A case report of rectal squamous cell carcinoma following radiation therapy for prostate cancer: a management dilemma

Introduction

Rectal squamous cell carcinoma (rSCC) is estimated to account for 0.1–0.3% of rectal carcinomas, making it an extremely rare tumor, with worse prognosis compared to rectal adenocarcinomas (rADC) and anal squamous cell carcinoma (aSCC) (1,2). Given its rarity, standard guidelines towards it staging or management are lacking. Literature on the outcome of treatment is scarce but does suggest benefit of radiotherapy within the treatment algorithm; outcome data in regional disease without radiotherapy is scarce (1-4).

The risk factors and etiologies underlying the development of rSCC is still not fully understood. Prior radiation therapy has associations with the development of rADC (5); it is seldom reported in rSCC but is believed to potentially also play a role alongside other environmental and genetic etiologies. The development of radiation associated rectal carcinoma adds complexity to management (5).

Here, we present the case of a patient who had prior radiation therapy for prostate cancer with subsequent development of rSCC, our management approach, and the outcome (Figure 1). We present this case in accordance with the CARE reporting checklist (available at https://jgo.amegroups.com/article/view/10.21037/jgo-2026-1-0029/rc).

Figure 1 Patient’s timeline and history. ED, Emergency Department.

Case presentation

A 76-year-old male with a past medical history of prostate adenocarcinoma, treated with 8,100 centigray (cGy) external beam radiotherapy to the prostate about 7 years prior, presented to the hospital with a one week of bright red bleeding per rectum. He denied prior similar episodes, abdominal pain, altered bowel habits, or systemic symptoms. He had severe protein calorie malnutrition, and 50 pounds (LB) of weight loss attributed to markedly reduced appetite due to major depression from the loss of his wife about a year prior. His prostate cancer was managed at a different facility. It was staged as T1cN0, with a Gleason score of 7 (3+4) and pre-radiotherapy prostate specific antigen (PSA) of 5.9 nanograms per milliliter (ng/mL). He received 8,100 cGy in 45 fractions (Figure 2) without neo-adjuvant/concurrent/adjuvant androgen blockage. His prostate cancer was in remission with no evidence of recurrence. Digital rectal examination revealed a firm mass in the distal rectum with bright red blood, with no masses in the anal canal or anal margin. He opted for discharge with outpatient gastroenterology follow-up given stability of his clinical status. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Figure 2 Dosimetry plan for prior prostate radiotherapy showing areas that received radiation and their doses. (A) Dosimetry plan transverse view. (B) Dosimetry plan coronal view. (C) Dosimetry plan sagittal view. Green, 2,430 cGy; orange, 4,050 cGy; purple, 4,500 cGy; blue, 7,290 cGy; yellow, 7,695 cGy; red, 8,100 cGy. cGy, centigray.

Eventual outpatient colonoscopy demonstrated multiple adenomatous-appearing and malignant-appearing masses within the distal rectum covering one quarter of the circumference with bleeding noted before intervention, managed with cold forceps biopsy with partial removal; the cecum was not reached (Figure 3A,3B). Pathology was confirmed as squamous cell carcinoma (SCC) of the rectum (Figure 4A-4C). Positron emission tomography/computed tomography (PET/CT) scan showed fluorodeoxyglucose (FDG) avid rectal mass with FDG foci in the pre-sacral region and left pectineus muscle (Figure 5A-5C). Magnetic resonance imaging (MRI) with and without contrast of the pelvis showed a craniocaudal 3.5 centimeter (cm) low rectal tumor 3 cm away from the anal verge, with approximately 1cm transmural extension, and a positive presacral lymph node; T3c, N1, M0 (Figure 6A-6C).

Figure 3 Colonoscopy images of rectum (A,B).

Figure 4 The biopsy consisted of multiple superficial portions of rectal tissue that underwent routine processing with fixation in 10% neutral buffered formalin followed by paraffin embedding. Sections were cut at 5 microns and stained with hematoxylin and eosin. Sections show tumor composed of intermediate-sized, moderately pleomorphic squamoid cells forming thick trabeculae associated with moderately dense mixed inflammation and focal ulceration. Tumor cells have round to oval nuclei with finely granular chromatin, small central nucleoli, relatively smooth nuclear contours, and moderate amounts of dense, basophilic cytoplasm. Mitotic activity ranges up to 3 mitoses per HPF. No keratinization is present. The histologic features are consistent with non-keratinizing squamous cell carcinoma. (A) Rectal mass biopsy at 40× magnification. (B,C) Rectal mass biopsy at 100× magnification. HPF, high-power field.

Figure 5 Positron emission tomography/computed tomography view. (A) Transverse view of rectal mass (blue arrow). (B) Sagittal view of rectal mass (blue arrow). (C) Coronal view of rectal mass (blue arrow).

Figure 6 Magnetic resonance imaging with T2-weighted sequence showing the rectal mass (orange arrows): (A) transverse thin slice, (B) coronal view, (C) sagittal view.

