Anal cancer in Sweden 2015-2019. Implementation of guidelines, structural changes, national registry and early results

Impact of the risk-adapted Nordic anal cancer group consensus guidelines on the contouring of the elective clinical target volume in anal cancer

BACKGROUND AND PURPOSE

The recently published Nordic anal cancer group (NOAC) contouring guidelines aim for improved oncological outcomes and reduced toxicity in anal cancer patients treated with radiotherapy. The present work describes how the elective clinical target volume (CTVe) would change when applying the NOAC guidelines instead of the previous Australasian standard. According to the Australasian guidelines, the cranial border of the CTVe is at the common iliac bifurcation for all patients, and the external iliac region as well as the ischiorectal fossa are always included.

MATERIALS AND METHODS

Retrospectively, 166 anal cancer patients treated with curative radiotherapy according to Australasian guidelines between 2009 and 2017 were studied in a single-center analysis. Pretherapeutic scans, and clinical information were used to categorize patients according to the NOAC guidelines for a comparison with the Australasian guidelines.

RESULTS

Applying the risk-adapted alternative of the NOAC guidelines had the external iliac region omitted in 41.0% of the patients. The cranial border was lowered from the common iliac bifurcation in 27.7% and elevated in 12.7% of the patients. Elderly patients (≥70 years) more often had the external iliac region omitted than younger patients (60.9% vs. 33.3%; p = 0.001). The entire ischiorectal fossa was included in 23.7% of the patients due to tumor extension beyond the levator ani muscles or external sphincter.

INTERPRETATION

Contouring according to the NOAC risk-adapted guidelines changed, and mainly reduced, the CTVe in about half of all patients. Prospective follow-up is needed to determine if this is clinically beneficial.

Clinical characteristics and treatment outcome in p16 negative anal cancer

BACKGROUND

Anal squamous cell carcinoma (ASCC) is linked to human papillomavirus infection with p16 being positive in about 85% of cases. Overall survival (OS) of ASCC is 60%-80%. Prognosis in p16 negative (p16-) ASCC is worse with an OS of 30%-60%. It is important to elucidate differences in p16+ and p16- ASCC characteristics and outcome.

METHODS

Consecutive ASCC patients (n = 380) treated with curative intent in Uppsala 2017-2022 were reviewed and analyzed retrospectively. A cohort of p16- patients (n = 30) from Gothenburg was included as a validation cohort.

RESULTS

Ninety-one per cent (n = 347) were p16+ and 9% (n = 33) p16-. Median follow-up was 33 months (range 4-78). p16- status was associated with higher age (≥65 years; p = 0.03), comorbidity (p = 0.03), male sex (p = 0.001) and perianal localization (p < 0.001). At 3 years progression free survival was 50% and 81% (p <0.0001) and OS 60% and 89% (p < 0.0001) for p16- and p16+ patients, respectively. Male sex, advanced T-stage (T3-4), N+ disease, advance treatment and p16- status were associated with inferior OS (p = 0.01 - p < 0.0001). In the p16- subgroup, advanced T-stage and intensive treatment were negative prognostic factors for OS (p = 0.007 and 0.009, respectively) but no clinical characteristic predicted persistent disease. The p16- validation cohort essentially confirmed the findings from the main cohort.

INTERPRETATION

p16- ASCC is a disease subset with specific clinical features and poor prognosis in need of improved treatment.

Reduction of elective lymph node volume in radiotherapy of early anal squamous cell cancer: a comparative study between two Swedish university hospitals

BACKGROUND

Anal squamous cell cancer (ASCC) in early stages (T1-2N0M0) is treated with chemoradiotherapy with a 3-year overall survival (OS) exceeding 90%. In Swedish guidelines, it has been optional to include the external iliac and presacral lymph node (LN) stations in radiotherapy (RT) treatment fields in early ASCC. Two Swedish hospitals treating ASCC (SU: Sahlgrenska University Hospital; UU: Uppsala University Hospital) have chosen different approaches since 2010.

MATERIAL AND METHODS

This study included consecutive patients with early ASCC (T1-2N0M0) treated between 2010 and 2017 at both sites (SU n = 70; UU n = 46). Data were retrieved from medical records and RT charts.

