Anal Canal SCC in an HIV-Positive Woman
A 49-year-old woman presents with a 6-month history of severe anal pain, rectal bleeding during defecation, tenesmus, and mucoid discharge. Her symptoms were initially attributed to hemorrhoids, resulting in delayed diagnosis.
Viral Status and Biomarkers
- HIV-1 positive and receiving antiretroviral therapy (ART) with virologic suppression.
- CD4 count: 420 cells/µL.
- High-risk human papillomavirus (HPV) type 16 positive.
- Strongly positive for p16 on immunohistochemistry (IHC).
Histopathology: Biopsy confirms infiltrating, non-keratinizing squamous cell carcinoma (SCC) of the anal canal.
Staging Work-up
Pelvic imaging demonstrates:
- Primary tumour measuring 4.2 cm, consistent with T2 disease.
- Extension into the internal sphincter.
- Bilateral inguinal and mesorectal lymph node involvement.
- No distant metastases on chest and abdominal computed tomography (CT).
Clinical stage: Stage IIIB (T2 N1b M0).
Discussion Questions
1. HPV, Biomarkers, and HIV
- How do high-risk HPV E6 and E7 oncoproteins promote carcinogenesis and p16 overexpression?
- What is the clinical significance of HPV-16 and p16 positivity in anal SCC?
- How does well-controlled HIV infection affect chemoradiotherapy tolerance, treatment delivery, and outcomes?
2. Definitive Chemoradiotherapy
- Why is definitive chemoradiotherapy preferred for most non-metastatic anal SCC, rather than surgery as the initial treatment?
- Compare 5-fluorouracil (5-FU) plus mitomycin C (MMC) with cisplatin-based regimens.
- What is the role of intensity-modulated radiation therapy (IMRT) in reducing treatment-related toxicity?
3. Response Assessment and Salvage Surgery
- How should tumour response be assessed after definitive chemoradiotherapy?
- What constitutes a clinical complete response (cCR), and when should response be reassessed?
- When is salvage abdominoperineal resection (APR) indicated for persistent or recurrent disease?
4. Resource-Constrained Setting
- How can treatment be adapted when there is limited access to linear accelerators, treatment interruptions, or mitomycin C shortages?
- What evidence supports alternative systemic regimens such as capecitabine-based treatment?
- How can treatment planning reduce financial and logistical barriers for patients paying out of pocket?
Question 1.
a. High-risk HPV drives transformation mainly through two viral oncoproteins, E6 and E7. Their expression becomes deregulated when the viral genome integrates into host DNA, which often disrupts the E2 repressor gene.
E6 binds the cellular ubiquitin ligase E6AP and targets p53 for proteasomal degradation. This removes the G1 checkpoint and apoptotic responses to DNA damage. E6 also activates telomerase (hTERT), which supports cellular immortalization. E7 binds and inactivates the retinoblastoma protein (pRb). This releases E2F transcription factors and drives unchecked entry into S-phase.
p16INK4a normally restrains the cell cycle by inhibiting CDK4/6, upstream of pRb. When E7 removes pRb, the negative feedback that would suppress p16 is lost, and E7 also induces p16 epigenetically. p16 therefore accumulates strongly in nucleus and cytoplasm, making diffuse strong p16 staining a reliable surrogate for transcriptionally active high-risk HPV. Because the tumour still depends on E6 and E7, TP53 is usually wild-type.
b. HPV-16 accounts for the large majority of anal SCC. p16-positive tumours have consistently better locoregional control, disease-free survival and overall survival after chemoradiotherapy than the roughly 5–10% that are HPV/p16-negative.
This finding is supported by several datasets:
• Retrospective series from Denmark and the Netherlands.
• Pooled multicentre analyses.
• Correlative work from RTOG 98-11.
The HPV-negative subgroup is often TP53-mutated and markedly radioresistant.
p16 status is prognostic, but it is not yet used to change treatment outside trials. De-intensification is being tested prospectively, for example in EA2182 (DECREASE) in early-stage disease. For this patient, p16 positivity is reassuring prognostic information; it should not lead to dose reduction.
