The induction of secondary cancers after radiotherapy has traditionally been taken as one of the ‘contra’ arguments against the use of radiotherapy in rectal cancer.
Claus Rödel, MD
Claus Rödel, MD, Director and Chair of the Department of Radiotherapy and Oncology, University of Frankfurt, Germany, and invited discussant of the study, pointed out that these investigators found “the opposite” of what most previous studies have shown: Others have found an increased risk for second tumors associated with radiation therapy. He cautioned, however, that the Dutch study was restricted to patients who received treatment for rectal cancer, not all cancers. “The induction of secondary cancers after radiotherapy has traditionally been taken as one of the ‘contra’ arguments against the use of radiotherapy in rectal cancer,” he said.
A study by the Swedish Rectal Cancer Group found a twofold risk in secondary cancers in patients who received radiotherapy, vs surgery alone.1 An analysis from the Surveillance, Epidemiology, and End Results (SEER) database of 647,672 patients also found an excess of 5 second cancers per 1,000 irradiated patients 15 years after diagnosis.2
The Dutch study’s findings, however, do not stand alone. They are similar to those from a SEER database analysis of almost 21,000 patients with rectal cancer. That study also found no overall increased risk associated with radiotherapy, although the risk was increased for certain cancers—those of the uterine corpus and cervix—and decreased for prostate and breast cancers.3
Ultimately, said Dr. Rödel, the use of radiotherapy in rectal cancer involves a benefit/risk ratio, where the “pros” are improved local tumor control and potentially a survival benefit in subgroups, and the “cons” are lack of an overall survival benefit, toxicities, and impaired functional outcomes. The question that remains unresolved is the “balance between radiotherapy induction and radiotherapy inhibition of second cancers.” ■
Disclosure: Dr. Rödel reported no potential conflicts of interest.
1. Birgisson H, Påhlman L, Gunnarsson U, et al: Adverse effects of preoperative radiation therapy for rectal cancer: Long-term follow-up of the Swedish Rectal Cancer Trial. J Clin Oncol 23:8697-8705, 2005.
2. Berrington de Gonzalez A, Curtis RE, Kry SF, et al: Proportion of second cancers attributable to radiotherapy treatment in adults: A cohort study in the US SEER cancer registries. Lancet Oncol 12:353-360, 2011.
3. Kendal WS, Nicholas G: A population-based analysis of second primary cancers after irradiation for rectal cancer. Am J Clin Oncol 30:333-339, 2007.
Second malignancies were not more common among patients who underwent radiotherapy for rectal cancer. In fact, radiotherapy appeared to offer some degree of protection against subsequent cancers, according to the findings of a study from the Netherlands reported at the 2016 Gastrointestinal Cancers ...