RESULTS

At SU, the external iliac and presacral LN stations were included in elective LN irradiation in 96.8% (n = 60) and 95.2% (n = 59) patients compared to 2.4% (n = 1) and 29.3% (n = 12) at UU. The mean elective LN volume was 2,313 cc (interquartile range [IQR] 1,951-2,627) in the SU cohort compared to 1,317 cc (IQR 1,192-1,528) in the UU cohort, p < 0.0001. No case of regional LN recurrence was seen in either cohort. Disease specific survival (DSS) at 5 years was 95.7% (confidence interval [CI] 90.1-100.0) in the SU cohort and 97.8% (CI 93.2-100.0) in the UU cohort (p 0.55). OS at 5 years was 84.5% (CI 76.1-93.0) in the SU cohort and 82.6% (CI 69.6-89.1) in the UU cohort (p 0.8).

INTERPRETATION

We found no differences in regional recurrence, DSS or OS between the cohorts treated with different elective LN volumes. In this population-based study, reduction of RT volume in early ASCC did not lead to inferior outcome.

MRI morphological characteristics of lymph nodes in anal squamous cell carcinoma

OBJECTIVES

Pre-treatment staging of anal squamous cell carcinoma (ASCC) includes pelvic MRI and [18F]-fluorodeoxyglucose positron emission tomography with computed tomography (PET-CT). MRI criteria to define lymph node metastases (LNMs) in ASCC are currently lacking. The aim of this study was to describe the morphological characteristics of lymph nodes (LNs) on MRI in ASCC patients with PET-CT-positive LNs.

METHODS

ASCC patients treated at Skåne University Hospital between 2009 and 2017 were eligible for inclusion if at least one positive LN according to PET-CT and a pre-treatment MRI were present. All PET-CT-positive LNs and PET-CT-negative LNs were retrospectively identified on baseline MRI. Each LN was independently classified according to pre-determined morphological characteristics by two radiologists blinded to clinical patient information.

RESULTS

Sixty-seven ASCC patients were included, with a total of 181 PET-CT-positive LNs identified on baseline MRI with a median short-axis diameter of 9.0 mm (range 7.5-12 mm). MRI morphological characteristics of PET-CT-positive LNs included regular contour (87%), round shape (89%), and homogeneous signal intensity on T2-weighed images (67%). An additional 78 PET-CT-negative LNs were identified on MRI. These 78 LNs had a median size of 6.8 mm (range 5.5-8.0 mm). The majority of PET-CT-negative LNs had a regular contour, round shape, and a homogeneous signal that was congruent to the primary tumor.

CONCLUSIONS

There are MRI-specific morphological characteristics for pelvic LNs in ASCC. PET-CT-positive and negative LNs share similar morphological features apart from size, with PET-CT-positive LNs being significantly larger. Further studies are needed to determine discrimination criteria for LNM in ASCC.

Patient reported long-term side effects on bowel function and anal pain in anal cancer survivors - 3- and 6-year results from the Swedish national ANCA study

AIM

The primary therapeutic option for anal cancer treatment is chemoradiotherapy resulting in 80% survival. The aim of this study was to assess long-term bowel function impairment and anal pain at 3 and 6 years after anal cancer diagnosis, based on a hypothesis of an increase in impairment over time. A secondary aim was to investigate if chemoradiotherapy increased the risk for bowel impairment, compared to radiotherapy alone.

METHOD

The ANal CAncer study (ANCA) consists of a national Swedish cohort of patients diagnosed with anal cancer between 2011-2013. Patients within the study were invited to respond to a study-specific questionnaire at 3- and 6-years after diagnosis. Descriptive analyses for the primary endpoint and ordinal logistic regressions for secondary endpoint were performed.

RESULTS

A total of 388 patients (84%) were included in the study. At 3 years of follow-up, 264 patients were alive. A total of 195 of these patients (74%) answered a study specific questionnaire, and at 6 years 154 patients (67%). Fifty-seven percent experienced bowel urgency at both 3 and 6 years. There was an increased risk for repeated bowel movement within 1 h (OR 2.44 [95% CI: 1.08-5.61, p = 0.03]) at 3 years in patients who had been treated by chemoradiation compared to radiotherapy alone.

CONCLUSIONS

Impairment in bowel function and anal pain after anal cancer treatment should be expected and remains after 6 years. This suggests that long-term follow-up may be necessary in some form after customary follow-up. The addition of chemotherapy increases long-term side effects of bowel function.