Today I will be talking about interstitial brachytherapy and its role in vulvar-vaginal malignancy. I will also show some cases that we have done in Kathmandu. So I will be talking about brachytherapy, what is interstitial brachytherapy, what is image-guided brachytherapy, its role in vulvar and vaginal malignancy. And I will conclude it. So talking about brachytherapy, there are two types of radiation. One is external radiation where the radiation source is outside the body and the radiation is given from outside to inside. While brachytherapy is a catheter-based delivery system in which radiation source is near the tumor or inside the tumor and the radiation comes from inside to outside. So the beauty of this technique is we get a very high dose in the vicinity of the tumor and low dose outside. So with this technique, the advantages will be there will be highly localized radiation dose to a very small volume which improves the control of the tumor. The surrounding structure gets lesser dose so it causes less side effect. It is also called the ultimate form of conformal radiotherapy. Treatment time is very short compared to external radiation. Usually the treatment is over in few days or around a week and the central portion of the tumor which is very hypoxic and relatively radio-resistant, it gets a very high dose and it is more effective for the hypoxic areas. Brachytherapy can be categorized into different ways like location of the implant. If it is inside the body cavity, it is called intracavitary. If needles are placed inside the tissue, it is called interstitial. Type of loading of the radiation source like preloading, afterloading, dose rate, high dose rate, pulse dose rate or low dose rate or duration of implant. You can do a temporary implant where you put brachytherapy source and remove it or permanent implant like sheets. Coming to gynae brachy, the most common brachytherapy done in gynae is intracavitary which is commonly done for cervical cancer. Another type is interstitial where needles and catheters are inserted in the tumor. We will be discussing it in detail. Third is intravaginal which is done for vaginal cough brachytherapy. You can see in the image the intravaginal brachytherapy and other are rarely used some of which are intraoperative brachytherapy, seed brachytherapy, etc. So interstitial brachytherapy, the concept is putting interstitial brachy needles inside the tissue. It is usually implanted through the perineum and it is relatively invasive compared to intracavitary but less invasive compared to surgery. This is old photographs from the textbook showing interstitial needles being placed and the imaging is x-ray based imaging. So the indication of interstitial brachytherapy, the most common indication is in carcinoma cervix where you have distorted anatomy and you cannot put standard applicators like Fletcher applicators. If there is narrow vagina, obliteration of fornices or can't be identified and you have to treat peripheral diseases like if there is bulky parametrial disease then interstitial brachytherapy is used. Postoperative stump recurrence or bulge recurrence also you can use interstitial brachytherapy. For vaginal cancer if there is paravaginal disease or distal vaginal involvement it is used. For vulvar cancer, early vulvar cancer, interstitial brachytherapy can be used as a radical treatment or boost treatment and in a recurrent disease of all these sides interstitial brachytherapy is one of a good treatment option. So talking about instrument, in this photograph we can see the different type of instrument that we are using for interstitial brachytherapy. It can be either freehand or template. The first image you see there is a periurethral disease just like in our case. It is from the literature. It is not our case. So the flexible catheters were placed without using any template. It's called freehand implant or you can use a template like you can see the green template which guides the needle placement. The needles can be steel needle which are rigid needles. You can see in the image or it can be flexible catheters which are made with plastic. So talking about the template, these are called templates which are placed in perineum for guiding the needle. They have got different holes from which you can insert the needle. It is usually made of plastic or rubber. The upper one is the Mupit template and the lower is Sayad Neblet template. This is one of the case, our case in which we have done Sayad Neblet template insertion. This is one of the example in which in cervix cancer with vagina stenosis where we could not do intracavitary brachytherapy, we have done a template brachytherapy. Talking about anesthesia, it can be done in spinal, regional or local. If it is template based, usually spinal or GA is needed but for vulvar interstitial, regional or field block is enough. So what is image guided brachytherapy? Image guided brachytherapy is using the modern imaging technology like 3D imaging to assist your implant or to do the dose planning. Previously, brachytherapy guidance was done using x-ray in which you cannot see the tumor or your target tissue and normal organ but now you can see, you can do CT scan for brachytherapy and more commonly MRI is being used for guiding the implant. Different type of imaging like x-ray, ultrasound, CT, MRI, PET-CT have been used for assisting and planning the implant. And the advantage of this is now with visualization of tumor, you can accurately place your needles and catheters, you can avoid normal structure like rectum or bladder which makes this procedure less traumatic and with image based brachytherapy planning, you can get a better estimate of the dose that you are giving to tumor as well as to the normal structure. So now talking about vaginal cancer, it is relatively rare gynecomastia and important thing is the spread of the disease. It has the predilection for nodal metastasis, pelvic nodes for the upper vaginal tumor and inguinal for lower vaginal treatment for tumor. Radiation is preferred treatment due to organ function preservation because curative organ sparing