Radiation Oncology/Head & Neck/RT Technique
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This page is for IMRT for head & neck.
Contouring targets[edit | edit source]
Dose regimens[edit | edit source]
Simultaneous integrated boost:
- PTV 66 (primary), PTV 60 (high-risk nodal), PTV 54 (elective nodal) in 30 fractions. (2.2 Gy/fx, 2.0 Gy/fx, 1.8 Gy/fx). Equivalent (acute effects) to ~69-73 Gy to the primary at 1.8-2 Gy/fx.
Thermoplastic masks[edit | edit source]
- Princess Margaret (2006-2008) -- standard immobilization mask vs skin-sparing immobilization mask
- Randomized. 762 CBCT scans in 20 patients. Arm 1) standard mask (SM) vs Arm 2) skin-sparing mask (SSM) modified with low neck cutouts
- 2010 PMID 20056344 -- "Cone-beam CT assessment of interfraction and intrafraction setup error of two head-and-neck cancer thermoplastic masks." (Velec M, Int J Radiat Oncol Biol Phys. 2010 Mar 1;76(3):949-55. Epub 2010 Jan 7.)
- Outcome: Initial interfraction sigma SM 1.6 mm or 1.1 degrees vs SSM 2.0 mm and 0.8 degrees. No difference after CBCT correction. Initial intrafraction sigma <1 mm and <1 degree for both masks.
- Conclusion: Interfraction and intrafraction setup error not significantly different between masks. Mask cutouts should be considered to reduce skin toxicity
Daily setup variations[edit | edit source]
- U. Wisconsin - PMID 15708257, 2005 — "The impact of daily setup variations on head-and-neck intensity-modulated radiation therapy." Hong TS et al. Int J Radiat Oncol Biol Phys. 2005 Mar 1;61(3):779-88.
- Study of 10 patients treated with conventional H&N radiotherapy techniques (not IMRT). Immobilization with standard thermoplastic mask, room lasers, weekly portal imaging. Setup accuracy was assessed daily by obtaining positioning errors (3 translations + 3 angular) using an optically guided positioning system. The positional errors were applied to 10 H&N IMRT plans for analysis of the impact of positional errors on the integrity of the IMRT plans over a 30 day course.
- Mean setup error in single dimension was 3.33 mm, composite vector of 6.97 mm. Tumor underdosing and normal tissue overdosing were common.
- Conclusion: More rigorous immobilization and patient setup are needed for IMRT.
Treatment technique[edit | edit source]
Risk of extracapsular extension:
- <1 cm - 17-43%, 1-3 cm - 65-83%, >3 cm - 67-95%.
- PMID 7316852 (1981, Johnson), PMID 7105450 (1982, Snow), PMID 4027895 (1985, Snyderman), PMID 3583851 (1987, Carter), PMID 2030629 (1991, Hirabayashi)
Margin around lymph nodes:
- PMID 16243444, 2006 — MDACC: "Determining optimal clinical target volume margins in head-and-neck cancer based on microscopic extracapsular extension of metastatic neck nodes." Apisarnthanarax S et al. Int J Radiat Oncol Biol Phys. 2006 Mar 1;64(3):678-83.
- 96 lymph nodes up to 3 cm with extracapsular extension were examined. Mean and median ECE extent was 2.2 and 1.6 mm. Was <5mm in 96% of nodes. No correlation with size of lymph node and distance of ECE.
- Recommend 1 cm CTV margins to cover microscopic nodal extension.
- Please see the Time-to-treatment section
Daily time of treatment
- NCIC HN3 -- morning RT vs. afternoon RT
- Randomized, proof of principle. 205/216 patients, receiving primary or postop RT. Arm 1) morning (8-10 AM) RT vs. Arm 2) afternoon (4-6 PM) RT; no chemo. Primary outcome mucositis
- 2008 PMID 18805649 -- "Comparison of Toxicity Associated with Early Morning Versus Late Afternoon Radiotherapy in Patients with Head-and-Neck Cancer: A Prospective Randomized Trial of the National Cancer Institute of Canada Clinical Trials Group (HN3)." (Bjarnason GA, Int J Radiat Oncol Biol Phys. 2008 Sep 19. [Epub ahead of print])
- Outcome: Grade 3+ mucositis AM RT 53% vs. PM RT 62% (p=0.2). In patients with RT dose 66-70 Gy, 45% vs. 67% (SS). Also longer time-to-mucositis >7.9 weeks vs. 5.6 weeks (SS). Significant benefit in patients who continued to smoke 43% vs. 76% (SS)
- Conclusion: Morning RT associated with significantly less weight loss, and reduction in oral mucositis in patients getting >=66 Gy
LN response by size
- Brisbane (Australia); 2008 (1997-2003) PMID 19032396 -- "Predicting regional control based on pretreatment nodal size in squamous cell carcinoma of the head and neck treated with chemoradiotherapy: a clinician's guide." (Porceddu SV, J Med Imaging Radiat Oncol. 2008 Oct;52(5):491-6.)
- Retrospective. 117 patients, HNSCC, N+, treated with concurrent chemo-RT. Median RT dose 70 Gy. Stratified into pretreatment LN <=3 cm vs. 3-6 cm vs. >6 cm
- Outcome: Regional control if LN <=3 cm 88% vs. 3-6cm 72% vs. >6 cm 50% (SS)
- Conclusion: Quantitative guide for regional control based on pre-rx nodal size
- West Florida; 1992 PMID 1616592 -- "A technique for postoperative irradiation of carcinomas of the larynx and hypopharynx." (Amos EH, Med Dosim. 1992;17(2):65-7.)
- Postop RT technique. 15 degree lateral kick-out of table and 15 degree gantry rotation for each of 2 lateral fields. Benefit lower dose to shoulder and avoid hotspot near cord
- Univ North Carolina; 1991 PMID 1869469 -- "A comparison of postoperative techniques for carcinomas of the larynx and hypopharynx using 3-D dose distributions." (Sailer SL, Int J Radiat Oncol Biol Phys. 1991 Aug;21(3):767-77.)
- Postop RT techcnique for larynx/hypopharynx. Comparison of minimantle technique (MGH), 3F technique (University of Florida), 3F technique (standard), and kicked out lateral technique
- Conclusion: Favor kicked-out lateral technique for better coverage and homogeneity