RTOG 0418 A Phase II Study of Intensity Modulated Radiation Therapy (IMRT) to the Pelvis +/- Chemotherapy for Post-operative Patients with either Endometrial or Cervical Carcinoma
Endometrial cancer patients: IMRT 28 fractions over 5.5 weeks.
Cervical cancer patients: IMRT 28 fractions over 5.5 weeks and concurrent cisplatin starting on a Monday or a Tuesday for 5 weeks.
Prescription dose shall be according to the following specifications:
The vaginal planning target volume (PTV) (ITV with 7.0 mm margin) and nodal PTV will receive 50.4 Gy in 28 fractions. Treatment will be delivered once daily, 5 fractions per week, over 5.5 weeks. All targets will be treated simultaneously. Breaks in treatment should be minimized. Total treatment breaks exceeding 5 consecutive days will be considered a major violation.
The prescription dose is the isodose which encompasses at least 97% of the vaginal PTV and nodal PTV. No more than 20% of any PTV will receive > 110% of its prescribed dose. No more than 1% of any PTV will receive < 93% of its prescribed dose. No more than 1% or 1 cc (whichever is smaller) of the tissue outside the PTVs will receive > 110% of the dose prescribed to the primary PTV.
The vaginal cuff may be boosted with a high-dose rate dome cylinder at the discretion of the treating radiation oncologist. If a boost to the vaginal cuff is used, the dose should be limited to 600cGy x1-2 fractions
The nodal CTV should include lymph nodes that drain the involved site and adjacent perinodal soft tissue. This should include the internal (hypogastric and obturator), external, and common iliac lymph nodes; if the cervix is involved (even with endometrial cancer), presacral lymph nodes and soft tissues should be included as well, down to the level of S3. Identification of the CTV usually begins with the identification of the iliac vessels. The nodal CTV will include the vessel , perinodal tissue (on the pelvic wall side, the margin will exclude psoas and piriformis muscle) and pertinent clips. The average margin will be 7 mm. Bone and intraperitoneal small bowel should be excluded from the CTV; also, iliopsoas muscle that lies adjacent to clinically negative lymph nodes should also be excluded from the CTV. Approximately 1-2 cm of tissue anterior to the S1, S2 and S3 sacral segments is usually added to the CTV for patients with cervical carcinoma in order to include the presacral lymph nodes and uterosacral ligaments. The most antero-lateral external iliac lymph nodes that lie just proximal to the inguinal canal should be excluded from the CTV (i.e., nodal CTV should stop right at the level of the femoral head). The CTV of the nodes should end 7 mm from L4/L5 interspace to account for the PTV. The PTV for nodes to stop at L4/L5 intespace.
The Gross Tumor Volume (GTV) is defined as all known gross disease determined from CT, clinical information, and MRI. In this study, which is used for post-operative patients with no gross disease, there should not be a GTV.
The Clinical Target Volume (CTV) is defined as areas considered to contain potential microscopic disease, delineated by the treating physician.
Internal Target Volume (ITV) is defined as the volume of the vagina that is in both the empty and full bladder CT scans that are done at the time of simulation and fused together. This volume accounts for internal organ motion.
The Planning Target Volume (PTV) will provide a margin around the ITV to compensate for the variability of treatment setup. Careful consideration should be made when defining the superior and inferior margins in three dimensions. organ motion. The ITV is drawn after the full and empty bladder scans are fused together, and it should encompass the vagina and paravaginal soft tissues from both scans. This is because patients are not able to maintain constant levels of bladder filling, despite careful counseling. Patients should, however, be treated with a full bladder, because full bladder pushes the small bowel up and out of the field. The inferior limit is usually around the level of the upper third of the symphysis pubis but can be individualized based on inferior spread of the patient’s tumor on prior pre-operative physical examination and post-operative pathology reports. The lateral margin of the vaginal PTV should be to the obturator muscle. However, at least 3 cm of the vagina needs to be treated or at least 1 cm below the obturator foramen.
The Planning Target Volume (PTV) will provide a 7 mm margin (anteriorly, posteriorly, laterally,as well as in the superior and inferior directions) around the nodal CTV. The vaginal PTV will be 7.0 mm around the vaginal ITV anteriorly, superiorly, inferiorly, laterally, and posteriorly
Normal structures will be contoured using the full-bladder CT scan.
Bladder – will be outlined on every slice, including the portion
inferior to the planning target volume.
Rectum – will be outlined on every slice, including the portion inferior to the planning target volume and superior to the level that it leaves the posterior pelvis around the region of the rectosigmoid.
Small bowel – will be outlined on every slice, including at least 2 cm above the planning target volume. It includes the volume surrounding loops of small bowel out to the edge of the peritoneum because the bowel may lie within this space at any time throughout the course oftreatment.
The femoral heads and the sacrum should be contoured in all slices.
Participants are strongly encouraged to remain within these limits:
Small bowel < 30% to receive ≥ 40 Gy, minor deviation 30% to 40
Rectum < 60% to receive ≥ 30 Gy, minor deviation 35% to 50 Gy
Bladder < 35% to receive ≥ 45 Gy, minor deviation 35% to 50 Gy