Cervix — Definitive Chemoradiation

GYNCervixCervical cancerIMRTVMATChemoradiationITVImage fusionMRIPETConventional fractionation
Overview

Definitive chemoradiation for cervical cancer: pelvic IMRT or VMAT with weekly cisplatin, followed by a brachytherapy boost. The external beam plan covers a target that moves with bladder filling and sits against bowel, bladder and rectum, and its dose is later added to the brachytherapy dose.

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Schedules

Definitive treatment has two parts: external beam to the pelvis, usually with weekly cisplatin, and a brachytherapy boost to the cervix. The external beam treats the tumor, uterus, parametria, part of the vagina and the pelvic nodes to 45 Gy in 25 fractions (the NRG template also lists 50 Gy in 25 and 50.4 Gy in 28). Brachytherapy then brings the tumor to a much higher dose than external beam could deliver safely — see GYN Brachytherapy.

Involved nodes or parametria can be boosted two ways:

  • Sequential boost — a second plan of 5.4–14.4 Gy at 1.8 Gy per fraction.
  • Simultaneous integrated boost (SIB) — one plan, with the involved nodes at a higher dose per fraction (the NRG template example is 50.4–59.4 Gy in 25–28 fractions).

When the common iliac or para-aortic nodes are involved, the field extends up the para-aortic chain, and the kidneys, duodenum and spinal cord come into play.

Overall treatment time matters. Protocols aim to finish external beam and brachytherapy within 56 days, so brachytherapy usually starts during the last weeks of external beam, and the two are not given on the same day. Your protocol sets the schedule, the boost approach and the dose to each volume.

Simulation & Setup

The cervix and uterus move with bladder and rectal filling. Simulation is built around measuring that movement and drawing the tumor on the right images.

Position and immobilization
Supine in a custom device for the legs, or prone on a bowel-exclusion board — extended to the abdomen for para-aortic fields.

What is it?

Usually supine with a custom immobilization device, or prone on a bowel-exclusion device. For pelvic fields the legs are immobilized; for pelvic and para-aortic fields, the abdomen and pelvis as well.

Why does it matter?

Reproducible pelvic position keeps the nodal volumes and the bony anatomy in the same place each day. Prone with a bowel-exclusion device can move small bowel away from the field; supine is common with IMRT and VMAT, which shape dose around the bowel instead.

Bladder filling and the ITV
Scanning with a full and an empty bladder shows how far the cervix and uterus move, and the two are combined into an ITV.

What is it?

A moderately full bladder for simulation and treatment, with a second scan taken with the bladder empty. The cervix and uterus are contoured on both scans and combined into an internal target volume (ITV). Planning is done on the full-bladder scan.

Why does it matter?

Bladder filling tips the uterus forward and back and moves the cervix, so a contour from one scan can miss the target on another day. The ITV covers the range between the two. A full bladder also pushes small bowel out of the pelvis. Some centers instead use a library of plans for different filling states, or adapt the plan daily.

Planning CT and markers
A thin-slice CT from the upper abdomen to mid-thigh, with contrast for the vessels and wires on visible disease.

What is it?

A CT with slices of 3 mm or less, from about L1 to mid-thigh (from the carina when the para-aortic nodes are treated). IV contrast and bowel contrast help show the pelvic vessels and bowel, and wires or markers can mark gross disease such as vaginal extension.

Why does it matter?

The nodal volumes follow the vessels, so contrast makes them easier to draw. Markers tie the CT to the clinical examination. One template advises against vaginal markers that stretch the vagina, because they change its shape. If contrast is present on the planning scan, its density is overridden for dose calculation.

Image fusion — MRI and PET/CT
Diagnostic pelvic MRI and PET/CT fused with the planning CT, matched on the tumor rather than the pelvic bones.

What is it?

Image fusion aligns an outside scan with the planning CT so the target can be drawn using information the CT doesn't show. For cervical cancer this is a diagnostic pelvic MRI and/or PET/CT. Ideally the MRI is taken close in time to the planning scan, and in MR-guided treatment the scans are fused to the planning MRI instead.

Why does it matter?

The tumor and its spread into the parametria and vagina are drawn using the MRI, and involved nodes using PET/CT and MRI. The uterus and cervix move independently of bone, so the MRI registration should focus on the primary tumor rather than the pelvic bones. One template discourages deformable registration of the diagnostic MRI, which can distort the tumor, and asks that any PET/CT registration be reviewed with caution.

