Vulvar cancer target delineation is demanding because the plan has to cover primary disease, adjacent soft tissues, pelvic nodes, and both inguinofemoral basins without losing control of morbidity. The chapter explains why IMRT has become the dominant approach: it handles large irregular targets better than historical techniques and improves normal tissue sparing.
For the broader framework, see our Target Volume Delineation and Field Setup – Complete Clinical Guide. If you want a nearby pelvic comparison, our article on definitive gynecologic IMRT fits naturally alongside this chapter.
In this article
Introduction
Radiotherapy for vulvar cancer remains one of the more difficult gynecologic sites to manage. The reason is straightforward: treatment volumes are large and morbidity can be substantial, especially when intensive chemoradiation is needed for advanced disease.
The chapter notes that IMRT is now widely used in routine practice and in contemporary trial protocols, largely because published series have shown less morbidity and high treatment efficacy when compared with older techniques. Consensus contouring guidelines and newer planning recommendations have also pushed practice toward more consistent delivery across institutions.
General Principles
Management starts with surgery when the disease is resectable, but radiotherapy enters early when pathologic risk increases. The chapter describes radical vulvectomy as the typical surgical approach, with wide local excision reserved for selected patients with small, well-lateralized tumors.
Nodal evaluation usually involves inguinofemoral dissection or sentinel lymph node biopsy, particularly when tumor invasion is >3 mm, lymphovascular space invasion is present, and/or the disease is high grade. After surgery, RT is typically delivered when there is lymphovascular space invasion, tumor invasion >5 mm, surgical margins <8 mm, microscopically positive margins, grade 3 disease, and/or positive lymph nodes. The text also notes that smaller margins, such as <5 mm, may still justify adjuvant treatment.
Unresectable disease changes the sequence. Those patients are candidates for preoperative RT and, at many centers, receive concurrent chemotherapy. Clinical and pathologic response rates can be high with chemoradiation in this setting. Even so, the standard backbone remains pelvic-inguinal irradiation. Brachytherapy plays only a limited role, mainly for women with a positive vaginal margin or for medically inoperable disease.
IMRT for Vulvar Cancer
IMRT keeps drawing attention because the target is large and toxicity matters. The chapter highlights that the completed GOG 0279 trial of definitive chemoradiation in locally advanced disease required IMRT.
Dosimetric work and preliminary clinical series reported better normal tissue sparing and lower acute and chronic toxicity than conventional approaches. The limitation is equally clear: long-term outcome data remain limited. In practice, that makes the published consensus recommendations and pictorial atlas especially useful for keeping contouring quality tight.
Simulation
Simulation has to reduce uncertainty before planning even starts. The chapter recommends the supine position with a modest frog-leg setup and customized upper and lower body immobilization to reduce skin folds.
Intravenous contrast-enhanced CT simulation is helpful because the vasculature works as a surrogate for lymph node position. The anus should be marked with a fiducial, and radiopaque wire should outline gross disease or surgical scars. The text also advises simulating all patients with 0.5 to 1 cm bolus over the vulva, especially in the preoperative setting or when gross disease is present. Groin bolus should be considered when there is clinically obvious skin involvement.
For locally advanced cases, especially with vaginal, urethral, and/or anal extension, the chapter recommends full-bladder and empty-bladder scans so that an ITV can be generated. If the rectum is distended beyond 3.5 cm at simulation, the scan should be repeated after bowel preparation.
Image Registration
Image registration matters most in the preoperative and definitive settings because GTV definition depends on more than one data source. PET-CT helps outline gross tumor volume, while gadolinium-enhanced pelvic MRI, with and without vaginal gel, improves assessment of tumor extent and its relationship to nearby normal tissues.
That sounds like a technical detail, but it changes the plan. Once disease approaches the vagina, urethra, bladder, or anal canal, poor anatomic definition quickly becomes poor target coverage.
Target Delineation
Vulvar cancer target delineation rests on three connected tasks: define gross disease, cover the primary site with adjacent uninvolved tissues at risk, and cover the bilateral pelvic and inguinofemoral nodal basins. The chapter structures this as GTV, CTV1, CTV2, and CTV3, followed by PTV expansions.
