World Journal of Colorectal Surgery

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 8  |  Issue : 3  |  Page : 79--83

Anorectal melanoma surgical management: A tertiary cancer centre analysis


Ravi Arjunan, C Ramach, Pavan Kumar Jonnada, Uday Karjol 
 Department of Surgical Oncology, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India

Correspondence Address:
Dr. Pavan Kumar Jonnada
Department of Surgical Oncology, Kidwai Memorial Institute of Oncology, Bengaluru - 560 029, Karnataka
India

Abstract

Background: Primary rectal malignant melanoma is an exceptionally rare neoplasm associated with an extremely poor prognosis despite aggressive treatment. The described management options for localized disease are abdominoperineal resection (APR) and wide local excision (WLE) with or without radiation. Objective: To assess the surgical outcomes of the patients with anorectal melanoma. Design and Setting: Retrospective study. Patients and Methods: This retrospective study describes the experience in surgical management of 18 cases of anorectal melanoma treated surgically at our center, between 2010 and 2015. Main Outcome Measures: To assess the median survival and recurrence rates of anorectal melanoma patients who underwent surgery. Sample size: Eighteen cases. Results: This is a retrospective study of 18 cases of anorectal melanoma. APR was performed in 77.8%, wide excision (WLE) in 16.7%, and posterior exenteration in 5.6%. The median survival of patients undergoing APR was 14.66 months and median survival of patients undergoing WLE was 18 months. No significant difference in median survival was observed in the patients undergoing abdominoperineal resection (APR) or wide local excision (P = 0.168). A significant difference in median survival between the node negative group and node positive group was observed (17 months vs 13.4 months P = 0.019). The median survival of patients with stage I, II, and III cancers were 17.28 months, 16 months, and 13.4 months, respectively. A statistically significant difference in median survival was found between patients with lympho-vascular invasive and noninvasive cancer (13.37 months vs 16.7 months P = 0.029). There was no significant difference in the recurrence rate between APR and WLE groups (86% vs 66% P = 0.893).Conclusion: Anorectal melanoma is an aggressive disease which require timely diagnosis. Nodal status is an important factor that impact median survival. There is no significant difference in survival when WLE compared to APR. Node positivity and lympho-vascular invasion confer poor prognosis. Recurrence rates are identical regardless of the surgical approach. Limitations: It is a retrospective series based on case records. A major drawback of this investigation is the limited detail available for each case. Not all patients who underwent local excision received radiotherapy. Conflict of Interest: None.



How to cite this article:
Arjunan R, Ramach C, Jonnada PK, Karjol U. Anorectal melanoma surgical management: A tertiary cancer centre analysis.World J Colorectal Surg 2019;8:79-83


How to cite this URL:
Arjunan R, Ramach C, Jonnada PK, Karjol U. Anorectal melanoma surgical management: A tertiary cancer centre analysis. World J Colorectal Surg [serial online] 2019 [cited 2020 Oct 1 ];8:79-83
Available from: http://www.wjcs.us.com/text.asp?2019/8/3/79/269822


Full Text



 Introduction



Melanocytes are defined as cells possessing the unique capacity to synthesize melanin within melanosomes.[1] They are derived from a neural crest. Melanocytes, although mainly concentrated in the skin, are also located in mucosal membranes lining respiratory, gastrointestinal, and urogenital tracts. Primary mucosal melanomas are rare entities that are more aggressive than cutaneous melanomas. Primary mucosal melanomas are common in the head, neck, and anorectum. The anorectum is the most frequent location of melanomas in the gastrointestinal tract and accounts for 0.4%–1.6% of all malignant melanomas.[2] Furthermore, anorectal malignant melanoma accounts for 1%–3% of all anal tumors.[3] In India, they account for 2%–4% of cancers of the rectum.[4] A surveillance, epidemiology, and end results (SEER) database review reported a 2.5% 5-year overall survival.[5] However, 20% survival has been reported in some patients.[6] There are no precise data for the management of these malignancies. Treatment modalities range from wide local excision (WLE) to abdominoperineal resection (APR). No randomized controlled trials were conducted to address this question because of the rarity in occurrence. Our study aims to analyze the surgical outcome of patients with anorectal melanoma from a tertiary cancer center treating a south Indian population.

