Somorat Bhattacharjee1, Sunil R.A.2, A. Pichandi3, C.A. Muthuselvi4, Souradeep Bhattacharjee5
BACKGROUND
Establishing the usefulness of adaptive radiotherapy in our setting with limited
data might help to ensure better conformity and reduce treatment related
morbidity. Hence we conducted this study to elicit the benefit of adaptive
radiotherapy with helical tomotherapy.
METHODS
This is a prospective study conducted among 25 head and neck cancer patients
undergoing radiotherapy with helical tomotherapy. All patients underwent initial
radiation therapy treatment planning simulation positron emission tomography
computed tomography (PET CT/ CT scan) [CT-1], followed by repeat PET CT/ CT
scan at 4th - 5th week of radiotherapy [CT-2]. Planning for full intended dose [66
Gy - 70 Gy] was done on both the scans, keeping the radiation therapy planning
parameters same. Changes in the volume of the clinical target volumes (CTV),
changes in the volume and dose to spinal cord, bilateral parotids, and mandible
were compared. A p - value of < 0.05 was considered for statistical significance.
RESULTS
A significant reduction in the volumes of tumour - CTV-1 [CT-1 v/s CT-2: 166.82
cc v/s. 150.63 cc] and of lymph nodal region - CTV-2 [CT-1 v/s CT-2: 260.29 cc
v/s 228.00 cc], contra lateral parotid gland [CT-1 v/s CT-2: 33.00 cc v/s 18.72 cc]
were observed (P < 0.05). The mean doses received by contra lateral parotid
gland [CT-1 v/s. CT-2: 23.14 Gy v/s 21.26 Gy] were significantly lesser in the CT-
2 scans (P < 0.05). The mean maximum doses were also significantly lesser to the
mandible and spinal cord i.e., CT-1 v/s. CT-2: 68.528 Gy v/s 67.39 Gy and 39.45
Gy v/s. 37.33 Gy respectively (P < 0.05). A significant reduction in standardised
uptake value (SUV), values of the primary tumour and involved lymph nodes was
observed between CT-1 and CT-2.
CONCLUSIONS
During 4th to 5th week of radiation therapy, significant reductions in the CTVs and
in dose to OARs were noted. Thus, we recommend at least one re-simulation scan
and re-planning during radiation therapy, irrespective of the type of technique of
radiation therapy.