For the primary site, the chapter stays anatomic rather than purely geometric. If the GTV extends beyond the vulva, CTV1 includes that region with a 1 cm margin. Vaginal involvement means gross disease plus 3 cm of vagina. Involvement of the anus, anal canal, or bladder means gross disease plus 2 cm of the anus or bladder. Periurethral disease requires gross disease plus 2 cm of urethra; extension to the mid or proximal urethra means the entire urethra and bladder neck are included. Preclitoral disease calls for gross disease plus 2 cm and coverage of the suspensory ligament of the clitoris to the pubic bone. Bone and muscle stay out unless directly involved. When there is no skin involvement, CTV1 should be cropped 3 to 5 mm from the skin.
CTV2 covers the bilateral pelvic and inguinofemoral nodes. Common iliac, external iliac, internal iliac, and obturator nodal regions are built from the pelvic vessels with a 7 mm expansion while excluding uninvolved bone, muscle, and bowel. The presacral region is added when there is vaginal involvement and consists of the soft tissues anterior, at least 1.0 cm, to S1-S3. Perirectal nodes are added when the disease involves the anus or rectum.
In the groin, the chapter treats drainage as a compartment, not as a simple vessel margin. Superiorly, the compartment begins where the external iliac artery leaves the bony pelvis and becomes the femoral artery; inferiorly, it extends 2 cm below the saphenofemoral junction or to the lesser trochanter. Laterally it reaches the medial border of iliopsoas; medially, the lateral border of adductor longus or the medial end of pectineus; posteriorly, iliopsoas laterally and the anterior aspect of pectineus; medially and anteriorly, the anterior edge of sartorius. No posterior or lateral margin is added around the femoral vessels, and any visible lymph nodes in adjacent fat or soft tissue should be included.
PTV margins assume daily soft-tissue-matched CBCT. PTV1 receives 5 to 10 mm, PTV2 receives 5 to 7 mm, and the final PTV is the union of both, with possible cropping from the skin in the inguinal region. If daily CBCT is not used, the chapter advises considering 1 cm margins.
Base treatment target volumes
The table below organizes the main treatment volumes and shows exactly where the chapter prefers fixed margins and where it insists on an anatomic boundary.
| Target volume | Definition and description |
|---|---|
| GTV | Primary tumor defined on physical examination, CT, or PET/CT in the preoperative or definitive setting. Pelvic and inguinal lymph nodes: all nodes ≥1.5 cm, biopsy proven, and/or FDG avid. |
| CTV1 | GTV plus the remaining uninvolved vulva and adjacent soft tissues as indicated below. If the GTV extends beyond the vulva, CTV1 includes that region with a 1 cm margin. If the primary involves the vagina: gross disease plus 3 cm of vagina. If the primary involves the anus, anal canal, or bladder: gross disease plus 2 cm of the anus or bladder. If the primary is periurethral: gross disease plus 2 cm of urethra. If the primary extends to the mid or proximal urethra: include the entire urethra and bladder neck. If the primary is preclitoral: gross disease plus 2 cm and cover the suspensory ligament of the clitoris to the pubic bone. Bone and muscle are excluded unless directly invaded by tumor. Without skin involvement, crop CTV1 3 to 5 mm from the skin. |
| CTV2 | Bilateral pelvic and inguinofemoral nodal regions. The pelvic nodal regions, common iliac, external iliac, internal iliac, and obturator, are defined by including the pelvic vessels plus a 7 mm expansion while excluding uninvolved bone, muscle, and bowel. The presacral region should be included in patients with vaginal involvement and consists of the soft tissues anterior, at least 1.0 cm, to S1-S3. In patients with anal or rectal involvement, the perirectal nodes should also be included. The inguinofemoral compartment begins superiorly where the external iliac artery leaves the bony pelvis and becomes the femoral artery; the inferior border lies 2 cm below the saphenofemoral junction or at the level of the lesser trochanter. Laterally, use the medial border of iliopsoas; medially, the lateral border of adductor longus or the medial end of pectineus; posteriorly, iliopsoas laterally and the anterior aspect of pectineus; medially and anteriorly, the anterior edge of sartorius. No posterior or lateral margin is added around the femoral vessels. Any visible lymph nodes in adjacent fat or soft tissues should be included. |
| PTV1 | CTV1 + 5 to 10 mm. |
| PTV2 | CTV2 + 5 to 7 mm. |
Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 23.1). Note: the final PTV is generated as PTV = PTV1 ∪ PTV2 and may need to be cropped back from the skin in the inguinal region. The common iliac coverage extends to L4-L5, which does not cover the entire common iliac region in many patients; at some centers, if pelvic nodes are negative, the superior border is limited to the bottom of the sacroiliac joints. The chapter also stresses that inguinofemoral nodes should be treated as a compartment rather than a vessel margin and that 1 cm margins should be considered if daily CBCT is not used.
