The role of haematological parameters in predicting the response to radical chemoradiotherapy in patients with anal squamous cell cancer

We retrospectively reviewed medical records of 53 patients who were treated with radical CRT for anal cancer between January 2009 and December 2019 at the Institute for Oncology and Radiology of Serbia. Patients who underwent palliative therapy (n = 6) were excluded, so the final analysis was conducted on 47 patients. All patients had a pato-histological diagnosis of anal squamous cell cancer confirmed by endoscopic biopsy. Prior to treatment, patients underwent physical examination, conventional radiography or computed tomography (CT) of the chest and CT or magnetic resonance imaging (MRI) of the abdomen and pelvis. Ethylenediaminetetraacetic acid (EDTA) peripheral blood was drawn by venipuncture and haematological parameters were derived from the absolute differential counts of a complete blood count (CBC). The neutrophil-to-lymphocyte ratio (NLR) was calculated as a ratio of circulating neutrophil and lymphocyte counts, and the platelet-to-lymphocyte ratio (PLR) was defined as the absolute count of platelets divided by the absolute lymphocyte count. Patients’ pre-treatment haemoglobin levels were obtained from medical history. The staging of the tumour was re-evaluated according to the eighth edition of the Union for International Cancer Control (UICC) TNM staging system for cancer of the anal canal.22 The general condition of the patients was classified using the ECOG Scale of Performance Status.23

RT began on the first day of chemotherapy and was administered 5 times a week with a daily fraction of 1.8 Gy. External beam RT was performed with either an anteroposterior-posteroanterior (2D technique) or three-dimensional conformal RT (3D-CRT).24 The target volumes and dose prescription were defined according to the International Commission on Radiation Units and Measurements (ICRU) Reports 50 and 62.25, 26 The gross tumour volume (GTV) encompassed the visible primary tumour on physical examination and imaging. Gross disease clinical target volume (CTV3) includes GTV with a 2 cm margin expansion but excluding uninvolved bone, muscle, or air. Nodal GTV was defined as all nodes that are ≥ 1.5 cm, or biopsy proven nodes. The clinical target volume (CTV1) included the gross disease CTV, areas at risk for microscopic spread, and regional lymph nodes (presacral, internal and external iliac, and inguinal nodes). The prescribed dose for this volume was 36 Gy in 20 fractions. After a two-week break in treatment according to the split course approach, RT was continued with a boost dose of 14.4 Gy in 8 fractions to CTV2, for a total prescribed dose of 50.4 Gy. The CTV2 included the gross disease CTV in addition with areas at risk for microscopic spread, and regional lymph nodes inferior to the sacroiliac joint. In cases with inguinal lymph node metastases, inguinal nodes were also included in this volume. The planning target volume (PTV) was extended from CTV with margins of 1 cm in all directions. After administration of 50.4 Gy, an additional boost of 9 Gy in 5 fractions was applied to the gross disease CTV (CTV3 = PTV3). Radiation was delivered with a 10 MV linear accelerator.

Chemotherapy consisted of two cycles of 5-FU and MMC. MMC (12 mg/m2) was administered on the first day of both parts of RT. 5-FU infusion (1000 mg/m2) was given on days 1 to 4 at the first and the second part of RT.

The treatment compliance and acute toxicity were evaluated weekly according to the common terminology criteria for adverse events (CTCAE) v.5.0.27

Tumour response was assessed at 24 weeks from CRT completion. The response to treatment was evaluated by a digital rectal examination, rectosigmoidoscopy, and radiologic evaluation (pelvic CT or MRI). Results of the clinical assessment were reported as complete clinical response (CR) or incomplete response (partial regression [PR], stable disease [SD] or progression [PD]).28 Patients with incomplete clinical response were referred to surgical treatment, as well as those with initial complete response who relapsed. In case of distant disease progression, patients were selected for chemotherapy.

Follow-up of patients was performed every 3 months during the first two years after completion of treatment, and every 6 months thereafter. Clinical examination and rectosigmoidoscopy were done at each follow-up. CT/MRI of the pelvis was performed every 3 months in the first year of follow-up and every 6 months thereafter.

Overall survival (OS) was defined as time from the date of beginning of CRT to the date of the last clinical control or the date of death. Anal cancer specific overall survival (ACSOS) excluded patients in whom death occurred for other reasons, and was calculated like OS. Progression-free survival (PFS) was calculated for patients whose response was assessed as PR, CR, or SD on initial evaluation 6 months after treatment completion, and was defined as time from the date of follow-up 6 months after treatment until the onset of progression, death or last follow-up for patients who did not progress. Disease-free survival (DFS) was based on the time from achieving a CR to the onset of progression, death, or the date of the last follow-up for patients who did not progress. Colostomy-free survival (CFS) was calculated only for patients in whom no colostomy was placed at the time of beginning of CRT, and was defined as the time from the start of treatment to the date of placement of a colostomy, death, or the date of the last follow-up for patients who did not have a colostomy. Overall treatment time (OTT) was measured as the number of days from the start of CRT to the end of treatment.

