A Phase II Randomized Trial Comparing Intensity Modulated Radiation Therapy (IMRT) With Conventional Radiation Therapy in Stage IIB Carcinoma Cervix
Carcinoma Cervix is the commonest malignancy seen in Indian women and constitutes
approximately 10% of all cancers at Tata Memorial Hospital (1). It is also the leading cause
of cancer mortality in India. Nearly 85% of the patients present with advanced stages (FIGO
Stage II/III). The main stay of treatment has traditionally been radical radiation therapy
with 80-90% of patients requiring radiation in their lifetime and over decades the survival
rates have achieved a plateau of 30 - 55% at 5 years.
Radiation therapy is usually a combination of external beam and intracavitary brachytherapy.
External beam radiation includes irradiation of primary tumor and nodal areas of risk.
Higher Doses of external beam radiation is limited due to normal critical organs namely,
small bowel, rectum and bladder. A major concern with pelvic radiation is the considerable
volume of both small bowel and rectum is included in the radiation treatment fields.
Unsurprisingly, gastrointestinal radiation reactions include diarrhea while late sequelae
include small bowel obstruction, enteritis and diarrhea are common (2-4). The benefits of
multiple fields, high energy beams, customized blocking and low fraction sizes are well
known (4). Various methods have been used to reduce the small bowel complications. Surgical
methods include absorbable meshes (5), tissue expanders (6) and omentoplasty (7). However,
these approaches are not feasible in patients undergoing definitive radiation. Apart from
small bowel toxicity, late rectal and bladder complications are also of a major concern. The
clinical manifestations vary from mild proctitis, stricture, bleeding ulcers and fistula
formation to hemorrhagic cystitis requiring cystectomy. Grade III radiation cystitis and
proctitis reported are in the range of 3-15% with radiation alone.
Moreover, of late the pattern of practice is increasingly being emphasized on concomitant
chemo radiation (8,9). The addition of chemotherapy though has no doubt improved the
survivals, but has also led to increase in normal tissue toxicities. In the RTOG 90-01 and
92-10 there is alarming increase in the gastro intestinal (35% grade III and grade IV) and
genitourinary (9% grade III and grade IV).
The changes in the treatment policies and the toxicities associated with wide pelvic
radiation therapy demand for better normal tissue sparing radiation techniques or
radioprotective agents. Three Dimensional Conformal Radiation Therapy (3D-CRT) to some
extent has successfully achieved some normal tissue sparing. Intensity-modulated
radiotherapy (IMRT) is an important recent advance in radiation therapy and is at the
forefront of Translational Research. With 3DCRT the radiation intensity is generally uniform
within the radiation portal whereas in IMRT the dose intensity within the portal varies with
the use of beamlets, thereby allows a higher degree of conformation to the tumor than
previously possible and allows concave isodose profiles to be generated.
Over last 10 years, IMRT has been successfully used in the treatment of prostate, head and
neck and brain tumors. IMRT in pelvic radiation has the potential to reduce the dose as well
as the volume of rectum, bladder and small bowel irradiated significantly and thereby
translating into a decrease in the incidence and severity, of acute and late
gastro-intestinal and genito-urinary toxicities. Several dosimetric studies have been
reported to confirm the role of IMRT in reducing toxicities with pelvic radiation therapy
(10,11). These dosimetric studies have reported that the volume of small bowel irradiated to
the prescription dose by a factor of 2 compared with conventional radiation. The average
volume of bladder and rectum irradiated is also reduced by 23% (12). In our series of 10
patients treated, IMRT in pelvic radiation therapy apart from reducing the hot spot volumes
and better conformity index to the target volume, also significantly reduces the volumes of
high dose regions in small bowel region (by 17%), rectum (by 50-60%) and bladder (by 40-50%)
[unpublished data]. In another series of early report on outcome of 40 patients treated with
IMRT to whole pelvis, Arno el al. have demonstrated that there is a significant reduction in
acute radiation related toxicities, but it is too early to comment on late sequelae since
the follow-up is short and has concluded that, this novel approach definitely needs to be
validated in a trial setting. (13)
Observational Model: Cohort, Time Perspective: Prospective
To compare the normal tissue toxicities (Acute & Late) of standard radiation therapy with IMRT
Shyamkishore J Shrivastava, MD, DNB (RT)
Professor & Head, Radiation Oncology, Tata Memorial Hospital
India: Department of Atomic Energy