There are also wider implications:
• She needs cervical cytology or HPV testing and vulval examination, because HPV-related multicentric intraepithelial neoplasia is common in HIV.
• Survivorship plans should include ongoing surveillance of the anogenital tract.
c. In the pre-ART era, HIV-positive patients had more severe haematological, skin and mucosal toxicity, more treatment breaks and worse outcomes. Many clinicians therefore reduced doses.
With effective ART, and particularly with CD4 counts above 200 cells/µL, multiple cohort series show:
• Complete response rates and colostomy-free survival broadly comparable to HIV-negative patients.
• Somewhat higher rates of acute haematological toxicity in some series.
• Possibly higher locoregional relapse in some cohorts.
This patient has virological suppression and a CD4 count of 420. She should receive full-dose standard chemoradiotherapy without empirical dose reduction.
However, it would be important to:
1. Review the ART regimen with the HIV team for possible drug reactions as Zidovudine potentiates myelosuppression when used with mitomycin.
2. Anticipate a fall in CD4 count. Pelvic chemoradiotherapy causes profound lymphopenia, and recovery may take a year or more. Start cotrimoxazole prophylaxis if CD4 falls below 200, and monitor for opportunistic infection.
3. Keep ART going throughout treatment. Mucositis, nausea or financial strain can cause ART interruption, so adherence support during radiotherapy matters.
4. Use pelvic bone-marrow-sparing IMRT. Marrow reserve is more critical in this group.
Question. 2
a. Before Nigro's work in the 1970s, abdominoperineal resection was standard. It gave five-year survival of roughly 40–70% at the cost of a permanent colostomy for every patient.
Nigro observed that preoperative 5-FU, mitomycin and modest-dose radiotherapy often left no residual tumour. That observation led to randomized evidence:
• UKCCCR ACT I and EORTC 22861 showed that adding chemotherapy to radiotherapy substantially reduced locoregional failure and improved colostomy-free survival.
• RTOG 87-04 established that mitomycin added to 5-FU is necessary, improving disease-free and colostomy-free survival over 5-FU alone.
Chemoradiotherapy now achieves complete response in around 90% of patients. Most keep a functioning sphincter, with survival at least equal to primary surgery. Surgery is therefore held in reserve for salvage.
For this patient, internal sphincter involvement is not an indication for primary surgery. Sphincter preservation is the explicit goal, and she should be counselled that most patients in her position keep reasonable continence.
b.
|
Trial |
Comparison |
Key finding |
|
RTOG 98-11 |
5-FU + MMC CRT vs induction cisplatin/5-FU then cisplatin/5-FU CRT |
Cisplatin arm had higher colostomy rate and, on long-term follow-up, inferior DFS and OS |
|
ACT II |
MMC 12 mg/m² (max 20 mg) d1 vs cisplatin 60 mg/m² d1 and d29; both with 5-FU 1000 mg/m²/day d1–4 and d29–32, 50.4 Gy in 28 fractions |
cCR about 90% in both arms at 26 weeks; similar survival; maintenance chemotherapy added nothing |
The RTOG 98-11 deficit is likely explained by the delay in starting radiotherapy and the loss of mitomycin, rather than cisplatin itself being ineffective. In ACT II, mitomycin caused more grade 3–4 haematological toxicity, and cisplatin more non-haematological toxicity.
The conclusion is that 5-FU plus mitomycin remains the standard. It is a single dose on day 1 in the ACT II schedule. Cisplatin plus 5-FU is an evidence-supported alternative when mitomycin is unavailable or contraindicated. If cisplatin is used, it must be concurrent, not induction. It needs hydration, renal monitoring and stronger antiemetics, which adds cost and chair time.
Local calibration. Before infusional 5-FU or capecitabine, flag DPYD variant risk. Variant profiles in West African populations differ from those in the European trial cohorts. If genotyping is unavailable, keep a low threshold for early review in week one.
c. Conventional anal fields cover the perineum, inguinal regions and whole pelvis. They irradiate small bowel, bladder, femoral heads, external genitalia and pelvic bone marrow heavily. In the 3D era, grade 3+ skin and GI toxicity was common, and treatment breaks were frequent.