Daily imaging
Daily IGRT, matched to bone with the soft tissue reviewed, because the uterus and cervix move between fractions.

What is it?

Daily image guidance with IMRT — usually cone-beam CT, matched to the bony anatomy with the soft tissue reviewed.

Why does it matter?

The ITV and PTV allow for some movement of the uterus and cervix, but CBCT shows when the bladder or rectum is very different from the plan. Small soft-tissue shifts may be accepted; larger ones may lead the physician to postpone treatment or re-simulate.

Target Delineation

What each volume represents. Expansions, nodal regions and dose levels come only from your protocol.

GTV — Primary tumor and involved nodes

Definition

All gross disease — the cervical tumor and its extension — and each involved node, from imaging, examination and biopsy results.

Why it matters

The GTV anchors the CTV and, for involved nodes, sets what gets a nodal boost. Its extent at diagnosis is drawn mainly on the fused MRI.

Contouring resources

Organ contouring guides →

Relevant protocols

CTV — primary — Cervix, uterus, parametria and vagina

Definition

The gross tumor with the whole cervix and uterus, the parametria and part or all of the vagina, depending on how far the tumor extends.

Why it matters

Cervical cancer spreads into the parametria and down the vagina, and the uterus moves with the cervix. The international consensus guideline gives the boundaries of each part.

Contouring resources

Organ contouring guides →

Relevant protocols

CTV — nodal — Pelvic ± para-aortic nodes

Definition

The external, internal and common iliac and presacral nodal regions, with the para-aortic nodes added when higher nodes are involved.

Why it matters

Cervical cancer spreads in an orderly way up the pelvic nodal chains. The nodes are contoured around the vessels, so a good contrast scan matters.

Contouring resources

Organ contouring guides →

Relevant protocols

ITV — Internal target volume

Definition

The primary CTV contoured on the full- and empty-bladder scans and combined.

Why it matters

It accounts for the movement of the cervix and uterus with bladder filling. With daily adaptive treatment an ITV may not be needed.

Contouring resources

Organ contouring guides →

Relevant protocols

PTV — Planning target volume

Definition

The ITV (or CTV) expanded for setup uncertainty, with any nodal boost volumes expanded separately.

Why it matters

The pelvic PTV sits against the bowel, bladder and rectum, so where coverage meets an organ goal is the main trade-off in the plan.

Contouring resources

Organ contouring guides →

Organs at Risk & Dose Constraints

Click an organ for its anatomy, why it matters and contouring resources. Superscripts link to the source behind each value.

Organ45–50.4 Gy / 25–28 fxPelvis ± nodal boost
Small BowelNRG limits apply to the bowel space (Spc_Bowel); EMBRACE II limits to its bowel contour. With para-aortic fields EMBRACE II allows V40 Gy <300 cc, V30 Gy <650 cc.
  • Bowel space D30% ≤40 Gy, D0.03 cc ≤59.4 Gy1
  • Bowel V40 Gy <250 cc, V30 Gy <500 cc2
Rectum
  • D50% ≤45 Gy, D0.03 cc ≤50 Gy1
  • V40 Gy <75%, V30 Gy <95%2
Bladder
  • D50% ≤45 Gy, D0.03 cc ≤50 Gy1
  • V40 Gy <60%, V30 Gy <80%2
Femoral Heads
  • D15% ≤30 Gy, D0.03 cc ≤50 Gy1
Pelvic Bone MarrowPelvic bones as a surrogate, including the femoral heads but not the necks.
  • Mean ≤27 Gy1
  • V10 Gy ≤85.5%, V20 Gy ≤66%1
KidneysWhen the para-aortic nodes are treated.
  • Mean <15 Gy (aim <10 Gy)2
DuodenumWhen the para-aortic nodes are treated.
  • V55 Gy <15 cc2,3
Spinal CordWhen the para-aortic nodes are treated.
  • Max <48 Gy2
  • NRG values are the template's per-protocol (ideal) levels for the pelvic IMRT plan including any parametrial or nodal boost; its variation-acceptable levels are higher (e.g. rectum D50% ≤54 Gy, bowel space D30% ≤50 Gy).
  • EMBRACE II volume limits are soft constraints for optimization, expected to be met in about 70–80% of patients. Its hard limits include a maximum below 105% of 45 Gy for bowel, sigmoid, bladder and rectum.
  • Brachytherapy limits (D2cc in EQD2, added to the external beam dose) are on the GYN brachytherapy page.
References (3)
  1. NRG cervix RT template — NRG Oncology Protocol Development Template for Radiation Therapy — Gynecological Cancer: Cervix, Uterine Cervix. NRG Oncology protocol template Source
  2. EMBRACE II — The EMBRACE II study: The outcome and prospect of two decades of evolution within the GEC-ESTRO GYN working group and the EMBRACE studies. Clin Transl Radiat Oncol. 2018;9:48–60 Source
  3. Verma 2014 — Dosimetric predictors of duodenal toxicity after intensity modulated radiation therapy for treatment of the para-aortic nodes in gynecologic cancer. Int J Radiat Oncol Biol Phys. 2014;88(2):357–362 Source

