What is Maximum recommended external beam radiation therapy dose for a case of Carcinoma cervix is? and explain in detail?
Ans. C. 50 Gy."External-beam doses of more than 40 to 45 Gy to the central pelvis tend to compromise the dose deliverable to paracentral tissues and increase the risk of late complications. However, recently IMRT (Intensity Modulated Radiotherapy) allows delivery of doses exceeding 60 Gy with relative sparing of adjacent critical structures"Discussion:RADIATION THERAPY IN CERVICAL CANCERAs with radical surgery, the goal of radical radiotherapy is to sterilize disease in the cervix, paracervical tissues, and regional lymph nodes in the pelvis. Patients are usually treated with a combination of external-beam irradiation to the pelvis and brachytherapy. Brachytherapy is a critical element in the curative radiation Rx of all carcinomas of the cervix. Even relatively small tumors that involve multiple quadrants of the cervix are usually treated with total doses of 80 to 85 Gy to point A.Teletherapy dose rates:# An initial dose of 40 to 45 Gy to the whole pelvis, is believed to deliver a homogeneous distribution to the entire region at risk for microscopic disease and the additional tumor shrinkage achieved before brachytherapy outweigh other considerations.# External-beam doses of more than 40 to 45 Gy to the central pelvis tend to compromise the dose deliverable to paracentral tissues and increase the risk of late complications.# Recently, there has been considerable interest in the use of IMRT to treat the pelvis in patients with endometrial and cervical cancer. Unlike standard two-field and four-field techniques, IMRT makes it possible to deliver a lower daily dose to the intrapelvic contents than to surrounding pelvic lymph nodes. IMRT allows delivery of doses exceeding 60 Gy with relative sparing of adjacent critical structures.Brachytherapy dose rates:# An effort should always be made to deliver at least 85 Gy (with LDR brachytherapy-csl37) to Point A for patients with bulky central disease.# If the intracavitary placement has been optimized, this can usually be accomplished without exceeding a dose of 75 Gy to the bladder reference point or 70 Gy to the rectal reference point.# The dose to the surface of the lateral wall of the apical vagina should not usually exceed 120 to 140 Gy.# A total dose (external-beam and intracavitary) of 50 to 55 Gy appears to be sufficient to sterilize microscopic disease in the pelvic nodes in most patients. It is customary to treat lymph nodes known to contain gross disease and heavily involved parametria to a total dose of 60 to 65 Gy (including the contribution from brachytherapy Rxs).