Boost volumes follow the same logic. For the primary site, CTV3 is the GTV plus 2 cm, anatomically confined to CTV1. For an involved node, the expansion is smaller and direct, which is useful when a simultaneous integrated boost is planned.
Boost target volumes
The chapter separates primary-site boost from nodal boost. That distinction keeps the biology and geometry of the primary bed from being blurred together with gross nodal disease.
| Target volume | Definition and description |
|---|---|
| GTV | Primary tumor defined on physical examination, CT, or PET/CT. Pelvic and inguinal lymph nodes: all nodes ≥1.5 cm, biopsy proven, and/or PET avid. |
| CTV3 primary | GTV + 2 cm and anatomically confined to CTV1. |
| PTV3 | CTV3 + 5 to 7 mm. |
| Nodal PTV | Nodal GTV + 5 mm. |
Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 23.2). The expansion assumes daily soft-tissue-matched CBCT; if daily CBCT is not used, the chapter recommends considering 1 cm margins.
The consensus figure makes one practical point obvious: even expert contours vary. In the example shown in the chapter, the modified consensus contour was pulled back from the space between the vulva and groin and from the skin surface when those regions were judged to be at low risk. That kind of reduction only works when the risk judgment is explicit.
The postoperative example in Fig. 23.2 is also useful as a dose-distribution reference: the pelvic and right inguinofemoral nodes received 45 Gy, the vulva received 50 Gy, and the left inguinofemoral region received 55 Gy, all in 25 fractions, with 5 mm PTV expansions because daily CBCT was used.
Prescription Recommendations
Dose selection in the chapter follows the treatment setting and the clinical goal. Primary-site boost is usually delivered sequentially with IMRT, a direct electron field, or interstitial brachytherapy, depending on response and tumor location.
When definitive treatment uses a sequential boost, the text recommends rescanning and adjusting the target volume before the boost phase begins. Grossly involved lymph nodes can be boosted with a simultaneous integrated boost. A common SIB schedule delivers 45 Gy in 25 fractions to the pelvis, with 2.25 Gy per fraction to positive pelvic nodes and 2.5 Gy per fraction to positive inguinal nodes, each with the relevant PTV margin.
The definitive example in Fig. 23.1 follows that logic closely. The pelvic nodes and primary were treated to 45 Gy in 25 fractions, the bilateral inguinofemoral regions received 50 Gy in 25 fractions, the FDG-avid right inguinal nodes received a simultaneous integrated boost to 62.5 Gy in 25 fractions, and the primary then received a sequential boost of 14 Gy in 7 fractions for a total dose of 64 Gy in 32 fractions.