surgery in this location is difficult. Usually combination of external beam and brachytherapy is used. External beam to cover a disease with margin and surrounding lymphatic and brachytherapy to boost the gross tumor. Brachytherapy can be of two forms in vaginal tumor. The first is intravaginal brachytherapy. This is a non-invasive technique in which you put a cylinder in vagina like you can see in the image. There is a vaginal cylinder. The green one interiorly is bladder and posteriorly it is rectum. It is non-invasive but you cannot treat a thick tumor like if it is more than five millimeter with this technique. Then you need to put needles in vaginal tumor. There is a guideline American Brachytherapy Society guideline for brachytherapy in a vaginal cancer. So they recommend interstitial brachytherapy for any lesion more than five millimeter. For upper vaginal template based brachytherapy is preferred and for lower free end is preferred. They strongly suggest using imaging for implant as well as planning and they have given different dose guidelines for different target. And for recurrent tumor this has to be adjusted considering the previous radiation dose. So they have given different external beam and different brachytherapy dose combination. You can choose any of this. However, there is not a standard fixed dose protocol for interstitial brachytherapy. This is one of our case in which we have done a transrectal ultrasound guidance for brachytherapy. We have used a Syed Neblet template. So template based brachytherapy was done with perineal template and steel needle you can see over there. And this is the dosimetry CT scan you can see the disease being covered by the needles. This is another case of vaginal brachytherapy which we have done. So after giving the external radiation there was a residual disease. The red one is the residual. If you see it is between the rectum and the vagina and it was located only in the posterior part. So what we did is we did intravaginal brachytherapy along with free needles. So with two needles we could target this tumor and give adequate dose to the tumor. Now coming to the carcinoma of vulva. It is also a relatively rare tumor and standard treatment as we know is surgery. Lymphatic involvement depends on depth of the tumor and size of the tumor and the pattern is from superficial inguinal femoral to deep to pelvic node. Surgical margin is very important prognostic factor for recurrence. Surgery is especially beneficial when patient has comorbidity and is not fit for surgery. It can be used as single modality or boost after external radiation which is more common. There are case series and case report which say that it gives good local control but toxicity especially vaginal necrosis vulvar necrosis is a concern with most of the series reporting rate of 10 to 25 percent. It is mainly because the lower vagina is more radiosensitive compared to upper vagina. So the major indication are small superficial lesion especially in central structure like around anus, clitoris or urethra where brachytherapy alone can be done to a dose of 45 to 50 gray. Large inoperable lesion where you can combine external radiation with brachytherapy boost The usual dose is 18 to 21 gray and in recurrent lesion where the dose is individualized based on previous radiotherapy details. So I will talk about only one literature. It is one of the largest case series reported from Tata Memorial in Mumbai. They have done interstitial brachytherapy in 38 patients in which in 29 they have used external therapy and brachytherapy as a boost while they have done radical brachytherapy in 9 patients. They have done mixed of template waste brachytherapy free and brachytherapy and both the local control rate was 77 percent in whole of the series and 5 year disease free and overall survival was 51 percent and 82 percent which is a respectable figure. Even in their series the concern was late toxicity which was seen in 22 percent of the patient. Underlying that case selection is very important in vulvar brachytherapy. This is from the literature from their paper in which they have shown that distal vulvar tumor, this is more of a varicose type of carcinoma in which they have done a free end implant with plastic catheters while if the tumor has got deeper component like in this second case apart from the free end catheter they have also put a template and done a combination of template and free end implant which is for the deeper tumor. So talking about one of our case, this is our case, she is a 51 year lady who presented with us after surgery for CA vulva, she had recurrence, she received external beam radiation and again she had recurrence so she was referred for interstitial brachytherapy. We can see the lesion it is in the right side, it was more of a distal lesion. You can see the lesion now and we took her for interstitial brachytherapy, this is our setup for doing interstitial brachytherapy. So we put four flexible catheters in the lesion, these are the images after inserting the catheters. This is the dosimetry, you can see that with interstitial brachytherapy you can localize the dose very much around the tumor. This type of dosimetry you cannot see in external radiation like IMRT. And these are the results, in one month there was some redness, some erythema but the bulk of the tumor was gone and in six month follow up she had a good local control and there was no late effect. So this shows the role of brachytherapy in difficult cases like recurrence. So in conclusion, interstitial brachy has established role in gyne cancer. It is a skill-based procedure so requires training and has got a learning curve. Outcome are promising. It is a team-based approach and the key is to identify proper patient and tumor board based discussion and proper selection of the patient is key for selecting patient for interstitial brachytherapy and getting good result. With this I would like to conclude my presentation. Thank you.

interstitial brachytherapy

vulvar-vaginal malignancy

catheter-based delivery system

image-guided brachytherapy

multidisciplinary approach