3-Dimensional Conformal versus Intensity Modulated Radiotherapy in Head and Neck Squamous Cell Carcinoma: Comparative Analysis of Compliance, Toxicities and Dosimetric Parameters

Abstract

Introduction: Advance radiotherapy conformal techniques
have an advantage over conventional radiotherapy in delivering
the dose more accurately to the target volume while limiting the
doses to organs at risk. 3-dimensional conformal radiotherapy
leads to sparing the surrounding normal tissue better than
2-dimensional radiotherapy, but it still causes significant
volumes of normal tissue irradiation because RT is delivered
in three dimensions with a uniform dose in each field. Intensity
modulated radiotherapy is a refinement of 3-dimensional
conformal radiotherapy, which modulates the radiation beams
so that a high dose can be delivered to the tumor target while the
dose to normal tissues can be reduced. The dose-modulating
ability of IMRT gives a theoretical advantage over 3D-CRT,
but it also has a drawback of delivering a higher dose outside
the planning target volume (PTV) due to more number of
fields used. The present study aims to analyze and compare
dosimetric parameters, compliance, and toxicities of these
two techniques.
Materials and methods: About 50 patients of head neck
cancers presented in our department were treated with
definitive concurrent chemoradiation after randomizing into
two groups of twenty-five each- Group I (3DCRT) and Group II
(IMRT). Inclusion Criteria- Histologically proven squamous cell
carcinoma; age >18 years; Karnofsky performance status >70;
normal hemogram, renal function test, liver function test and 2D
ECHO. Exclusion Criteria - prior or synchronous malignancy or
previous history of head and neck surgery; distant metastasis;
previously treated patients with radiotherapy. Radiotherapy
dose of 70 Gy in 35 fractions over 7 weeks, along with weekly
cisplatin 35 mg/m2, was given. Treatment compliance (overall
treatment time and number of weekly chemotherapy cycles),
toxicities (hematological and radiotherapy-induced), clinical
response assessment and dosimetric parameters of PTV
and organ at risk were compared. Statistical analysis was
done using an unpaired t-test to compare the mean of two
independent groups and a chi-square test for compliance and
toxicities.
Results: The mean and median age in Group I is 57.2 years
(35–77 years) and 60 years and in Group II is 62.08 years
(42–76 years) and 63 years. The male-to-female ratio in groups
I and II is 11.5 and 5.25, respectively. The majority of the cases
were locoregionally advanced, 76% in Group I and 84% in
Group II. There was no statistically significant difference in
overall treatment time above 51 days in both groups (40 vs 24%)
and patients receiving 5 to 7 cycles of chemotherapy (54 vs
46%). Similarly, there was no statistically significant difference
in hematological and radiotherapy-induced toxicities. Complete
response seen in both groups (80 vs 72%, p = 0.51). The PTV
parameters were achieved in both groups, but were statistically
better in IMRT. Dose constraints for OARs were achieved in
most organs, though they were statistically better in IMRT.
Conclusion: Both techniques, 3-DCRT and IMRT, did not
have any statistical difference in treatment compliance and
toxicities. Dosimetric parameters were achievable, though they
were better in IMRT. Different forward planning techniques may
improve and make 3DCRT plans comparable to IMRT