Comparison of bone marrow sparing intensity modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3DCRT) in carcinoma of anal canal: a prospective study

Rajit Rattan, Rakesh Kapoor, Amit Bahl, Rajesh Gupta, Arun S. Oinam, Satinder Kaur

Abstract

Background: Chemoradiation (CRT) is the standard of care in anal canal carcinoma. CRT leads to suppression of iliac bone marrow (BM) leading to hematological toxicity. Intensity modulated radiation therapy (IMRT) technique can be used to decrease radiation dose to iliac BM and thus decrease haematological toxicity. This study aims to compare the haematological and gastrointestinal toxicity in BM sparing IMRT with three-dimensional conformal radiation therapy (3DCRT) in anal carcinoma patients.
Methods: Twenty untreated, biopsy proven anal canal carcinoma (stages I–III) patients were randomized into IMRT and 3DCRT arm. All patients received CRT with 45 Gy in 25 fractions at 1.8 Gy/fraction and weekly concurrent inj. cisplatin and 5-FU. Patients were evaluated for acute haematological and gastrointestinal toxicity during treatment. Additional dosimetric comparison was made between the two groups.
Results: Incidence of worst hematological toxicity grade II (GII) and GIII was seen in 40% [4] vs. 30% [3] and 20% [2] vs. 0% [0] respectively, in 3DCRT and IMRT group. However these did not come as statistically significant (P=0.228). Incidence of worst gastrointestinal toxicity during treatment in terms of GII was 30% [3] vs. 50% [5] and GIII was 60% [6] vs. 0% [0] in 3DCRT and IMRT group respectively (P=0.010). Other parameters indicating better tolerance of treatment with IMRT arm than 3DCRT arm were lesser need for administration of parenteral fluid 10% [1] vs. 60% [6] (P=0.019); lesser need for blood transfusion 0% [0] vs. 20% [2] (P=0.060) in IMRT arm than in 3DCRT arm respectively. Patient requiring supportive care during treatment like need for anti-motility drugs and WHO. Step II analgesics also favored IMRT arm. Overall treatment time for Arm B (33.40 days) was less than what was seen in Arm A patients (36.8 days), although difference was not statistically significant (P=0.569). In terms of dosimetric analysis, arm B with the use of IMRT showed superiority over arm A with 3DCRT. The mean volume of bladder receiving ≥30 and 40 Gy respectively was 100% and 96% for group A (3DCRT) as compared to 68% and 31% for the group B (IMRT) (P<0.05). For bowel, although, the V30 and V40 for 3DCRT versus IMRT respectively were 51% and 27% vs. 27% and 13%, statistical significance was not reached (P>0.05). There was also less mean BM receiving ≥10 Gy (80.4%) and ≥20 Gy (65.6%) for group B using IMRT, than in 3DCRT (group A) were it was 91% and 73% respectively. Although for V10 it was significant (P=0.04), it did not reach statistical significance for the V20 (P=0.550).
Conclusions: Preliminary outcomes suggest that BM sparing IMRT for anal canal cancers can decrease both haematological and gastrointestinal toxicity as compared to 3DCRT and thus CRT course can be completed effectively without treatment breaks.