Adjuvant radiation prolongs locoregional control of pancreatic cancer

The receipt of adjuvant radiotherapy in addition to chemotherapy appeared associated with lower risk for locoregional recurrence in patients with surgically treated pancreatic cancer, according to the results of a retrospective study.

Thus, radiotherapy should be considered standard adjuvant locoregional treatment in patients with pancreatic cancer who are surgical candidates.

“The role of radiation therapy in operable pancreatic cancer has been somewhat controversial,” Christopher L. Hallemeier, MD, assistant professor of radiation oncology at Mayo Clinic in Rochester, Minnesota, said in a press release. “There have been some studies that have shown a benefit and some studies that have not shown a benefit.”

Hallemeier and colleagues sought to observe risk factors for locoregional failure among patients with pancreatic cancer, as well as their impact on OS.

The researchers reviewed data from 458 patients (median age, 64.5 years; range, 29-88) with nonmetastatic exocrine pancreatic cancer who underwent surgical resection between March 1985 and January 2011 at Mayo Clinic. The majority of patients (82.5%; n = 378) received adjuvant chemoradiotherapy; the remaining patients (17.5%; n = 80) underwent chemotherapy alone.

The median follow-up for living patients was 84 months (range, 6-300).

Seventy percent of patients received six cycles of adjuvant gemcitabine; 95% completed more than four cycles. The median radiation dose was 50.4 Gy (range, 45-55) in 28 fractions delivered concurrently with chemotherapy, most frequently 5-fluorouracil.

The researchers observed an overall crude incidence of locoregional failure of 17% (n = 79), with a median time to locoregional failure of 15 months (range, 3.6-90).

Sixty-one percent of patients developed locoregional failure with distant metastases; the remaining 39% did not.

A greater proportion of patients who underwent adjuvant chemoradiotherapy achieved 5-year locoregional control than those who underwent chemotherapy alone (80% vs. 68%; HR = 0.45; 95% CI, 0.28-0.76).

In multivariable analyses, the researchers observed a significant association between the receipt of radiotherapy and a reduced risk for locoregional failure (HR = 0.23; 95% CI, 0.12-0.42).

A positive lymph node ratio greater less than or equal to 0.2 also appeared associated with locoregional control (HR = 1.78; 95% CI, 1.1-2.9).

The entire cohort had a median OS of 31.2 months. Twenty-eight percent remained alive after 5 years.

Locoregional failure significantly increased the risk for mortality (HR = 5; 95% CI, 3.9-6.3).

The researchers acknowledged study limitations, including the lack of randomization. Further, because follow-up imaging remained at the discretion of the treating oncologist, the rates of locoregional control may have been overestimated.

“Our large study suggests that adding radiation treatment in combination with surgery and chemotherapy reduces the rate of cancer recurrence,” Hallemeier said. “With tailored approaches to treatment before surgery — for example, using chemotherapy first to see how the tumor responds and then selectively using radiation — we can personalize treatment for patients who are most likely to benefit.” – by Cameron Kelsall

Disclosure: The researchers report no relevant financial disclosures.