The RTOG 0529 was a phase II study of dose-painted IMRT. Compared with the conventional arm of RTOG 98-11, it significantly reduced:
• Grade 2+ haematological toxicity.
• Grade 3+ GI toxicity.
• Grade 3+ dermatological toxicity.
It also produced fewer treatment interruptions. That matters for outcome, because analyses of RTOG 98-11 and other datasets show that prolonged overall treatment time worsens locoregional control.
Dose-painting prescribes different doses to different targets in one plan:
• Primary and involved nodes over 3 cm: 50.4–54 Gy, for example 53.2 Gy in 28 fractions under UK guidance, or 54 Gy for larger tumours under RTOG 0529.
• Smaller involved nodes: 50.4 Gy.
• Elective nodal regions: about 40–45 Gy.
Applied to this patient:
• The 4.2 cm primary and the confirmed inguinal and mesorectal nodes receive the higher dose level.
• Elective coverage includes the mesorectum, internal and external iliac, presacral and inguinal regions.
• Contours should follow a consensus atlas (RTOG or AGITG).
• Pelvic bone marrow sparing is worth adding because of her HIV status.
The trade-off is that IMRT requires careful contouring, daily image guidance and physics QA. A poorly contoured IMRT plan can miss target in a way a generous 3D field would not.
Question 3
a. Anal SCC regresses slowly, often over several months after treatment ends. The key evidence is the ACT II secondary analysis by Glynne-Jones and colleagues (2017). Many patients without a complete response at 11 weeks reached one by 26 weeks, and complete response at 26 weeks best predicted long-term outcome.
First assessment, at about 8–12 weeks after completion:
• Clinical examination by an experienced examiner.
• Digital rectal examination.
• Anoscopy or proctoscopy.
• Inguinal node palpation.
• MRI pelvis as a baseline for comparison.
PET-CT at about 12 weeks has good negative predictive value where available, but it is not essential.
What to do at the first assessment depends on the finding:
• Regressing tumour: observe and re-examine at about 26 weeks.
• Clear progression: biopsy promptly.
Avoid routine biopsy of a regressing area or post-radiation scar. It risks a non-healing ulcer or radionecrosis, and residual viable-looking cells at 8 weeks may still be dying.
b. A clinical complete response means all of the following:
• No palpable or visible tumour on digital examination and endoscopic inspection, accepting smooth scarring.
• Resolution of nodal disease on clinical examination and imaging.
• No new disease.
MRI after radiotherapy is often hard to interpret because fibrosis and oedema persist. A low-signal fibrotic scar without restricted diffusion is reassuring, but clinical examination remains the anchor.
After a clinical complete response, follow-up is:
• Every 3–6 months for the first 2–3 years, with clinical examination including DRE and anoscopy.
• Imaging annually for about 3 years.
Most recurrences occur within the first 2–3 years.
c. Salvage abdominoperineal resection is indicated in two situations:
• Persistent disease: biopsy-proven residual tumour at about 26 weeks, or proven progression at any time point.
• Locoregional recurrence after an initial complete response: biopsy-proven, with no distant disease on restaging.
Before surgery, it is important to complete restaging with MRI pelvis and CT chest, abdomen and pelvis (or PET-CT) and confirm resectability. However, at surgery salvage APR in irradiated tissue is an extended operation, often with en bloc resection of the posterior vaginal wall in women. The perineal defect usually needs myocutaneous flap reconstruction, such as VRAM or gracilis, because perineal wound breakdown in irradiated fields is common. R0 resection is the strongest predictor of survival. With a five-year survival after salvage is roughly 30–60% across series.
Isolated inguinal nodal relapse is managed with groin dissection, sometimes with further radiotherapy if the groin was not previously treated to full dose.
Non-oncological indications include severe incontinence, fistula or radionecrosis. These may need a defunctioning colostomy rather than APR.
Specific counselling for this patient:
• She should understand from the outset that permanent colostomy is a salvage option, not the plan.
• Referral to a stoma therapist is wise if salvage becomes necessary.
• Her HIV status does not by itself preclude salvage surgery, but wound healing and nutritional status need optimization.
