Dental and Medical Myths

Introduction:
Radiotherapy is the art of using ionizing radiation to destroy malignant tumors while minimizing damage to normal tissues ( J.coate).

CIN and Cancer Difference

Radiotherapy is the important modalities of therapy for human cancers apart from surgery. It is very useful in the treatment of many cancer specially female reproductive tract.

fibroscopic visualization technique for urinary bladder visualization

Mechanism action of radiotherapy

1)Radiation causes ionization of water of the cancer cells into hydrogen and hydroxyl ions which are toxic and causes damage to DNA of the cell and thereby cell death. [The target for radiation is injury to DNA, which is responsible for cell mitosis. So injury to DNA causes mitotic cell death.]
2)It stimulates fibrous tissue reaction in the surrounding stroma and resulting filorosis causes entanglement of the tumour cells and prevents local spread.
3)Reducing vascularity by radiation end arteritis.

Technique/Methods of radiotherapy

For gynecological cancers therapeutic
radiation is delivered as –

• a) External radiation (Teletherapy)
• b) Internal radiation (Brachytherapy)

a) Teletherapy- The goal of teletherapy is to ensure that radiation is delivered to the target tissue without affecting uninvolved tissues from distance (usually 100cm). Cobalt 60 is the common teletherapy source for external radiation; other one is cesium 137. External radiation is used to treat large volumes of tumours, lymph nodes, parametrium.
b) Brachy therapy (internal radiation)

Here source of therapeutic ionizing radiation is placed close to the treatment area, chief advantages of it is that a relatively high dose of radiation can be applied to a limited anatomic region.
Commonly used sources are caesium-137
Cobalt - 60
The application may be

1. Intracavitary
2. Interstitial Intracavitary – The devices for brachytherapy consists of hollow stem; intrauterine tandem, which is placed within the uterine cavity. Special devices used for vaginal placements are called vaginal ovoids or colpostats.
   Interstitial – Using needles, wires or seeds used as radio active sources within tissues.
   

   Indication of radiotherapy

   a) Cervical cancer- It is used in all stages. In squmous cell type, response is best for radiotherapy.
   b) Endometrial cancer- Adenocarcinoma response to radiohterapy.
   c) Vaginal cancer – Here radiotherapy is best than surgery.
   d) Vulval cancer – Generally radiothery is not used, as vulval skin is moist, Causing irritation & distort the shape of vulva.
   e) Orarian cancer – Actualy no role of radiotherapy but in dysgerminoma, responsed of radiotherapy is good.
   f) Choreocarcinoma – When metastasis to liver & brain.
   

   Uses of radiotherapy in specific cancer

   Cervical cancer: Treatment of cervical cancer is a prime example of successful application of radiotherapy.
   Radio therapy can be used in all stages of carcinoma of cervix but in stage 0 or pre-invasive carcinoma we do not use radiotherapy due to damage of ovarian tissue.
   In cancer cervix
   
    
   In early stage – option of stage 1 + upto stage II A
   Mode of treatment –
   a) Only surgery
   b) surgery + Radiotherapy
   c) Only Radiotherap
   
   
   But stage IIB & on wards option of mode of treatment
   •Only radiothery
   •Here surgery is not possible.
   Goal of external radiation – in cervical cancer is to Sterilize metastatic disease to pelvic lymphnode and parametrium and to decrease the size for cervix to allow placement of intracavitary radio active sources.
   It is also used as palliative radiation for
   advanced cervical cancer for-
   •Control of bleeding
   •Pain relief.
   Radiotherapy combined with chemotherapy specially platinum based cisplatin or carboplatin provides better survival.
   Dose of radiotherapy
   Bnachytherapy – in the form of intracavitary.
   The goal is to deliver a dose of 70-80 Gy at point A, which is situated 2 cm above the mucosa of lateral vaginal fornices & 2 cm lateral to the central uterine canal.