new invention since the introduction of the linear accelerator. Approximately 1000 articles have been published on this topic to date, more than 200 of which focus on head and neck cancer. IMRT is based on computer-optimized treatment planning and a computer-controlled treatment delivery system. The computer-driven technology generates dose distributions that sharply conform to the tumor target while minimizing the dose delivered to the surrounding normal tissues. The high dose volume that tailors to the 3D configuration of the tumor along with the ability to spare the nearby normal tissues allows the option of tumor dose escalation. The head and neck region is an ideal target for this new technology for several reasons. First, IMRT offers the potential for improved tumor control through delivery of high doses to the target volume. Second, because of sharp dose gradients, IMRT results in the relative sparing of normal structures, such as the parotid glands, in the head and neck region. Third, organ motion is virtually absent in the head and neck region so, with proper immobilization, treatment can be accurately delivered. Although this is a relatively new technology, single-institution retrospective studies show better dosimetric profiles compared with conventional radiation techniques, as well as excellent clinical results. Salivary gland sparing using IMRT has also resulted in reduced incidence and severity of xerostomia, and this has been tested in a randomized trial against conventional radiotherapy for early-stage nasopharyngeal cancer. The results do confirm that IMRT does decrease xerostomia compared with conventional radiotherapy.

Adaptive biological image-guided IMRT with anatomic and functional imaging in pharyngo-laryngeal tumors: impact on target volume delineation and dose distribution using helical tomotherapy

BACKGROUND AND PURPOSE

Adaptive image-guided IMRT appears to be a promising approach for dose escalation in pharyngo-laryngeal tumors. In this framework, we assessed in a proof of concept study the impact of anatomic and functional imaging modalities acquired prior and during radiotherapy on the target volume delineation and the dose distribution using helical tomotherapy.

MATERIALS AND METHODS

Ten patients with pharyngo-laryngeal squamous cell carcinoma were treated by concomitant chemo-radiation delivered in 7 weeks. CT, T2-MRI, fat suppressed T2-MRI, and static and dynamic FDG-PET were acquired for each patient before the start of treatment and during radiotherapy, after mean prescribed doses of 14, 25, 35 and 45 Gy. GTVs were manually delineated on CT and MRI images while PET images were automatically segmented by means of a gradient-based method. From these volumes, CTVs and PTVs were derived using consistent guidelines. Simultaneous integrated boost IMRT planning was performed using helical tomotherapy.

RESULTS

GTVs significantly decreased throughout the course of RT for all imaging modalities (p<0.001). Clinically non-significant differences and high correlations were found between GTVs delineated on CT and MRI, irrespective of the sequence used. By contrast, FDG-PET-based GTVs segmented from pre- and per-treatment images were significantly smaller compared to anatomical imaging modalities, without any difference existing between static and dynamic acquisition. These differences in GTVs translated into parallel reductions of both prophylactic and therapeutic CTVs and PTVs. Resulting FDG-PET-based and adaptive IMRT planning reduced the irradiated volumes by 15-40% compared to pre-treatment CT planning (V(90), V(95) and V(100)), but did marginally impact on doses to the OAR such as the spinal cord and the parotid glands.

CONCLUSIONS

Adaptive IMRT with FDG-PET images has a significant impact on the delineation of TVs and on the dose distribution in pharyngo-laryngeal tumors. Such an approach might thus be considered for dose escalation strategies.

[18F]fluoro-deoxy-glucose positron emission tomography ([18F]FDG-PET) voxel intensity-based intensity-modulated radiation therapy (IMRT) for head and neck cancer

BACKGROUND AND PURPOSE

Focused dose escalation may improve local control in head and neck cancer. Planning results of [(18)F]fluoro-deoxy-glucose positron emission tomography ([(18)F]FDG-PET) voxel intensity-based intensity-modulated radiation therapy (IMRT) were compared with those of PET contour-based IMRT.

PATIENTS AND METHODS

PET contour-based IMRT aims to deliver a homogeneous boost dose to a PET-based subvolume of the planning target volume (PTV), called PTV(PET). The present PET voxel intensity-based planning study aims to prescribe the boost dose directly as a function of PET voxel intensity values, while leaving the dose distribution outside the PTV unchanged. Two escalation steps (2.5 and 3 Gy/fraction) were performed for 15 patients.

RESULTS

PTV(PET) was irradiated with a homogeneous dose in the contour-based approach. In the voxel intensity-based approach, one or more sharp dose peaks were created inside the PTV, following the distribution of PET voxel intensity values.

CONCLUSIONS

While PET voxel intensity-based IMRT had a large effect on the dose distribution within the PTV, only small effects were observed on the dose distribution outside this PTV and on the dose delivered to the organs at risk. Therefore both methods are alternatives for boosting subvolumes inside a selected PTV.

Sclerosis of the Pterygoid Process in Untreated Patients with Nasopharyngeal Carcinoma

PURPOSE

To retrospectively evaluate the prevalence of pterygoid process sclerosis in patients with untreated nasopharyngeal carcinoma.

MATERIALS AND METHODS

This retrospective HIPAA-compliant study was performed after the institutional review board deemed it to be exempt from review and patient informed consent. Contrast material-enhanced computed tomographic (CT) scans of the neck obtained in 31 patients (22 men, nine women; mean age, 42 years; age range, 27-68 years) with untreated nasopharyngeal carcinoma and in 31 control subjects (17 men, 14 women; mean age, 43 years; age range, 19-62 years) were evaluated independently by two neuroradiologists. The presence of sclerosis of the pterygoid process-defined as increased attenuation in the medullary cavity and/or thickening of the cortical bone-was assessed. Other findings noted included pterygoid process erosion, enhancing tumor adjacent to the pterygoid process, and CT evidence of parapharyngeal extension of the tumor. The data were evaluated by using generalized estimating equations based on a binary logistic regression model.

RESULTS

The prevalence of pterygoid process sclerosis averaged for the two readers was 60% (37 of 62 subjects) among the patients with nasopharyngeal carcinoma but only 3% (two of 62 subjects) among the control subjects, indicating a highly significantly increased prevalence (P < .001) of this finding in the patients with nasopharyngeal carcinoma. The overall prevalences of pterygoid process erosion, parapharyngeal extension of tumor, and enhancing tumor adjacent to the pterygoid process were 27% (17 of 62 subjects), 47% (29 of 62 subjects), and 77% (48 of 62 subjects), respectively. Pterygoid process sclerosis was the sole skull base abnormality in 36% (11 of 31) of the patients with nasopharyngeal carcinoma.

CONCLUSION

Sclerosis of the pterygoid process, which was present in about half of the patients with untreated nasopharyngeal carcinoma, may reflect tumor proximity to or tumor invasion of the pterygoid process.

Intensity-Modulated Radiation Therapy in Head and Neck Cancers

Intensity-modulated radiation therapy (IMRT) is an exciting new modality in radiation therapy. The head and neck region is an ideal target for this new technology for several reasons. First, IMRT offers the potential for improved tumor control through delivery of high doses to the target volume. Second, because of sharp dose gradients, IMRT results in the relative sparing of normal structures in the head and neck region. Third, organ motion is virtually absent in the head and neck region, so, with proper immobilization, treatment can be delivered accurately. Although this is a relatively new technology, preliminary studies show excellent dosimetric profiles and clinical results. Salivary gland sparing has also resulted in reduced incidence and severity of xerostomia. Early reports of improvement in tumor control with better side effect profiles versus conventional techniques are promising, but will need to be confirmed with longer follow-up.