Question 4
a. The biological priority is overall treatment time. Anal SCC repopulates during gaps, and unplanned interruptions lower locoregional control. Splitting the course to manage access is the wrong compromise.
When machine breakdown or a public holiday causes missed fractions:
• Compensate within the same overall time.
• One option is treating on a Saturday.
• Another is two fractions on one day, at least 6 hours apart.
• The department should have a written gap-correction protocol rather than improvising.
When IMRT is not available, 3D conformal radiotherapy with CT planning, multileaf collimation and careful field design is acceptable. Counsel the patient to expect more skin and GI toxicity; proactive skin care and early diarrhoea management matter more.
Cobalt-60 can deliver curative treatment in this disease. However, lower dose to deep pelvic nodes and higher skin toxicity need careful planning.
Hypofractionation is not established for anal SCC. Fellows should not adopt shortened courses from rectal cancer practice.
When mitomycin is unavailable, the evidence-supported substitute is concurrent cisplatin, based on ACT II. It can be combined with infusional 5-FU, or in practice with capecitabine.
5-FU alone with radiotherapy is clearly inferior based on RTOG 87-04. Reserve it for patients who cannot receive a second agent.
A temporary mitomycin shortage is not a reason to delay starting radiotherapy, because the delay itself costs outcome. Switch agents instead.
b. Capecitabine 825 mg/m² twice daily on radiotherapy days replaces infusional 5-FU, usually with mitomycin 12 mg/m² on day 1. The supporting evidence is:
• EXTRA (UK phase II): high complete response rates with acceptable toxicity.
• Retrospective cohorts from the Netherlands and the US: locoregional control comparable to 5-FU-based treatment, with less neutropenia in some series.
• Meta-analyses: consistently non-inferior response and acceptable toxicity.
There is no randomised phase III comparison. Despite that, capecitabine with mitomycin is accepted by NCCN and widely used in UK practice. Capecitabine with cisplatin has been reported from Brazil and other middle-income settings with reasonable results, on lower-quality evidence.
For a West African practice, the practical case for capecitabine is very strong:
• No ambulatory infusion pump.
• No central venous access device.
• No inpatient admission for the 96-hour infusion.
• Fewer central line infections, which matters for an immunosuppressed patient.
The cautions are:
• Adherence. Use a pill diary and dispense weekly at review.
• Hand-foot syndrome.
• DPYD risk. As in Domain 2.
• Drug interactions. Check interactions with her ART regimen; clinically significant ones are uncommon but need checking.
c. For a patient paying out of pocket, choose the regimen and schedule to minimise visits, admissions and consumables without compromising efficacy.
Regimen:
• A single day-1 mitomycin dose (ACT II schedule) with oral capecitabine needs one chemotherapy chair visit for the whole course.
• The alternatives are two mitomycin doses plus two 4-day infusions, or two cisplatin doses with hydration.
Workup:
• Order only what changes management. MRI pelvis, CT chest, and FNA of the inguinal nodes are essential.
• PET-CT is a luxury rather than a requirement.
• Coordinate laboratory tests with existing HIV clinic visits.
Planning:
• Complete simulation, planning and the start of treatment as early as possible.
• Agree the full cost of the course at the outset, ideally as a bundled package. Running out of funds mid-course is the most common avoidable cause of interruption in this setting.
During treatment:
• If she lives far away, help arrange accommodation near the centre for the 5½ weeks.
• Use patient navigators or social work to engage NHIS cover, employer schemes or charity support.
• Prescribe inexpensive supportive care proactively: barrier creams, sitz baths, loperamide, analgesia and antiemetics. This keeps toxicity from forcing breaks.
Coordination with HIV care:
• Align HIV clinic and oncology reviews so ART supply and monitoring continue without extra trips.
Follow-up:
• Schedule surveillance at the 12-week and 26-week reviews, then 3–6 monthly.
• Avoid early scans that add cost without changing decisions.
Teaching point for the cohort: diagnostic delay. Six months of "haemorrhoids" is a classic local pattern. Persistent anorectal bleeding or pain in an HIV-positive patient warrants digital examination and proctoscopy before haemorrhoids are accepted as the diagnosis.