Comparison between 3 Dimentional Conformal Radiotherapy, Sequential Intensity Modulated Radiotherapy and Simultaneous Integrated Boost Intensity Modulated Radiotherapy as a Boost for Pelvic Lymph Nodes for Patients with Cancer Cervix

Aim: The study aims to Compare 3 Dimentional Conformal Radiotherapy (3DCRT), sequential Intensity Modulated Radiotherapy (sIMRT), Simultaneous Integrated Boost-Intensity Modulated Radiotherapy (SIB-IMRT) for positive pelvic lymph nodes for patients with cancer cervix treated with concurrent chemo-radiotherapy.

Materials and Methods: C-T simulation was done for 10 patients with cervix cancer who had pelvic nodes, the clinical target volume (CTV) included the upper vagina, parametria, uterus, cervix, presacral area, and draining lymph nodes. One cm was added to form the Planning Target Volume (PTV). The organ at risk (OAR) included the bladder, rectum, pelvic bones marrow (PBM). Nodal CTV was expanded 7 mm to form nodal PTV. 3DCRT, sIMRT and SIB-IMRT planes were done. Doses of 3DCRT and sIMRT plans were 50 Gy to pelvic PTV with a nodal boost of 16 Gy in a total of 33 fractions while SIB plan treating the targets to the same doses in 25 fractions (i.e., 2 Gy per fraction to the pelvic PTV and 2.4 Gy per fraction to the boost PTV).

Results: Comparable target volume coverage (V95%) was achieved with the 3 plans, maximum dose was significantly reduced using conformal plan for the boost plans with p= 0.01. Median dose for V45 of the rectum was the lowest with sIMRT (p= 0.015), the median dose for V50 of the bladder was the lowest in sIMRT plan (p= 0.007), the V10 of the bone marrow was low in the sIMRT plan (p= 0.015).

Conclusion: The sIMRT boost for pelvic lymph nodes produce the same coverage as 3DCRT and SIB-IMRT and spares significantly the OAR.