 and invasion of adjacent organs. We also focus on the role of MRI in detecting vulvar cancer recurrence. It occurs in 30–50% of patients within two years after initial treatment, the majority appearing near the original resection margins or in ipsilateral inguinal or pelvic lymph nodes. Finally, we describe early and delayed complications of CRT, such as cellulitis, urethritis, vulvar edema, bone changes, myositis, and fistulization. By describing the role of MRI in assessing LAVC response to CRT and detecting recurrence, we hope to provide suitable indications for a personalized approach.


Introduction
Vulvar cancer is a rare gynecologic tumor, representing 4% of all gynecologic malignancies [1]. Approximately one-third of patients with vulvar carcinoma are diagnosed with locally advanced disease at presentation [2]. This has severe implications for patient survival, as 5-year survival rates range from 86% for localized disease to 53% for locally advanced disease, and 19% for patients with distant metastases [3]. However, there is little consensus regarding the definition of the best initial therapeutic approach.
Historically, the term LAVC has been used to describe different clinical scenarios, including: (a) large primary tumors (>4 cm) invading adjacent perineal organs; (b) tumors presenting with bulky inguinal lymphadenopathies, which may be fixed to the fascia, muscle, or vessels; and (c) tumors that cannot be managed with radical vulvar resection [4]. A staging system has been proposed by the International Federation of Gynecology and Obstetrics (FIGO), and was revised in 2021 (Table 1). According to this system, stages IIIA and IVA are considered LAVC [5]. Tumor of any size with extension to lower one-third of the urethra, lower one-third of the vagina, lower one-third of the anus with negative nodes III Tumor of any size with extension to upper part of adjacent perineal structures, or with any number of nonfixed, nonulcerated lymph node IIIA Tumor of any size with disease extension to upper two-thirds of the urethra, upper two-thirds of the vagina, bladder mucosa, rectal mucosa, or regional lymph node metastases ≤ 5 mm IIIB Regional lymph node metastases > 5 mm IIIC Regional lymph node metastases with extracapsular spread IV Tumor of any size fixed to bone, or fixed, ulcerated lymph node metastases, or distant metastases IVA Disease fixed to pelvic bone, or fixed or ulcerated regional lymph node metastases IVB Distant metastasis The baseline evaluation of vulvar cancer is based on imaging investigations that are chosen according to the first clinical examination. This is the first approach to assess the extent of disease, providing information about the number of vulvar lesions and the relative site and size, the distance to midline, and finally, the presence of palpable inguinal lymph nodes. A concurrent ultrasound of the inguinal lymph nodes provides more accurate information about lymph node status [6,7].
When at clinical examination, the surrounding perineal tissues or medial structures are infiltrated. Additional imaging is essential to assess the involvement of the deep organs such as the vagina, urethra, bladder, anal canal, and rectum, and specifically, MRI is recommended given the high soft tissue resolution [8,9].
Additional investigations could be required as appropriate, such as endoscopy (cystoscopy/ano-rectoscopy), to evaluate the mucous membranes of infiltrated pelvic organs, and CT or FDG PET/CT to assess the involvement of pelvic lymph nodes and distant organs [10][11][12].
Therefore, a combined clinical and imaging evaluation is essential in addressing the specific individualized treatment approach. Currently, this may include radical surgery with or without plastic reconstruction, external beam radiotherapy (RT), chemoradiotherapy (CRT), and interventional radiotherapy (IRT, Brachytherapy), which may be used in combination [13][14][15] or with other local therapies, such as electrochemotherapy [16]. The chosen approach depends not only on tumor extent, but also on the patient's performance status and clinical characteristics. In fact, patients with LAVC are often older women with age-associated comorbidities [17][18][19]. Because more than 50% of patients develop severe post-surgical complications, sometimes motivating additional procedures, the frequently required radical surgery is not normally recommended in these patients [20]. Adjuvant RT or CRT may follow, depending on residual disease and the risk of recurrence [15,21]. However, there is no robust evidence on the benefit of neoadjuvant CRT and RT, which can be explained by small sample sizes, study heterogeneity, and divergent CRT and RT protocols [22]. Several groups have also evaluated definitive CRT by comparing the results obtained from patients treated with neoadjuvant CRT. Compared to upfront radical surgery, definitive CRT (+/−IRT) allows organ preservation with good clinical outcomes and no significant differences in patient survival [23]. Curative treatment may not be possible due to the advanced stage of disease or poor patient performance status. Moreover, local RT can be used to achieve symptom palliation and improve quality of life [24]. IRT may also be useful, particularly in patients with severe comorbidities and contraindications to surgery [18,25]. The technique allows the delivery of a high radiation dose to the tumor, while sparing the adjacent perineal organs. Research is currently focused on intensity-modulated RT for VC [1,26], which maximizes the radiation dose to the target volume, reducing toxicity and exposure to adjacent organs. Target therapies are also under development [13].
MRI plays an essential role in contemporary RT planning due to its high soft tissue resolution and tumor delineation, as well as its ability to detect the invasion of adjacent structures [9,27,28]. Moreover, assessment of tumor response is a key factor in defining the appropriate approach after CRT. Although MRI is generally accepted in the evaluation of tumor response after multimodal treatment, there is no sufficient supporting evidence in the literature. When there is no evidence of residual disease, clinical observation is recommended. On the contrary, patients with residual disease must be considered for tumor resection or additional RT/CRT [1,14,25,26]. Therefore, the multidisciplinary tumor board is crucial in defining the best approach for each patient with LAVC, either before or after multimodal treatment [8,14,25,29].
In this pictorial review, we will discuss the role of MRI for patients with LAVC who are candidates for CRT, and describe the MRI features of LAVC during treatment and follow-up, highlighting the findings that influence clinical management. In addition, we will address the MRI features of local recurrence according to its type and location.

