Comparison of Overall Response to Neoadjuvant Short Course Radiotherapy Followed by Consolidation Chemotherapy with Long Course Chemoradiotherapy in Locally Advanced Rectal Cancer

Abstract

<h3>Purpose/Objective(s)</h3> Primary objective of this study was to compare the clinical and radiological response rates between patients receiving pre-operative Short Course Radiotherapy (SCRT) followed by chemotherapy versus conventional long course CRT in patients with locally advanced rectal cancer. secondary objectives included comparison of rates of pCR and acute toxicities among the 2 groups of patients. <h3>Materials/Methods</h3> 33 patients with locally advanced rectal cancer were randomized to standard long course CTRT arm (arm A) and SCRT followed by sequential chemotherapy (arm B) arm (17 and 16 patients respectively). Patients in arm A received long course RT at dose 45 Gy in 25 fractions over 5 weeks with concurrent oral capecitabine on days of radiotherapy. Patients in arm B was prescribed short course radiotherapy at dose 25 Gy in 5 fractions over 1 week. 3 cycles of 3 weekly CAPOX chemotherapy was followed. Patients were planned with 3DCRT technique in Versa HD with 6 MV and 15 MV photons. Clinical response assessment was done by comparing the 2 arms in terms of per rectal examination findings before starting radiotherapy and after completion of RT, right before surgery. The parameters used for assessment were palpability of lesion, tone, mobility, distance from anal verge and location of the lesion. Radiological response assessment was done by comparing 5-point tumor regression grades (TRG) post treatment in the 2 treatment arms. <h3>Results</h3> Radiological tumor regression showed statistically non-significant trend favoring the experimental arm (rates of complete tumor regression 35.7% in SCRT followed by chemotherapy arm versus 23.1% in long course CTRT arm, higher percent of patients with greater tumor regression in SCRT+CT arm). pathological tumor regression also favored experimental arm without showing statistical significance (pCR rates 20% in long course CTRT versus 30% in SCRT+CT). Most of patients in the interventional arm presented with higher pathological tumor regression (TRG 0 and TRG 1) while the most common TRG in the long-course CTRT arm was TRG 3. Higher rate of acute grade 3 bowel toxicities was seen in the interventional arm. Grade 3 acute skin toxicity occurred in the standard arm compared no skin toxicity in the interventional arm. This difference was also not statistically significant. <h3>Conclusion</h3> Short course radiotherapy followed by 3 cycles of CAPOX chemotherapy is comparable to Long-course CTRT in terms of tumor regression. In resource limited setting, short course radiotherapy and chemotherapy is favored due to smaller radiotherapy duration and lesser chances of treatment interruption