Patient selection: nasopharyngeal carcinoma
Planning volumes:
(1) GTV = gross tumor volume = primary tumor and metastatic lymph nodes
(2) CTV = clinical target volume = entire nasopharynx, parapharyngeal space, clivus, base of the skull, pterygoid fossa, posterior half of ethmoidal sinus, inferior sphenoidal sinus, posterior edge of nasal cavity and posterior edge of maxillary sinuses
(3) PTV = planned target volume = extends 3-5 mm around GTV or CTV
Radiation dosing:
(1) T1 and T2: 66 Gy in 30 fractions
(2) T3 and T4: 70.4 Gy in 32 fractions
(3) positive lymph nodes: 66 Gy in 30-32 fractions
(4) high risk CTV: 60 Gy in 30-32 fractions
(5) low risk CTV: 54 Gy in 30-32 fractions
Parameters from dosimetry:
(1) D0.5cc in cGy (range 5,000 to 9,000), minimum dose to most exposed 0.5 cc of the target
(2) D10 in cGy (range 2,000 to 7,000), dose delivered to 10% of the planned target volume
X =
= (0.00036 * (D0.5cc)) + (0.00054 * (D10)) - 7.36
probability of temporal lobe necrosis =
= 1 / (1 + EXP((-1) * X))
A risk < 5% is considered low-risk, while a risk > 10% is considered high-risk.
Performance:
• The area under the ROC curve is 0.69.
