The Role of Pelvic Reirradiation in the Treatment of Locally Recurrent Rectal Cancer: A Systematic Review

Background: Local recurrence of rectal cancer is a challenging problem for patients and clinicians. Surgical resection is associated with good outcomes if R0 margins are achieved; however, it is often complex, requires suitable patient fitness, and is associated with long term physical and psychological consequences. Meanwhile, continuing technical advances in radiotherapy have enabled the delivery of highly conformal treatment, thereby enabling dose escalation or pelvic reirradiation to be safely considered—either as definitive management or in the neoadjuvant setting—for patients with locally recurrent rectal cancer. Pelvic reirradiation may refer to patients who have received primary rectal radiotherapy with the aim of neoadjuvant downstaging or reducing the risk of locoregional recurrence, versus radiotherapy for a previous unrelated non-rectal pelvic malignancy. Methods: A literature search of pelvic reirradiation for non-metastatic, locally recurrent rectal cancer was conducted for full text articles published over the last 20 years. Additional papers were identified within the references of these papers. Studies focusing on non-rectal cancers, and patients having primary radiotherapy for locally recurrent rectal cancer were excluded. Due to the heterogenicity of the data, no meta-analysis was performed. Results: A total of 15 papers were included, containing a cohort of 840 patients. Several reirradiation modalities were reported, including external beam radiotherapy, brachytherapy, stereotactic ablative radiotherapy and heavy particle therapy (carbon ion). Carbon ion radiotherapy was the most common reirradiation treatment modality utilised with a median cumulative dose of 70.4 Gray (Gy). Treatment response, defined as either complete or partial improvement in tumour size, was only reported in seven studies, and varied from 14 to 88%. Overall 3-year survival was also variable with rates reported between 18 and 85%. These observations may be due to variation in patient selection, treatment intent, and technique. Pelvic reirradiation was associated with acceptable toxicity, low rates of G3+ toxicity, and improved symptom control. Conclusions: Our review describes the multitude of approaches to pelvic reirradiation for locally recurrent rectal cancer. Reviewing the radiobiological and patient outcomes is challenging in view of the degree of heterogeneity in patient selection, treatment approach, and reported outcomes. However, there is consensus that pelvic reirradiation—either for long term control or to downstage prior to definitive surgery—is feasible with potential utility in this setting.