 Patients and Methods



This is a retrospective study conducted in the Department of Surgical Oncology for patients who were referred for the evaluation of rectal or anal canal malignancy. We retrospectively identified 18 patients with biopsy-proven anorectal melanoma. However, metastatic anorectal melanoma was excluded from our study. All patients were evaluated using a contrast-enhanced CT (CECT) scan of the abdomen and pelvis, Pelvic Magnetic Resonance Imaging (MRI), and colonoscopy. All patients underwent a biopsy of the lesion, and IHC was done using the following panel of markers: S100, DOG1, HMB45, desmin, CK, MELAN A, SMA, CD 34, MYO D1, CALDSEMON, and CD 117, chosen at the discretion of the pathologist. After diagnosis, patients underwent APR or wide excision. Pathological staging was done, and all patients were followed up every 2 weeks for the initial month; thereafter, every 3 months for the first 2 years by clinical examination and ultrasonography of abdomen and CECT abdomen and pelvis, if needed. Median survival data was collected until the last follow-up or death. Statistical analysis was done using ANOVA one-way analysis and Kaplan–Meier survival analysis using SPSS software version 24.

 Results



Between 2013 and 2018, 150 patients were referred for resection of a rectal or anal malignant lesion. Of these, 18 patients were identified with anorectal melanoma, who underwent surgical therapy in the Department of Surgical Oncology. The mean age of diagnosis was 58.61 (23–84 years). There were 13 females and 5 males. Of the 18 patients who underwent surgery with curative intent, 14 underwent APR, 1 underwent posterior exenteration, and 3 underwent WLE. Follow-up ranged from 6 months to 36 months. The clinical variables are shown in [Table 1].{Table 1}

A total of 61.1% and 16.7% of the cases presented symptoms of bleeding per rectum and difficulty in passing stools, respectively. A total of 11.1% of the cases presented symptoms of mass per rectum and abdominal pain. IHC was done in 95% of the cases for diagnosis.

APR was performed in 77.7%, wide excision was performed in 16.7%, and posterior exenteration was performed in 5.6% of the cases. The T-staging observed in our study were 11.1% involved submucosa, 44.4% involved muscularis, 38.9% invaded subserosal fat, and 5.6% had adjacent organ invasion. Stage 1 was observed in 27.8%, stage 2 in 11.1%, and stage 3 in 61.1%. The median size of the tumor in our study was 5 cm. The median size of the tumor in patients undergoing WLE was 2.66 cm. The median size of tumor in patients undergoing APR was 5.04 cm. The mean distal margin observed in our study was 1.23 cm. The pathological variables are shown in [Table 2].{Table 2}

The median survival of patients undergoing APR was 14.66 months and median survival of patients undergoing WLE was 18 months as shown in [Table 3] and [Figure 1]. No significant difference in median survival was observed in the patients undergoing APR or WLE, (P = 0.168). The median survival of patients with T1, T2, T3, and T4 were 17 months, 15.8 months, 13.7 months, and 9 months, respectively. The median survival of patients with N0, N1, N2a, and N2b were 17 months, 14.12 months, 13.2 months, and 13 months, respectively. Node-positive patients had a median survival of 13.44 months, and node-negative patients had a median survival of 17 months. It was observed that there was a significant difference in median survival between the node-negative group and node-positive group, (P = 0.019). The median survival of patients with stage I, II, and III were 17.28 months, 16 months, and 13.4 months, respectively. A total of 83.3% of patients experienced recurrence, with 44.4% being local and 38.9% distant. A total of 66.6% of patients experienced local recurrence in WLE group and 86% experienced local recurrence in APR group.{Table 3}{Figure 1}

 Discussion



Anorectal melanoma is a rare and aggressive malignancy. It is more common in western countries than Indian subcontinent. However, when melanomas of rectum are considered, the incidence is more in Indian subcontinent when compared to western countries.[7]

Anorectal melanoma is predominantly a disease in elderly patients, most commonly observed in the 60–80 age group.[8],[9] However, anorectal melanoma has also been reported in the second decade of life.[10] The mean age of our patients in this study was 58.61. Anorectal melanoma is more common in women, and a majority of the case series reported female predominance of 75%.[8] Our study showed similar results with a female incidence of 72.2%. Majority of the rectal neoplasms present with bleeding per rectum and anorectal melanoma is no exception. Though bleeding is a major presenting symptom, patients also have symptoms like the presence of a mass, a sensation of tenesmus, pruritus, change in bowel habits, and pain.[11] The nonspecific presentation can lead to a delay in diagnosis.[12]

Metastatic anorectal melanoma has a poor prognosis with a median survival of 4–6 months.[13] A recent SEER data analysis showed that survival is closely associated with the stage of diagnosis. Median survival for metastatic disease is 6 months.[14]

However, for anorectal melanoma without distant metastasis, surgical resection is the traditional standard of care. Survival benefit is seen when surgery is implemented for localized or resectable metastatic disease. Surgery with an emphasis on achieving R0 resection can improve median overall survival and disease-free survival.[13] The traditional surgical standard of care for the management of anorectal melanoma was APR. However, there exits data that emphasize on WLE for localized anorectal melanoma showing a similar benefit achieved with APR.

