14 Nasopharynx Cancer

Nasopharynx Cancer

11

THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 10/09/2019

Table 2. The classic Levendag system [Levendag, 1997] Point

Designation

Definition

Targets Nasopharynx, right and left

Na (R)(L)

Intersection of the Pa-BOS line with the bony outline of the base of skull Intersection of the line drawn between the anterior clinoid process and point R and the line drawn from the contralateral outer canthus and tragus Ventral part of corpus of the atlas

Base of skull, right and left

BOS (R)(L)

Node of Rouviére

R

Organs at Risk Pituitary Optic chiasm Retina, right and left Cord Palate, right and left

P OC Re (R)(L) C Pa (R)(L)

0.5 cm from center of sella 1.5 cm ventrally from P 1 cm posterior to the line drawn from the contralateral outer canthus and tragus Posterior to R at the posterior border of the atlas Junction of soft and hard palate

Figure 18. Orthogonal radiographs of the Rotterdam applicator in-situ. Left, lateral view; Right, anteroposterior view. A modified Rotterdam applicator, to which incorporated a thin lead shield at the base, is used, to decrease soft palate dose. [Courtesy of Dr. Duc Hoang Lam, Ho Chi Minh Oncology Center].

Table 3. Dose Prescription and Constraints at the Ho Chi Minh Oncology Center a [Courtesy of Dr. Duc Hoang Lam] Point Designation Dose Constraints Targets Nasopharynx, right and left Node of Rouviére Na (R)(L) R 95-105% PD 95-105% PD

Organs at Risk Pituitary Optic chiasm Retina, right and left Cord Palate, right and left

P OC Re (R)(L) C Pa (R)(L)

≤30% PD ≤25% PD ≤20% PD ≤30% PD ≤110% PD

a A modified Rotterdam applicator, to which incorporated a thin lead shield at the base, is used, to decrease soft palate dose. PD, prescription dose. At the Ho Chi Minh Oncology Center, boost for definitive RT is given as four 3-4 Gy fractions given twice daily, and palliative brachytherapy as three to four 5-7 Gy fractions given once weekly.