Comparative Analysis of Dose Volume Histograms of Pelvic Bone Marrow and their Clinical Correlation in Patients of Cancer Cervix Treated with Conventional and 3-Dimensional Conformal Radiotherapy

Abstract

Introduction: Radiotherapy (RT) is the treatment of choice
for cancer cervix in FIGO stage IIB and beyond and also in
selected cases in initial stages. Conventional RT is planned
on the basis of bony landmarks. Three-dimensional conformal
RT (3D CRT) is planned on computed tomography (CT)
which includes three-dimensional (3D) identification of visible
tumor and organs at risk (OAR) that need to be included or
avoided. Dose-volume histograms (DVH) are excellent tools for
evaluating and compare isodose distribution in the concerned
volumes. Hematological toxicity in cancer cervix is due to bone
marrow radiation and concurrent chemotherapy given. The
present study focuses on the delineation of bone marrow and
comparing the DVH in conventional and 3D CRT to find clinical
correlation in both groups.
Materials and Methods: A total of 50 patients were randomized
into two groups - Group A treated by conventional radiotherapy
and group B treated with 3D CRT. All patients received 50 Gy
in 25 fractions at 2 Gy per day along with concurrent cisplatin
followed by three fractions of intracavitary brachytherapy of 7
Gy each. Conventional planning was based on bony landmarks.
3D planning included the delineation of gross, clinical and
planning target volumes along with different Organs at risk
(OAR) s, including the bone marrow. Dosimetry parameters
evaluated were D-max, D-mean and PTV-95 for planning
target volumes (PTV) and V10, V20, V30, V40 and V50 for all
subsites of bone marrow and as a whole bone marrow. Clinical
correlation of hematological toxicity with dosimetric parameters
of bone marrow were evaluated and statistical significance was
seen using paired student t-test.
Results: Mean age of the patients was 48.22 years (range
28–70 years). The commonest symptom was yellowish/whitish
discharge per vagina 44 (88%), and most patients had FIGO
stage II(60%). Field sizes used in the 3D-CRT arms were
significantly larger than those used for the conventional plans
(p = 0.000). The difference in dosimetric parameters for PTV
in both groups were not statistically significant. After 6 months,
the complete response was 88% in group A and 92% in group
B. No grade III and IV hematological toxicity was found except
two patients who had grade III haemoglobin toxicity. In group
A the whole bone marrow and ilium showed a significant
correlation with the incidence of haematological toxicity for
V-10, LSS forV-10, V-20, V-30 and lower pelvisbonefor V-10,
V- 20, when compared to the other volumes. In group B, the
whole bone marrow and ilium showed a significant correlation
with the incidence of hematological toxicity for V-10, LSS and
lower pelvis for V-10 and V-20 when compared to other volumes.
Conclusion: Bone marrow sparing should be done as much as
possible to reduce hematological toxicity. Newer radiotherapy
techniques like intensity-modulated RT may help achieve bone
marrow's dose constraints.