Suggested dose and fractionation schemes
The table below summarizes the suggested schedules for preoperative, definitive, and adjuvant treatment while keeping the base plan separate from the boost volumes.
| Radiotherapy timing | PTV1 | PTV2 | PTV3 / boost |
|---|---|---|---|
| Preoperative | 45-50.4 Gy / 25-28 fractions | 45-50.4 Gy / 25-28 fractions | 57.6 Gy / 32 fractions |
| Definitive | 45-50.4 Gy / 25-28 fractions | 45-50.4 Gy / 25-28 fractions | Primary: 59.4-70.2 Gy / 33-39 fractions. Lymph nodes: 59.4-70.2 Gy / 33-39 fractions. |
| Adjuvant | 45-50.4 Gy / 25-28 fractions | 45-50.4 Gy / 25-28 fractions | Gross residual disease: 54-64 Gy / 30-32 fractions. For ENE: 64-66 Gy / 32-33 fractions. |
Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 23.3). If a simultaneous integrated nodal boost is used, the chapter recommends using the EQD2 dose equivalent in 25 fractions. It also advises considering a higher dose for close or positive margins and for lymphovascular space invasion.
Organs at Risk
In vulvar cancer, organs at risk are not a side note. They shape the plan. The chapter treats bowel, bladder, rectum, anus, and both femoral heads as routine OARs and adds pelvic bone marrow when chemotherapy is being given.
The practical priority is explicit: small-bowel constraints take precedence over coverage of the nodal SIB volume. That is the kind of planning decision that matters in a treatment where toxicity is already a major concern.
OAR definitions
Before dose can be discussed, the chapter standardizes what each structure actually includes.
| Organ | Definition and description |
|---|---|
| Bowel bag | Abdominal contents excluding muscle and bone. Inferiorly, contours start at the lowest small- or large-bowel loop, or above the anorectum, whichever is more inferior. Extend the contours at least 2 cm above the most superior portion of the PTV. |
| Rectum | Outer rectal wall, contoured inferiorly at the level of the ischial tuberosity and superiorly to where the rectum loses its round shape and connects anteriorly with the sigmoid. |
| Anus | Outer anus wall, contoured inferiorly from the anal verge identified by the radiopaque marker placed at simulation to the level of the ischial tuberosity in the axial plane. The anal canal is approximately 4 cm long. |
| Sigmoid | Bowel contoured inferiorly where the anorectum contour ends and ending where it connects to the ascending colon laterally. |
| Bladder | Outer bladder wall, contoured inferiorly from the bladder base and superiorly to the bladder dome. |
| Bone marrow | The pelvic bones serve as a surrogate for pelvic bone marrow. Included regions are the os coxae, L5 vertebral body, entire sacrum, acetabulae, and proximal femora. |
| Proximal femurs | Femoral head and neck, contoured inferiorly from the lowest level of the ischial tuberosities and superiorly to the top of the femoral head, including the trochanters. |
Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 23.4).
Normal tissue dose constraints
After the anatomic definitions, the chapter summarizes the constraints used in the consensus guidelines, based on RTOG 1203 and RTOG 0529 and already used in practice at Mayo Clinic in Rochester.
| Critical structure | Recommendation |
|---|---|
| Small bowel | Maximum ≤52 Gy. ≤30% receiving ≥40 Gy. <195 cm3 receiving ≥45 Gy. |
| Rectum | ≤80% receiving ≥40 Gy. |
| Anus | ≤80% receiving ≥40 Gy. Maximum ≤65 Gy. |
| Bladder | ≤35% receiving ≥45 Gy. |
| Femoral heads | ≤50% receiving ≥30 Gy. ≤35% receiving ≥45 Gy. ≤5% receiving ≥44 Gy. |
| Bone marrow | ≤37% receiving ≥40 Gy. ≤90% receiving ≥10 Gy. ≤80% receiving ≥20 Gy. |
Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 23.5). The chapter notes that small bowel takes priority over coverage of the pelvic nodal boost volume and that the anus constraint may not be achievable when tumor is immediately adjacent to or directly involves the anus.
Image-Guided Radiation Therapy
For daily setup, the chapter prefers CBCT for localization and soft-tissue matching. It allows a combination of kV imaging and/or CBCT, but the preference is clear: daily CBCT is the more reliable platform for this site.
That preference ties the whole chapter together. PTV margins, confidence in skin cropping, and the decision to stay with 5 to 7 mm or 5 to 10 mm expansions all depend on consistent image guidance. For the larger picture across disease sites, return to the Target Volume Delineation and Field Setup – Complete Clinical Guide.