In a report from Memorial Sloan Kettering on anorectal melanoma, they suggested female gender, negative lymph node status, and tumor size of < 2.5 cm may achieve a long-term survival benefit with APR.[6] Similarly, survival benefit favoring local excision with additional chemoradiotherapy was shown by the MD Anderson group with an overall survival benefit of 31%.[15]

This finding of improved survival benefit in patients treated with WLE and adjuvant radiation therapy when compared to those treated by either APR or wide excision alone was observed in a study of 63 anorectal melanoma cases. They showed the median survival of patients treated by WLE with adjuvant radiation, WLE alone or APR was 34, 12, and 10 months, respectively.[7] These findings suggest that the addition of radiotherapy to wide excision could improve survival.

No difference in survival between APR and WLE was seen in many studies.[16],[17],[18],[19],[20],[21],[22] These findings were highlighted in [Table 4]. These findings are similar to the observations found in our study. The answer to choosing radical surgery than local excision remains uncertain because findings showing similar survival benefits were observed in both groups. Therefore, it is evident to emphasize the factors responsible for aggravating the biology of the disease to tailor the appropriate therapy.{Table 4}

Prognostic factors that impact outcome are tumor stage, tumor size, margin status and perineural invasion, and nodal status. Lymph nodal status is an important factor that can prognosticate disease. In our study, node-positive patients had a median survival of 13.44 months, and node-negative patients had a median survival of 17 months. In a study of 64 cases, it was shown that the lymph node metastasis was a significant predictive factor.[23] It could be emphasized that increasing nodal count could impact prognosis, indicating that lymph node metastasis is an important contributory factor in prognosis. It was observed in our study that there is significant difference in median survival between the node-negative group and node-positive group (P = 0.019) as shown in [Figure 2].{Figure 2}

Many groups have extensively studied the impact of resection margins on the prognosis of anorectal melanoma. In a Swedish study of anorecal melanoma in 251 patients, it was reported that irrespective of the surgical approach, patients in whom R0 resection was achieved had a better overall 5-year survival than patients with involved margins. They reported a 19% 5-year survival with R0 resection compared to a 6% 5-year survival with R+ resection.[20]

Tumor size is an important consideration that could impact prognosis. The median tumor size in our study was 5 cm, but the median size of tumor in patients undergoing WLE was 2.66 cm when compared to 5.04 cm of the lesion in patients undergoing APR. It has been observed that there is a significant difference in survival when the tumor size is >2.5 cm than <2.5 cm.[20]

Tumor invasiveness is a prognostic factor and forms the basis of staging. In a similar study of 63 anorectal melanoma cases, it was observed that the median overall survival in stage I patients was 12 months, while it was 7 and 4 months in those with stage II and III diseases, respectively.[7]

Adjuvant postoperative radiation therapy has been implemented in the management of anorectal melanoma. The limited available data obscured the effect of radiotherapy alone or in combination with surgery. In the initial small volume studies, it was observed that radiotherapy was effective in controlling local symptoms, but inguinal lymph nodal recurrence was observed leading to the inclusion of groin lymph nodes in the radiation field.[24] Radiotherapy was implemented in the event of WLE as an adjuvant and studies demonstrated some benefits.[7] In a study of 54 cases, it was observed that the local control and lymph nodal control could be improved by radiation therapy, but it did not control the rate of distant metastasis and overall survival.[25] There are opinions that anorectal melanoma is an aggressive disease, and WLE is advocated whenever feasible because these patients eventually succumb to metastasis regardless of surgical therapy.[26]

Recurrence in the form of regional, nodal, or distant recurrence is an important factor that determines prognosis. In a study comparing WLE with radiation therapy and APR, the local recurrence rate was about 75% in WLE group and 0% in APR group.[9] In a study by Zhang et al., there was 100% recurrence in WLE group when compared with 26% recurrence in the APR group. In another study comparing APR with WLE, 18% local recurrence in WLE and 50% in APR group was observed.[9] One study stated 100% recurrence rate with APR and 71.1% with WLE.[21] So, it can be realized that recurrence of disease does not depend on the surgical approach and is related to disease biology.

Our study has its limitations as it is a retrospective series based on case records. A major drawback of this investigation is the limited detail available for each case. In our study, 3 patients underwent WLE, and not all of them received radiotherapy.

This study provides insights into the aggressiveness of the disease and the current status of its management. Further, it shows that the nodal status is an important prognostic factor and highlights the importance of nodal status and lymphovascular invasion status, suggesting lymphovascular invasion and node positivity result in poor prognosis.

 Conclusion



Anorectal melanoma is an aggressive disease that requires a timely diagnosis. Nodal status is an important factor that impacts median survival. There is no significant difference in survival when WLE is compared to APR. Node positivity and lymphovascular invasion result in poor prognosis. Recurrence rates are identical regardless of the surgical approach.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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