Patient refused surgery and colostomy and thus management with chemoradiation was considered. However, on discussing with the radiation oncologist, his history of previous radiation to the same area precluded further therapeutic radiation due to concerns of major toxicities like fistulas, perforation or bleeding. Following discussion at the tumor board and shared decision making with the patient, he had robotic assisted abdominal perineal resection (APR) with removal of the distal sigmoid colon and rectum, and colostomy creation. Post-operative pathology confirmed invasive, moderately differentiated, non-keratinizing SCC; pT2 pN1a. The sigmoid colon was not involved.

He was managed as stage IIIB rSCC. Adjuvant chemotherapy was started 2 months after surgery with carboplatin with an area under the curve (AUC) of 4 and paclitaxel at 140 milligrams per meter squared (mg/m²), both 80% of the original dose due to his poor nutrition and performance status. He received four cycles instead of the originally planned six cycles before treatment was held due to his continued severe depression and worsening malnutrition from extremely reduced oral intake. He continued to refuse multiple psychiatric, nutritional and social intervention. He has had repeated CT scans since completion without signs of recurrence, 3 months following his last treatment. He passed away four months after his last treatment following an admission for respiratory failure and severe mitral regurgitation where he was made comfort measures only.

Discussion

The incidence of rSCC is extremely low which makes management consensus difficult due to the paucity of evidence. It is associated with worse prognosis compared to rADC and aSCC (1,2). The staging is inconsistent; tumor, node, and metastasis (TNM) staging for rADC in rSCC due to their similar anatomical locations, as well as staging for aSCC in rSCC due to their similar histological features has been published (1,3). In the patient, the anatomical location was used as a guide as it was felt to more accurately reflect prognosis based on the staging at diagnosis and guidance on decision-making (1,2,4). A consensus on staging would be a helpful initial step to streamline guidance on treatment in this rare entity to improve monitoring of outcomes, and provide useful information to patients and other healthcare providers.

Various management approaches have been published with varying results, but chemoradiotherapy (CRT) as part of the treatment regimen appears to be associated with better outcomes (1-4,6), especially in stage 3 rSCC like this patient (4). The preferred chemotherapy regimen is however not established; majority of those that have been used are based on aSCC treatment choices including 5-fluorouracil (5-FU) with mitomycin (MMU) and platinum-based combinations, given alongside radiotherapy (1,6). Comparison of systemic therapies to evaluate efficacy between each other is difficult due to very low numbers of patients. Importantly, especially for this patient, the outcome of therapy in locoregional disease without radiotherapy is extremely scarce (4). In our case, this played a role in choosing carboplatin and paclitaxel, usually used as first line in metastatic aSCC (7). After 4 cycles of adjuvant carboplatin and paclitaxel, there has been no evidence of recurrence. Understandably, this is within a short follow-up time.

The etiologies underlying the development of rSCC is still not fully understood, with varying mechanisms proposed including prior radiation or inflammation to the affected region (1,8). One case report mentions the occurrence of rSCC 21 years after radiotherapy for cervical cancer (9). Generally, while it is estimated second solid organ malignancies need at least a 10-year latency period to manifest after radiation exposure, studies show it may take less than this, as low as 5 years, including rectal cancers (5,10-12). Admittedly, it is difficult to ascertain which solid organ cancers arise truly as a result of radiation or simply as co-incidence, especially within a short latency period. Tests that can help in this regard exist but were not done in this patient (13). In our case, the development of rSCC within the same region that received substantial radiation was enough to raise questions and concerns about likely radiation related development of his rSCC.

The association between prior radiation therapy for prostate cancer and rADC has been reported and poses a management dilemma regarding the use of further radiotherapy like in our rSCC case (5,14). This is because of two major reasons: firstly, reirradiation poses a risk of major toxicities and side effects that could be poorly tolerated by patients; and secondly, providing radiation treatment for a cancer felt to have developed secondary to radiation treatment may feel “counterintuitive” (5). Hence, the need for an understanding of what the outcome without radiotherapy for patients with potentially radiation induced rSCC would be.

Conclusions

Staging and guidelines for management of rSCC is scarce and would benefit from a consensus on the way forward to improve information and help track outcomes. Staging based on rADC as opposed to aSCC seems more intuitive based on location, but the choice of systemic treatment should be aSCC based given similar histology. Radiation exposure is a potential risk factor for rSCC. CRT may not be feasible in radiation-associated rSCC, which is rarely reported, and poses a management dilemma which should drive further research and discussion on how to best approach the disease. The next steps should be the development of cohort studies and trials, where feasible, to better describe risk factors, etiologies, and outcomes of treatment modalities for rSCC, to help create streamlined guidelines on staging and management.

Acknowledgments

We would like to thank George Varsos, MD and John Fisk, MD for their contributions to this study.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://jgo.amegroups.com/article/view/10.21037/jgo-2026-1-0029/rc

Peer Review File: Available at https://jgo.amegroups.com/article/view/10.21037/jgo-2026-1-0029/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jgo.amegroups.com/article/view/10.21037/jgo-2026-1-0029/coif). A.V.P. reports serving on speakers bureaus for AstraZeneca, Regeneron, Boehringer Ingelheim, and Bristol Myers Squibb. The speaker arrangement does not have any impact on the case report. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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