Incomplete Neoadjuvant Radiation Linked to Worse Outcomes for Rectal Cancer

Completing a course of preoperative radiotherapy prior to undergoing surgical resection for rectal cancer was associated with improved survival compared with patients who had an incomplete course of radiotherapy, according to the results of a study published in JAMA Surgery.

“In what we believe to be the first population-level study examining the outcomes of patients with locally advanced rectal cancer who received an incomplete radiotherapy course, we found that completion of planned neoadjuvant radiotherapy as part of a neoadjuvant chemoradiotherapy regimen was associated with superior overall survival,” wrote Kyle Freischlag, BA, a student at Duke University School of Medicine, and colleagues.

“Our study … shows that patients with an incomplete radiotherapy dosage have a 10% lower 5-year overall survival rate and a higher risk of long-term mortality,” they wrote. “This finding is in concordance with the results seen in other cancers when preoperative treatment was interrupted.”

It was previously known that failure to complete chemotherapy adversely affects survival in patients with colorectal cancer; however, there was little research on the effects on incomplete radiation therapy prior to undergoing surgical resection.

In this study, the researchers collected data for 17,600 patients with stage II and III rectal adenocarcinoma from the National Cancer Database (NCDB). All patients had received neoadjuvant chemoradiotherapy prior to undergoing surgical resection of their disease. Outcomes including 30-day readmission, 90-day mortality, and overall survival were compared among patients who received complete (45.0–50.4 Gy) compared with incomplete (< 45.0 Gy) preoperative radiation.

The majority of patients included in the study (95%) received complete doses of neoadjuvant radiation. Among the 874 patients who received incomplete doses, the median radiation dose was 34.2 Gy. Data showed that being female (adjusted odds ratio [OR], 0.69; 95% CI, 0.59–0.81; P < .001) and receiving radiation at a different hospital than the surgery (adjusted OR, 0.72; 95% CI, 0.62–0.85; P < .001) were both independent predictors of failing to achieve a complete radiation dose.

“Notably, receiving cancer care in multiple facilities is associated with higher rates of incomplete therapy, but we found no significant difference in rectal cancer survival outcomes between academic, community, and specialized cancer centers,” the researchers wrote.

In contrast, those patients with private insurance were more likely to complete their radiation (OR, 1.60; 95% CI, 1.16–2.21; P = .004).

At 5 years, the estimated survival probability among patients who completed radiation was 73.2% compared with 63% among those with an incomplete course (P < .001). In addition, having completed a full course of radiation was also association with a lower risk of long-term mortality (adjusted hazard ratio, 0.70; 95% CI, 0.59–0.84; P < .001).

After data adjustment for demographic, clinical, and tumor characteristics, the researchers found no differences between the two patient groups for resection margin positivity, permanent colostomy rate, 30-day readmission rate, or 90-day mortality.

“A detailed analysis of socioeconomic factors leading to incomplete radiotherapy treatment would be salient in this investigation; however, this analysis was impossible using NCDB data, limiting our ability to pinpoint the exact causes of incomplete radiotherapy on a patient-by-patient level,” the researchers wrote.