MRI Technique
The currently accepted MRI protocol for patients with VC has been proposed by the European Society of Urogenital Radiology (ESUR) ( Table 2) [9]. Recommendations for optimal patient preparation include fasting 4-6 h before the examination, anti-peristaltic agent administration, and bladder voiding; vaginal opacification with gel is optional. The patient should be imaged supine, with a phased array pelvic coil [11] or an eight-channel cardiac coil [12].

Imaging Protocol
-T1-weighted fast spin-echo (FSE) sequence in axial plane -T2-weighted FSE sequences in two imaging planes (axial/sagittal) -Small FOV T2-weighted FSE sequences in axial oblique plane (perpendicular to the long axis of the urethra) -Small FOV T2-weighted FSE sequences in oblique coronal plane (parallel to the long axis of the urethra) -DWI using a single-shot spin-echo echo-planar imaging sequence with high b-values (0, 1000 s/mm 2 ) with the same orientation and location used to acquire axial oblique FSE T2-weighted images -T2-weighted FSE sequence in axial plane up to renal hila -Three-dimensional spoiled gradient-pulse FS T1 weighted before and after administration of 0.1 mmol/kg of gadolinium at a rate of 2 mL/sec, followed by a 20 mL saline bolus injection, in the axial/axial oblique plane and in the coronal/coronal oblique plane, pre-and post-contrast administration, after an 18 s of delay and at 15 s intervals for 3 scans to better obtain arterial portal and equilibrium phases

MRI Findings of LAVC Prior to CRT
MRI is considered the best imaging technique with which to perform local staging [9,27]. VC manifests as a mass of intermediate-to-high signal intensity on T2-weighted images (WI), with avid enhancement and restricted diffusion. According to the new updated 2021 FIGO staging system, stage I tumor is confined to the vulva; stage II tumor extends to the lower one-third of the vagina and/or of the urethra, and the anus; stage III tumor involves the adjacent perineal structures (upper two-thirds of the vagina and/or urethra, bladder or rectal mucosa; IIIA) or not fixed, nonulcerated inguinal lymph nodes (IIIB and IIIC). Differently, stage IV is defined by the extension to the pelvic bone (IV A) or the presence of distant metastasis, including pelvic lymph nodes (IV B) [5].
In order to ease communication between radiologists and referring physicians, and to allow for accurate treatment planning, we propose a point-by-point MRI report.

Vagina
LAVC extension to the vagina manifests as a disruption to the vaginal wall caused by the intermediate-to-high signal intensity mass on T2-WI [10], with simultaneous loss of the linear appearance of the vaginal vault. Obliteration of the paravaginal fat is also seen when the tumor extends beyond