Haematological toxicities are seen in rectal cancer patients receiving concurrent chemoradiotherapy (CRT) with capecitabine.

To compare dose volume histogram (DVH) parameters and acute haematological toxicities using RapidArc with or without bone marrow constraints for rectal cancer patients receiving pelvic chemoradiation as part of curative treatment.

This is a prospective randomised controlled study including patients with rectal cancer initiated on chemoradiation. Patients were stratified into two arms, bone marrow sparing (BMS) arm and non-bone marrow sparing arm (NBMS).

DVH parameters and weekly toxicity data were collected. Grade 2 or more anaemia, leucopenia, neutropenia, or thrombocytopenia, any blood transfusions, colony-stimulating factor injection, platelet transfusions were considered as an event in acute haematological toxicity (HT).

Independent t-test was used to compare quantitative parameters, and Mann–Whitney U-test was used for ordinal parameters between groups.

A total of 43 patients were enrolled. Bone marrow constraints were achieved without compromising the target coverage. There was a significant reduction in the bone marrow dose with BMS technique (p < 0·05). A 16·7% reduction in the HT (33·3% versus 50%) and a 21·9% reduction in the grade 2 or more anaemia (19% versus 40·9%) were noted in the BMS arm when compared to NBMS arm, though not statistically significant. However, in the preoperative setting, a significant reduction in grade 2/more anaemia (7·1% versus 41·1%, p = 0·035) was noticed in the BMS arm.

Pelvic BMS radiotherapy may benefit patients receiving chemoradiation for locally advanced carcinoma rectum as part of curative treatment.