For normal distribution data testing, the Kolmogorov-Smirnov and Shapiro-Wilk tests were used. Descriptive methods (frequencies, percent, mean, median, standard deviation [SD] and range) were used to summarize the data. The statistical significance level was set at p < 0.05. For comparison of disease and treatment characteristics among different risk subgroups the Wilcoxon rank sum, Pearson chi-square and Fisher exact tests were used. Methods of survival analysis were used for DFS, OS, PFS, ACSOS, CFS (median with corresponding 95% confidence interval (CI) for description, Kaplan-Meier product-limit method for illustration and log-rank test). Also, for evaluating potential predictors of the response, univariate and multivariate logistic regression was used (odds ratio (OR) with 95% CI for description, Likelihood Ratio and Wild test), and the CR after 6 months (coded as 0) vs. non-CR (coded as 1) was set as a dependent variable. The receiver operating characteristics (ROC) curve methods were applied to investigate the discriminative potential of NLR and PLR for the presence/absence of CR (Area Under the ROC curve [AUC ROC] according DeLong’s method; Likelihood ratio test for AUC ROC; the best cut-off value was set as value with maximum sensitivity and specificity). The statistical analysis was performed using the program R (version 3.3.2 (2016-10-31) –“Sincere Pumpkin Patch”; Copyright (C) 2016 The R Foundation for Statistical Computing; Platform: x86_64-w64-mingw32/× 64 (64-bit); downloaded: January 21, 2017).

All analyses presented in this study are part of routine clinical practice approved by the Ethics Committee of the Institute for Oncology and Radiology of Serbia and were performed in accordance with the Helsinki Declaration of 1975, as revised in 2013.

The response to treatment was evaluated after 6 months of completion of therapy. The CR was detected in 30 patients (63.8%), 24 females (80%) and 6 males.

Comparison of characteristics of complete responders and non-complete responders to chemoradiotherapy are presented in Table 2. Patients with N0 responded to treatment significantly better than patients with N1. Primary tumour size also influenced the response.

Although median times to events for DFS/PFS/ OS were not reached, patients with CR after 6 months had significantly increased DFS, PFS, and OS after treatment completion compared to patients with non-CR response (Figure 2, Table 2).

Figure 2

A logistic regression model included nine variables (gender, age, clinical T stage, clinical N stage, tumour size, haemoglobin level, RT technique, treatment break period, and chemotherapy completion) (Table 3). It was found that patients with shorter period of treatment interruptions, a tumour size ≤ 4cm, the initial haemoglobin level more than 120 g/L, and lymph node negative patients, responded significantly better to treatment. The final model included pretreatment haemoglobin level and treatment break period.

Next, we examined if there were differences in the response to treatment after 6 months according to the cut-off values obtained by ROC analysis for NLR and PLR. (Figure 3, Table 4) According to the cut-off value obtained by ROC analysis (145.2), a statistically significant difference in the response was confirmed for PLR (p = 0.03). For NLR, a statistically significant effect on the response was not confirmed (p = 0.23). The patients were further divided into two group based on literature cutoff value for NLR in rectal cancer (0–3 vs. ≥ 3).29 A positive trend (p = 0.06) was found when 0–3 vs. ≥ 3 groups were tested, in regard to the nonCR vs. CR response. (Table 5)

Figure 3

The one patient who had disease progression was selected for chemotherapy. All other patients (n = 16) who did not achieve a CR after 6 months were referred to surgical treatment, as well as two patients who had a CR after 6 months but then relapsed. From the 11 patients that underwent surgery (APR), 9 were incomplete responders to CRT and 2 initial complete responders that relapsed. Within this surgically treated group, 9 patients (82%) achieved a complete response after surgical treatment. One patient died in early postsurgical period due to acute renal failure. Four patients relapsed after surgery, 3 of them were initial complete responders to surgery, but presented with distant metastases within two years of follow-up. All patients who relapsed after surgery were treated with postoperative chemotherapy and continued follow-up. With combined CRT and surgical salvage treatment CR rate was 80.9%. Two patients had palliative postCRT colostomy, due to medical comorbidities which didn’t allow radical surgical treatment. The remaining five patients were closely followed-up without any additional treatment because they had a poor general condition or refused surgery.

Six patients developed distant metastasis during the follow-up period and five of them were referred to chemotherapy. Two of them had dissemination to the lungs, 2 to the liver and the other sites were retroperitoneum, bones, and peritoneal metastasis. Three patients had multiple metastases.