title: Dose-response relationship for radiation therapy of recurrent, residual, and primarily inoperable colorectal cancer.
abstract: One hundred and thirteen patients with advanced locoregional recurrent (77), residual (18) or primarily inoperable (18) colorectal carcinoma were treated with radiotherapy. Eighty-five patients had locoregional disease only and 28 had both local disease and distant metastases. The treatment was given with varying dose levels (23-73 Gy) in daily fractions of approximately 2 Gy in 3-8 weeks. This dose variation allowed an evaluation of the dose-response relationship for radiation treatment of this tumour. A good subjective response was obtained in 63%. This effect showed no dose-response relationship except for doses greater than or equal to 56 Gy, where all patients received relief of symptoms. Eighty-two per cent of evaluable patients achieved an objective response (PR 53%, CR 29%). The frequency and duration of the complete responses showed a marked dose-response relationship. Thus, at doses greater than or equal to 56 Gy, a 2-year actuarial complete response rate of 40% was found compared with 7, 4 and 0% at doses of 46-55 Gy, 36-45 Gy and less than or equal to 35 Gy, respectively. The dose-response relationship for local control also influenced the survival rate, although a number of patients died from distant metastases even when local control was obtained. However, with regard to locoregional disease, the 2-year survival was 53% for patients with complete tumour regression but only 8% for patients without complete tumour regression.
mesh_terms: D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use; D003110:Colonic Neoplasms / Q000401:mortality / Q000532:radiotherapy*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D011878:Radiotherapy / Q000009:adverse effects; D012004:Rectal Neoplasms / Q000401:mortality / Q000532:radiotherapy*
chemical_list: D000970:Antineoplastic Agents