Comparison of Various Radiotherapy Planning Strategies for Locally Advanced Hypopharyngeal Cancer

1
Comparison of Various Radiotherapy Planning
Strategies for Locally Advanced Hypopharyngeal
Cancer Received Resection with Ileocolic Free
Flap Reconstruction Hung-Chi Tai1, Chen-Hsi
Hsieh1, Yi-Shing Leu2, Yih-Fang Chang3, Ming-Zhe
Huang3, Hung-Tao Hsiao4, Yuan-Ching Chang5,
Yu-Jen Chen1 1Department of Radiation Oncology,
2Otolaryngology, 3Hematology, 4Plastic Surgery,
5General surgery Mackay Memorial Hospital,
Taipei, Taiwan

• Background and Purpose
• With an attempt to restore organ function of
  locally advanced hypopharyngeal cancer patients,
  surgical resection followed by reconstruction
  with ileocolic free (ICF) flap has been becoming
  accepted. This study was aimed to compare the
  target coverage and critical organ sparing effect
  of intensity modulated radiation therapy (IMRT),
  3D conformal radiotherapy (3DCRT) and
  conventional radiotherapy (CRT) for
  post-operative treatment.
• Methods
• From April 2003 to December 2006, 3 patients with
  locally advanced hypopharyngeal cancer were
  treated with radical surgery and reconstruction
  with ICF flap to rebuild phonation and swallowing
  function.
• Each patient received planning CT scan for
  intended IMRT. By using a treatment planning
  system (PLATO RTS v2.6.3), we performed planning
  for IMRT, 3DCRT and CRT for each patients with
  the same dose constraints.
• Spinal cord (SC) and ICF flap were considered
  critical tissues to be spared.
• A linear accelerator with 6MV energy equipped
  with an 80-leaf multi-leaf collimator (6 MV,
  Elekta Precise) was used to set all the
  parameters.
• For IMRT and 3DCRT, dose at 64 Gy and 59.4 Gy
  were prescribed to surgical bed with adequate
  margin (PTV64) and prophylactic nodal RT area
  with margin (PTV59.4), respectively. For CRT, 64
  Gy was planned to deliver by using opposite field
  technique with subsequent spinal cord blocking.
• Inverse planning for IMRT was performed with dose
  volume optimization to minimize the planning
  organ at risk volume (PRV) of ICF flap and SC
  irradiated. Dose volume histograms of the target
  volumes and critical structures were computed and
  compared.
• Results
• The average conformity index by the IMRT, 3DCRT
  and CRT planning was respectively, for the PTV64
  0.95, 0.73 and 0.87 and for the PTV59.4 0.99,
  0.89, 0.88.
• For PRVICF, only IMRT planning achieved the
  reduction of dose (IMRT Dmean 51.8 Gy, 3DCRT
  Dmean 64.9 Gy, CRT Dmean 64.5 Gy) The volume
  received more than 50 Gy ( IMRT V50 75.1, 3DCRT
  V50 99.3, CRT V50 100).
• For PRVSC, both IMRT and 3DCRT enabled reduction
  of the dose and V45 by 51 95.

Figure 1. Illustration showing that ileocolic
flap reconstructs trachea, pharynx and esophagus
by anastomosing ileum, cecum and proximal colon,
respectively.
Figure 2. Dose Distribution for IMRT, 3DCRT and
CRT
Figure 3. Demonstration of dose volume histograms
of PTV64, PRVICF and spinal cord for comparing
radiation planning of conventional radiotherapy
(CRT), three-dimensional conformal radiotherapy
(3D-CRT) and intensity-modulated radiotherapy
(IMRT).
Table 1. The mean percentage dose of the planning
organ at risk volume (PRVICF) and spinal cord
(SC)

• Conclusions
• Among RT plans of IMRT, 3DCRT and CRT, only IMRT
  could provide
• acceptable sparing of the ileocolic free flap
  and better conformity of PTVs.
• IMRT planning might accomplish the aim of
  ileocolic free flap reconstruction, namely
• restoration of swallowing and speaking function
  in locally advanced hypopharyngeal cancer
• patients received radical resection.
• Evaluation of the clinical outcome of these
  patients is undergoing.

Table 2. Conformity index of planning target
volumes (PTVs)