Values quoted from NRG cervix RT template and EMBRACE II, checked by DoseLab on 2026-09-30. Verify against your protocol, institutional policy and physician directive before clinical use.

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Protocols & Literature

Clinical resourceSource Verified
NRG Oncology Protocol Development Template for Radiation Therapy — Gynecological Cancer: Cervix, Uterine Cervix
Lee YC, Benedict SH, Tsai P, Liang X, Padgett K, Portelance L · NRG Oncology Medical Physics Subcommittee / Radiation Oncology Committee · 2024

The template NRG Oncology gives investigators for writing the radiation therapy section of a cervical cancer trial, covering external beam (photon, MR-linac and proton) and brachytherapy. It describes supine or prone setup, full- and empty-bladder simulation scans fused to build an internal target volume, diagnostic MRI and PET/CT fusion, standard structure names (including Spc_Bowel and BoneMarrow), example prescriptions, HDR point A and volume-directed (CTV_HR) brachytherapy, and per-protocol and variation-acceptable compliance criteria for both the external beam plan and the combined EBRT + brachytherapy dose. Its values are examples meant to be edited for each trial. DoseLab's cervix tables quote its per-protocol levels.

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Landmark trialSource Verified
The EMBRACE II study: The outcome and prospect of two decades of evolution within the GEC-ESTRO GYN working group and the EMBRACE studies
Pötter R, Tanderup K, Kirisits C, et al. · EMBRACE Collaborative Group / GEC-ESTRO GYN · 2018

The overview of the EMBRACE II study of image-guided IMRT with chemotherapy followed by MRI-based adaptive brachytherapy for locally advanced cervical cancer. It sets out the study's external beam dose constraints (hard and soft, with separate bowel limits when the para-aortic nodes are treated), the brachytherapy planning aims and limits for the high-risk CTV, GTV, point A, bladder, rectum, sigmoid and bowel in total EQD2, and the vaginal dose points. Open access.

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Contouring atlasUnder Review

International consensus guidelines for the clinical target volumes in IMRT for the definitive treatment of cervical cancer, drawn mainly on MRI: the gross tumor, cervix, uterus, parametria, vagina and nodal regions. Citation checked against Europe PMC.

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Landmark trialUnder Review

EMBRACE-I, a prospective multicenter cohort of chemoradiation with MRI-guided adaptive brachytherapy for locally advanced cervical cancer, reporting high local control and the dose–response relationships behind the EMBRACE II planning aims. Citation checked against Europe PMC.

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Contouring atlasUnder Review
Female RTOG Normal Pelvis Atlas
Gay HA, Barthold HJ, O'Meara E, et al. · NRG Oncology / RTOG · 2012

NRG Oncology's hosted copy of the RTOG female normal pelvis atlas (from the RTOG pelvic normal tissue consensus): bladder, rectum, sigmoid, bowel, femoral heads and other pelvic organs, as a PowerPoint and an interactive viewer.

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AAPM reportUnder Review

AAPM Task Group 132 report on image registration and fusion in radiotherapy. It reviews rigid and deformable registration, points out that every registration carries an uncertainty that should be understood and communicated, and gives recommendations for commissioning and quality assurance of registration software and for checking individual registrations. Citation checked against Europe PMC.

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Clinical resourceSource Verified

Endorsed eviQ protocol for definitive external beam radiotherapy for cervical cancer, given with brachytherapy and usually with weekly cisplatin. It covers supine setup with a comfortably full bladder, MRI and PET/CT for delineation, an optional internal target volume from full- and empty-bladder scans, 45 Gy in 25 fractions with a sequential or SIB nodal boost, and an organ table (small bowel, duodenum, rectum, bladder, femoral heads, kidneys, bone marrow and, for extended fields, spinal cord). Several of its organ values are credited to post-operative trials (RTOG 1203, RTOG 0724) and EMBRACE II. Its review is due 31 December 2026.

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