IntensityModulated Radiotherapy for the Treatment of Vulvar Carcinoma: A Comparative Dosimetric Stud

1
Intensity-Modulated Radiotherapy for the
Treatment of Vulvar Carcinoma A Comparative
Dosimetric Study with Early Clinical
Outcome Sushil Beriwal, MD1 Dwight E. Heron,
MD1 Hayeon Kim, MS1 Gwendolyn King, MS1
Jeffrey Shogan, MD1 Kristina Gerszten, MD1 Joe
Lee, PhD2 John Comerci, MD1 1. University of
Pittsburgh Cancer Institute, Department of
Radiation Oncology, Pittsburgh, PA 15232, USA 2.
D3 Radiation Planning, Pittsburgh, PA 15232 USA
Table 2. Acute Gastrointestinal, Bladder and Skin
Toxicity
Table1. Volume of critical structures receiving
greater than 30 Gy (V30)
Purpose Concomitant irradiation of inguinal
lymph nodes in patients diagnosed with primary
vulval cancer poses significant dosimetric
challenges involving abutting fields at groin.
Intensity modulated radiotherapy offers potential
advantage of eliminating dose modulation across
the overlapping region. To date there is no
clinical data on intensity-modulated radiotherapy
for treatment of vulvar cancer. To our knowledge,
this is the first report IMRT effort reporting
early clinical outcome in vulvar cancer and
comparing dosimetric parameters with conventional
3D conformal radiotherapy. Methods Twelve
patients with median age 76 yrs and FIGO stage II
to IVA vulvar cancer were treated with
intensity-modulated radiotherapy. Planning was
performed using Eclipse Planning System (version
7.1.59, Varian, Palo Alto, CA) and treatment was
delivered using Varian 2100 C. The median number
of fields used was 7 (5-8) Figure 2. 3D planning
was performed using the same planning system and
the field arrangement was AP-PA with 6/18MV
photons with matching electron fields (9-20 MeV)
Figure 1. Seven patients were treated with
pre-operative chemoradiation and five patients
with adjuvant radiation. The preoperative
chemoradiation used a hyperfractionation regimen
with infusional chemotherapy used during first
and last week of treatment with planned break in
between. The volume of treatment included
bilateral external iliac, internal iliac and
iguinofemoral nodes with or without entire vulvar
region. Bolus was used for vulval region and TLD
was used for in vivo dosimetry. Median dose was
46 Gy in preoperative group and 50.4 Gy in
postoperative group. Results The volume of each
organ of interest (small bowel, bladder, and
rectum) receiving doses in excess of 30 Gy was
compared in the IMRT and 3D treatment plans. The
mean volume of small bowel, rectum and bladder
receiving doses in excess of 30 Gy was reduced by
27, 41 and 26, respectively with IMRT compared
with 3D, Table 1. There was no difference in dose
to the femoral heads. Median TLD reading was 112
(83-115) at the primary site. Median follow up
was 12 months (3- 27 months). Out of 7 patients
in preoperative group, 5 patients (71) had
clinical complete response (cCR). All but one
patient underwent wide local excision with
pathological complete response (pCR) seen in
three patients. One patient with cCR was treated
with definitive radiation with further boost and
remains NED. In the adjuvant group, 3 patients
had central vulval recurrence salvaged with
surgery and/or radiation. One of these
recurrences was in the treatment field while
other two were outside the field. Acute toxicity
was RTOG grade 2 dermatitis in 9 patients, grade
3 small bowel toxicity in 1 patient, grade 2
small bowel toxicity in 2 patients and grade 2
rectal toxicity in one patient, Table 2. Median
planned treatment days break in pre-operative was
14 days (6-21 days). There was no treatment break
in adjuvant group and no late grade 3 toxicities
were seen. One patient has died because of co
morbidities. The 2 yrs actuarial disease specific
survival was 100. Conclusions
Intensity-modulated radiotherapy appears to offer
advantages over conventional 3D radiotherapy (3D
CRT) planning for treatment of vulvar cancer by
eliminating dose modulation across overlapping
region and reducing treatment volume for bladder,
rectum and small bowel. Early results with small
number of patients show promising results with a
low incidence of severe toxicity. Prospective
trials are necessary to better evaluate the
efficacy in a larger group of patients.
DVH Analysis on One Patient
Figure 1. 3D beam arrangement showing matching
photon and electron fields
Figure 2. Axial view showing IMRT beam arrangement
Figure 3. PTV (red) covered with prescription 95
isodose line
Figure 4. PTV (red) covered by prescription 97
isodose line