Haematological toxicity in cancer cervix patients treated with concurrent chemoradiation by conventional technique- correlation with bone marrow radiation dose

Introduction: The standard of care for treatment of cancer cervix is concurrent chemoradiation followed by brachytherapy in the majority of cases. Conventional radiotherapy with chemotherapy causes haematological toxicities which may be related to radiation to pelvic bone marrow. The present study aims to study the haematological toxicities and correlate with the mean dose to the bone marrow. Material and Methods: Retrospective data of cancer patients treated in the institute in the year 2019 was retrieved. Haematological toxicities were analyzed in terms of CTCAE criteria. Mean dose to bone marrow was calculated after the delineation in the CT scan. The correlation between haematological toxicity and mean bone marrow was done using a paired t-test for statistical significance. Results: The data of 20 patients were retrieved. Anaemia Grade, I and Grade II-IV was seen in 65% and 35% respectively. Leukopenia Grade I and Grade II-IV were seen in 85% and 15% respectively and Lymphopenia Grade I and Grade II-Iv were seen in 55% and 45% respectively. The mean dose to bone marrow did not show any statistical significance with the severity of haematological toxicity. There was no Grade II-IV toxicity of neutropenia and thrombocytopenia. Conclusion: Conventional radiotherapy can safely be practice for patients with cancer cervix with acceptable haematological toxicities.

Reducing planning target volume margins decreases dose to parotid glands in head and neck cancers - a dosimetric analysis

Introduction: Radiotherapy in head and neck cancers is treated for several weeks and daily setup and reproducibility is a challenge. This daily variability causes setup errors which accounts planning target volume margins. Reduced PTV margins have to be taken to decrease the dose to the parotid glands, without compromising on loco regional control rates. The present study is done to identify setup errors and see the feasibility to decrease the PTV margins by creating dummy radiotherapy plans in order to decrease dose to parotid glands. Material and Methods: 420 portal images were evaluated for setup errors in three dimensions (Antero Posterior, Left to Right and Superior to Inferior) which were performed in ten patients of oropharyngeal squamous cell carcinoma. All patients were treated in supine position using immobilization cast. After target volume delineation a PTV margin of 7mm was given. Dosimetric parameters of PTV and organs at risk were assessed. PTV margins were calculated according to three methods proposed by Stroom, Van Herk and ICRU 62. Dummy radiotherapy plans were generated using new PTV margins and compared with 7mm PTV margins. The data was analyzed using 3-way ANNOVA test for statistical significance. Results: The optimum PTV margins were 4mm in LR and SI direction and 7mm in AP direction. The PTV parameters (V95, D95, Dmax, Dmean, HI and CI) had no significant difference among different radiotherapy plans with different PTV margins. There was a significant decrease in the dose to right parotid (39.12 Gy to 32.88Gy; p-0.04), left parotid (37.90 to 31.21Gy; p-0.03) and parotid combined (38.65 to 31.45 Gy; p-0.01) when 7mm PTV margins were reduced to 4mm PTV margins. The results of dummy radiotherapy plans using asymmetric PTV margins (LR-4mm, SI-4mm and AP-7mm) and symmetrical PTV margins (4mm in all directions) are compared with PTV margins (7mm in all directions), in terms of PTV and OAR dosimetric parameters. Conclusion: The decreased PTV margins of 4mm decreases the dose to the parotid significantly. The implementation of radiotherapy plans needs to be supplemented by daily IGRT.

Dosimetric comparison and clinical correlation between conventional four field radiotherapy versus three-dimensional conformal radiotherapy in cancer cervix

Introduction: With sectional imaging, wide variations are reported in pelvic anatomy of individual patients raising concerns over adequate coverage of target volume with conventional radiotherapy based on standard bony landmarks. Three-dimensional conformal radiotherapy (3DCRT) is reported to decrease normal tissue toxicity, along with decrease in chances of geographic miss. Present study is done for dosimetric comparison of Planning Target Volume (PTV) and Organs at Risk (OAR) in cancer cervix patients treated with conventional and conformal radiotherapy along with clinical correlation in terms of side effects and tumor response. Materials and Methods: Fifty patients of cancer cervix underwent planning contrast enhanced CT scan. Target volumes & OAR were contoured. Patients were randomized into conventional & conformal arms. Conventional fields were planned using standard bony landmarks. CT based radiotherapy planning was done for 3DCRT arm. Field sizes &dose volume histogram (DVH) were recorded & compared for target coverage & OAR sparing in both arms. All patients received concurrent chemotherapy followed by brachytherapy. Results: Field sizes used for the 3DCRT plans were significantly larger than those used for the conventional plans (p= 0.000). Optimal PTV coverage was significantly improved using 3DCRT as compared to conventional radiotherapy (p= 0.0001). Dose homogeneity in both arms were almost similar (p= 0.292), while conformity index was better in 3DCRT which was statistically significant between the groups (p= 0.000). Mean dose to the Planning Target Volume was increased significantly in the CT based plan when compared with the standard four field plan (p= 0.0001).Difference in doses to the organs at risk (urinary bladder, and small bowel)and their side effects were statistically significant across both groups. There was no difference in tumor response. Conclusion: The present study showed significantly better target volume coverage & dose homogeneity with 3DCRT which may translate into better local control & survival but longer follow up is required to validate it.