Rectal Cancer after Prostate Radiation: A Complex and Controversial Disease

Clinical and Genomic Characterization of Secondary Rectal Cancer After Radiotherapy for Prostate Cancer

Importance

Patients treated with radiotherapy (RT) for prostate cancer (PC) have increased risk of secondary rectal cancer (SRC) and more limited treatment options.

Objective

To assess the tumor molecular profile, clinical characteristics, and oncologic outcomes of SRC after PC and compare them with those of primary rectal cancer (PRC).

Design, Setting, and Participants

This case-control study included patients with SRC diagnosed 5 or more years after RT for PC and patients with PRC who were treated at Memorial Sloan Kettering Cancer Center in New York between February 1, 1994, and September 31, 2022.

Main Outcomes and Measures

Clinical information and DNA sequencing data were analyzed. Oncologic outcomes were compared between patients with SRC and clinically matched patients with PRC using log-rank tests and Cox proportional hazards regression models. Numerical and categorical variables were compared using the Wilcoxon rank sum test and Fisher exact test, respectively.

Results

The analysis included 604 male patients with PRC (71.6%; median age, 55 [IQR, 46-66] years) and 64 male patients with SRC (median age, 78 [IQR, 72-82] years). Patients with SRC had more distal rectum (37 of 63 [58.7%] vs 131 of 581 [22.5%]; P < .001) and anterior rectal wall (20 of 57 [35.1%] vs 67 of 496 [13.5%]; P < .001) tumors, were less likely to receive neoadjuvant treatment (33 of 64 [51.6%] vs 570 of 604 [94.4%]), and had shorter 5-year overall survival (45.7% vs 64.9%; P = .01) and disease-free survival (40.3% vs 71.2%; P = .006) compared with clinically matched patients with PRC. Targeted DNA sequencing data from 31 SRC tumors identified lower mutational burden (median, 4.4 [IQR, 3.2-6.7] per megabase [Mb] vs 5.8 [IQR, 4.4-7.0] per Mb; P = .047), lower frequency of APC alterations (15 [48.4%] vs 432 [79.9%]; P < .001), and higher rates of SMAD4 inactivation (8 [25.8%] vs 54 [10.0%]; P = .01) compared with 541 PRC tumors. Whole-exome sequencing data from 17 SRC tumors identified a higher rate of frameshift deletions compared with 28 PRC tumors (median, 5.0 [IQR, 4.0-9.0] vs 2.5 [IQR, 1.0-4.2] variants; P < .001).

Conclusions and Relevance

In this case-control study, patients with SRC after RT for PC had worse survival and different molecular profiles than patients with PRC. These findings may help improve the clinical management of SRC.

Risk and survival outcomes of secondary pelvic neoplasm after radiotherapy in female patients with genital neoplasms: A large Population-Based cohort study

BACKGROUND AND PURPOSE

To investigate the impact of radiotherapy (RT) on the risk of secondary pelvic neoplasms (SPN) and the survival outcomes of patients following a diagnosis of female patients with genital neoplasm(FGN).

MATERIALS AND METHODS

Utilizing SEER databases, this study involved 102,895 patients from nine oncology centers, spanning 1990 to 2015. We employed the Fine-Gray competing risks regression methodology to chart the trajectory of SPN development and used the Kaplan-Meier method to calculate the 10-year overall survival rates.

RESULTS

This study included 25,774 patients in the RT group and 77,121 in the non-radiotherapy (NRT) group. The cumulative incidence rate of SPN was 5.10 % in the RT group and 3.42 % in the NRT group. The RT group showed a significantly higher incidence of bladder cancer (adjusted hazard ratio [HR]: 1.75; 95 % confidence interval [CI]: 1.43-2.14; P < 0.05), colon cancer (adjusted HR: 1.32; 95 % CI: 1.16-1.49; P < 0.05), and rectal cancer (adjusted HR: 1.34; 95 % CI: 1.10-1.65; P < 0.05) compared to the NRT group. After propensity score matching, patients in the RT group who developed bladder cancer had significantly reduced 10-year survival rates compared to patients with primary pelvic tumors (P = 0.01).

CONCLUSION

RT is identified as an independent risk factor for the development of SPN in patients with FGN. Patients with FGN who undergo RT demonstrate a significant increase in the risk of developing secondary neoplasms, specifically bladder cancers, and experience a reduction in 10-year survival rates.

Malignant Small Bowel Obstruction from Hernia Mesh Invasion by Jejunal Adenocarcinoma: A Report of a Rare Case

BACKGROUND Small bowel obstructions (SBO) are common and can be caused by various pathologies including intra-abdominal adhesions and hernias. Less frequently, these obstructions are caused by malignancy. The following article will review the etiology and treatment of SBOs, discuss complications of hernia repair with mesh, and examine if there is an association between mesh and cancer. CASE REPORT We present the case of a man who was over 89 years old who presented with an SBO that failed non-operative management. He previously had bilateral inguinal hernia repairs with mesh and pelvic radiation for prostate cancer. Imaging obtained during the workup was concerning for malignancy. Exploratory laparotomy revealed an ascending colon adenocarcinoma and small bowel obstruction secondary to jejunal adenocarcinoma. The jejunal adenocarcinoma was adhered to and invaded into the mesh from a previous hernia repair. He underwent successful resection and anastomosis, had an uneventful postoperative course, and was discharged. Given his advanced age, he refused further workup or treatment. CONCLUSIONS The etiology and management of small bowel obstructions is multifactorial. Small bowel obstructions affect a large portion of the population worldwide and the subsequent management accounts for significant health care spending. This case shows an exceedingly rare and possibly novel case of jejunal adenocarcinoma that invaded into the hernia mesh, leading to a malignant small bowel obstruction. While there is not a clear explanation behind this patients' pathology, we hypothesize that his prior hernia surgery led to an intra-abdominal adhesion, and subsequent pelvic radiation may have facilitated the malignancy invading the mesh and causing a high-grade small bowel obstruction.

Association of radiotherapy for prostate cancer and second primary colorectal cancer: a US population-based analysis

BACKGROUND

Radiotherapy (RT) is a common treatment for prostate cancer, yet the risk of second primary colorectal cancer (SPCRC) in patients with prostate cancer undergoing RT has not been adequately studied.

METHODS

This study employed a population-based cohort design using the US Surveillance, Epidemiology, and End Results (SEER) database to identify individuals diagnosed between January 1975 and December 2015. The cumulative incidence of SPCRC was estimated using Fine-Gray competing risk regression. Poisson regression analysis was used to estimate the risk associated with RT. Survival outcomes of patients with SPCRC were evaluated using the Kaplan-Meier method.

RESULTS

A total of 287,607 patients diagnosed with prostate cancer were identified. The cumulative incidences were higher in patients who did not receive RT (2.00%) compared to those who underwent RT (2.47%) after 25 years. After adjustment for multiple variables, RT was associated with an increased risk of developing combined SPCRC (adjusted HR 1.590). Additionally, the overall survival was significantly lower in patients who developed colorectal cancer after receiving RT as compared to those who did not receive RT.

CONCLUSION

These findings underscore the need for diligent long-term monitoring and effective management strategies to detect SPCRC in patients treated with RT for prostate cancer.